texts: What are the odds that I'm the next most qualified pilot on a given flight?

texts:
On a given flight, let's say a commercial flight with about 100 passengers and a few flight attendants, what are the odds that I (or any other individual) am the most qualified person to fly the plane, after the pilots?

I call myself a pilot very loosely here. I fly paragliders (so I trust my own life to my flying skills, and know a little bit about airspace, etc.), I've flown lots of simulators, RC aircraft, and have started ground school, but haven't yet done any actual flight in powered aircraft.

I'm sure many aviation enthusiasts and non-commercial pilots have thought about a scenario where the pilots of their flight are somehow incapacitated. Maybe someone frantically gets on the PA and asks if anyone knows how to fly a plane. I've wondered if I should even speak up in that situation? (should that be a separate question?) I'm not a great choice to fly the plane, but what are the chances that I'm the best we've got?

I guess to generalize the question, what are the odds that a given person on a flight has some reasonable level of flight experience?


texts: How is thrust vectoring controlled by the pilot?

texts:
Thrust vectoring is used to extend the manoeuvrability of aircraft outside a `normal' flight envelope, by providing (optionally differential) vectored engine thrust, as explored in many previous questions (this and this).

How is the direction of vectoring actually controlled by the pilot during flight? Does a flight control computer automatically interpret "traditional" control surface inputs under extreme conditions and move the nozzles appropriately to create the desired effect? Or is vector direction a separately controllable interface?

I've noticed in my flight sim of choice, XPlane, that the configuration panel allows the mapping of an analogue axis on my joystick/pedal setup to 1D vectored thrust. I've no idea if this is representative of any real fast jets, but if it is, it seems that this approach could create a lot of extra "pilot workload" -- given that it's another one (to three!) control axes to be manipulated -- and manipulated at the same time as pulling potentially very aerobatic manoeuvres with little room for mistakes. This seems like a Bad Idea.

On the other hand, it might be the case that independently controlled vectored thrust allows for a wider range of aircraft manoeuvres than that which could traditionally be 'expressed' by control surface movements alone. Giving fast jet pilots the extra workload would, therefore, be worth the risk.


texts: How much hydraulic fluid is in a jet airliner?

texts: Hopefully the title is self-explanatory. I am wondering how much hydraulic fluid - in mass and volume - is carried in normal operations for a jet (the bigger the aircraft in your answer the better).


texts: Are there design guidelines for sizing vent/surge tanks?

texts:
Could someone explain the sizing process of Vent/ Surge tank of Aircraft fuel system? I understand the Vent tank is to collect fuel overflow from the main fuel tanks. The reason could be due to Fuel thermal expansion or fuel over flow during manoeuvre or can be during pressure refueling.
The link
What is the capacity of the vent surge tank in an A320?
discuss about the fuel over flow by Thermal expansion. But can we size vent tank based on the pressure refueling fuel over flow? If so, for how long overflow to be considered? Though it is based on the Vent relief system and flow rates of specific aircraft, requesting any general guideline/ Reference for the design.
Thank you


texts: How are condensation cones created by supersonic airplanes?

texts:
There are many awesome pictures of this phenomenon such as this one:

What is the physical explanation of how this occurs? Does it occur only when the airplane crosses the sound barrier or does it continue throughout the whole supersonic regime if enough water vapour is present in the atmosphere? What factors does this condensation depend on?


texts: Can the FAA 8130-3 have "modified" status if a part is converted by replacing piece-parts from IPC?

texts:
I have been trying to identify if the FAA 8130-3 Instructions have some clarity but am unable to deduce if this situation is indeed acceptable. A sequence of events (Of sorts) is given below:

A Part had a defect and was removed as Unserviceable and shipped to Shop
The Shop has replaced certain piece-parts which are fitted on a newer design
The Shop has then released the original part with the FAA 8130-3 stating "Modified" in Block 11
As per the Shop, the replacement Modifies the part and the status in Block 11 is acceptable


texts: Is it "cutting off" in the pattern when I go before a plane that is going faster than I am but let me in first?

texts:
While turning from the 45˚ to the downwind leg for a downwind pattern landing in a Cessna 182, a Cheyenne was calling 5 miles out on a GPS approach for a straight in landing.  Clear day, both flying VFR, uncontrolled airport.  He and I had been communicating for 5-6 minutes, and I called my base turn knowing I had entered the pattern well ahead of him and had time to land ahead of him.  The Cheyenne pilot acknowledged me and was good with this.

Seconds before I touched down, I heard from a pilot evidently taxiing to take off from the same runway, "Dude ... you just cut off that Cheyenne ... you realize he's going about 4 times faster than you."

Now aside from his ignorance by not hearing the leadup conversation to our opposite direction approaches, when is a plane in a straight-on landing considered to have the right of way over one "in the pattern" and when, apart from communicating between pilots, is it proper regulation to land ahead, vs. extending the downwind leg and falling in behind him?

I was specifically trained that until you are within 4 miles, you are technically not on "final" during a straight-in approach ... but that common sense must prevail, so even if you reach the pattern first, it may be courteous and safer to allow a faster aircraft in ahead of you.


texts: What happens to the fuel lines when a jet engine falls off?

texts: Going off this question, what happens to the fuel lines to the engine when it falls off? Does it automatically shut off or do the pilots have to manually do it?


texts: Why aren't airports built identically (like aircraft)?

texts: Considering the delays and mishaps in super-projects (e.g. the new airport in Berlin), wouldn't it be rational to standardize airports in the same ways aircraft are: Building them all according to the same designs and not in a "one-off" fashion? Why is this not done?


texts: Is the "glory" optical phenomenon frequently seen by aircraft pilots?

texts:
A glory being this optical phenomenon:

(Source)

It reveals the presence of supercooled water, a hazard for an aircraft (see answers).
Due to the way it can materialize, the center of the rings indicates the position of the observer in the airliner. So this one was not shot from the cockpit.

Does it represent a specific icing hazard?
How frequent is it?


texts: Can tower clear aircraft for take off with traffic still on the runway?

texts:
How much separation is required after an aircraft lands before ATC can clear another aircraft to take off from the same runway? On longer runways are small aircraft allowed to commence take off roll or be cleared for take off while the preceding landing aircraft is still on the runway? I looked and was unable to find any ATC instruction requiring separation between landing and departing traffic on the same runway.

While this would be unsafe, it seems to me that I have been cleared to take off while there was still an aircraft finishing its landing roll. By the time I had lined up for take off the preceding traffic is alway clear but is this still a "legal" practice to be cleared for take off before the preceding air craft calls "clear of the active"


texts: Why don't aircraft owners put vortex generators on the top of their flaps to extend single flap lift creation past 40 degrees?

texts:
Why don't ultralight/LSA aircraft owners put vortex generators (VGs) on the top of their flaps?
I understand that the maximum flap angle for a single lift creating flap is 40°, but 80° with a double flap, if each flap is rotated at 40°.
Why not put VGs on the top of a single flap to increase its maximum lift creation angle, and thus lift, to 45°, 50° or maybe even 60°, which would allow for a slower landing speed, hopefully in the 15-20mph range?
While Vg's might have been designed for wings, they are now used for elevators as well, which is very similar to an upside down wing and flap.  See picture below. Source: Zenith


texts: Is a trimmed flight not always an unstable system?

texts:
As soon as I am flying in trimmed flight condition, my pitching moment around the center of gravity becomes zero. So my center of pressure has to be located in the center of gravity, so that there is no resulting turning moment.
But assume, there comes a wind gust, and the angle of attack will increase. This causes the center of pressure to move forward in front of my gravity location. So the aircraft will become instable because the angle of attack will further increase (nose up). The only thing the pilot could do is to use the elevator to trim in pitch.
So in the end, as long as I want to use the principle of "trimmed flight" , I will always have to use control surfaces to counteract the unstable flight condition. So why to care about stability, in trimmed flight it will always come to an unstable flight condition as long as I do not use the elevators?
Can you follow me? Is this true?


texts: How to determine the compressive force in the spars of a strutted wing?

texts:
How does one calculate the compressive force that the inner section of a strutted or braced wing (from the strut attach point to the wing root) experiences?

I know how to calculate the tension in the struts (or flying wires), which is simply

$$ \mathrm{Tension} = \cfrac{\mathrm{Lift}}{\sin \theta} $$

but I don't know to calculate the compressive force that a strutted or braced wing experiences.


texts: Do any UK universities include PPL/Commercial flight training as part of an aviation degree?

texts:
I recently became interested in becoming a commercial pilot after buying Flight Simulator X and a Saitek Yoke system. I'm still studying my GCSE's, and I am now debating between computer science and a career as a pilot.

I currently don't have the money to get my private pilot license, and very much doubt that I'll have the money for commercial training in the future. Therefore, I am curious as to whether or not some universities offer both PPL and commercial flight training as part of an aviation degree program.


texts: Can I log time in an RV-12 towards a commercial certificate, and is it a TAA?

texts:
Can I legally log hours flying RV-12 towards commercial airplane rating?

Does RV-12 qualify as a TAA?


texts: Do aircraft that operate at lower altitudes tend to have more cycles?

texts: I've heard that aircraft cycles depend on the number of missions, regardless of the distance, because the pressurisation of the aircraft at altitude is what causes cumulative damage to the fuselage. If that's the case then does it tend to be true that aircraft that fly lower have more cycles? I'm particularly wondering about the difference between turboprop (FL240) and jet aircraft (FL410). Do turboprop fuselages tend to have more cycles?


texts: How much simulator time can I use towards a part 61 instrument rating?

texts:
I am doing Instrument Rating under part 61 with a CFII.

To meet the 50 hours cross country requirement (d 1), can I log some of the PIC time in a simulator?
There is a 20 hours limitation on the use of simulator (h 2). So, if I have 40 hours of simulator time and 15 of them are cross country, can I use those 15 hours towards the cross county requirement and the other 5 hours towards the 40 hours requirement (d 2)?

