texts: How dangerous was the turbulence on this commercial flight?

texts:
EDIT: Having read these great answers I feel a little ashamed for the fear I felt on this recent flight. However, judging by my reaction to the experience and the reaction of those around me on the flight I imagine I am not the only one who felt this way. As others have mentioned here I will agree that passengers are pretty bad at judging turbulence. For those who come to this Stack Exchange site with similar concerns, I hope that you read these answers from those knowledgeable in the field to assuage your concerns.

I was recently on a flight that flew in to central Texas coming from Denver. There was bad turbulence on the flight in the last 45 minutes -- the worst I have ever experienced -- and I was curious about what else was going on behind the scenes from the perspective of the pilot and crew.

I do not know the airplane model. It has ~38 rows and 3 seats on each side of the aisle. I was in row 35. It was a standard commercial airplane that would fly across the United States.

We were first told that we were about to enter a turbulent area based on reports of other airliners in the region. We soon entered an area of lightning and dense clouds so thick that there was no visibility outside the windows.

The first drop came unexpectedly in what I can only describe as similar to a bad, bumpy landing on the freeway. The bags rattled pretty hard and loudly and I felt myself leave the seat. It was loud and jarring enough for most of the people in my area to scream out loud. Over the next 45 minutes, these drops happened continuously and randomly, up to 15 times.

Between these big drops the plane felt like it was swaying from the left and right. There were also many tiny dips between the bigger dips. It was extremely tense for everyone on the plane and generally it felt very uneven below us so there was a constant anticipation of another drop.

After the landing gear went down, it was clear that we were ascending again. The pilot explained that there was a "spacing" issue on the ground so he was going to fly around and try to land again. The guy next to me said (jokingly?) that this meant the pilot was too scared to land.

The cabin crew looked pretty terrified, and they were chatting to each other throughout the whole ordeal. People were sobbing and weeping all around me and they would yell every time a drop happened.

Obviously, you have little information to go off of but I was curious, from what I have provided, about the following questions:

Many people on board were fairly traumatized by the experience. Was there any real danger from turbulence this bad? Is this something a pilot might encounter routinely that they would be equipped to handle or does this seem unusually bad?
What was happening behind the scenes? How does a pilot handle a situation like this? Was there other information about the turbulence that we were not being told?

Any other interesting, related information to give me insight into this experience would be appreciated.


texts: Which tail type is better in order to obtain higher speed?

texts:
If I want to design an aircraft that can fly with high speed while loaded, which tail type should I choose.

The mission is to design an aircraft that can move a certain distance with high speed while carrying certain load.


texts: Why do METARs report wind relative to true north rather than magnetic?

texts:
Why isn't the wind in a METAR given in magnetic heading, to match the runway numbers? Especially for areas where there is a double-digit magnetic declination.

Secondary/optional question: does the ATIS broadcast in true or magnetic?

Example: BGGH 281550Z 36004KT (an airport in Greenland, var 27.55°W).

Source: Wikipedia (click for full image)


texts: How accurate is the barometric altimeter in the Tu-154?

texts:
If the Smolensk disaster was to be traced down to a single decision (other than attempting landing in the first place), it would probably be the choice of radio altimeter to control altitude over a very unfortuitously shaped terrain (a wide valley, with steep slopes). This made the airplane to descend to 80 meters above the bottom of the valley, instead of 80 meters above the runway located 60 meters higher.

Someone mapped the black box recordings of the navigator's altitude readouts to speed and terrain profile, interpreting them as barometric altimeter readouts and it came out as an unreasonably bumpy ride (the orange line). I tried to follow up with mapping these same readouts at the same intervals, but relative to ground surface - treating them as radio-altimeter readouts - and it follows the blue line; judge for yourself which can depict a large passenger plane trajectory more accurately.

An unbiased comparison would include both advantages and disadvantages of the two types of altimeters. In this specific case (unknown, uneven profile terrain) the one main disadvantage of the radio altimeter is obvious: it doesn't provide accurate information about altitude of the airplane relative to the runway. I wonder though, what redeeming properties does it have - what are the advantages (if any) of using a radio altimeter over a barometric altimeter during landing - any inherent flaws of the barometric altimeter, like accuracy, reaction speed, or such, in which one type excels over the other?

(yes, I'm asking for a biased comparison; one with focus on superiority of one of the other. I realize both have their correct applications, both have strengths and weaknesses, applications where one or the other is better. Here I'm specifically asking for one side of this argument; half of the full image; look at it not as "why is A better than B" but "which traits of A are better than B")


texts: What happens if a passenger passes through the boarding gate, but doesn't get on the aircraft?

texts:
At one time, I was bored because of a delayed flight and that question arose in my mind just for curiosity. I haven't observed any mechanism that checks or counts the passengers who get on the aircraft, so there is a possibility of abuse.

I guess airport security is responsible for that. The passenger may try to get on another aircraft or may get in the airport through a different gate. It must be a bigger problem at international airports and terminals.

If the passenger is caught, what does airport security do, just arrest? What does the airline do if they realise the incident before or after the take-off?


texts: Could high density abrasion-resistant ceramic turbine blades allow for the use of borane fuels?

texts:
In the late 1950s the U.S Air Force searched for a fuel with similar characteristics to jet fuel but with higher energy density allowing longer flight range for bombers. In 1947 the British had discovered elemental boron to be the ideal replacement to carbon as it had lower bond dissociation energy leading to higher heat of combustion, 68 MJ/kg vs 42.8 MJ/kg for JP-4.$^1$

Pentaborane B5H11 was found to be unstable, so B5H9 was used as it possessed much better stability. Pentaborane B5H9 performed well in turbojet combustors but it was found that emissions of solid boron particles upon combustion caused severe erosion of the high pressure turbine blades. Is it possible that new ceramic matrix composite turbines blade with higher density and abrasion resistance could solve this problem?

$^1$ Frietas 2018 handbook of energy density Robert A. Freitas Jr., “Energy Density,” IMM Report.


texts: Why would a pilot request an unusual approach/runway to ATC?

texts:
In another SE Aviation question about the preferred approach for commercial aviation (Visual vs ILS) there's the following useful explanation:

  In most ATC facilities, the Tower decides what runway to use, and the
  approach control calls the type of approach generally on offer(this
  can vary depending on facilities and how they agree to run things). A
  pilot can always request a different approach... they might be
  delayed, sometimes significantly if they insist on something way out
  of the loop

I'm curious what would be examples of a pilot insisting on "something way out
of the loop"?

What's the preferred approach for a passenger jet?


texts: Flying a twin engine aircraft with 2-axis control

texts:
I believe a twin engine aircraft, with 2-axis control (i.e. Rudder and Elevator), under normal circumstances is flyable.
But is it safe at all?
If one of the engine dies, will the rudder alone be sufficient to counter the consequent  roll/yaw?


texts: What about an airfoil's shape makes air flow faster around it?

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An airfoil's shape causes air above the wing to move faster than below the wing to allow for the difference in air pressure as dictated by Bernoulli's principle. This is what many sources say, but I have yet to see any explain what about the airfoil's shape or why exactly air speeds up above but doesn't below the airfoil. If I were to assume, maybe it would have something to do with the law of conservation of momentum or energy?
If you could send any sources, that would be much appreciated too!


texts: What is primary cause of shock induced separation (shock stall)?

texts:
In the video link above describing Prandtl Meyer Waves, lecturer stated (at 22:40) a very important fact on which he based his first half of the lecture. "Mach wave (mach lines) deflect the flow through an infinitely small angle".

Now, lets look at the flow over the airfoil. First the flow over the top surface will accelerate to supersonic speeds(and above) until it reaches the point(roughly) of maximum camber. Due to acceleration, mach lines will diverge and of course no shock wave will form. But, after the point of maximum camber, where adverse pressure gradient will be introduced and decelerate the airflow than mach lines will start to converge (coalesce). Once they do it the shock wave will form above an airfoil (picture below). If aircraft countinues to accelerate, the mach lines would intersect each other more lower and lower to the airfoil bringing a shock wave down, until it meets the airframe (this sentence is my assumption and I would like confirmation if it is correct). At that point(once it touches the airframe) the boundary layer will always separate and cause a shock stall(also my assumtion, will it happen always?).
My question is:

Is boundary layer separation caused by the extreme instantaneous pressure increase on the airfoil surface, or because of the convergence of mach lines and deflecting the airflow regardless of the pressure(and density) change? Or is it combination of both?
Also if the statement from the lecturer is correct, shouldn't the mach lines deflect the airflow sooner and not only at the point when they all merge together?


texts:
I have a Garmin 530 in a Cessna 550.
It has a constant display of NXRG:x:xx in the upper right corner of a map page. It changes color (yellow and green are common) and the value of x:xx changes to some sort of code (see pictures)
Any idea what this is telling me?


texts: Is it possible to get a list of Cl/Cd values for various NACA Airfoils?

texts:
There are a lot of links which give the shape of the airfoil for any given set of camber thickness, position and max. thickness values, but I would like to know if it is possible to get the Lift vs. Angle of attack graph, i.e., in turn lift curve slope, and also Cl/Cd values for every NACA airfoil specified.

Actually, I needed the values to begin the designing of a basic propeller blade for my project.

I have tried searching a lot. It would be really helpful if anyone could help me proceed.


texts: What level of G-force does our body experience when we are traveling in a passenger plane?

texts: I have some understanding on g-force. But never come across how much g-force acts on a passenger who is traveling in a plane, especially when taking off.


texts: Does a flight instructor rating supercede a ground instructor rating?

texts: In the FAA jurisdiction, if an instructor candidate were to become a ground instructor (advanced and instrument) and receive that certificate, then later become a flight instructor (and CFII), would there be any value in retaining the ground instructor certificate? The flight instructor certificates held at that point provide all the same privileges. Is the ground instructor certificate superceded?


texts: What are the differences between PNL and PNR messages?

texts: What are the differences between Passenger Name List (PNL) and Passenger Name Record (PNR) message in CRS systems?


texts: Why do airline toilets delay for a few seconds before flushing?

texts:
I have noticed that when I push the toilet flush button in a regular passenger airliner, it takes several seconds (perhaps 2 or 3) before the toilet actually flushes.

