texts:
Why did the Bede Bd5 have strakes on the horizontal tail?

Is it a sexy way of adding horizontal tail volume or reducing the span of the horizontal tail by increasing it's chord?


texts: Can the dome gunner on a B-17 Flying Fortress shoot the plane's tail off?

texts:
I was at the California Capital Airshow on Mather AFB over the weekend, and came across a beautifully maintained B-17 Flying Fortress. The crew were kind enough to allow people to go inside and take a look - what a magnificent machine!

While inside, I noticed the dome gunner seems to be in a position to accidentally shoot the tail off the plane!

Are there any confirmed instances of this happening? Was there some way to prevent it - either be it training or some mechanism that stopped the guns while in this position? I can imagine, in the heat of battle, sweeping an enemy fighter and nicking your own tail in the process!


texts: Will Lockheed Martin Flight Services send me ACAS, EasyActivate™, and other text messages if I file my flight plan through ForeFlight Mobile?

texts:
ForeFlight Mobile users who file flight plans without being authenticated to CSC DUATS will effectively file through Lockheed Martin Flight Services (LMFS).
Considering that the LMFS route does not require my personal  1800wxbrief.com credentials (unlike filing through CSC DUATS), will additional services connected to my LMFS profile such as Adverse Condition Alerting Service (ACAS), EasyActivate™/EasyClose™, Close Reminders, ATC Notices, and Surveillance Enhanced Search and Rescue (SE-SAR) be accessible through my mobile phone?
In other words, will Lockheed associate my ForeFlight flight plan with my LMFS profile in order to send me text messages with information about TFRs, links to open and close flight plans, and so on?


texts: Does the wing to fuselage fittings of an airplane ever experience shear load?

texts: Do wing attach fittings of semi-cantilevered plane (i.e. ultralights) ever get subjected to shear force? For example during roll, does the centrifugal force of the wings load the wing attach fittings with shear?


texts: What happens if a student busts Dallas Fort Worth bravo airspace?

texts:
What would happen if a student busts a corner, exceeds the floor of Bravo airspace by 500 feet then descends after one minute?

The pilot is on the frequency of a Golf airport heading towards a Delta controlled airspace, both within the Bravo 30 nm veil.

Does the Bravo tower have a way of knowing the aircraft involved?


texts: What system is there in the UK to prevent collisions between small aircraft?

texts:
I met someone the other day who owns a small plane and he was going to fly from Cambridge to the Isle of Wight.  I asked him whether he had to file a flight plan and he said no.

Just wondering therefore how such collisions are prevented?


texts:
I have been trying to understand how a PESA radar works. Essentially, it uses one signal that is electronically delayed. How is the reception coordinated and known by the receiver?

I am interested in understanding the logic behind in delay of signal and reception/identification.


texts: How are lavatory smoke detectors connected to the flight deck?

texts: How are the smoke detectors in aircraft lavatories connected to the flight deck so the crew there can see the warning alarm? Do they have wires all the way from the lavatory to the flight deck, or are they connected in some other way?


texts: What are the limits to lateral Centre of Gravity imbalances?

texts:
I've never seen lateral CG limits prescribed for aircraft (though I have very imited experience in this realm).  Presumably, aircraft are designed to keep the center of balance as close as possible to center of lift, with any imbalances are far more likely to occur fore to aft than side to side.

But, for instance, what if fuel only drained from one wing during flight?  How much of an imbalance would this create?

Are there on-board systems in general aviation to prevent this?

What are the effects of a lateral imbalance on handling, and how could pilots compensate, if possible?

Edit 1: Please do not restrict your answers to fuel loads.  Is there a percentage-based (e.g. greater than X % aircraft total wingspan) or positional-based (e.g. lateral CG moved outside of the fuselage) DNE from an engineering standpoint?

Edit 2:

Also seeking design input, considering experimental and purpose-built aircraft such as White Knight Two exist.

I also note that despite the larger cargo volume of the Airbus Beluga, it cannot carry near as much weight as the smaller-volume C-5 Galaxy.  Is this a benefit of the C-5's design in placing the wings above the fuselage or is there such a thing as vertical CG limits?


texts: Why are turbofan inlets circular- or oval-shaped instead of square-shaped?

texts:
Source: materialsengineeringconsultant.com and initious.blogspot.com.

Most of the engines are circular except for some that are oval. The oval shape provides a better ground clearance.