  (d) Aeronautical experience for the instrument-airplane rating. A
  person who applies for an instrument-airplane rating must have logged:

  (1) Except as provided in paragraph (g) of this section, 50 hours of
  cross-country flight time as pilot in command, of which 10 hours must
  have been in an airplane; and

  (2) Forty hours of actual or simulated instrument time in the areas of
  operation listed in paragraph (c) of this section, of which 15 hours
  must have been received from an authorized instructor who holds an
  instrument-airplane rating, and the instrument time includes:

  (i) Three hours of instrument flight training from an authorized
  instructor in an airplane that is appropriate to the
  instrument-airplane rating within 2 calendar months before the date of
  the practical test; and

  (ii) Instrument flight training on cross country flight procedures,
  including one cross country flight in an airplane with an authorized
  instructor, that is performed under instrument flight rules, when a
  flight plan has been filed with an air traffic control facility, and
  that involves—

  (A) A flight of 250 nautical miles along airways or by directed
  routing from an air traffic control facility;

  (B) An instrument approach at each airport; and

  (C) Three different kinds of approaches with the use of navigation
  systems.

  (h) Use of full flight simulators or flight training devices. If the
  instrument time was provided by an authorized instructor in a full
  flight simulator or flight training device—

  (1) A maximum of 30 hours may be performed in that full flight
  simulator or flight training device if the instrument time was
  completed in accordance with part 142 of this chapter; or

  (2) A maximum of 20 hours may be performed in that full flight
  simulator or flight training device if the instrument time was not
  completed in accordance with part 142 of this chapter.


texts: Why are airports in Greece blurred and low res in Google Maps?


texts: In lost comms situations, when and where do the pilots of big commercial jets expect to get green light from tower?

texts:
In the event of lost comms, GA pilots are generally expected to circle over the airport looking for light gun signals from the tower. What about big commercials jets? Are they also expected to circle over the airport until they see green light from the tower?

One of my flight instructors once told me, in real lost comms situations, don't circle over the airport and just take a traffic pattern and land, because the tower is already aware of your situation and they will clear traffic for you accordingly, if you were squawking 7600. I was not sure at the time he was right on this, but maybe that's the case for big commercial jets.

So what does the tower expect from the pilots of Boeing or Airbus in lost communications? Do they expect you to circle over them looking for light signals or just go ahead land expecting to get the signals on the pattern?


texts:
In case you want to say spherical coordinate system: no it is not a spherical coordinate system.

I found this image in a book about flight management systems where they explain the different types of coordinate systems it can use.

The ukrainian name for it is: "ортодромічної" coordinate system

What is the English name of this coordinate system and what advantages may it offer over another (eg spherical coordinate system)?


texts: Is it practical to descend in a lost communication scenario?

texts:
This is a follow-up to my previous question here -
  Lost radio communication after take-off in IMC - what are my options?.
  Please refer to that to understand the scenario of this question.

If, for e.g, at one point during the flight, I see a minimum en-route of 9000' and so I climb up to 9000' from 8000'. Now, if the next segment has a minimum en-route altitude of 3000', shall I go back to my previously held altitude of 8000' (which became my assigned altitude before and is now the maximum amongst all the other available altitudes) or shall I maintain 9000' and consider it to be my "new" assigned altitude?

Apart from a regulatory perspective, I'd also like if someone could weigh-in on practical perspective - would it be better in terms of traffic separation for ATC, etc.

So the question really is - is it practical to descend, or do the regulations want you to descend and hence ATC does not expect you to descend?

I've had different answers to this particular question from different Flight Instructors, and hence looking for a definite answer.


texts: How to calculate the shear centre of a wing?

texts: How is shear centre of a wings calculated? i.e. how can I calculate the wing shear centre of a two spar wing with main spar at 0% of wing chord and rear spar at 75% of wing chord? (Assuming the two spars have the same stiffness.)


texts: Why do new engines have a case with a triangular tiling pattern?

texts:
Take a look at the case of new engines such as the F-135:

or the F-119:

Why do they have a case with a triangular tiling pattern? Is this a new technology? A new material?


texts: Can excessive G-force break or dislocate bones during pilot maneuvers?

texts: Was wondering if the pilot would faint, could g-force be enough to maybe break the neck bone with the head and weight of a helmet being pulled downwards. Another relay to this is the effects on the inside of the body, more specifically, the brain. Like a boxer, after taking a few too many knockouts. Is there a limit, or an event horizon to permanent brain damage and bone structure deterioration concerning g-force and pilots in aircraft maneuvers?


texts: Can astronavigation be used during flight?

texts: In an aircraft, can you look at the sky to get your bearing and position like sailors do?


texts: Could hydrazine be used as a scramjet propellant?

texts: Hydrazine is used a monopropellant in Satellite OMS rockets. But interestingly enough, it's highly exothermic decomposition into ammonia, nitrogen, and hydrogen provides heat for an endothermic reaction with additional hydrazine to form hydrogen gas. So a scramjet using hydrazine would have to reactions inside it's combustion chamber: The decomposition of hydrazine and the combustion of the resulting hydrogen gas with air. And unlike hydrogen gas, hydrazine has much higher propellant density. Has this ever been considered by aerospace engineers and even tested?


texts: Are there any runways that aren't labeled reciprocally to each other?

texts:
Runways are generally labeled by their magnetic azimuth between 01 and 36. This means that runways are normally labeled on each end with a number that is reciprocal to the other by 180 degrees.

Do any runways exist where the approach ends aren't labeled reciprocally to each other?


texts: How much performance penalty is incurred from a WW2-era folding wing mechanism?

texts:
I'm interested in WW2-era single-engine piston-prop monoplanes. I'm interested in the folding wing mechanisms from the perspective of performance, chiefly two things:

How much extra weight does it add?

How much extra drag does it add?

I did see this pdf about the sto-wing, but the only thing about weight is

  The initial STO-Wing design was operated with hydraulic cylinders, but the added weight of the system reduced performance, so a lighter manual system fitted with safety locks was selected for production.

Wikipedia's folding wing article is pretty short, both in words and in data. It did lead to 2 external links.

This article has no numerical data on the sto-wing, but does cite some book: Richard Thruelsen. The Grumman Story. New York: Praeger Publishers Inc., 1976. 125. I was able to find it on Google Books but it looks like you can't search things there like you used to. "Folding Wing" and "Sto-wing" returned very limited results.

The other link is a dead link.

I really hope someone knows where to find these numbers. It would be really nice to see just how much weight goes into this mechanism. To me it seems pretty significant if you're gonna have a strong pin to make sure the wing won't snap-fold in flight, almost like you need another main wing spar in the joint.


texts: Does the Fokker 70/100 Flight Management Computer really contain the ability to play Pong?

texts:
This clip now circulating on Facebook (YouTube link) shows two pilots playing a game of Pong on the Fokker 70/100 Flight Management System (FMS). The manufacturer is presumably Honeywell.

Does this feature really exist?

Thoughts:

I would have hoped they had better code review to catch this, but then again I'm not sure how these work. A few veteran old employees who know ADA or whatever sitting in a dark room down the corridor when the new intern shows up?
The hardware is fairly old with corresponding limitations. As much as the flight displays (EICAS) can do decent graphics, the FMC seems pretty 'paginated' and slow to react to button presses.

Update: Thanks for the input. I was fairly certain it was fake but couldn't find the error. It also provoked some interesting software debate :)


texts: Why don't El Al 747's stay at the gates at JFK?

texts:
I was recently travelling through JFK in New York City and saw the El Al 747, presumably arrived as ELY1 and departing as ELY4, sitting on the apron near terminal 4. What I saw was similar to as shown in the video capture below. The fellow plane-nerd I was travelling with claimed that it was parked there because the onboard missile defense systems of a El Al 747 include a pyrotechnic MAWS, which is considered dangerous to ground personnel. He claimed that this, in turn, is why the plane sits on the apron rather than at the gate or in a hangar (where it would be closer to maintenance personnel).

(YouTube)

Which, if any, of these facts are true?

The MAWS on the 747 is the pyrotechnic type (such as flight guard) rather than the newer
laser.
The MAWS on the 747 is considered dangerous by whichever
governing body is salient.
The MAWS is the reason the plane is sitting where it is.

OR is this just a convenient spot to keep a massive object for the 5 hours it's not needed?

I would split these questions into three separate posts but they seem too closely related for that.


texts: What are the most significant risks to life for the airline passenger?

texts:
Suppose that I start taking long-distance airline flights, and that after each flight I immediately jump on to another aircraft that takes off for another faraway destination - and continue doing this, indefinitely.

In other words, I'm going to live the rest of my life travelling on airliners.

What's going to kill me first:

an airline accident or incident
excessive radiation exposure
some other flying-related health risk
old age?

If the answer is old age, then let's suppose for the sake of the question that I'm also going to live indefinitely, until one of the other factors does me in.

Exclusions

I'm only interested in risks that are specific to flying. I suspect that breaking my neck falling down the steps or choking to death on an in-flight peanut might be higher, but they don't count, because I use stairs and eat peanuts regularly anyway.

I guess exposure to infectious diseases (and other risks associated with the airline cabin environment) should count, since air travel does  increase those significantly.

The health risks of an airline food diet are excluded though, especially if I decide to fly economy class. So is dying of despair.

However, the risk of severe food poisoning should be included.

Finally, I'm only flying on scheduled flights on reputable airlines.

The comparison

As you can probably gather, the device of the hypothetical permanent travel  is simply a way of framing the risks for the sake of comparison. I'm not really interested in what it might be like to fly forever, but in the quantum of risks in airline travel.

On the other hand there presumably come a point where the frequency of travel means that some risks become disproportionately more significant (e.g. eating 70 airline meals a year might be simply unpleasant, but eating 700 would be to suffer from a genuinely unhealthy diet).

However I can't think of any risks of that kind that would start to increase at a rate greater than frequency of flying, within any normal flying frequencies.

Future risk changes

I assume that flying is going to continue to become ever-safer, which could mean that the risk of an incident or accident will fall over time while (say) health risks don't. For the sake of a fair comparison, let's say that even into the far future the risks will remain as they are today.


texts: How did they solve the compressor stall issue of the F-14A in the B?

texts: I know that the F-14A was notorious for having compressor stalls during high AOA or with quick thrust changes, and most of the issues were solved in the B. Externally there doesn't seem to be much difference in the intake, so how did they solve it?


texts: How do pilots detect and respond to windshear while landing and taking off?

texts: How does wind shear affect aircraft while landing and taking off? How do pilots detect that they are encountering wind shear and what would they have to do to prevent it from turning into a bad situation?


texts:
(fireair.co.uk)

Why is a weight and balance graph lozenge-shaped? I have tried to find the answer but it seems to be really hard to find. Why is it not a square?


texts: What are the regulations regarding plane spotting in the US?

texts: I was told that certain plane spotting activities like taking photos of aircraft taking off and landing could be illegal in the US since 9/11? What are the regulations on this, and what should I be aware of before I set my camera up at the end of the runway?


texts: Do pilots have the ability to bypass customs when utilizing jump-seat privileges?

texts:
I wonder if anyone can help with a hypothetical question. Its for a novel I am researching
All passengers with a ticket for a flight will pass through normal passport controls but I am told that Pilots can jump a flight if theres a spare seat. I know it might be outside of procedure but...
Is it feasible that he might join his buddies and get on the plane with them and avoid the official record of him entering and leaving another country say between the USA and Canada?


texts:
I was just curious as to how you would make a glider glide in a circular pattern ( or helical ).