What is the reason for this delay?


texts: How does stall risk in paramotors differ from that of conventional fixed-wing aircraft?

texts:
I happened to be walking past a small outdoor fair today, and saw someone flying a paramotor. The craft took off and started a steep ascending turn losing speed rapidly, seemed almost to come to a stop (relative the ground, but the flags nearby didn't show much wind, either) before the pilot brought it back to more level flight and got some way again.

I'm not a pilot, but I'm roughly aware of the mechanism of stalls and the consequent danger of high angle of attack, low speed maneuvers and I was briefly worried that there was going to be a problem.

In hindsight, the craft clearly has a very low stall speed (not much more than walking speed, I guess) but it did leave me wondering.

Are these craft are more or less at risk of stalling than conventional fixed wing aircraft?


texts: When has a pilot legally accepted an ATC clearance or instruction?

texts: At what point is a pilot considered to have accepted an clearance or instruction? Upon simple acknowledgement (e.g., Roger or Wilco), any readback, correct readback, or something else?


texts: Are there any feasibility studies or research regarding the possibility of using Jet A in tropical countries?

texts:
Based on the ASTM D1655 standard specification for turbine fuels, the only difference between Jet A and Jet A-1 is the freezing point. Max [min?] -40 degrees Celsius (-40° F) for Jet A and max -47 degrees Celsius (-53° F) for Jet A-1.
Also, Jet A is widely available in the US (high latitudes).

From my understanding, if Jet A (with higher freezing point) is suitable in colder regions (e.g., the US), it should also be suitable in warmer regions (e.g., tropical countries), as it is already hard to reach -40 degrees Celsius (let alone -47 degrees Celsius) in tropical regions. Assume that both have the same altitude.

So, my questions are:

Are there any feasibility studies or research regarding usage of Jet A fuel in tropical countries? Please share!

and

Could someone provide information of the cost production differences between Jet A and Jet A-1?

Much appreciated guys!


texts: Why were rotary vane compressors never used in jet engines?

texts:
It seems like a rotary vane compressors have ideal characteristics for a jet engine. They can generate high pressure ratios (up to maybe 10-12) compared to older axial compressors and I think they can have a high flow rate at ~90% energy efficiency. They also seem simpler to construct/cheaper than axial compressors.

I understand that modern axial compressors can generate a higher pressure ratio, but historically why didn't rotary vane compressors have a place over at least centrifugal compressors in earlier jet engines?


texts: I'm a student starting a research project on sustainable aircraft technologies. I've been particularly interested by distributed electric propulsion (DEP), which is currently being tested by NASA with the X-57 Maxwell (I'm thinking the added efficiency of DEP combined with progress in battery technology could eventually make electric flight a more feasible option). My supervisor has also pointed me to ion drives. Are there any other technologies in development that I should be aware of? Information on progress, potential, who is developing the technology, as well as links to scholarly articles are all appreciated.


texts:
Can an S-duct fit a turbofan exhaust instead of the intake? The idea here is to merge 2 exhausts into one at the exact center of the tail. This would be for twin-engine aircraft that have both engines at the tail, like the Boeing 717.

There are of course S-ducts for intakes, like on the Tu-154. I have never seen them for exhausts, however, probably because it's much harder due to the heat.

I know it is engineeringly possible somehow, because I've seen vectored thrust devices with variable geometry, like the iris types and swivel types. For a large commercial jet, it would be easier because the geometry would be static--no moving parts.

But I want to know if it is economically feasible. To take the heat, I think it just needs some super-pure graphite, which does not sound so expensive to me. But I am not an expert.


texts: Why would a flight take a detour on clean weather?

texts:
I was in a flight recently (march 22nd) from SBCF to SBGR (Brazil). It's usually a 1h10m flight, but mine took roughly 20 minutes more. I saw the flight path in FlightAware and there's an unexpected (to me) detour mid-flight:

I looked for other instances of this scheduled flight and there are more extreme cases, such as this one:

In this case, the actual flight distance was 833km whereas the straight-line distance is measly 496km.

Obviously it would be difficult to pinpoint the exact reason why this happened, but what factors could lead to taking such a different than expected route?


texts: Are sequenced waypoints still displayed on the Navigation Display / FMS legs page?

texts:
This question relates to the Flight Management System of a large airliner, e.g. Boeing 787:

During a flight, when the aircraft passes a waypoint, is this just passed waypoint (and the previous ones) still shown on the legs / FPLN page of the Flight Management System? Asked differently, can I scroll through all the past waypoints or are they automatically deleted once I have passed them?

Does the same apply to the Navigation Display (if I'd zoom out enough), would I still see all already sequenced waypoints and the past route, or do I only get to see the upcoming route and waypoints?

If they are not visible any more, why so?


texts: In an aircraft with tab-flown control surfaces, how can a jammed surface be detected during preflight examinations or flight control checks?

texts:
Some aircraft use control surfaces that are driven indirectly through a flying tab system -- this is used to aerodynamically boost control forces, and works well enough in the normal case.  However, it is possible for such a system to mechanically fail in a way such that the flight control and the tab are both capable of free movement throughout the control range, but the control surface does not respond to the tab's movement correctly, causing a reduction or loss of control authority.

How can a pilot catch this type of failure in a preflight or during a flight control check? "Full and free" clearly isn't enough to catch such a failure, since the tab will move freely throughout the entire control range even if the actual surface is frozen in place.  Is it the case that the only way to catch this sort of failure is to disengage the gust locks and then try to move the control surfaces by hand through their full movement range?  Should the control surface position be fed back to cockpit instruments in these aircraft, or is that already a requirement/feature on such types?  Is it common practice or required in a "full and free" check to verify surface followup on such cockpit instruments when they are fitted?


texts: How do airport authorities deal with with birds? Which procedures have acutually been used in order to minimize or even avoid birds on airside and landside? Is there any procedure that crew can perform in order to minimize the danger caused by birds?


texts: How dangerous are Polar Routes, if an aircraft must land on water or wild land?

texts:
Should an emergency landing be necessary for a commercial aircraft on a Polar Route on water or in the unoccupied, secluded Arctic outback (e.g. Siberia, Far Northern Canada).

What is the time interval for aid to arrive (I write 'interval' because I know that this question depends on the location)?
How likely would the passengers survive in the freezing cold (for brevity, I call this 'frigidity') in their cabin clothes? Assume that they are not equipped with clothes or gear for frigidity.


texts: Did any VTOL aircraft implement an airfoil with engine-blown exhaust?


texts: Can a 737 be on final at 160 knots, and also touchdown at 160 knots?

texts: Would the 737, going 160 knots, float a bit more before touching down?


texts: Would it be frowned upon that with a uncommanded nose up, the pilots just do a full loop?

texts: So what I’m asking is that if a uncommanded nose pitch up happened and was so bad that it reached a pitch angle of 50 degrees, the pilots were unable to stop the pitch up by applying the control column forward, would it be justified if the pilots just applied more back pressure, ultimately doing a full loop?


texts: How did the two F35 planes get from Fort Worth to Williamtown?

texts:
I am curious how the the F35 that recently arrived in Williamtown Australia arrived there.
Were they transported at any point, or were they flown the entire way?
How many stops did they make?
Did Australian pilots land them in Australia? If so did Australian pilots take off in them from Fort Worth?


texts: How is crew resource management trained?

texts:
Pilots are taught that pilot monitoring should speak up if something seems wrong, and take over the controls if the pilot flying does not respond adequately, even if the pilot flying is a senior captain. However, do they actually train such situations?

For example recently a final report for accident of US-Bangla Airlines flight 211 was published. The accident involved a badly disoriented captain trying to salvage a really botched approach, and while the rookie copilot did try to be helpful, neither she nor the tower controller was assertive enough to explicitly call go-around.

I would think that some practical training would help in this kind of simulation. I am thinking of a simulator session that would start with the instructor being pilot flying, doing something wrong and acting confused and expecting the trainee to intervene appropriately. The trainee would know the instructor expects them to intervene, and thus wouldn't have qualms about it, but the trained reaction would still help overcome interpersonal issues in real flight.


texts: Why does a plane shake while passing through clouds?

texts:
Why does a plane shake while passing through the clouds?

During my last journey all the other passengers started shouting when the plane was passing through clouds. It was the third time I was travelling by plane and was a fearful experience. Can someone explain what the reason is for the shaking? So the next time I can travel free of fear.


texts: You are a commercial airline pilot flying between two large US airports. Who do you talk to along the way on the radio and for what purpose?

texts:
I am a non-pilot who has been listening to various ATC feeds and trying to understand what is going on. I've been able to find surprisingly little information on the various layers that make up the air traffic management system but from listening to SFO atc feeds online, I've come up with the following outline of what radio contacts on a domestic US flight would look like:

ramp control - I know it exists, but have little idea what they do. I would think they manage push back requests, but I hear that on ground frequencies so that cant be strictly correct.
ground control - request pushback, get taxi instructions and hand off to tower when near runway
tower - get takeoff clearance. hand off to departure during climb out
departure - request bearing and altitude, receive vector out of departure airspace in proper direction
center controller (various) - not sure what the relationship is here (pilot requests bearing, altitude, or is it all automated and known to controller) controller maintains separation mins.
approach - there seem to be two stages here? One controller asks for intentions, gives a waypoint and altimeter data. A hand-off is then done to another approach controller who vectors traffic into the pattern for landing, calls base, etc.
tower (arrival) - everything should be all spaced out, so controller just works on fitting departures in. Announce your intention and be granted clearance with initial taxi instructions.
ground (arrival) - get further taxi instructions to gate.

So how accurate is my picture of whats going on? I'd be interested to know exactly how the whole process works from the pilot's perspective. Some specific questions about the process:

How automated are aspects? Do controllers ever have information from filed flight plans or is all info passed over radio?
Whats the deal with the two approach controllers? (BSR2/MOD2 versus landing)


texts: Where is an EASA PPL valid outside of Europe?

texts:
I am considering obtaining an EASA PPL in the U.K. I would like to know where exactly in the world the license is recognized with little to no additional paperwork/training outside of Europe. Specifically I would like to know what is needed to fly in the Caribbean, Colombia or Chile with this license.