Why aren't the intakes square-shaped? Is there some aerodynamic reason for the circular / oval intake shape?


texts: Does the A-10 Thunderbolt fly without the GAU-8?

texts: Has the A-10 Thunderbolt ever flown without the GAU-8? Can it be done with a ballast in place of the gun? I'm not referring only to the combat role of the A-10, a plane used for training or a ferry flight would also qualify.


texts: Is passenger weight distribution important on a commercial flight?

texts:
This is something I've wondered about for a long time.  On really large airplanes, like a 747-400 or A380 for example, I would assume that the weight of the passengers on board is a significant to the flight characteristics of the plane. And it seems like it would be pretty easy to put all the passengers in an odd place (like all at the front or back) and as a result significantly change the flight characteristics of an aircraft.

So, assuming I'm right (tell me if I'm not), how do commercial aircraft counter this problem? Do they do their best to distribute passengers throughout the craft with seat assignments? Or do they have ballast they can move around (like fuel ballast)?  Or is the weight shift not significant enough to warrant anything along these lines?


texts: What happens if a language other than English is used over the radio?

texts:
In many non-English speaking countries, communication with ATC may be conducted either in English or the native language. Famous examples are China, Russia, France and possibly Germany.

When a pilot who is a non-speaker of the native language hears such communication, which is he to do? Just sit back with no idea of what is going on?


texts: What are these two holes on the forward fuselage of a Boeing 747?

texts:
Does anyone know what are the two holes are on the Boeing 747, on the left forward part of the fuselage?

Source: airliners.net

I guess the right hole is the E/E compartment smoke override valve, is that correct?

Another hole under the belly just before pack inlet:

What is the function or name of this one?


texts: Where can I find articles about Handley Page multi element segmented airfoils?

texts: Can anyone direct me to a source containing the complete article on Handley Page's 6 and 8 element airfoils from Flight magazine Feb 24, 1921 (PDF) or further more detailed information on this subject.


texts: Why does aircraft stability increase when it transitions from subsonic to supersonic flight?

texts:
I am puzzled why would the aircraft be more stable at high speed flight at high altitudes. Given that the Centre or Pressure moves gradually towards the 50% MAC region, once past Mcrit.

Has this got to do with moments and the neutral point?


texts: Is a French PAC skydiving license equivalent to an AFF license?

texts: I am planning to do a skydiving course and I was thinking of doing the course in France. That means, I would get a stage PAC license course instead of AFF. I want to know how PAC is different from AFF (previously I have only heard of AFF) and can I use the PAC license to skydive anywhere in the world?


texts: Is the Falling Leaf maneuver used for UAV recovery?

texts:
The Falling Leaf maneuver is a way to lose altitude by descending like a tree leaf. Is this maneuver used in the recovery of UAVs?

Source.


texts:
Droops are deployed on the leading edge of a wing of an aircraft, and they work by changing the camber of the wing.

How do they help in delaying stall?


texts:
My flight (in Spain) was delayed for 6h and after I submitted the claim the airline worker answered me that it was delayed due to KALP114A regulations imposed by ATC, but I didn't find any info, that such regulation even exists.

  the regulation KALP114A, which caused delay, was introduced directly on the flight by Air Traffic Controllers

The flight was on the 14th of April, 2019, from Spain to Germany.


texts: To what FAA office or personnel should one direct an inquiry about the reasons behind the airspace design at a particular airport?

texts:
The airspace design process is extremely complex.  See for example this FAA document, Order 7400.2M.

To what FAA office or personnel should one direct an inquiry about the reasons behind the design of the airspace around one particular airport?

I'm seeking real-world, practical insight as to why the unusual airspace configuration we see at KACV and KTVL was selected, over the common configuration that we see for example at KONP and KCEC.

I'm specifically seeking information about why the airspace was designed that way, not about how it is being handled now in actual practice by ARTCC etc.

These two airspaces are rather unusual and it's unlikely that a satisfactory answer will be obtained just by perusing the FAA documents giving general guidance on how to design airspace to handle existing/ proposed instrument procedures, etc.

However any kind of actual "paper trail" relating to the design of the airspace at these two particular airports could possibly be helpful, if it were not too "dense" to interpret -- how might that be obtained?

But I'd prefer to speak to an actual person, if he/she had some relevant insight on the design process for the airspace at either of these airports.