Will there be a large difference when considering a conventional glider vs a delta wing glider?


texts:
I mean the optimal taper ratio for an unswept trapezoidal wing for minimising induced drag.
I see a lot of places recommending a value of 0.45 to give as close to an elliptical distribution, therefore maximising Oswald efficiency (to 1). However, Hoerner (Fluid-Dynamic Drag, chapter 7-2) has this plot which suggests the optimal taper ratio is about 0.356 (graphical line fit).

Similar graphs are produced in this paper: Induced Drag of High-Aspect Ratio Wings
Tommy M. Chen and Joseph Katz
This exact taper ratio is used by BAe regional jets also.
I haven't read about this thoroughly enough. Maybe this value considers root chord and wing area to be fixed, therefore as taper ratio is decreased the aspect ratio must increase to maintain a constant area. The increased AR (really the increased span) reduces the induced drag.
Does anyone know the answer? I'd really like to be able to justify my taper ratio for an aircraft design assignment.


texts: What are the issues with building modular aircraft?

texts:
This might make sense as

commercial aircraft basic design has remained the same for the last 50 years or so, but materials used have changed
parts such as wings, landing gear, nose, tail, jet engine, fuselage, avionics and seats all come from different specialized manufacturers
so OEMs like Boeing, Airbus, etc., can build modular planes where each of the above mentioned parts should be replaceable with a better upgraded part
and this can prevent wastage


texts:
In the US, in the last 50 years, have there been any accidents known to involve a student pilot intentionally practicing stalls in solo flight?

This question is asked in the context of civilian flight training in single-engine land airplanes.

I've heard of at least one flight school prohibiting student pilots from practicing stalls solo.


texts: Can the Landing gear be lowered when system A hydraulic pressure is lost in Boeing 737?

texts:
In the FCOM OF BOEING 737 HYDRAULIC SECTION I went through the part Landing gear transfer unit that it is used to raise the landing gear at a normal rate when system A EDP volume is lost.
My query is if only the hydraulic system A is lost with landing gear up position can it lowered using system B hydraulic or do we need to use manual gravity gear extension?


texts: How is NASA going to get high fuel economy on the X-57?

texts:
This X-plane is meant to fly soon.

It's a modified Tecnam.
The propeller direct wash over the wings, increasing lift. This allows the use of a smaller, high-aspect ratio, low drag wing.
But this isn't quite clear to me. Here's what I know about this.

Light aircraft have oversized wings for cruise, needed due to a mandatory minimum 61 knots stall speed, and the lack of cabin pressurization generally prevents them flying high enough to make good use of the extra wing area at higher cruise speeds.
The propwash from the Maxwell would act like a blown flap at low speeds, achieving the above requirement without a large wing but presumably sufficient redundancy to not matter.
At cruise however, the propwash would increase friction drag by causing faster airflow over the wings, and possibly interfering with any laminar flow.
The giant propellers at the tips are somehow meant to reduce induced drag - but how?
This is a glorified blown flap.

What am I missing?
EDIT: I just discovered/remembered that at cruise the inner propellers fold to reduce drag. But the point remains: what is so special about this glorified blown flap?


texts: How are composite materials on aircraft joined?

texts: Answer for the question Why are planes using rivets & not welded construction? describes why rivets are preferred for joining aluminium alloy components. But how are carbon-fibre-reinforced plastic components in new aircraft joined?


texts: Why was the A380 built with a gull-wing design?

texts:
I've noticed that the wings on the A380 are very curved in comparison to the 747. I mean the 747 has a lot of wing flex but the A380 has less wing flex and the wings are flexed down in comparison to the 747. Here there are two photos that might help you understand what I'm writing. So why are the A380 wings like that and what are the benefits?
Source

Source


texts:
I've just read an article from SkyNews just here where they said it's expected that one day air traffic control will be the target of cyber attacks.

So my question is "Is ATC connected to the Internet and why ?"

Are they just connected (if they are) to exchange information between the various ATC Centers and in this case I think they use VPN connections with military grade encryption or do they use Internet for other reasons ?


texts: What are these openings around the Comet's engine intakes?

texts:
What are all these openings surrounding the Comet 1's engine intakes...

(Original image by Tony Hisgett at flickr, via Wikimedia Commons; modified by me)

and what is this opening between the Comet 4's intakes?

(Original image by Ian Dunster at Wikimedia Commons; modified by me)


texts: Is a destination airport necessary for cross-country VFR departure clearance?

texts: New flyer here. When you’re requesting departure clearance for a cross-country VFR, do you have to specify the destination airport to the controller, or can you just specify a direction (eg. “VFR to the south”)?


texts: How do single engine airplanes handle changes in torque?

texts:
In multirotors, there is a regulation of torque from the rotors which keeps it stable. However, in single engine airplanes, there is only one engine with one propeller.

How is the aircraft able to stabilize itself in such a case?


texts: How is fuel drawn from drop tanks in WW2 airplanes?

texts:
Low-wing tanks typically have fuel supply lines at the bottom. For external drop tanks, I thought they came built with internal lines that mate with the plane.

That appears to be the case for more modern tanks – though I'm not sure yet – based on a mid-50s patent. Earlier patents (image shown) that correspond with WW2, as far as I've seen, don't mention any relevant internal structures. And two Wikipedia articles weren't helpful:

Aircraft fuel system
Drop tank

Most I could find was an F-86 manual on Google Books. And it mentions the jet engine providing compressed air into the tank to draw fuel (the mechanism isn't yet clear to me, but I'll pursue that later).

For now, WW2 aircraft. For example: Where electric motor compressors used instead of bleed air? Were there internal tank structures that assisted?

If there are differences between implementations, then the most common/typical would do or the typical American-fighter implementation (to assist with references since they're typically much easier to find).


texts: Why does the 1090 ES use the same frequency for both uplink and downlink?

texts:
The 1090 ES is the transponder system used in ADS-B.
Why does the 1090 ES use the same frequency (1090MHz) for uplink as well as downlink? 1090 ES is an extension of Mode S. The Mode S used 1030MHz for uplink and 1090MHz for downlink. Why did the 1090 ES change that? Having two frequency channels would be better (More space less noise due to message collisions) for communication right?


texts: Why is airflow forced to be speed up on the upper surface of an aerofoil?

texts:
As the title says: Why is airflow compelled to flow further over the upper surface of an aerofoil? I understand because it has a larger distance to travel, but why can't the airflow travel at the same speed as the airflow underneath the lower surface?
I understand how the Bernoulli effect works but there is no constriction in an aerofoil, why does it speed up with the Bernoulli effect; without the constriction?
I also understand that the there is a wrong theory that airflow over the top of the wing wants to meet the airflow on the lower surface at the end of the aerofoil, at the same time.


texts: What is the altitude of the nose vs tail in airplane flight?

texts:
Suppose you have an airplane flying level on a long flight. Now suppose you place one altimeter sensor in the tail, and one in the nose. Suppose you record and store these values independently (perhaps take 10 readings per second.)

And then suppose you graph this data.

This is the graph i'm looking for. Has anyone ever seen data like this?

In other words, i'm looking for experimental data which has logged a comparison of the altitude of the nose, vs. the altitude of the tail, (several times per second) on a long flight.

The intent is to study how the pitch of the aircraft is constantly in flux -- e.g. by turbulence, wind speed changes, the curvature of the earth, and (of course) by the pilot's inputs themselves, etc.


texts: How are these parameters derived from readings of sensors in an aircraft: angle of attack, slip angle, and airspeed?

texts:
From what I've learned, the reading comes from

an angle of attack sensor and a slip angle sensor. Let's call the readings $\hat\alpha$ and $\hat\beta$ respectively. These are of either the weathervane type or the differential pressure type.
airspeed sensor, i.e. a pitot tube. This probe measures the total and static pressure $\hat p_\text{total}$ and $\hat p_\text{static}$, and the airspeed $\hat u$ is obtained from them.

Here's the catch: in real flight, the measured angles $\hat\alpha$ and $\hat\beta$ may depend on not only the true values $\alpha$ and $\beta$ but also other factors which include true airspeed $u$, and the measured airspeed $\hat u$ may depend on $\alpha$ and $\beta$ too. How is this problem solved? How are these sensors calibrated? Are they tested in a wind tunnel where every possible combination of $(\alpha,\beta,u)$ is given to produce $(\hat\alpha,\hat\beta,\hat u)$ and form a lookup table?


texts: Do runways need some special kind of tar or protective layer?

texts: Do runways of the airports have some special kind of tar or protective layer to avoid the wear and tear in comparison to that of the Highways as they need to handle the much high pressure and the weights than normal highways?


texts: Is there a way to calculate thrust without running experiments?

texts: Is there any way to calculate the thrust generated without conducting experiments? In my case I need to figure out thrust generated by electric duct fans and/or turbojets.


texts: How much drag do the gear doors create during retraction?

texts: It's been said that if you retract the gear at a critical moment that performance will actually be worse than if you left the gear down. However, is this really true, and just how long is the performance worse for? Obviously in the long run it'd be better to have the gear up, so how much drag is there actually?


texts: Why is mixture lean recommended on the ground?

texts:
Mixture lean is typically recommended during the ground operations at sea-level pressure in the POHs of most small aircraft equipped with a carburetor system. Why is it?

I heard some people saying it's because the engine requires less power for the ground operations, but that doesn't persuade me. If it's the amount of power output at stake, we just need to pull back the throttle and reduce power, which we exactly do for taxiing and holding short of the runway. Mixture is about controlling the ratio of fuel and air entering the cylinders, and we change it according to the variations in air density, not the power output required. If that's the case, then why do the POHs recommend a mixture lean for the ground operations at sea level?