I am a complete aviation beginner so apologies if this is a silly question.


texts: Do jetliners carry radar that can detect other aircraft?

texts: If not, why not? For example, if a civilian jetliner is flying at night over the Ocean, or a remote area with no airports/ground radar stations, and another airplane is also heading towards it on a collision course, shouldn't the pilot be able to spot the oncoming airplane on its airborne radar to perform evasive maneuvers? My understanding is that military aircraft have such airborne radar, which I believe is called ACAS, so they need not depend on ATC/ground stations for collision avoidance.


texts: What is the impact of thermal Anti-Ice on descent performance?

texts:
I am just another one of the passionate flight simmers trying to understand more about Anti-ice system mechanics. I am talking about the Boeing 737-800 here if it makes a difference.

What bothers me is: Why is turning on TAI systems having negative impact on descent performance? Given a constant speed that we want to keep a shallower descents can be experienced.

Let's imagine a descent with thrust levers in IDLE position. From my research about aircraft systems and jet engines I would assume that turning on TAI would (in that order):

get more bleed air -> less air to burn -> turbine turning slower -> decreased N1

But from what I can experience and read on the web N1 is actually increased instead. I can guess the aircraft it trying to compensate something - but what is it if we're in idle descent? Also, I am assuming the decreased vertical speed comes from somehow increased thrust, which I would also suspect to be lower (or at least kept on the same level as before TAI) not higher than originally.

I understand this is a complex system and each part has impact on each other but maybe you can point me in the right direction ;)


texts: Why are there age limits to becoming a pilot in the armed forces?

texts:
This may be more related to the armed forces as opposed to aviation but I have to ask:  Does anyone know why most armed forces put an age limit on being a pilot in the service?  Most set the cutoff at 26-30 years of age depending on the service in question.

One hypothesis I always had on this subject is the large amount of money that it costs to train a military pilot (2-3 million USD from basic flight training through advanced training and assignment to a fleet squadron) combined with a long service commitment (7-10 years once training is completed) where the individual must maintain good health and good eyesight to meet the medical standards required to fly and the mid 30s- mid 40s is when a lot of medical problems begin to crop up and can interfere with this.  As such the service limits the age so they enter this range at the tail end of their military flying careers.  But that's just a guess.

Another is that the competitive nature of military flight slots allow the services to be choose and only select young candidates to weed out the applicant pool.

In the civilian world there is an age limit of 65 for being a commercial airline pilot as the only real restriction to flying commercially but people frequently enter into that career in their 30s and 40s.  It does seem abnormal, if you meet the other medical requirements for the armed forces to limit a career as a pilot considering that other military occupations allow people to enter well into their late 30s or early 40s.  Does anyone have any information on this limit and the reasons why?


texts: What is the CPIOM in the IMA architecture. Which is the difference between the CPIOM in the A380 and the CPIOM in the B777?


texts: Can airlines recover costs if they dump fuel for a medical emergency?

texts: As per the title, can airlines recover costs if they dump fuel due to a medical emergency on board shortly after takeoff?


texts: Why do many commercial aircraft have a red circle on the wing?

texts:
Many commercial aircraft operated by japanese airlines like JAL and ANA have a red circle on the wing. Look:

Source: Airliners.net
And on this ANA plane, also:

Source: Airliners.net
Why do they have that red circle there?


texts: How are NOTAMs distributed and received?

texts: Can you only receive NOTAMs via teleprinter? If so, how do you receive them in flight in a plane without a printer? Also, how is a NOTAM generated? I'm trying to read an Oxford Air Law book and it is so hard to understand.


texts: Would it help airlines, if they knew passenger weight before hand?

texts:
Its known that pilots and technicians calculate the weight of the plane once everything is loaded, then they can decide on how much fuelling etc. needs to be done.

Would it help airlines, if they knew the weight of all the passengers before hand, say at the time of ticket booking. Having that information, would it help them in optimizing the amount of cargo/fuel etc for the flight?


texts:
Do ultralight engines need a thrust bearing?

Most gas engine applications only have a radial load ( perpendicular to the shaft).

Aircraft, not only have a radial load but also an axial prop thrust load pushing/pulling the shaft out/into the engine depending on whether the prop is a tractor or pusher prop, which usually requires a different kind of bearing able to take a thrust load.

So...do ultralights need a thrust bearing?

If so...

I assume the bearing of the output shaft of a reduction drive would have to be a thrust bearing.

However, we see 1/2 VW engines being used in direct drive applications, and I don't think they change the final bearing into a thrust bearing.

The reason I'm asking is, that I'm thinking of using a $400 15hp 4 stroke industrial engine for an ultralight application, just as we see in Rutan's quickie(?), ultralights using the vanguard brigs and stratton engines, and M Columbine's new design ( designer of the Cri Cri). Yes they are heavy, but they are cheap, 4 stroke, a TBO of 2,000 hrs, and are rated for continuous duty.

I plan to run at 75% power, which is about 2,500 rpm so I really don't need a reduction drive.

If I need a thrust bearing,  I could have a reduction drive with something with a 1.1 reduction. I could also have just a support thrust bearing bolted directly to the engine.

If I don't need a thrust bearing, then I would be off to the races.

I don't think the Lazair had a thrust bearing or a reduction drive when they used the non rotax engines.

So... do GA airplane engines need a thrust bearing, in the 15 to 30 hp range?


texts: How to avoid getting trapped on top VFR?

texts:
This question addresses whether it is legal to fly VFR over-the-top.

One of the comments mentioned the difference between safety and legality, i.e. doing so may not be safe even if it is legal (in some places, for some pilots). The most obvious concern would be whether a VFR-only pilot could find a hole in the clouds to descend for landing. (There may be others.)

How exactly does one mitigate this risk to an acceptable level? Or is it generally accepted that, even though regulations don't say so, that it should only be done by pilots with an instrument rating?


texts:
Let imagine that we put wind indicator on rotating merry-go-around.
Will wind indicator stay prepedicular to the radius of circle,showing tangetinal  airflow velocity?
(Wind indicator has equal mass and distance from pivot point so moment about pivot point is zero.It desing like this to stop centrifugal force to move one end out of turn..)
I think wind indicator will be prependicular to radius of rotation..
(I ask this because of glider yaw string...)


texts: How universal are air traffic control systems, training and practices?

texts:
A commercial pilot, especially in the airline industry, is in a role that is essentially the same as that of a pilot who is employed and was trained in just about any other part of the world.

Does this also hold for air traffic controllers? How similar will the training and practices and the systems that they use in their work be?

For example:

Are qualifications obtained in one country or region recognised in others?
How much additional training would be required for a controller who has trained and worked in one European Union country, in order to take a similar role in another? Or in a non-EU state?
Would the hardware and software used by a controller in one country be familiar to a controller from another?


texts: Are the single-engine Piper Malibus required to have a black box?

texts: Is the single engine Piper Malibu required to have a black box?


texts:
Tyre failures on aircraft during takeoff are fairly common, and are usually (though not always) caused by flat or underinflated tyres (via the overdeflection and overheating experienced by tyres with abnormally low internal pressures).  If an aircraft tyre fails during takeoff, this is dangerous in several different ways:

Flying tyre fragments can damage other parts of the aircraft, as well as, potentially, other nearby aircraft or ground personnel.
Wheels with blown tyres are useless for braking, thus greatly increasing the chance of a runway overrun should it become necessary to reject the takeoff.
A tyre failure(s) can greatly degrade directional control, especially on smaller aircraft that only have a few wheels to begin with.
A failed tyre dragging on the runway can easily heat up enough to ignite and burn, dooming the aircraft if the crew then retract the landing gear without knowing that said landing gear is on fire.

Run-flat tyres are designed to remain useable even in the event of a total loss of internal pressure (generally by incorporating an internal weight-bearing skeleton inside the tyre’s air chamber); given the potentially catastrophic consequences of a flat tyre failing during takeoff, why don’t aircraft use run-flat tyres?


texts: Can audible warnings be heard from the cabin?

texts:
When I fly in the front row on an all-economy A320, I can very clearly hear the autopilot disconnect sound shortly before landing.

Can passengers in the cabin also hear other warnings like EGPWS (Terrain!), TCAS (Descend, descend!) or others?


texts: Why aren't "radioactive items" allowed on flights?

texts:
I've done physics, I completely understand what nuclear radiation is and why it is harmful. What I can't seem to figure out are the rules surrounding radioactive emitters/items on flights. Surely it's not just any radioactive items, because everything is at least slightly radioactive.

You get about 12 times the sieverts per hour at 35,000 feet than you generally do at sea level (3 μSv/hr in the air, 0.25 μSv/hr at sea level). And even then it's essentially harmless.

What if I had a strong radiation source, but encased in thick lead shielding? Or a strong emitter of only alpha particles? Do they measure it in Sieverts per hour, or Becquerels? Or Gray? All of it makes a difference.

Something that measures high in Gray or Becquerels could be damn near close to undetectable in Sieverts per hour - arguably the only relevant unit in terms of radiation effects on human health.

There's not enough info available to nerds like me, so insight would be greatly appreciated.


texts: Why were the space shuttle’s flight controls only certified for low airspeeds?

texts:
Somewhat ironically for a vehicle designed to reach orbital speed, the space shuttle’s flight control system was only certified for airspeeds up to 333 KIAS, and exceeding 470 KIAS (the maximum allowable in dire emergency) would have led to an immediate loss of control.  This constraint was the reason for at least two, and possibly three, of the low-survivability zones in the event of a triple engine failure (go to page 14 of the linked PDF and look at the number of times it says “excessive EAS during pullout”1).

In contrast, essentially all modern jets have flight controls certified to well over 500 KIAS, and capable of safely controlling the aircraft at airspeeds considerably higher still.

Given the lethal effects of an overspeed-induced loss of control during an emergency situation, why were the shuttle’s flight controls certified with such a ridiculously low maximum airspeed?

1: Technically, it uses KEAS (knots equivalent airspeed) instead of KIAS (knots indicated airspeed), but, assuming that your airspeed indicator is properly calibrated and the pitot-static system on your aircraft is working properly, KEAS=KIAS.


texts: What is the aircraft in the 'Be Altitude' album cover?

texts:
In 1972, the Staple Singers released the "Be Altitude" album, which has them posing in a jet engine's intake.