Edit) I guess my question is put too poorly for some people to understand easily. Let me try again. Plug foulings happen when mixture is set too rich for the given density altitude. For this reason, many of the GA aircraft's POHs recommend pilots to start leaning mixture from 3000 MSL up. That means as long as the aircraft stay below 3000 MSL, the pilots have no reason to lean mixture, at least for the purpose of avoiding plug foulings. Yet, the same POHs recommend pilots to lean mixture for ground operations even when the elevation where ground operations are performed is below 3000 MSL. So my question is: "Why do the POHs recommend pilots to lean mixture for ground operations even when the density altitude of the ground does not require it?".


texts: How many active pilots are there in the US? How many are women?

texts: How many active pilots are there in the US?  Also, how many active flight instructors are there?  Out of all of active pilots and flight instructors how many are women?


texts: What Microcontroller(s) is/are used inside the ECU of a CF6-80C2 engine?

texts: The question came up at work today and no one knew the answer. Did some digging online and could not find anything definitive.


texts: What altitude to fly on a STAR when it reads "expect"?

texts:
I just took the instrument knowledge test and one of the questions referred to this STAR. Like many of the questions, there were two right answers and you were supposed to pick the one that was most right.

(airnav)

The question stated that you were cleared for the STELA ONE arrival from the west and asked what altitude you should be at when crossing STELA. My understanding of a clearance for a STAR is that, unless otherwise instructed, you should use both the lateral and vertical guidance on the chart. So at STELA, you should be at 11000'. The notation for expect isn’t applicable unless you were told to fly at a higher altitude when given your clearance. Even then, you wouldn’t descend to 11000' until instructed.

Is my understanding correct, or am I missing something?


texts:
The Dassault Mercure was a French regional jet that first flew in 1971 and received its type certificate in February 1974; it resembled an enlarged, shorter-range 737-200, and was designed to serve higher-capacity short-haul routes.  The Mercure was an abysmal failure, with only eleven aircraft ever sold, all to French domestic carrier Air Inter.  Wikipedia states, citing Dassault’s own website, that the killer was its short range, only 2,080 km (1,125 nmi) with a typical payload, and reducing to 1,700 km (920 nmi) at maximum capacity.

Except... that doesn’t actually explain the Mercure’s failure to sell!

Sure, it didn’t have the range for long transcontinental or transoceanic crossings, but you don’t need that much range to be successful as an airliner, as evidenced by the profits made by regional-jet manufacturers.  The Mercure’s Wikipedia article - citing Dassault - admits as much, even as it makes the claim that the aircraft was doomed by its short range:

  This lack of interest was due to several factors, including the devaluation of the dollar and the oil crisis of the 1970s, but mainly because of the Mercure's operating range – suitable for domestic European operations but unable to sustain longer routes; at maximum payload, the aircraft's range was only 1,700 km.  [emphasis added]

1,700 km is plenty of range for European routes, and there are numerous other markets for high-capacity, short-range aircraft.  Japan, land of the 747 regional jet, comes immediately to mind, along with the other dense areas of East, Southeast, and South Asia and the Middle East.  Even infamously-spread-out North America should have been fertile ground, what with the multitudes of short routes (and even not-so-short ones; the Mercure would have had enough range to comfortably fly between New York and Chicago in a typical passenger configuration, although not in all-up sardine mode) in the northeastern and midwestern United States, eastern Canada, parts of the South, the West Coast, and the Caribbean.  As a point of comparison, the earlier Sud Caravelle - the fourth jetliner to enter revenue service,1 and the first-ever regional jet - had an even shorter range (1,700 km was its maximum range), and it was riotously successful, to the tune of 282 aircraft (some of the very last of these, ironically, going to Air Inter at the very same time they were contemplating the Mercure), despite also having a smaller passenger capacity.

What am I missing?  Why wasn’t the Dassault Mercure successful in the short-haul market?

1: Preceded by the Comet, the Tu-104, and the 707, in that order.


texts: Why is not every airplane equipped with 3 angle-of-attack sensors?

texts:
For critical systems, redundancy is built into the system. It is common knowledge among designers/architects to have three different inputs so in case one is faulty, input from the remaining two can be used to find (and shut off possibly) the faulty one (two against one).

Why is not every airplane equipped with 3 angle-of-attack sensors and triple modular voting when these devices are critical for the safety?


texts: How to find the location of the Aerodynamic centre?

texts:
Everywhere I look I'm only able to find information about airfoils.

How do I find out the location of the Aerodynamic centre of an arbitrary aircraft irrespective of its type or shape?


texts:
Is it fairly common for student glider pilots to have wing tip strikes, especially in gusty cross wind conditions?
I understand gliders are landed level, slow down and then the wing drops onto a wing tip wheel or skid plate when coming to a stop.
Which begs the question, are gliders more prone to wing strikes by student pilots prior to or after landing due to the mono wheel arrangement and low wing tip clearance, or have poor cross wind landing ability in gusty conditions (say 10-15mph gusts above the headwind) when compared to a tail dragger or tricycle wheel arrangement?
Yet thousands of gliders around the world are used every week with the mono wheel arrangement, with a mid wing arrangement that is only 2-3' off the ground.
My gut feeling says no, as gliders have been around probably for 100+ years and they would have changed from mono wheel to a tail dragger, at least on the trainers by now if wing strikes were common among student glider pilots. This is probably due to the lateral stability of a long wingspan and the mid wing arrangement means the glider is landing in a nice stable pillow of air in ground effect.


texts: Under 3rd Class Medical Reform, When Do I Need To See My Doctor?

texts:
Lets say I'm a 35 year old pilot who just had a medical renewed so that it doesn't expire until 2021. 3rd class medical reform (although not law yet) requires that I visit my regular physician once every 4 years.

When do I need to see my doctor?

Anytime prior to the expiration of my 3rd class medical?
Do I surrender my 3rd class medical and go to the doctor immediately (after regulations pass of course)?
Do I go to my doctor in 2020? 2019?
Do I wait until my 3rd class medical expires (or within a month or two)?
4 years after the expiration of my 3rd class medical?

And a bonus question:

Does the 4 year clock start ticking when my medical expires, when regulations are enacted, or some other time?

114th Congress Senate Bill 571 - Pilots Bill of Rights 2


texts: Do most aircraft require a nose-up attitude for level flight?

texts:
I recently saw a picture of a HUD on a commercial plane, and I noticed the nose was level to the horizon but the flight path indicator is almost always under the horizon line no matter the speed, does this mean most commercial jets require a slight nose-up attitude to fly at a level and consistent altitude?
https://c8.alamy.com/comp/PJJCKW/aircraft-heads-up-display-hud-on-a-modern-boeing-787-airliner-PJJCKW.jpg
Similar to that


texts: Helicopter retreating blade stall: Increasing the fwd speed decreases the tip speed on retreating side and angle of attack. So why limit on V_n.e?

texts:
On Retreating side: Speed of wind over blade tip  = blade rotation speed - forward speed.
So, with an increase in forward speed, the speed of the wind over tip is getting reduced. In airflow diagram, this will decrease the angle of attack. So, why is there a limitation on forward speed in form of V_ne?
Let's consider a case where rotor of radius 10m rotating at 300 rpm anti-clockwise and chopper is moving forward at 30m/s. So, now the retreating side has got a larger angle of attack of 15 degrees (critical angle is 17 deg) due to blade flapping down. Blade tip speed being = RPM x radius - forward speed = 314-30 = 284m/s.
"Now" if the helicopter fwd speed increases to 50m/s, then the blade tip speed will decrease to 264m/s. Consequently, the angle of attack should reduce.


texts: Why not leave an electric fuel pump on all the time?

texts:
This question is related to single-engined piston airplanes equipped with an electric fuel pump like the Piper Dakota/Arrow etc. The POH states that the fuel pump should be switched on for takeoffs/landing/approach and maneuvers.

I understand that the fuel pump is a backup system and switching it on provides an extra margin of safety in such situations. My question is, why does the POH recommend that we switch off the fuel pump after reaching a safe altitude (say 1000 ft). Wouldn't it be safer to just leave it on? Is there potential for harm in leaving the electric fuel pump on? Or this is done on common sense grounds: just to save maintenance and prolong the life of the backup system so that it is there when you really need it?


texts: What is the maximum wind speed a Boeing 737-800 can deal with during takeoff and landing?

texts:
I'd like to know how safe the Boeing 737-800 is during takeoff and landing when it's windy. What are the maximum wind speeds for cases of tail, head and cross winds?

EDIT

I've found this resource http://www.b737.org.uk/limitations.htm#Wind_Limits, but I'm quite unable to understand the data:

According to the table (which only shows x-wind data), the max wind speed depends on the so called "braking action", but I don't know what exactly is nor what it depends on.

EDIT 2

The same resource points out the max tailwind speed, as well as other info:


texts: How to know which NVIS Class is used in an aircraft?

texts:
I wonder if NVIS (Night Vision Imaging System) class for a fighter jet is fixed or not?
Is it possible that the pilot can wear any NVG (Night Vision Goggle)?
If I want to find out the NVIS Class that is used in a 1950's and 60's Mirage aircraft then will that be a specific class, for example Green Class A, Class B etc or there is no fixed class and the pilot can use a goggle of any class?
Edit: When we refer to 'Class A, B or C' of a NVIS then is it referring to the 'filter' used in the lighting systems for NVIS compatibility  OR is it referring to the technology used in NVG's (night vision goggles)?


texts: How do you convert true airspeed to indicated airspeed?

texts: Is this something found in the POH? I know there is a IAS and CAS chart.


texts:
How does the debris rejection system in the CFM LEAP engines work?

LEAP - The debris rejection system


texts: What are these small propellers in the A330 MRTT's wings?

texts: In actual flight there are small propellers rotating at the front of these "pillars". What are they? They are visible in this video.


texts:
In the commercial side, who determines the fuel load required for any given flight?

The PIC/Captain? Company/Airline? FBO/Airport?


texts: When was the Speed Trim System implemented on the Boeing 737?

texts:
The Speed Trim System (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust when the autopilot is not engaged.

Was the Speed Trim System implemented on the original Boeing 737 or just the Boeing 737 NG series?


texts: How do pilots in the US identify the circuit (pattern) height?

texts:
In the UK, aerodrome weather information includes not only QNH (the air pressure at mean sea level), but also QFE, the air pressure at runway level. To arrive at an aerodrome, normally one obtains and sets the altimeter to QFE, so that it reads height above aerodrome level. Then if the circuit (traffic pattern) height is 1000 ft (which it usually is), you just read 1000 ft on the altimeter all the way around the circuit; for a standard overhead join it says 2000 ft; and so on. At any aerodrome the altimeter reads the same thing, because you always set QFE.