My question is what aircraft does that engine belong to? And why would someone let them use it for a photo shoot?


texts: Why would an airplane fly in parallel, straight, closely spaced lines?

texts:
I am not an expert with this kind of stuff and I seek an expert explanation.
Is this pattern related to a ground scan?


texts: What are the US regulations governing experimental aircraft?

texts:
There are more experimental class aircraft in the USA than any other.  That being said, what type of requirements does an experimental aircraft have to meet?

Also, are there ways around certain regulations?  For example, the guy in the picture below was battling with the FAA so they would let him fly his jet pack in the USA over the grand canyon, which they originally said no to, but they eventually let him - is this because he is "famous" and therefore has less rules he needs to follow?


texts: Could an airliner (in theory) fly truly "backwards"?

texts:
Very much a hypothetical question:

At Trondheim a few days ago we had quite a long, fast (to my experience) pushback: now obviously we didn't hit anything close to Vr, but it started me wondering if an airliner could theoretically fly in reverse.

Say for the sake of argument that we flipped the engines round without introducing any other problems, and stuck a window in the tail with a seat, controls and flight instruments in front of it... then put the plane on a runway and tried to take off. Would the airfoil allow the aircraft to take off? Would it be in any way controllable? Obviously I'm not expecting the plane to be flyable by a pilot, merely curious if it's theoretically possible aerodynamically (perhaps computer controlled).


texts: Can a kite take advantage of crosswinds to gain speed?

texts: In a form off a kite can wind be redirected like a sail boat in any direction? Can cross winds around a jet stream be helpful in speed in such a design?


texts: Have B-25's and B-26's been converted for private business use?

texts:
In the movie Cash McCall, the main character, McCall, owns an aircraft that looks remarkably similar to a B-25 or B-26, but is painted yellow and has no turrets.

Have these aircraft been converted for private business use or were there business aircraft based on the design of WWII bombers?


texts: Where should I sit to experience the least turbulence?

texts: Following on from Why are first/business class seats at the front?, in which part of a large commercial jet cabin would I experience the least turbulence? On the one hand I would have said that sitting near the wings (near the centre of gravity) is best, but subjectively it feels like the ride near the front is "smoother". Can anyone give me some more solid information? I imagine it also depends on the aircraft type?


texts: Why do (almost) all military transports have high wings and civilian transports low wings?

texts:
I've observed that almost all military transports have high wings (with a pronounced anhedral) and almost all civilian airliners have low wings (with a pronounced dihedral) — why is this?

The high-wing configuration gives the military the advantage of easier loading and unloading (especially when operating from irregular airfields), and lower overall height for the aircraft, but then why do civilian aeroplanes hate this design?

Except in the erstwhile USSR, I haven't really seen high-winged military aircraft being used as civilian airliners (Boeing 737 size and beyond), though I can't think of any reasons why not.


texts: How can I convert a SACAA (South Africa) AME license into a Belgium (EASA) licence?

texts: I have a SACAA (South Africa) AME license and would like to convert it into a Belgium EASA licence part 66. What are the steps to follow?


texts: Why is it advised to turn the aileron away from quartering tail-wind during taxiing?

texts:
This question is related to a single engined cessna tricycle gear airplane. e.g, C152/C172.

The theory states that if the quartering tail-wind is from the right, the aileron needs to be all the way to the left with elevator held down. Can someone explain the physics behind this?

I understand this when you have a quartering headwind from the right. In this case you set the aileron on the right thereby reducing the lift on the right wing and increasing the lift on the left wing. This helps keep the right wing pressed down. But somehow the picture is not clear for the quartering tailwind.

Another way to look at this is to look at the wind as a vector. For a quartering headwind, the wind can be thought of as a wind component from the front and a wind component from the right. The wind component from the front is not a problem and the wind component from the right is balanced by the ailerons as discussed earlier.

Taking a similar approach for the taiwind from the right, the wind component from behind is taken care of by the elevator. That leaves only the wind component from the right. So the same aileron action should be required. But the books state the complete opposite.


texts: In what circumstances do passengers or flight attendants have to take their shoes off?

texts:
Three shoes-related facts:

A passenger and a flight attendant in this Аэрофлот/Aeroflot aircraft have their shoes off or are ready to take them off:

It's suggested that shoes are taken off for evacuation.

In United 93 film, an attendant can be seen seated in the jump seat without her shoes during the climb phase.

I'm wondering whether there are safety policies applied here. What are the regulations, policies or best practices about:

Crew taking off shoes in critical flight phases?
Passengers asked to take their shoes off?

In case regulations strongly vary by country, US/Russia/EU can be taken as examples.


texts: What is the correct use of the verb "to leave," for exiting the runway?

texts:
What's the correct way to say, according to the phraseology;

I will leave the runway; I will vacate the runway; or I will exit the runway?


texts: Why would a diverted airline flight return to its departure airport rather than land at the nearest one?

texts:
The Vueling flight VY2119 Barcelona-Malaga yesterday (see flightradar) got diverted 50 min into the flight. The nearest airport then was Valencia, but they chose to turn around and fly all the way back to the origin airport, even flying by another airport, Tarragona. Indeed, the whole flight takes regularly 1h40, they could well have flown all the way to Malaga and would  have spent the same amount of time in the air.

Why have they chosen to fly back? Wouldn't an emergency require landing in the nearest airport?


texts: What are the correct names of the parking spaces for turn-around?

texts:
A plane can be parked at the terminal and the passengers can board through a jet bridge. Also it can be parked somewhere else, far away from the terminal and the passengers would need to take the bus to get there.

What is the correct name of those parking spaces?


texts: What's the reasoning for safety wire on aircraft, and the reasoning behind the way it's routed?

texts:
I'm assuming saftey wire is used near propeller assemblies where a lot of vibration occurs, or where the different speeds and altitudes aircraft are at could cause expansion or contraction based on temperature.  Is that correct?

I'm also wondering the reasoning for routing them in this manner. Is it done this way to counter vibration so both bolts don't loosen? If one is going counter-clockwise due to vibration, I'm assuming it'd be tightening the other bolt or vice versa?


texts: Why are jet fuel prices very similar in North America and Europe, yet automotive fuel prices are very different?

texts:
Why is the pricing difference of jet fuel between North America and Europe extremely small, unlike automotive gasoline?

As of June 22, 2018, the prices in USD per barrel of it between the two continents are 88.0 and 87.8 and slightly older data confirm the existence of a small difference (I have not encountered a comprehensive dataset). Yet automotive gasoline in Europe usually costs 2-3 times the price it does in the US, comparing each US region to the very roughly analogous European one (based on income, geography, etc.). Why is this?


texts: what would couse uneven fuel levels in a cessna 207?

texts: I have problems whit the level in each tank after a flight of 3 hours. I usually use the right tank the first hour and then I change to the opposite, but when I check the level after that the rigt tank seems as if have not burned the fuel.


texts: Why are Category II ILS approaches prohibited in an E-Jet with inoperative pitch trim?

texts:
Part of the Pitch Trim Runaway checklist for the E-Jet family states that Category II ILS approaches are prohibited if neither pitch trim channel is available:

If both pitch trim channels are failed:
Cat II Approaches are prohibited.
[E170/175 QRH, page 8-32, quoted in page 2 of NTSB ASR-20-01]

Why are ILS-II approaches (but not ILS-I or ILS-III approaches, or any non-ILS approaches) prohibited in an E-Jet with inoperative pitch trim, even if adequate elevator control is available to do so safely?


texts: Who should handle an emergency when there's both a certificated pilot and a CFI on board?

texts:
While practicing for my commercial certificate in a T-tail Piper Arrow IV, I put the gear down on downwind, and one green light didn't come on.

In the right seat was a CFII/Multi, who had over 1,000 hours but less than 10 hours in Pipers, whereas I had about 300 hours, and over 200 in Pipers, having done my PPL in stiff-legged Cherokees.

As a certificated pilot, I was PIC, but we talked about how to handle the emergency, and the CFI and I decided that since I had so much more experience in Pipers, I would handle the emergency tasks, while he handled the radios and looked for traffic.

We did the proverbial tower fly by (although they wouldn't say anything except the gear "appeared to be down"), and they cleared me to land on any runway. Our landing was uneventful, and it turned out to be an electrical MX issue.

When we landed, however, the flight school nearly fired the CFI for not having taken control of the aircraft during the emergency.

Did we make the right decision for me to handle the emergency? Or should I have let the CFI/CFII/MEI with over 1,000 take over as PIC and handle the airplane?


texts: Why is mid-air refueling worth it? (or is it at all?)

texts:
Surely, mid-air refueling is a cool thing, but is it worth it?

It's obvious that the military, for one, has some requirements to keep aircraft airborne so that they can keep patrolling, for example.

However, that is due to the need to keep the aircraft airborne and is not necessarily because the method is cost-effective.
Flying another aircraft carrying lots of fuel just doesn't seem very money/environment-friendly – you waste more fuel needed to power the fuel-carrying aircraft in addition to the fuel you would already need.

Is mid-air refueling cost-effective under any circumstances? Or is it just an emergency practice?


texts: Can I make an ILS-Approach when I am VFR?

texts:
When doing a VFR-Flight, the runway to land on is usually approached visually. However, I would like to do some ILS-Training but in VFR.

Is that possible?
If yes: What's the procedure? Do I have to include something in my flightplan? Do I have to notify the Approach/Tower-Controller? In VFR the control zone is approached via pre-defined entry points like Echo or Sierra. But then I can't do an ILS-Approach because there is usually no entry point on runway track.


texts: Do thermals stop rising when clouds are formed?

texts:
Glider pilots know that one indication of thermal lift is the formation of cumulus-type clouds.

My question is: Does the rising air (that lifted the moisture to form the the cloud) stop rising after the water vapor condenses?  Is there rising air above a cumulus cloud, or does the condensation somehow stop the upward movement of the air?


texts: How to calculate aerodrome elevation given QNH and QFE

texts:
Would someone be able to explain how to get the answer to the following question?

13) The QFE for the aerodrome is currently 985 hectopascals. The QNH you have been given is 1031 hectopascals. Approximately what would you expect the aerodrome elevation to be?
A 1380 ft
B 690 ft
C 2663 ft
D 875 ft

Correct answer is A.