I've heard that QFE is not used in the US. Do you just have to work out the circuit height in your head by adding 1000 ft to the published aerodrome level? Or are circuit heights given amsl?


texts:
I was thinking, what would happen if the radio systems for an ATC tower fail due to power loss or faulty systems?

Is there any kind of backup radio that would be used to contact the planes and/or any procedures that the planes and ATC would follow?

Edit: And if there is a backup radio, what happens if that fails too?


texts: How can I approach analyzing the basic performance characteristics of an unknown aircraft?

texts:
I am working on a project for one of my classes. My group and I have been given information on an unknown aircraft, and we must find the max velocity, max R/C, max range, and max endurance of the aircraft at sea level assuming max fuel and payload.

We know its max velocity at an altitude of 21500ft, its wing span, platform area, fuel tank capacity, engine fuel flow rate, payload capacity, empty weight, C(Do) and that its airframe is similar to the A-10 Thunderbolt 2. We are having trouble figuring out how to actually calculate these values. We have been able to calculate it's AR, chord, Oswald efficiency factor, and Reynold's number at altitude, but we don't quite know where to go from here.

We think we might have to calculate the velocity at sea level using the $V(alt) = V(SL)\cdot\sqrt{\frac{\rho(SL)}{\rho(alt)}}$ formula or that we might have to try and solve for the angle of attach by assuming that L=W at altitude and solving backward from L=qSC(L). We are basically lost after this point, though.

If anyone could give us a hint on the correct direction to go from here or let us know if we are approach this problem in the correct way that would be much appreciated! We just need a hint, though, because we want to try and figure out as much of this as we can on our own!


texts: What are the regulations and testing that determine whether a "Spins Prohibited" placard is required in an aircraft?

texts: Clearly some flight testing and certification process is used to establish whether or not a type of production GA aircraft is or is not placarded "SPINS PROHIBITED". What type of testing and what results determine the outcome/certification? What does such a result mean for the aircraft's actual performance in a spin/recovery situation? I know spin certification is completed with a recovery parachute mounted to the tail in case of an unrecoverable spin and that an aircraft must recover within 6 turns to be certified (unless you are Cirrus and have a parachute) but what else is there?


texts: Can structural damage be detected or predicted using historical data?

texts:
Can software simulations and structural health monitoring techniques accurately predict damage occurrence in aerospace structures using historical data(stiffness,damping and vibration measurements over a considerable period of time)

or

Are these techniques more suited to real time damage detection rather than damage prediction ?

  For eg. SHM techniques such as parameter estimation using Frequency Response, or Non Destructive Inspection.


texts: What plane is this, appearing in the movie Rampage?

texts: The plane's registration number is barely visible. Unfortunately it's the best quality I could find.


texts: Why does the MiG-15 have a cruciform tail?

texts:
The horizontal stabilizers of the MiG-15 are halfway up the tail. This is called a cruciform tail.

Why did they put them there? Why not a T-tail or the normal tail where the stabilizers are on the fuselage?


texts: How much can falling down due to a stall influence the angle of attack?

texts:
I am trying to understand the af447 incident, more precisely, how a professional pilot having an attitude indicator available failed to understand that the angle of attack was too high. Was it that the angle of attack may be too high at the horizontal attitude, or close to that? As I understand, the aircraft stalled due to pilot error.

Over the longer range it cannot be just a free fall; the air friction would stabilize even a round ball to some stable falling velocity.

Knowing the downward velocity, as well as forward velocity, we can compute the angle of attack for horizontal attitude, and various different attitudes. Seems that if it falls with the same speed as it moves forward, the angle of attack would be 45 degrees just for a normal horizontal orientation. Is this situation realistic?


texts: When does a Maximum Taxi Weight Restriction happen on a 737-800?

texts:
This is the first time I experienced restriction in taxi weight on B737-800. Have you experienced that before? All I know that restrictions will be from MZFW/MTOW/MLW.

When does it happen?


texts: How is Horizontal Visibility and RVR related and how does it affect the Low Visibility Operations?

texts:
So on my foggy landing  the METAR 9 minutes before the touchdown stated Horizontal Visibility as 0000 and RVR 100
whereas the metar 21 minutes after my landing stated Horizontal Visibility 0100 and RVR 750
Now when I landed the visibility was very poor even the runway borderline were blurred by fog for the much part of rolldowm however,I could see around 46 to 50 something meters as per my own research on Google earth based on the markings and taxiway signs I could see presumably from the centreline.
So I wanna know why is the visibility 0000 when I could still see 46ish meters though vaguely but I could see it ?
Also,Does dos horizontal visibility effect the Low visibility procedures ? I mean if RVR is above CAT I conditions however the rest of airport has 100 meter visibility then would it still be Low Visibility procedures or just normal operations ?
Thanks


texts: What causes these losses in this propeller simulation?

texts:
While running a CFD simulation comparison of 2 vs 3 blade propeller versions (48" diameter, 23" pitch, 3570RPM), I've come up with:

2-blade: 347N of static thrust @ 110Nm Torque
3-blade: 220N of static thrust @ 108Nm of Torque

What is the main destructive force seen in the 3-blade propeller particle flow?

Are these "not so tippy" blade tip losses, happening even 60% radius?

The number of particles shown is the same, but in the 3-blade version the same particles are being sucked-back into the flow, which explains the drop in the propeller performance.


texts: In an emergency near a remote island is it better to land resulting in the airport closing or ditch in the water?

texts:
Consider a landing at a remote island (like Easter Island or perhaps one with a calm lagoon, like YLHI) in which the aircraft is likely to crash and close the airport. (For example a gear-up landing at a single-runway airport.) Under these circumstances would it be better to ditch than to attempt the landing at the airport, thus keeping the airport open for emergency aircraft?

If the above question is unanswerable: Has there been advice issued from an aviation safety authority regarding such a scenario?


texts: Why is the magneto drop check done at 1700 RPM?

texts: In our Cessna 152, we carry out the mag drop check at 1700 RPM, following the POH. My question is why it is done at 1700 RPM? What will happen If I check it at 2000 RPM or less than 1700 RPM? And if I do check it at another RPM setting, will the RPM drop get be acceptable, or will it give an incorrect result?


texts:
For what reasons would a pilot want to file a PIREP?

If a pilot wanted to file a PIREP, how would he/she go about filing one?


texts: Is skydiving in IMC (through clouds) legal and safe?

texts:
(1) What are the legal considerations for skydiving into clouds? I see many skydivers did fall into and out clouds in online videos. However, the clouds are mostly scattered or thin-layered. How about in widespread hard-IMC, say OVC 008?

(2) What about maintaining the actual safety? How does a skydiver maintain attitude and stable position in IMC and not disoriented? and separation from other traffic?

EDIT: The legal consideration of my context is within US, but open to legal regulations worldwide.


texts: Why has the 777x been designed with folding wingtips?

texts:
I recently visited the Boeing factory outside Seattle, WA and noted in the distance a new 777x being built with, what looked like very large winglets.

However, on closer inspection they're not - the ends of the wings are designed to fold up.

Source: aviation today

I didn't get a chance to ask our tour guide, so I was wondering if anyone here can explain why this aircraft has been designed with folding wingtips. I'm presuming this is only for ground operations, and my guess is something to do with size - but are they really so big that they need to fold up? I would have imagined that other large wide body jetliners would have similar dimensions.

Please note that I'm not asking about whether this should have winglets, or if winglets provide any benefits, I'm asking specifically why the ends of these wings fold up rather than just fixed as per previous 777 models.


texts: How does an aircraft designer increase dynamic stability?

texts:
This question explains that an aircraft can be statically stable (it will seek to return to equilibrium) but dynamically unstable (the amplitude of the oscillations increase) if there isn't enough damping in the stability equation.
That's fine from a mathematical point of view, but what practical change would increase the damping and dynamic stability?
I've seen quite a few radio-control trainers that are dynamically unstable, and would love to know how to fix the problem so that they're easier for the student pilot to fly.
These planes typically pull out of a dive on their own, but then climb excessively and stall, leading to another dive. Each subsequent stall and dive is more dramatic than the last.


texts: Calculating thrust and required propeller size for a given engine power

texts:
I am looking to build an Airplane, the weight of Airplane will be around 20 to 25 kg and I am going to use a 70cc motorcycle engine as an Airplane engine.

I want to know how I can calculate the engine thrust. The 70cc engine is an air-cooled, four-stroke, single cylinder, OHC petrol engine generating a maximum power of 5.19Ps at 7500 rpm and a maximum torque of 0.519kgm at 5500 rpm.

So will it work as a plane engine or not, and can you give me any rough idea about how much thrust will it produce and how big propeller do I need for this engine.


texts: How do most fighters slow down after landing?

texts: I understand that many fighters use drogue parachutes and wheel brakes. But aren't there other methods of slowing down after touchdown?


texts:
Does anybody know any limitations of flight control weights?
For instance elevators must have same weight? What is the acceptabld difference/limits and what would be the reason of overweighting? (Paint, bushings, repairs etc).
Please consider A320s and B737s for giving example


texts:
How do airliners cross the ocean without GPS?

Do they use dead-reckoning or are there navigation aids floating out there?


texts: What is this strange cutout in Class B of Kansas City International Airport?

texts:
To the Northwest of the KMCI Class B airspace, there is a strange cut out in SFC/80 airspace, which I highlighted at this link (and shown in picture below):

highlighted in purple - Image Source: www.skyvector.com

There's no airport there, and no obvious reason for the cut out.

What possible reasons could there be for a strange shape like this?


texts: How can I convert a frozen ATPL from South Africa to an Iranian one?

texts:
I have got a frozen ATPL license from South Africa and I'm from Iran. I came back home last year and I have converted my CPL/IR license to the Iranian piloting license by doing Air Law and Human Performance exams plus a skill test.

I'm willing to get the frozen ATPL license in Iran but I don't know what the rule is and if I can get it without doing the ATPL exams again.

I checked Annex 1 (Eleventh edition) but there wasn't anything about it.
I assume both countries are following ICAO rules so I would appreciate it if someone helps me to know where or what the rule is.


texts:
I saw an article from the BBC about the Eviation Alice this morning that left me puzzled. The design is a tail wheel tri-motor with the power plants located in a pusher configuration at the wing tips and tail.

The article describes the aircraft thusly:

  "Alice is an unconventional-looking craft: powered by three
  rear-facing pusher-propellers, one in the tail and two
  counter-rotating props at the wingtips to counter the effects of
  drag."

I'm wondering about what drives the configuration of the Alice? What compelling benefits does the configuration offer to balance the challenges it poses:

Controllability in the case of the failure of one of the wing tip power plants - even with the ability to fly (and presumably continue a worst case take off) on only the rear motor - why wouldn't you move the wing mounted engines inboard and have even better "engine" out performance?
Ground clearance and crosswind problems for the tail gear.
Designing a light and efficient wing with tip mounted power plants.

Obviously Eviation thinks that their configuration makes sense, has anybody heard or seen their arguments?


texts: What should the inlet to throat area ratio be for a CD rocket nozzle on an aircraft flying at Mach 10?

texts:
I am analysing a rocket CD (convergent-divergent) nozzle at a altitude of 15,000m. I am stuck on how to calculate the areas so that at the throat of the nozzle Mach number equals to one. The atmospheric parameters at 15,000m I have taken to be:

temperature=216.7k,
P=12,110pa and
speed of sound to be 295.1m/s.

The weight of the hypersonic plane being 164kg, fuel used is hydrogen so gamma=1.4 and R=4.124KJ/kg.k. For the total temperature at the inlet I have to be 2527.039K and assumed the pressure to be 1000kpa.
I want the aircraft to fly at Mach 10. I am really struggling on how to get the inlet area to throat area ratio.


texts: How is it an advantage for the L1011 to not right itself?

texts:
A friend who flew the L1011s loved them because of their stability. His joke was that you could put the plane into a banked turn , go to the bathroom, come back, and you would still be in the same banked turn. He felt that other planes like the 767 require far more concentration.

Quote from Source
Can a pilot explain to me how an aircraft not returning to straight and level flight on it's own decreases workload? Would you not have to correct every small bank error just to not go off course?
Edit Jan Hudec is correct when he says that it may involve s comparison of spiral dive tendency. But

still be in the same *banked" turn. H

Makes me wonder why it doesn't right itself


texts: Does burning fuel to get to your max landing weight violate any regulations?

texts:
Consider a hypothetical situation where where an unexpected tailwind will cause a flight to arrive at its destination above maximum landing weight. After reviewing all reasonable changes to altitude and airspeed, it is clear that on the flight plan route nothing short of a hold or delay vector would allow for a landing within the weight limits.

The SIC suggests including the dispatcher in the decision, and asking for a delay vector or or hold that adds 8 minutes to the flight.

The PIC elects to land overweight, citing a regulation in FAR 121 that precludes any undue delay to burn fuel. Not a specific regulation, just that there is something like this in there.

Is there a regulation in FAR 121 (or any of the other 14 CFR/FAA regulations that govern the flight) that would be violated by adding distance to the route or a hold in order to facilitate additional fuel burn and a landing within the limitations?


texts: How can you navigate "Writing" onto FlightRadar Plans?

texts:
Sorry if the question title here is a bit misleading, the graphic here should explain all:

I read a news story this morning about how a guy flying a Robin DR400 regularly creates inventive patterns in his flight tracks.

Source

The question is, how would the pilot be able to create this writing (and other creative patterns)?  Autopilot instructions?  Watching himself on FlightRadar?


texts: Where do countries under international sanctions find spare parts?

texts:
Some countries are being touched by American or European sanctions. Such sanctions affects the possibility to import spare parts for American-made or European-made aircrafts (e.g. Iranian F14 and Venezuelan F16 or Puma). Yet these countries still have their aircraft flying.
Where do the sanctioned countries find their spare parts?
Do they still follow the required MRO process?


texts: Why aren't departures separated by minimum distance rather than minimum time?

texts:
Normally, two departures are required to be separated by a minimum amount of time depending on the weight class of the aircraft.  However, I was wondering if someone could explain why departure-departure separations are not assigned by a minimum distance instead of a minimum time.  It seems that using a minimum time is potentially more inefficient, especially if the time to reach a safe distance for wake effect purposes is considerably less than the minimum.

As a related question, are there any research projects or articles that someone can point to that talk more about this subject?

Thanks!


texts: Are there advantages to slotted wingtips?

texts:
Are there advantages to the way some birds' wingtips end in separate feathers instead of a more solid shape?

As an example, separate-feathered wingtips:

more solid wingtip:


texts: How can I estimate the minimum runway needed to take off with a hang glider?

texts:
I'm interested in short, or trick, take-offs - such as from platforms, tall trees, etc.

I think that I should have

a wind speed and direction measure
an understanding of my wing surface area

This will let me add to my intuition from regular launches (from sites with known-good launch conditions), and estimate how much velocity I need to add via a run / push.

The methodology to count the wind measure seem a bit more grey, right now.

I can have a sense of the wind where I am, but it may quickly change beyond my launch site.  Since I'm considering how to launch from a stationary position, it would be good to feed my senses / calculations more data like this.


texts:
I want to see if a propeller is bad or good for generating static thrust. This is what I know about the propeller and the engine used to turn it during a test:

Engine shaft power, $P$ = 0.58 hp

Propeller diameter, $D$ = 8.5 ft

Revolutions per minute, $RPM$ = 245

Static thrust, $T$ = 18.75 lbf

Can I calculate the efficiency of the propeller? What is the maximum achievable efficiency?

Additional explanations

The formula I was suggested to use could be exactly what I need. However, using it, I do not get some reported experimental results like:

Engine shaft power, $P$ = 6 hp

Propeller diameter, $D$ = 8.5 ft

Static thrust, $T$ = 66 lbf

Propeller efficiency, $\eta_{prop} \geq 66\%$

Gear efficiency, $\eta_{gears} \geq 85\%$

Doing the calculations: $\eta_{prop} = \sqrt{\frac{T^3}{(P^2 \cdot \pi \cdot \eta_{gears} \cdot \frac{D^2}{2} \cdot \rho )}} = 37.2\%$ which is well below 66%.


texts:
I'm flying VFR circuits at a towered aerodrome, and the circuit is quite busy. With traffic ahead of me to land, the tower calls on the radio and asks me to orbit on downwind. I know it's good airmanship to keep a neat orbit, centred over one point on the ground, but how tight should I make it?

A tight orbit takes up less space (I've known there to be three aircraft all orbiting on downwind at once), but at the same time, it seems like a waste of effort and fuel to be making tight turns the whole time when the point of orbiting is to kill time. A lazy orbit (at say rate 1) would kill time just as effectively while flying at a much more comfortable attitude - and more stable in windy conditions.


texts: When did pilots start making announcements to passengers?

texts: It's common practice now, and maybe required for most airlines. But I don't think that earlier pilots made the same announcements that they do today. When did pilots start making in-flight announcements to passengers? And all the announcements sound the same, is there a standard format for making announcements?


texts:
What are some of the differences between piston engines used in aircraft and automobiles?  It seems aircraft engines are much more expensive, I imagine some of that cost must be due to the more extreme environment (temperature, air density, roll angle) that an aircraft engine is expected to run in.

In particular:

Are aircraft engine parts expected to be less likely to fail?
What is done to allow the engine to function at extreme temperatures / altitudes / air densities?
Do changes have to be made to allow a piston engine to function while upside down (in a roll)?
What components are different on an aircraft vs automotive piston engine (magnetos vs. spark plugs, oil system)?


texts: What is required to 'upgrade' software from DAL C to DAL A?

texts: What are the things to be noted or considered if a software which was initially treated as DAL C and later wanted to be considered as DAL A?


texts: How can I tell apart an Airbus from a Boeing?

texts: When looking at an airplane, what are the main external features I should look at if I want to determine if it is an Airbus or a Boeing (shape of the tail, fuselage, winglets, wings, etc.)? Same questions from a passenger point of view, quietly seated inside?


texts: What is the true meaning of the word “wilco” when used on the radio? What is its origin?

texts: Pilots often learn to use the word "wilco" on the radio through contextual interpretation. During my experience as a pilot communicating on the radio I have often observed pilots using the word "wilco" improperly. What is the true meaning of the word "wilco" and what is its origin?


texts: Why hasn't Boeing updated the 747 with technology from the 787?

texts:
Why hasn't Boeing updated the 747 with technology/designs from the 787 Dreamliner? Surely this would be a very successful aircraft as it could have the best of both designs.

Has Boeing explained why? Are there any reasons this couldn't or shouldn't be done?


texts: What type of hoops do I have to jump through to launch high power rockets?

texts: If I want to launch high power rockets NOT at a NAR or TRA sanctioned launch, assuming I am properly certified, what do I need to do?  I looked in the FAR|AIM, but I couldn't find anything on rockets, but I think the rocketry section has been omitted from the PPT FAR|AIM.


texts: Has research into the aerodynamic properties of non-smooth surfaces suggested any promising directions for future aircraft design?

texts:
As you might gather from Can planes benefit from Mitsubishi's Air Lubrication System? I'm interested in what possibilities there are for radically different approaches to aircraft body surfaces.

Aircraft body surfaces appear to be as smooth as possible, but not all things that fly well are smooth:

golf balls are dimpled (see the very interesting discussion of Is a golf ball surface a good idea for wings or fuselage?)
birds are feathered
sharks have placoid scales (yes, I am aware that sharks don't actually fly through the air...)

Has scientific or industry research indicated useful possibilities in new surfaces for aircraft body skins - or maybe alternatives to skins altogether?


texts: How hard is it to fly with night vision goggles?

texts:
I was talking to a Sheriff's Department helicopter pilot and he was saying they fly around at night with night vision goggles.  I know the military does too.

What are some of the considerations that pilots flying with night vision goggles have to deal with when learning to fly with them?

How long does it take for someone to be certified/trained to fly with night vision goggles?

What is the most difficult part about it? Could civilians do it if they owned the gear?


texts: What are typical control surface deflections?

texts:
How can I tell what a reasonable control surface deflection is?

For example, is a 10 deg aileron deflection reasonable? Or a 0.5 degree aileron deflection? Is that too little? Too much? Same question concerning stab/rudder. I'm  not a pilot, I've never seen these surfaces actually in action, so it's kind of difficult to tell what (roughly) a reasonable surface deflection would be. As I go through flight data, I find myself seeing this type of data a lot, so an idea of what's reasonable would be really useful!


texts: What job opportunities are there for low time pilots in Malaysia?

texts:
Does a new pilot who has just obtained ATPL license has job opportunities?