Thanks


texts: Does the 737 MAX's engine nacelle camber affect the pitching moment?

texts: A side view of the B737 MAX's engine nacelle shows a positive camber at the top. As nose camber of any lifting shape (wing or nacelle) generally allows more lift at higher AoA, do you think this feature plays a role in the nacelle destabilizing pitch up moment?


texts: Are there any training maneuvers that are only allowed when flying with a flight instructor?

texts:
My understanding of dual instruction training with a flight instructor and a student in a cockpit is, that certain maneuvers, that else would be not permitted, are okay, e.g. simulated engine failure and forced landing on some field (until doing a go-around from 100ft AGL). Is that correct?

For a trained and licensed pilot who currently isn't in training for a new license and just wants to train those things for him-/herself to stay trained, is there a way to do those maneuvers as well without a flight instructor in the cockpit? If that's not possible, does it change, if the single pilot is a flight instructor themselves? Or do they also need to have another flight instructor in the cockpit to train that?


texts: Why can't armrests be raised on window and aisle seats?

texts:
I noticed that armrests on all the flight's I've taken recently can't be lifted on aisle and window seats (the edges of a row).

Last time I flew, I got lucky: I was alone on my row and as such I was able to lay down to sleep. However, it was hard to make myself comfortable as that armrest was pressing on my spine when I tried laying down with my back to the window.

Also, it would be much easier to get out of my aisle seat if I could lift the armrest. I'm a pretty tall guy, so I always feel like a contortionist trying to get out of my seat.

What's the problem with letting people raise the armrest on window and aisle seats?

I'm guessing it's some sort of safety issue, because the mechanism seems to be the exact same one as the other seats, just with an extra locking mechanism added.


texts: Are some airline's flights more noisy than others for security reasons?

texts:
LHR has published a table ranking the noise and pollution levels of the different airlines using the airport. At the bottom of the list is Israel's El Al.

El Al, in their official statement, say that this is because they are using older 747-400 planes which are due to be replaced by Dreamliners. However, somebody was trying to explain to me that the extra noise was due to particular flight methods and manoeuvres which they implement for purposes of security and defence, being a high risk airline.

I'm not sure what they could do differently, especially as they should be under UK ATC control.

Does anyone have any concrete knowledge (obviously not classified info) or an educated guess whether this guy's theory is rational or not.


texts: Why require a minimum of 1500 hours to become an airline pilot?

texts:
In the United States, under parts 61 standards for pilot certifications, for a person to apply for an airline transport pilot certificate one of the aeronautical experience minimums is a minimum of 1500 hours total flight time. Most ICAO compliant countries require similar numbers.  My first question on this would be why so many? It’s true that you want airline pilots to be experienced and no doubt I would not expect an airline to make someone a captain of a large, turbine airplane without a minimum of say 2000 hours with a lot of that being hard instrument and weather time but why require a first officer to need a minimum of 1500 hours for an ATP?
I’m aware prior to 2014 that the FAA allowed part 121 first officers to fly with only a commercial pilot’s license for the right seat and the 1500 hour rule only came about after the Colgan air crash in 2009.  People argue that this is what is resulted in only one commercial airline fatality over the past 10 years.  Still I wonder why an arbitrary number 1500 was chosen for an airline transport pilot certificate. Now I am also aware that this is not always the case. For instance graduates of approved part 141 schools can get a ATP with only 1200 hours TT with a aviation related associates degree, 1000 hours TT with an aviation related bachelor’s degree and military pilots with 750 hours TT can apply for an ATP directly.  My only thoughts would be, if part 61 training is so terrible that it requires a person to put in 1500 hours in a Cessna prior to applying for an ATP, what makes an aviation bachelors program superior or military flight training as compared to it, and why not simply train pilots under parts 61 to the same standards as the military does?
EDIT
Some other thoughts on this topic:  Well the military does allow people to operate large turbine powered aircraft with FAR less that 1500 TT, they’re in a position where they simply have no other alternative.  You can’t give a fresh 2nd Lieutenant 1500 in T-6 or T-38 prior to dispatching him/her to an F-16 squadron somewhere as its simply not affordable with trainer aircraft costing several thousand an hour to operate and training budgets already tight.  So they’re sent off to a active unit with 200 to 300 hours total time.  The downside is that, even in peacetime, military aviation units suffer horrendously hi accident rates as opposed to their Part 121 counterparts.  As I understand it, the USAF alone had 39 class 1 mishaps in 2018.  It’s an unfortunate fact that, as much as primary flight training could teach you, it’s only a license to practice your craft; flying is an artform and takes a lifetime to master and there are a lot of dangers out there.  That being said, mass hours alone are really not good experience.  It requires APPLICABLE experience to matter.  An aviator train did a small part 61 flight school in central Iowa and logs 1500 hours flying Cessnas locally as a CFI is nowhere near ready for the rigors and stress of an airline pilot, but a pilot with 500-600 hours TT with complex, instrument, and multi-engine turbine time in high density airspace around major cities is far more likely to success here.
It bothers me that these kinds of regulations are written this way, without any thought to the practicality of it. It’s also strange that way, since, most of the FARs are very practical and based on well researched information as well as accidents in the past.  It also bothers me that it causes new pilots to bear an extreme burden to build those kinds of flight hours for a career, which may or may not be beneficial to them. I’m just curious what the FAA’s thought process was in recommending the scheme


texts: Is it possible to power an ultralight airplane with a single-cylinder weed-whacker engine?

texts:
Plane:
Weighs 200 pounds.
16 FT wingspan,
36in. by 5 in. airfoil

Engine: 3,000 RPM, 2 HP

Propeller: 4ft with 4 blades and weighs 4 lbs.

Is there perhaps an equation that could determine this?


texts: Is there a rule of thumb for spacing between jet engines?

texts:
While viewing this week's press release for the taxi test of the Stratolaunch I noticed how closely the engines seemed to be spaced. It would seem the ideal position would be near the fuselage to minimize asymmetric thrust.

The B-52 places engines directly next to each other, while the 747 spaces them far apart. Is there a rule of thumb for ideal engine spacing?

[This question deliberately excludes propeller aircraft due to the many mechanical and aerodynamic differences.]

The Stratolaunch engines are approximately one engine diameter apart and very close to the fuselage.

The 747 has much larger spacing between engines (~3 engine diameters) and further from the fuselage.

Engine spacing on the Antonov 225 compared to the 747 is much closer to fuselage but about the same spacing.


texts: In the traffic pattern, what is the appropriate distance from the runway for the downwind leg?

texts: Specifically for a piston general aviation aircraft, is there a recommended distance from the runway to fly the downwind leg? Does this change based on the speed of the aircraft?


texts: What is the most efficient way to get your instrument rating?

texts: For someone that has recently completed their private pilot SEL, what would be the suggested next steps/process to getting instrument rated as efficiently as possible (both time and money)?


texts: How does the aneroid wafer expands? (ASI)

texts:
So, how does it expand? (aneroid wafer - intend to the airspeed indicator) I have two “theories” (from what I’ve learned) which are :

The ram air entering through the pitot tube physically hitting, pushing the aneroid wafer forcing it to expand - giving us the actual indication in the cockpit. faster airspeed—> more air hitting, pushing  the aneroid wafer at higher velocity —> greater  expansion?
The ram air rapidly filling the aneroid wafer making the air more dense —> more pressure, therefore forcing it to expand due the pressure differential between the aneroid wafer and the sealed case, which contain the outside atmosphere pressure. Faster airspeed —> more air —> increasing pressure inside the aneroid wafer —> larger pressure differential—> greater expansion?

Which one is true ? or both maybe ?


texts: What is the weight budget of a fully loaded A380?

texts:
Wikipedia provides some numbers (typical empty weight, MTOW, max fuel capacity, etc.), but I can't seem to find more detailed figures. For a purpose of this question, let's assume a fully loaded A380 in typical 3-class configuration (~530 passengers) and fuel for a long haul flight (>10h).

So, what is the typical weight of the passengers + luggages? Is any additional cargo typically carried? If so how much? What about the weight of crew and catering? And fuel weight? (Fuel weight will depend on actual flight duration, so the answer should mention the corresponding flight duration.)


texts: How do the Airbus Beluga's wing/control surfaces deal with its high center of gravity?

texts:
This is the Beluga:

It's used for carrying pieces of a fuselage (of much larger planes) from one place to another so they can be fitted together to make a plane.

As I recall, it's based on an Airbus A300, and then they added on the huge bulging fuselage piece so it could carry more stuff and moved the cockpit down a bit to make way for the huge door at the front of the bulge.

My question is what did they do in terms of wing/control surface design to keep the plane from becoming unstable.  Clearly when this plane is fully loaded the CG is much much higher than a regular A300.  Which seems like it would make it more likely to want to tip over in some fashion. What did they do to counter-act this?


texts: Can plane climb without increase pitch angle?

texts:
As I know plane climb "with nose up", but can plane climb without change pitch angle?
Can I force plane to climb like this:
If I  fly in straight level flight at 100km/h and now increase just speed at 180km/h without any change at tail/wing.
1.Will plane climb with no change in pitch angle?
2.Or maybe will plane pitch up by itself?


texts: Is there an aircraft that can go supersonic at sea level without using afterburner? Quick look through the "supercruise" capable aircraft might be helpful in narrowing down the possibilities, though I haven't seen anything specifying the top speed without afterburner and at sea level simultaneously. If I remember correctly, the F-15 is not capable of doing that; this gives you an idea, however, it's not the fastest jet in the world, so I'm still looking for the answer.


texts: Which airfoil to use for high subsonic flight?

texts:
I am desigining an aircraft, which shall fly up to Mach=0.9 in cruise flight in an altitude of 10 km.
So when I think of which airfoil to choose, I have to consider aspects like

max. lift coefficient required
max. necessary/allowed angle of attack
...