When I search at pilot job offered on Internet, they mostly required more than 3,500+ flying hours. What I knew about those who obtained ATPL license have flying hours aroun 1500 hours. It mostly includes aviation academy training used turboprop engine plane and they are very light weight. The jobs ads require those pilot who have flown aircraft more than 40,000 lbs.

Will a new pilot get an opportunity to get such a job? How does new pilot get their job under these kind of conditions?


texts: Why are military planes painted differently than civil planes?

texts:
I read Why are planes generally painted white?, and got interested in knowing, why don't military aircraft follow this? Rather than the advantageous white, most of the military aircraft are rather painted pretty darker, green or black or some other color. Why is this done?
Probably, it is not for distinguishing military with civilian aircraft .Becuase, the RADAR knows which aircraft is what.


texts: Is it harder to get a first pilot certificate in a motorglider compared to a normal powered aircraft (near St. Paul, MN.)?

texts:
Is it harder to get a first pilot certificate in a motorglider (glider - self launch) vs. normal powered aircraft near St. Paul, MN.

It seems like a self launch glider certificate would be a great way to start because of better stick and rudder skills, lower age requirements (for my son), cheaper operating costs, glider hours apply toward power aircraft requirements, etc but I'm concerned that it might be a bad path because it appears to be rare and hard to find instruction near St. Paul, MN.


texts: Between a helicopter and an airplane, which requires more power to fly, for a given TOW?

texts:
For the given same mass (say it 400kgs), which one requires more power (in HP) between helicopter and airplane? Say that both are designed maximum (the required material are considered during design) to minimize the required power.

Edit: Question should be like this: Which one is requires more power to lift a helicopter (to make it hover) and to make a fixed wing airplane fly? Not to make them move at the same speed.


texts: Does the F-16's neutral stability also extend to the negative-G flight regime?

texts: If an F-16 pilot pushes the stick forward hard enough to send the aircraft into negative-G flight, does the jet tend to accentuate the new flightpath, requiring the pilot to counter that, or not?


texts: How much do you have to respect checklist order?

texts:
In a fighter aircraft, if the checklist says turn on the radar then turn on the Heads Down Display, and the pilot turns on the HDD first would he be reprimanded for that if it makes no difference?
Is there any leeway in checklist order or are you expected to follow it to the letter? Does it just depend on the organization?


texts: What should be the relative positions of a wing's aerodynamic center and center of gravity?

texts:
A positively cambered wing with finite length L has its aerodynamic center AC located 25% from the wing's leading edge. What about the CG of the wing itself (not the CG of the whole plane)? Is there any recommendation for the wing's CG position along the chord?

What about the position of the AC along the wing's span axis? Should the AC be ideally located halfway at L/2 on the wing? What about the position of the wing's CG relative to AC? Should the CG also be at L/2? Why?


texts: Substitute Suitable RNAV system for Inop Radar on approach “requiring” Radar

texts:
Assuming my aircraft's navigation equipment is a "Qualified/Suitable RNAV System," as defined by AC 90-108, is it legal for me to fly the LDA Y Rwy 19 IAP to DCA  with ATC Radar out of service?

Here is a copy of FAA AC 90-108

Paragraph 7. a. (AC 90-108) states: (emphasis is mine)

  Uses of Suitable RNAV Systems.

  a.  Usage of Suitable RNAV Systems.
   Subject to the operating requirements in this AC,
  operators may use a suitable RNAV system in the following ways.

  (1)  Determine aircraft position relative to or distance from  a VOR (see first note in subparagraph 7b), TACAN, NDB, compass locator (see
     second note in subparagraph 7b), DME  fix; or a named fix defined by
     a VOR radial, TACAN course, NDB bearing, or compass locator  bearing
     intersecting a VOR or Localizer (LOC) course.

  (2)  Navigate to or from  a VOR, TACAN, NDB , or compass locator.

  (3)  Hold  over a VOR, TACAN, NDB, compass locator, or DME fix.

  (4)  Fly  an arc based upon DME.

Here is the approach plate in question:


texts: During an engine restart procedure, what are the purposes of a.) throttle back to idle and b.) primer "in and locked"?

texts:
I was making some study flashcards today for Emergency Procedures in the Cessna 162 POH, and realized that I don't quite understand steps 2 and 6 of the ENGINE FAILURE DURING FLIGHT (Restart Procedures):

  1. Airspeed .................. 70 KIAS (best glide speed)
//2. THROTTLE Control .......... IDLE (pull full out)
  3. CARB HEAT Control Knob .... ON (pull full out)
  4. FUEL SHUTOFF Valve ........ ON (push full in)
  5. MIXTURE Control ........... RICH (if restart has not occurred)
//6. PRIMER (if installed) ..... IN and LOCKED
  7. MAGNETOS Switch ........... BOTH (or START if propeller is stopped)

I think understanding the why behind all of the checklist procedures will help me remember them better.


texts: Why do piston engines have a lower fuel consumption with higher temperatures?

texts:
It is very common to find in the AFM/POH, Section 5 of most piston engine airplanes (C152, C172, PA28, BE76, etc) charts that indicate the fuel consumption for cruise/economy power settings.

You will notice that in all cases, for a given set of pressure altitude, RPM and manifold pressure (if constant speed propeller) the fuel consumption will depend on the OAT. The question is: why does the fuel flow (in PPH or GPH) decrease for higher temperatures?

I should make sense to me that higher temperatures (hot atmosphere) would decrease the overall performance of the engine, as we all know, since the air is less dense which directly impacts in the engine's operation. If the engine's performance is degraded in a hot day, why does it burn less fuel?

All manufacturers publish similar results, but I can't figure out a physical explanation to it. If you could point out an official reference in any textbook I would really appreciate.


texts: How were astronomical observations performed from Concorde?

texts:
In addition to passenger flight and charter flight, Concorde has been used for astronomical observations, including the longest solar eclipse observation on 30th June 1973(PDF) and observation of Halley's Comet on April 1986.

How was Concorde modified for astronomical observations?
How is safety ensured with equipment installed when flying at supersonic speed and at 60,000 feet?


texts: Why is the compressed air (from engine compressors) taken from High Pressure (HP) stage instead of Low Pressure (LP) stage?

texts:
An aircraft that uses Turbofan or Turboprop engines would be taking the compressed air from 3rd stage and 6th stage (varies) and supplying it to the Pressurisation and Air Conditioning Kit (PACK). This air is cooled, filtered, and then supplied to the Fdeck, FWD and AFT cargo zones for temperature control and breathing. If my understanding is correct, PACK is a kind of compressor itself which cools the bleed air for circulation purposes.

Because the engine has got LP and HP stages (i.e compressors), why can't the engine send the LP stage air into PACK just for filtering? Because LP air is surely cool air which I understand still requires filtering. Without knowing further , it surely saves a lot of effort for installing more compressors and therefore, creating a more complex pneumatic system. Has this not been done or is there something I am missing?

KR,


texts: Do two of the same model of aircraft feel different to fly?

texts:
How does it feel when you change from an aircraft to another but of the same model?

Sometimes when you change a car and drive another one of exactly the same model you do feel differences due to various factors like wear and tear, mileage, different service schedules etc.

Does this apply also to aircraft or are they exactly the same?


texts: How is tire rubber removed from the runway?

texts:
Every time an aircraft touches down, the tires are spun up rapidly. As a result, some rubber is left at the touchdown zone.

(image source)

As time goes on, more rubber is accumulated at the touchdown zone. How is this rubber removed from the runway surface?


texts: What's the minimum legal height in Europe for a low pass at an airport?

texts:
Does anyone know in which document I can find the legal minimum height for a low pass at an airport, assuming the pass has been approved by ATC? I have been discussing this topic a lot with several flight instructors but we haven't found any official document where a specified height is set.

I'd like to know about EASA regulations if possible, but FAA or others are also appreciated.


texts: What happens if an aircraft's hydraulic system starts leaking during a flight?

texts: What will happen if hydraulic fluid starts leaking during a flight? What will happen to the overall performance of the flight, and how will the pilot compensate for the loss of the system?


texts: Who applies an airworthiness directive when the airframe is newer than the AD?

texts: For example, an AD was issued in 1990 while the aircraft was manufactured in 2002? Who applies the AD, the manufacturer or the owner?


texts: Will there be dynamic or variable separation minima in future?

texts:
In the future, is it possible to apply in the same airspace different separations between pairs of aircraft? Depending on the relative speed, navigation capacity of the aircraft, intersection geometry, etc.

What will be necessary to be able implement this type of separation?


texts: Difference between ETA and On-Block time?

texts:
I see that the definition of the ETA (Estimated Time of Arrival) according to Eurocontrol is:

(SESAR) the time computed by the FMS for the flight arriving at a point related to the destination airport
(ICAO) For IFR flights, the time at which it is estimated that the aircraft will arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigation aid is associated with the aerodrome, the time at which the aircraft will arrive over the aerodrome.

For VFR flights, the time at which it is estimated that the aircraft will arrive over the aerodrome.

However I do not understand what is the difference with the Estimated On-Block time.
Would you be able to explain the difference please?


texts: Is there a new "best practices" technique for demonstrating stall recovery?

texts:
This is a question that is probably best suited for active flight instructors. I was doing an FBO checkout and the CFI asked me to demonstrate power on and power off stall recoveries, but well before the stall he asked me to recover. His explanation is that it is the new best practices for teaching and demonstrating stalls to recover "before" the aircraft actually stalls. In essence, the recovery demonstrations consisted of setting up the plane for landing and take-off config, and slowing it down till the stall warning came on, then almost immediately "recovering." It seems too easy. However, his reasoning made sense, but I have never heard it before:

It prevents new pilots from getting comfortable flying with the stall warning buzzing.
It teaches pilots to avoid the stall in the first place. (Prevention)
Its safer.

While his points are all factually correct, I think this defeats the purpose of knowing how to recover from a stall.

Any current CFIs out there that can explain if this is a new "best practice" for demonstrating stall recovery?


texts: What’s the difference between a tail number and a Manufacturer's Serial Number?

texts: What’s the difference between a tail number and a Manufacturer's Serial Number (MSN)? How and when are they generated?


texts: How difficult is it to avoid ground loop in practice?

texts:
In my simulator (flightgear) directional control during take-off of most tail-draggers is extremely difficult. When the tail lifts off, it immediately starts to turn to the left with no crosswind, but with sufficiently strong crosswind from the right it might be to the right. It takes very swift and hard rudder application to arrest and then easing the pressure to avoid overcontrolling. Otherwise the turn rate keeps increasing and ground loop occurs.