But what comes first in my mind is, that I have to prevent shock waves forming on my airfoil, because drag will dramatically increase. So actually, this is my first demand for the airfoil.
NACA 64006 is a supercritical airfoil. In order to prevent Mach=1 on the airfoil, I would need a swept wing with an angle of more than 50° to reach Ma_crit=0.88 .
I am wondering now, if this is normal that I need such a high sweep angle? Or did I choose the wrong airfoil. So normal commerical aircraft have angles between 30 to max. 40° ?
So the only way to have less sweep angle: find another airfoil (I think 64006 is already one of the best free available airfoils)  or I accept higher values of drag coefficient ?
How do airliners tackle the problem? I think I read that they allow mach numbers a little bit higher until the drag divergence velocity?


texts: How should these translated takeoff and climb settings be interpreted?

texts:
I am having difficulties understanding this transcript. It is originally not in English, so I was wondering if anyone could help me to make sense of this and also help me  with the correct wording in English. The training cap originally says

  after the ground roll (four engine turboprop) : 12 degrees nose-up; 1500 feet; decrease power/ reduce engine thrust power (?); climb speed (?); flaps up.

I know that usually at around 1000 feet agl the pitch is lowered so I imagine that was an order to lower the pitch to 12 degrees nose up or a confirmation of that. Does that make sense? Would one lower it after the final phase of the initial climb?

Then there is the mention to decrease power. Would power be reduced at height?

I've found a document from a flight school that says power is reduced to remain in the traffic pattern, but that was after 2500 feet. And I found a skybraero page that says that after 1500 ft aal one would "reduce thrust to climb power". Would reducing thrust make more sense than reducing power? I thought they both meant the same thing. How are they different?

At the end, when (I think) he says climb speed. I found nothing about climb speed specifically... since this is said after the final phase of the initial climb out (that goes up to 1500 ft), when climb to cruise phase starts, would it make more sense if that read climb to cruise speed/ cruise climb speed (Vcc)?


texts: How can an inexperienced pilot tell if the weather is good enough for flying?

texts:
When I look at weather in the morning of my flight, it looks good. However, the actual determination can be made later during the day closer to my flight time.

Being a student pilot, how can I efficiently make a decision about flight based on weather? Is there a particular way which can help me?

My flight is at 2PM. When I check weather at 8:30AM using this website I get the METAR for my closest airport as shown in these pictures:

There are a few details available. I want to know how can I make an informed decision at 8:30AM about my flight, instead of waiting until around noon time?


texts: How can I calculate the cabin pressure following a decompression?

texts:
What are the calculations to determine the level of cabin pressure at a given altitude once the cabin is punctured?

I was unable to determine the window size and the flow rate of the compression system on the recent Southwest accident aircraft, for example.


texts: Why does the spool speed increase with altitude for a turbofan engine (single spool & double spool)?

texts:
So, I want to see the effect of altitude on the compressor characteristic of a single spool & double spool turbofan engine at constant flight speed and TIT (turbine inlet temp).

I am aware that as the altitude increases, density decreases, mass flow decreases which ultimately reduces thrust.

As well as, with an increase in altitude the fuel consumption decreases, due to a decrease in inlet temperature which leads to a lesser amount of compressor work to be done* (From e.g. seventh edition Gas Turbine Theory by H.I.H. Sarvananamuttoo, G.F.C. Rogers, H. Cohen, P.V. Straznicky and A.C. Nix).

But as the compressor work is directly proportional to the spool speed, I would expect the spool speed to be lower as well. (Correct me if I am wrong). But in the plot shown, the shaft speed parameter (N/$\sqrt(T_{02})$) seems to increase from 0.73 to 0.89 for single spool and 0.86 to 0.91 for double spool with increase in altitude. Why does the spool speed increase with altitude?


texts: What aircraft fly faster than 250 knots indicated airspeed under 10,000 feet for safety reasons?

texts: 14 CFR 91.117 limits aircraft to 250 knots indicated airspeed below 10,000 feet, but 91.117(d) allows aircraft to fly a higher speed if the minimum safe speed is higher. What aircraft and aircraft conditions might require an indicated airspeed higher than 250 knots?


texts: Is there's any risk using modern C++ compiler on DAL A Display Application Flight Software?

texts:
I am C++ enthusiast and I like to design and architecture my software with latest C++ features specially with templates,  but I have been struggling hard to find a way.
The compiler we use for LynxOS-DO178 RTOS with PowerPC architecture is more than decade old, with poor optimization, lack of several features, and often times just ending up in "internal compiler error". Code bloating occurs with simple template instantiations, which could be easily remove with latest compilers.
All ideas and innovative improvements are simply stopped by the fact that our compiler cannot support this and that.
I believe I could get a tool chain for my cross-platform development supporting somewhat latest versions of GNU GCC/G++. But not sure if that can be ever certified for DAL A SW.
We have now C++14, approaching to C++17, still I have this question do we have anything modern yet from C++ that sees "light of sun" on a critical SW ?
What are the risks, cons, etc for a flight critical SW ?
Bjarne Stroustrup recently announced core C++ guidelines, that resolves around use of modern C++11/14 and templates, but can we ever use those on Flight DAL A SW ?
Not sure if this a right platform to discuss this, if someone knows a better platform please direct me to that.


texts: Can turboprop blades break the sound barrier?

texts: This question doesn't relate to the actual speed of the aircraft, but of the blades themselves. I have heard helicopters had problems of this happening if the rotors spin too fast it can break the sound barrier, so could this happen to a turboprop?


texts: Is there a Risk of Tail Tipping during Push-back of a passenger aircraft?

texts:
I remember that there were countless incidents occurred in which the aircraft sits on the tail as the aircraft was heavily loaded at the back of the cargo and/or cabin compartments or the cargo compartments were offloaded incorrect order. I know that these incidents are more commonly happen in cargo aircrafts.

Is there a risk that the aircraft will sit on the tail during the pushback process as a result of the tri-cycle design of the aircraft?

Is there any tail tipping incident reported during pushback/towing operation?

Which types of aircraft (narrow/wide body) can this risk be higher?


texts:
I found the above in the Jeppesen Airport Chart Legend.

What would be an example of a transmit-only frequency? Is it related to Flight Service Stations? If so, how?

Where can I find an example for transmit-only frequency on a chart?


texts:
I have never been in Hot air balloon

But today I was wondering, what if someone in Hot air balloon wanted to pee?

how will they do it??

if there are no toilets in there, can they just do it from there to the ground? what if there was people down there?


texts: For routes over oceans, are slide rafts fitted with first-aid items, food, water, radio, etc?

texts:
Nowadays life rafts are often replaced by slide rafts, the slides having a double function: Evacuation and when detached survival. However they are packed tightly in the aircraft doors, so they probably don't contain a survival kit.

Nice illustration by Ron Wilson
Though it would be typical of ditching on Lake Michigan, not in heavy sea

For routes over oceans, what is the equipment that is available aboard rafts when they are used? (first-aid items, food, water, radio, etc). Where is this equipment stored before evacuation? Who takes care of making this equipment available in each raft?


texts: Why are most helipads in São Paulo blue coated and identified by a "P"?

texts:
ICAO Annex 14, Vol II and FAA (AC 5390-2C) standards establishes 'H' and there is no mention to coating TLOF or FATO.
Brazilian National Regulation (RBAC 155 - ANAC) does not provide any guideline for the blue painting.
I would like to know where this common São Paulo helipad pattern comes from.

Examples:

Google Maps (1)
Google Maps (2)
Google Images


texts: What are the black boots on this Extra 300's prop?

texts:
I normally think of black boots on a prop as being for de-icing. However, the Extra 300 is not suitable for known-icing conditions, or even IMC flight. (It's AFM says "Only VFR flights at day are allowed").
Considering the Extra 300's aerobatic mission, the gyroscopic loads on the engine are fierce. The upshot is that the manufacturer would not include a single extra gram more than necessary here.
So why are they there/what do they do? It has the owner and I stumped.


texts: Is it normal practice to refuel commerical planes whilst boarding is taking place?

texts:
The other day, I was on a KLM Boeing 737. I had just sat down in my seat, and the captain was making announcement. He said something along the lines of,

  As we are refuelling at this moment, please take your seat quickly, leaving your seat belt open, and follow any instructions by the cabin crew immediately

This suggests to me that refuelling whilst boarding is not normal, as I've never heard this before, and it sounds like they want us to be ready to evacuate if something goes wrong with the refuelling.


texts: How does drag change with Reynolds number?

texts: If you want to scale down an airframe, i.e., for wind tunnel testing, you have to adjust for the Reynolds number. I want to ask if in case I forgot to adjust the Reynolds number, would the drag on the airframe be greater or smaller after scaling down than what could be predicted from change in frontal area?


texts: What is the registration number of the 10,000th Airbus?

texts:
Recently, Airbus delivered its 10,000th aircraft (an A350 to Singapore Airlines). What is its registration number?

I understand the registration number is specific to the airline, and has nothing to do with the manufacturer.


texts: How do wing ribs withstand lateral lift force?

texts: During roll,there is a vertical component of lift that keeps the plane in the air and an horizontal component that actually rolls the plane,how are wing ribs designed to help withstand this vertical(now sideways to ribs) lift force since wing ribs are inherently weak laterally?


texts: Is a weak battery a valid reason to reject a rented aircraft?

texts:
Today I had rented a Piper Archer III for a local flight. After taxing to the fuel and filling up, I went to start the plane again and it did not want to turn over. This particular plane is somewhat fussy and sometimes doesn't start right away. As I continued to crank the engine over, you could tell the cranking lulled and the battery was having difficulty turning the engine over as effortlessly as it typically would. At one point the prop wouldn't even rotate.

I eventually got the plane started after a series of cranking / resting periods. I made the decision to not fly given the battery issue and returned the plane to its hangar.

The owner of the flight school was initially reluctant to comp the 1/3 of an hour I had on the hobbs (from taxing to gas pumps, etc) stating that once I had the plane started, I could have flown since it would have been powered by the magnetos.

My question: I know that the plane is powered by the magnetos once started, however, was my decision to not fly unfounded and unnecessarily cautious or would there be good reason not to fly knowing that the battery was weak and unreliable?

Update: It seems that some answers and comments have a focus on the financial aspect of my question. To be clear, this is not about money or how much. No one should pay for goods or services that were not rendered. The FBO's argument was that the choice not to fly was my own and not due to a responsibility of the FBO's to fix a "broken" plane. The money aspect is just an indicator of where the responsibility lies, on my shoulders or the FBO's.


texts: How is windspeed scaled in wind-tunnel tests?

texts:
Let's say you have a scale model that is 1:10th the size of the real thing. You want to test this in a wind-tunnel.