It is worse with some models than others. Some models are almost impossible to take off at full or normal take-off power and while most are, it is very difficult to keep them on the runway, because even if I manage to arrest the initial swerve, the aircraft is then turned a bit and attempts to re-align it tend to again provoke ground loop.

Controlling propeller aircraft with tricycle landing gear is on the other hand never difficult, even for the more powerful ones.

I suppose some of the models are wrong. For example the Pitts S1C model is almost impossible to take off. But how difficult should it really be to keep the plane aligned?

And, what would likely be wrong with model that is too difficult to control? Centre of gravity too far aft of the mail landing gear? Or something with the vertical stabilizer? There does not appear to be any parameter for vorticity of the propeller slip stream; it is apparently calculated from the power.

Or is this one of the cases where simulator is much more difficult than the real thing, because in the real thing you have force feedback and get to use your built-in accelerometer (vestibular system) and in the simulator you don't?


texts:
I have a rather easy(?) question. Why is VHF radio still the main communication method between the ATC and pilot?
Is it because there is no better solution at the moment?

Best regards


texts: How can the zero-lift drag coefficient (parasitic drag) be calculated?

texts:
Consider a 3-D wing made from an arbitrary airfoil, say a NACA0012 airfoil. The wing has a trapezoidal shape, with a fixed span, root chord, and tip chord. Also, assume that the wing loading is known as well. I am trying to calculate the speed at minimum drag of this wing (assume that there are no other parts of the aircraft, just the wing!) My thought process is as follows:

We know that, to a reasonable degree of accuracy, that there are two types of drag on the wing in steady, level, flight: parasitic drag and lift-induced drag. This can be shown mathematically as:

$$ C_D = C_{D_0} + C_{D_i} = C_{D_0} + \frac{C_L^2}{\pi e AR}$$

Also, assume that the AR and efficiency factor are known. Now, for minimum drag to occur, there has to me a maximum lift to drag ratio. The formula for drag is

$$ D = \frac{1}{2} \rho V^2 S C_D = \frac{1}{2} \rho V^2 S \Big(C_{D_0} + \frac{C_L^2}{\pi e AR}\Big) = \frac{1}{2} \rho V^2 S C_{D_0} + \frac{\rho V^2 S}{2\pi e AR} C_L^2$$

Lift has a similar formula to drag, and in steady, level flight, is equal to the weight of the aircraft. Lift is related to the lift coefficient as $L = \frac{1}{2} \rho V^2 S C_L$. So we solve for the lift coefficient as follows.

$$ C_L = \frac{2L}{\rho V^2 S} = \frac{2W}{\rho V^2 S}$$.

Plugging into our original formula, we obtain

$$ D = \frac{1}{2} \rho V^2 S C_{D_0} + \frac{\rho V^2 S}{2\pi e AR} \cdot \frac{4W^2}{\rho^2 V^4 S^2} = \frac{1}{2} \rho S C_{D_0} V^2  + \frac{2W^2}{\pi e AR \rho S}\frac{1}{V^2}$$

This is great for us, because now we have a relationship between drag and lift, and to find the speed at minimum drag, all we have to do is take the derivative and set it equal to 0. I've done this and the resulting answer comes out to be

$$V_{md} = \Bigg( \frac{4W^2}{\rho^2 S^2 \pi e AR C_{D_0}} \Bigg)^{1/4},$$
where the 'md' stands for minimum drag. My problem arises because I cannot for the life of me figure out how to analytically calculate $C_{D_0}$. It can also be shown that at minimum drag, $C_{D_0} = C_{D_i}$ so that the total drag coefficient becomes $C_D \equiv C_{D_0} + C_{D_i} = 2C_{D_i} = \frac{2C_L^2}{\pi e AR}$, but then we are back to our starting point, which confuses me again.

My last resort was to read some papers that said that there is a method to finding $C_{D_0}$ using the skin friction coefficient, because at subsonic speeds, a large part of the parasitic drag is due to skin friction (and a little due to pressure drag). Anyways, this led me to the formula $C_{D_0} = C_{fe}\frac{S_{wetted}}{S_{ref}},$ where you use an equivalent skin friction and wetted area. Now I don't understand what a wetted surface area is, since in this example we are only dealing with one wing (would it just be twice the regular area??) As you can see, I am greatly confused. How do you find this zero-lift drag, and subsequently the minimum flight speed.


texts: Could a plane land inside or on top of another plane in flight?

texts: I'm sorry if this is a little fantastical, but I'm just wondering if this type of maneuver is possible in any way. I understand if this question gets pulled. I'm trying to make a little action-animation-cgi and just wondering if this was ever a last-resort option for maybe two planes, maybe one is a bit larger than the other but maybe similar speeds could be maintained for the one plane that is running out of fuel could latch-on somehow.


texts: How do the flight decks work in unison on the Stratolaunch?

texts:
This article implies that the Stratolaunch has two flight decks. How are the dual flight decks arranged on the Stratolaunch aircraft?

I'm curious if things are fly by wire or if there are separate controls?
Are the flight decks both fully operational and mirror images of each other?
If there are duplicate switches and controls, how do the counterparts reflect changes initiated from the cross side?


texts: What is “Weather and Chaff” information provided to pilots by ATC?

texts:
This one appears in an entry under "Additional Services" in the FAA Pilot/Controller Glossary and claims that ATC provides a wide range of additional services to pilots, including "Weather and Chaff" information, which seems like an unusual entry.  What does "chaff" mean in this context?
Originally chaff was the remains of a wheat plant cut down and with the grains in the head thrashed out, which is then discarded.  It's also a biblical reference to the wicked condemned by God to hell i.e. "the chaff, which the wind driveth away".  In modern times, it is associated with a physical countermeasure to radar whereby thousands of metallic strips are ejected out of an aircraft to confuse enemy radars or break the track of radar guided anti aircraft weapons.  I though the phrase in the P/CG might have been a reference to some sort of anachronistic term about the environment which was termed "chaff" but I don't know.  I did locate this story from NOAA's website where their weather radar in Louisville, KY, was spoofed by military chaff which had been dispersed during nearby training exercises.  This gives though to another risk of an aircraft flying through a cloud of chaff and ingesting it into the engines, or causing some other kind of system damage.  This would seem to be a remote possibility but who knows.  Anybody know what the P/CG meant by chaff in this reference.


texts: How are the navaids that are on the airport ground powered?

texts: How are navaids (such as the ILS localizer) that are on the airport ground powered? Are they connected to the airport's power? Do they have their own backup power?


texts: Do vertical stabilizers create vortices like wingtips do?

texts:
On a wing, a wing tip vortex is unavoidable no matter what configuration you use, but does a vertical stabilizer form a wing tip vortex? I noticed this picture and saw two vortices coming off of the vertical stabilizers, so was this a result of moving the rudder or does the vertical stabilizer generate lift just like an aircraft wing?

Source


texts: In Vmc situation (minimum speed where pilot can maintain altitude), How can pilot figure out the Vmc? And also, why critical altitude is important to know?


texts: Can an airline schedule two same-number flights to leave the same airport on the same day?

texts:
I've read: Why have different flights with the same flight number?
and I guess I understand this can make sense. But - is it allowed for a domestic US airline to schedule two flights with the same number, on the same day, with intersecting routes? Specifically, which have legs scheduled to fly out from the same airport on the same day?
This would be potentially quite confusing for passengers, even if the departure times are spaced many hours apart.
Motivation: I'm seeing what seem to be records of this occurring a few times in a USDT flight data table. Concrete example (edit: this is a significant example, but the question is about the general case) - some US airways flight legs from 2006:

uniquecarrier
flightdate
flightnum
origin
dest
crsdeptime
crsarrtime
tailnum
deptime
arrtime
cancelled

US
2006-01-25
634
LAS
PHL
645
1416
N632AU
642
1407
false

US
2006-01-25
634
LAS
PIT
2257
607
N808AW
2252
556
false

US
2006-01-26
634
LAS
PHL
645
1416
N621AU
650
1428
false

US
2006-01-26
634
LAS
PIT
2257
607
N833AW
2303
603
false

US
2006-01-27
634
LAS
PHL
645
1416
N633AU
643
1404
false

US
2006-01-27
634
LAS
PIT
2257
607
N832AW
2249
545
false

US
2006-01-28
634
LAS
PHL
645
1416
N629AU
645
1404
false

US
2006-01-28
634
LAS
PIT
2257
607
N806AW
2256
544
false

US
2006-01-29
634
LAS
PHL
645
1416
N602AU
640
1409
false

US
2006-01-29
634
LAS
PIT
2257
607
N827AW
2256
602
false

US
2006-01-30
634
LAS
PHL
645
1416
N632AU
641
1422
false

US
2006-01-30
634
LAS
PIT
2257
607
N801AW
2250
536
false

US
2006-01-31
634
LAS
PHL
645
1416
null
null
null
true

US
2006-02-01
634
LAS
PHL
645
1416
N628AU
652
1420
false

US
2006-02-01
634
LAS
PIT
2257
607
N810AW
2300
549
false


texts: How does banner tow attach and release work?

texts:
Planes can sometimes be seen towing banners around large cities or events.

How is the banner attached for takeoff?

How does the plane land after towing a banner?


texts: Which aircraft maintenance repairs require a test flight?

texts:
14 CFR 91.407 requires an "Operational Check Flight" of an aircraft before passengers may be carried in certain situations:

  §91.407   Operation after maintenance, preventive maintenance,
  rebuilding, or alteration.

  ...

  (b) No person may carry any person (other than crewmembers) in an
  aircraft that has been maintained, rebuilt, or altered in a manner
  that may have appreciably changed its flight characteristics or
  substantially affected its operation in flight until an appropriately
  rated pilot with at least a private pilot certificate flies the
  aircraft, makes an operational check of the maintenance performed or
  alteration made, and logs the flight in the aircraft records.

  ...

Does the FAA have any guidance that includes examples which better explain the bolded section from the regulation? It seems like that could be open to interpretation which could lead to different people having different ideas about when an operational check is required.

For example, is one required for routine maintenance like an engine change or prop change?  What about a flight control change or a flap change?  A new paint job (including the flight controls)?