Do you also scale down the windspeed 10x? Why or why not? I would think it has to be scaled down in order to get the right results for things like propeller tip speed.

Edit: I saw this question. It could be a duplicate, except I did not see an answer to my concern there. I want to know if windspeeds are scaled down in a windtunnel, whereas that one asks about how windtunnels are used in general and doesn't seem to mention any scaling of windspeeds.


texts: What is this trio of fins at the back of a T-38?

texts: On a T-38 Talon on static display at a museum, I spotted a trio of aerodynamically shaped devices located aft of the vertical tail and between the engine aftbodies fore of the nozzles, as shown in the photos.  If these are vortex generators (VGs), what in the world are they doing there where there's no aerodynamic surface aft of them for the energized vortices to flow over? Could they be some other sort of protuberance, such as antennae for some system on the aircraft?


texts:
Does Ryanair lease any of its aircraft?

And if they do, could the end of the lease period coincide with the start of the low passenger periods? E.g. during the autumn to spring months when holiday traffic is slow, there may be a need to reduce the fleet size.


texts: From this cockpit picture I cannot identify this aircraft. Any ideas?

texts: It seems a kind of hybrid for testing. The overhead panel looks similar to BAe 146, Any ideas?


texts: Within a quadcopter, I know usually it's all the propellers facing upwards or all of them facing downwards. Why hasn't anyone tried making two propellers facing upwards and the other two facing downwards? Do some forces cancel out and renders that method ineffective?


texts: Why would one wing stall before the other?

texts:
Reading about the Douglas C-133, I see this:

  The second issue discovered was stall characteristics gave very little
  warning to the crew. The left wing was found to stall before the right
  wing. The fix was simple, a small strip of metal was attached to the
  right wing causing it to stall at the same time the left wing would
  stall.

The issue affects the whole type. What would cause one wing to reliably stall before the other?


texts:
I plan to operate an ultralight aircraft domestically (in Oregon, USA) in uncontrolled airspace and will not venture out of the country nor will I come near the Canadian or Mexican borders.

I have searched a bit and found that as long as I'm going to be operating domestically, I don't need an FCC license, however in AC 103-6 it states

  c. Traffic Advisory Practices at Uncontrolled Airports.

  In all radio communications, ultralight operators should state the word
  "ultralight" followed by the call letters assigned by the F.C.C. on your
  radio license, i.e., "Ultralight 12593U".

How can I use FCC call-letters if a license is not required domestically?  Since ultralights aren't required to be registered, I won't have a tail number to use either.  Do I just make something up like "ultralight whisky bravo" (my initials)? I do have an amateur radio license, but I'm guessing that isn't relevant here.


texts: I want to ask about the jet fuel purchasing cycle. Is it the airport that buys the jet fuel from refineries and then sells it to the airlines? Or do airlines buy fuel directly from refineries?


texts: Can I circle to a different runway if cleared for an instrument approach without circling minimums?

texts:
Tom is flying a C172S/G on ILS RWY 31 approach to KSNS. He just established on the localizer at 6000, from the SNS-22 DME Arc. He obtained weather from ATIS, wind 240@20G23, ceiling OVC006, visibility 1 1/2 SM. The wind favors RWY 26 but he notice there is no published circling minimum associated with his current ILS RWY 31 approach. He checked other approaches and found RNAV (GPS) Y RWY 31 @ KSNS has a published circling minimum of 500-1. He thinks since the two approaches are for the same runway and final leg should be similar, he may use the RNAV 500-1 circling minimum and to land on RWY 26.

X-Wind quick notes:

Wind angle for RWY 31 is 70˚.
Crosswind component for Landing on RWY 31 (18~22 knots)
Maximum demonstrated crosswind for C172S is 15 knots

In this case, what should he do?

A) Continue the ILS RWY 31 straight-in approach and land on RWY 31
B) Advise tower circle south to land on RWY 26. Start to circle upon reaching 500.
C) Change to RNAV (GPS) Y RWY 31 @ KSNS (approach without vertical guidance), re-intercept final approach course (WIGGL-IVUVY leg) and circling to RWY 26.
C*) Change to LOC/DME RWY 31 @KSNS (load a new approach) and circle at 560 to RWY 26
D) Once he has the airport in sight, cancel IFR and advise tower enter left base for RWY 26
E) Low-approach flying over RWY 31 until reaching 31-26 intersection, turn left and land on RWY 26.
F) Others, your suggestions.


texts: Why is a procedure turn required if you are more or less on the final approach course?

texts:
From this question.  I am not instrument rated.  The answers to the question explain, from the point of view of the plate instructions, if a PT is required or not.  The OP was failed for not performing a hold.

However, I can't see why a turn or hold is required at all.  If you are approaching within say 30 degrees, why would you not simply turn onto the final approach course and fly the approach (assuming that you are cleared of course)?

  If you were simply cleared direct to BEJCY and cleared for the approach, then your instructor is correct and you should have completed the procedure turn as charted.

The OP was approaching from SSW from AUGIE so continuing to BEJCY puts him 21 degrees to the South.  Why not just turn right onto 007?

I am assuming no ATC instructions to do anything other than the published approach.


texts: Is there a wordpress plugin for live NOTAMs?

texts:
How can I embed live notams to my wordpress webiste?
Is there a plugin to get live NOTAMs updates on my website?


texts: Does the FAA prescribe radar cross-section requirements for civilian aircraft?

texts: Are there any FAA regulations stipulating the minimum permissible radar cross section for civilian aircraft (i.e., making sure that civilian aircraft are at least such-and-such cross-section visible to primary radar)?


texts: Is axial dynamics important for the helicopter equations of motion?

texts: While analyzing helicopter performance, why do we always ignore the axial dynamics from the equations of motion?


texts: How similar/different are the roles performed by Military and Civil pilots?

texts: Broadly, Military and Civil are the only two categories in which the Pilots can be classified on the basis of the roles performed by them. What are the similarities and differences in tasks performed by them?


texts:
Usually, pilots will check NOTAMs during pre-flight prep. Are there some situations where they use them in a specific flight phase? If yes, in which case would it be useful?

Thank you


texts: Where is the modification of an aircraft from floats to wheels and vice versa logged?

texts: How does a maintenance professional, or pilot if allowed, log the change when the airplane is switched back and forth between land and sea? Do they cite the change in the maintenance logbook as performed via STC #, or performed via maintenance manual section XYZ?


texts: How far should the two propellers on a twin engine plane be apart?

texts: I was wondering if there are any specific ways to calculate the appropriate distance between two propellers for a twin engine twin fuselage planes like a Twin Mustang plane?


texts: NOTAM - What means "no shoulders along taxiways" in German?

texts:
can anyone explain to me what "no shoulders along taxiways" means?
I know what shoulder markings are, but I don't know how to translate them.

Are there German people? :)
Thank you!


texts: What happens when you apply full cyclic + collective?

texts: Can a helicopter apply full cyclic and then full collective at the same time? Would'nt the blades on one side (opposite of the intended tilt direction) have already maxed their aoa, resulting in a net dissapearence of dissymmetry of lift, with the effect equal to just applying full collective? Or does full collective + cyclic result in even greater aoa (the inputs add up)?


texts: Do negative angles-of-attack create lift?

texts:
(wikimedia.org) A typical curve showing section lift coefficient versus angle of attack for a cambered airfoil.

Based on the graph above, do negative angle-of-attack values create lift? How?


texts: How are IRUs and AHRSs different in terms of their functions?

texts: By my understanding, both systems use gyros and accelerometers to provide aircraft's attitude and heading information. Given that the information they produce are more or less the same, why do the modern aircraft have them both? What are major functional differences of the two systems?


texts: What is formula for induced drag in stalling regime?

texts:
I'm wondering what is the formula for induced drag in a stalled regime, i.e. in a regime where the $C_L$ (coef. of. lift) has started to decrease but is still nonzero.

I've a feeling that the conventional formula for induced drag
$$D_i = \frac{L^2}{\frac{1}{2}\rho V^2   \pi b^2 \epsilon}$$ (taken e.g. from this answer) which in essence depends on lift $L$, does not explain induced drag in stalling regime (if it would, it would erroneously imply that the induced drag is equal for a pair of AoAs $\alpha_{\text{before-stall}} < \alpha_{\text{after-stall}}$ which both correspond to the the same $C_L$).

I've come across the evidence that induced drag continues to grow as square of AoA even in stalled regime (e.g. schematic Fig. 4.14 from av8n.com)

but can't find more.

Thanks.


texts:
A small boat could be part of general cargo, but that would typically just mean it's unloaded at an airport and transported to the nearest body of water by land infrastructure. This is not what I'm looking for.

Instead, is there any aircraft that can directly deploy a boat to (or retrieve one from) water?

I would imagine there are cases when moving a boat by plane could be useful, especially when there's little or no infrastructure available on land.

Does such an aircraft exist?


texts: I want to fly at 77° 38' and 38° 56'. This is in the DC SFRA, in class B airspace (starting at 1500ft MSL). Can I fly here as a part 107 pilot without asking permission?


texts: What is the largest taildragger in history?

texts:
Large, modern multi-engine airplanes do mostly have the 'tricycle' landing gear type. But it hasn't always be the norm. I remember at least one big plane with 'conventional landing gear', the German four-engined FW 200 'Condor'...

But, was it the largest of them all...?


texts: Is a first class medical to be an airline pilot eventually possible?

texts: I have a history of ocd and a little depression when I was younger . Up until now I’ve taken a number of SSRIs and finally recently risperidone which I’m almost tapered off of for ocd.I have been symptom free for a while and believe I can be a pilot. I have a number of hours of flying time from over the years. The issue is I have a history of taking abilify and an SSRI and risperidone which is also an anti psychotic and cymbalta. I’ve never been diagnosed with psychosis but the risperidone (antipsychotic) can help with ocd. If I’ve been off of all of medicine and am stable is a first class medical eventually possible? They say it’s unacceptable to have a history of multi drug agent psychiatric drug used in conjunction with an SSRI. Is my airline pilot career not possible and has this ever been done. Thanks


texts: Can a VFR flight reference a waypoint in communication?

texts:
Can a VFR flight reference an IFR Waypoint when communicating position to tower or centers?
For example: “N1234 at 3500’ at FERMY, request blah blah blah?”

Thanks
RHD!

****Adding additional circumstance after the last two responses. Apologies for not being able to comment inline but apparently given the length of the below text I must edit my original post. Sorry for any confusion. ***

After some thought on the answers I want to add a little more to the discussion and my situation that prompted the question. I am using more of an EFB solution as you can see from the screen shot. This is a heavily trafficked area of SoCal as well as multiple airspace’s under multiple controls butted up to one another. I use a display on FF which very clearly defines those airspace’s without a lot of study. Aeronautical map to be exact and then Jeppesen when necessary. This map is super clean and minimizes head down time when head up is critical. I was in a particular area where I was not 100% sure on the closets VFR reference point. What however was very clear was one of the primary IFR waypoints (just using FERMY in this example only). The amount of time for me to be able to reference my altitude and FERMY was less than two seconds. On the other hand, switching to VFR sectional refinding myself, finding nearest VFR point and communicating, was infinitely longer. Hence the prompting of the question. I see the importance of other VFR pilots also knowing my position is of course most critical in an uncontrolled or fringes of controlled airspace at same time I further expect Tower or Center to also reference my nearest landmark. So now a bit more info and two “needs” (tower knowledge of my location and of course fellow traffic) does this change the discussion at all?


texts: Will the blade angle of a constant speed propeller be at its least angle (fine pitch) during full throttle and prop full?

texts:
During low power settings, low throttle setting and prop full during taxi, the blade angle will be at its finest pitch. As we increase the throttle for take-off, will the blade angle remain in its finest pitch to cater for increasing RPM ?
Will the propeller be at its finest pitch at full throttle & full prop setting ?


texts: For aircraft with variable-sweep wings, how unstable is it to have each wing in a different position?

texts:
Wikipedia presents this photograph of an F-14 Tomcat, with one variable-sweep wing swept forward and the other back:

I was surprised to see that this configuration was possible; much less feasible or safe to fly with. My idle assumption, not being an aviator of any kind, was that this would be extremely unstable and difficult to handle. I would have assumed, given the prior assumption that the aircraft would be unstable, that the wings would have interlocks requiring them to be swept symmetrically, as a safety feature.

Is this photograph of a maneuver that is manageable and safe enough to perform routinely, or would doing this with the wings be an exceptional event or done only for testing? What kind of impact would this have on the aircraft's handling, given a forewarned, experienced pilot?


texts: What is the best prop location for distributed propulsion - pusher, tractor or blown flap for an ultralight?

texts:
What is the best prop location for distributed propulsion - pusher, tractor or mid top wing ( blown flap) for an ultralight, max speed about 60mph, for MINIMUM takeoff distance ( 20-40') and about 15mph stall speed?

I would assume Blown flap, as the wing and prop would see clean air, and the flap sees the highest air speed increase due to exit speed of the prop, assuming 100% coverage.

My assumptions are:

Tractor configuration: entire wings sees prop exit speed but air is turbulent, so less lift, prop is in clean air, so max thrust.
Blown flap (prop on top of wing): wing is in clean air, so max lift, flap sees highest increase in air speed in this configuration, so max lift, prop is in clean air, so max thrust.
Pusher configuration: wing and flap in clean air, so good lift, prop in dirty air, so less thrust

Is this correct?


texts: What are the differences between blue airports and green ones on the low en-route chart?

texts: As far as I know, a brown airport on the low en-route chart does not have an approach procedure but blue and green airports do. But what exactly are the differences between these colors?


texts: How much does a Hundred Dollar Hamburger actually cost?

texts:
Recently, the Technical Difficulties discussed the \$100 hamburger on their show Citation Needed.
A "\$100 hamburger" refers to the practice of flying to another airport, eating a hamburger there, and flying back again.
The hamburger is used as an "excuse" for flying — the actual reason is just getting flight time to meet minimal flight hours. Presumably, it once cost around \$100 to do this, which is a lot for just getting a burger.
The Wikipedia article mentions that a hundred dollar hamburger likely costs more than \$100 these days, due to increased fuel prices.
Is it feasible to accomplish this mission (in the United States) within a \$100 budget today (2017)?


texts: How can ADS-B replace primary radar when FlightRadar24, using ADS-B, is so inaccurate?

texts:
I read the following on Flightradar24.com's 'How it works' page.

The percentage of aircraft equipped with ADS-B receivers is steadily
increasing though, as they will become mandatory for most aircraft
around the world by 2020. When mandatory, ADS-B will replace primary
radar as the primary surveillance method used by ATC.

Sure, that sounds lovely, but it it seems to me that a large portion of aircraft do not actually use GPS, but instead rely on inertial navigation systems or similar. Of course, the ATC doesn't need millimeter precision, or even an accurate position within a kilometer, but whenever I check flightradar24, there is quite a large bunch of airplanes reporting their position with offsets up to a few kilometers - if I were to judge by the ADS-B data, I would report a major emergency every few minutes.
How will ADS-B actually reliably replace primary radar? Will GPS have become mandatory by 2020? Or is Flightradar24.com just being optimistic?
(Side note: I know that redundancy is very popular in the aviation world, but I don't think you can call something 'replaced' when primary radar is still used for a large portion of the flights)
Edit: some parts of some answers seem to be concentrating on update rate / transmission losses and errors. For clarification, I included a screenshot (which I could literally take the second I looked at fr24.com, indicating how often this happens).

At the time this picture was taken, the 36R runway was in use for landing ('yellow' aircraft top right just landed). The selected aircraft is however happily taxiing in a field (pattern matching 36R's adjacent taxiways). This is not caused by update rate or transmission losses (i.e., this can't be old information, the plane was never in that field). Transmission error also seems out of the question, since the entire track is a smooth line (errors sometimes do happen, but are not 'hidden' on fr24 - a large 'jump' in the track can be seen sometimes). So either the plane is reporting a 'wrong' position (how is this handled by ATC?) or fr24 somehow messes up the data (how is that possible?


texts: Has the Beechcraft company considered building a single-engine turboprop?

texts:
I was passing a stack of magazines at a friend's office and I could have sworn I saw a cover article about a single-engine King Air. I went looking for that article and haven't been able to find it, but it got me thinking. Has the Beechcraft company ever released any information in any form that might indicate that they've considered building a single-engine turboprop?

I'm curious more on airplanes comparable to the King Air. I believe I remember reading that they played with the idea of a turboprop Bonanza, not to be confused with any STC modifications that make a Bonanza or Baron a turboprop.

I also realize that now Textron owns Cessna and Beechcraft, so if you consider the question in the larger frame of reference it looks a bit different as well.


texts: This is the first Cessna Skycourier during certification. Why are the two exhausts oriented upwards?


texts: In researching for this question, I came across some reports from EASA referring to TAPS. What is the meaning of TAPS in this context?


texts: Can the CG move out of bounds as fuel is used?

texts:
I've never bothered to check the weight and balance when the tanks are empty. I always assume that if the Center of Gravity is within range when the tanks are full, then it will remain within range as the flight progresses.

Am I correct? Should I compute the W&B on both ends?

I know some airliners have complex fuel systems which require fuel to be moved around during flight (e.g. B747-100, Concorde). I am interesting in small aircraft in general, i.e. General Aviation and perhaps personal and up to regional jets.


texts: What was the first plane that allowed walking during flight?

texts:
What was the first plane that allowed crew members and/or passengers to stand and walk during flight?

P.S. I mean walking inside the cabin, as part of normal operation intended for by the plane designers, not walking outside the plane, on wings and other acrobatic activity.


texts: Is it economically profitable for airports use jetties that use all the airbus A380's 16 exits at the same time

texts: Does it make economic sense or is it economically profitable for airports to build jetties or jetty facilities that use all the airbus A380's 16 exits at the same time.  This would be very convinient for passengers with less time waiting in a que to embark and disembark the aircraft and would be beneficial to airliners because they'd spend less time waiting for passengers to disembark the aircraft, cleaning crews entering the plane quicker getting it ready for a new set of passengers sooner who would enter the plane quicker.  They'd also pay less for parking space at airports as they'd spend less time there.  The airports would free up their parking spaces quicker and would service more planes per day and get more revenue. Win... Win... Win!!!


texts: Could Henri Farman have steered his plane with ailerons on January 13, 1908?

texts:
It is known that Henri Farman flew (over) 1 km in a circuit on January 13, 1908, and gained a 50000-franc prize. Orville Wright even witnessed Farman on November 18, 1907, attempting to make the full circle but each time touching the ground before completing the required course. The altitude of the machine dropped while the French pilot attempted some turns. (Farman did not use ailerons till after September 1908.)

The question is: Would the ailerons have made the Farman plane to steer more efficiently without losing altitude, which was critical because, for technical reasons, the plane could not fly higher that what you can see in the picture?

Henry Farman flying on January 13, 1908. The picture appeared in many French publications of the time.

The image below apparently shows that a plane loses altitude while taking turns using its ailerons. Does the airplane also go down if it is steered just with the tail?


texts: Where to obtain a list of active NDB approaches?

texts: Does anyone know where to find a list of active NDB approaches? I can find a list of ones proposed to be eliminated, but I'm having a problem coming across a list of remaining ones.


texts: Are engines automatically stopped in an emergency landing?

texts:
This answer made me wonder if engines are stopped automatically after an emergency landing as soon as one of the exit doors are opened.

  (...) if the engine is still running, you're about to run forward into the area where you're at risk of being sucked into the running engine.

I'm not sure how high the risk would be to be sucked in or being blasted away by the jet-blast, I guess a lot of the emergency landings are because of engine failure so they aren't running anymore.

Maybe as an added extra - how long does it take for an engine to spin down to a safe RPM (so that it won't suck in people or blast them away)?


texts: Can someone actually "fly under the radar"?

texts: It is quite a common phrase, usually without having anything to do with radar or aviation. But. Is there such a thing as 'flying under the radar'? If so, why is this (and how low is that)?