Although guidance concerning my specific case is most welcome, also I'm seeking an answer crafted in such a way as to be helpful to anyone seeking  to answer a similar question for any airport in any region of the nation-- how to go about locating an appropriate person or FAA office to direct such a query toward?


texts: Is hypersonic flight possible with a Busemann's Biplane?

texts:
The modifications to the Busemann's Biplane design reported in this article have proven that it is possible to design a modified Busemann's Biplane wing design that actually produces lift at supersonic speeds. Is it then possible to fly the same plane at hypersonic speeds of say Mach 10 (and ground speeds of above 10,000 km/h)? What are the other technical limitations?

The engines can achieve it and the air frame could be cooled, is noise once again an impediment at those speeds? Are there any effects on the human body for flying that fast given gradual acceleration? What about fuel, is it fuel efficient? Do we have a type of fuel that could power today's engine designs at those speeds given the complexities of using hydrogen?


texts: Is there any non-experimental way to obtain CL, CD, and CM as a function of the angle of attack and the control surface deflection angle?

texts:
I am working on a flight simulator for control algorithm testing. The issue I am facing is to come up with a relationship between CL/CD/CM and the angle of attack ($\alpha$) and the control surface deflection angle ($\delta$).

Since I'm developing a control algorithm for a flying wing, it is crucial to know how not only $\alpha$ but also $\delta$ affect the forces and moments on my flight vehicle. And I cannot afford to measure the forces and moments experimentally.

In the Gazebo simulator, the LiftDragPlugin's approach is to assume that the lift curve shifts up and down by $\delta$ times some constant. However, that is not the case, as can be seen from the numerical results from XFLR5 below.

Where “Plane Name $\pm\delta$” describes the curve for any $\delta$.

We can see that the curve shifts in both direction from zero-$\delta$ position. For instance, the stall angle decreases as $\delta$ increases.

My current approach is to construct a three-dimensional lookup table by using the curves at $-\delta$ and $+\delta$ as endpoints and linearly interpolate the two curves along the z-axis. When I need the aerodynamic parameter (CL, CD, or CM) at some $\alpha_0$ and $\delta_0$, I can just locate the point in this three-dimensional space from $\alpha_0$ and $\delta_0$.

Is this a valid way to determine CL/CD/CM as a function of $\alpha$ and $\delta$ numerically? If not, how should I approach this problem?


texts: Why did the CAA not use Monarch aircraft to repatriate stranded Monarch passengers?

texts:
This week Monarch airlines went bust, leaving hundreds of thousands of passengers stranded abroad.

The CAA has been secretly planning for some weeks a repatriation 'airlift' in case the airline folded. Apparently they are chartering 30 or so planes from airlines including Qatar Airways for this.

Since Monarch is now bust, all the Monarch aircraft are sitting idle on the tarmac. Why not use those planes to repatriate people? Surely, it would be a lot cheaper and easier than chartering a whole bunch of other aircraft. They could even use the Monarch crews, who are all now unemployed, after all.


texts: Can I model propellers used in electric aircraft the same way as I model RC quadcopter drones?

texts:
I am writing an article about mathematically modelling a flying car, using D'Alembert's principle. I need some information about the propellers ... When I worked with the mathematical model of a small RC quadcopter I found that many researchers consider the thrust of the propeller proportional with the square of its angular velocity and the same for the torque of the propeller. I am interested in something similar for the bigger propellers ... Is the assumption still holding? Can someone give some numerical values for the constants? The flying car (VTOL vehicle) I am modelling has six propellers, therefore I need less then 1000 N of thrust for each propeller. Therefore my first question is: Is it ok to say

$F = a \cdot \omega^2$
$T = b \cdot \omega^2$ for big propellers? $F$ is the thrust of the propeller along its axis, and $T$ is the torques developed by the motor to rotate the propeller. Please give some examples of commercial products ... if possible. Thank you!


texts: How does VFR work in countries other than USA? What does hi and lo mean?

texts:
I saw that at https://skyvector.com/ the VFR sectional charts were available for the USA only. Do other countries use the same format for sectional charts?

Additionally What does Lo and Hi mean at this website?


texts: Is there a minimum weight requirement for an commercial aircraft?

texts: For an aircraft to be approved for commercial usage (like Boeing 747s or Airbus 320s), is there any minimum weight requirements, just the aircraft (without passengers and crew).


texts: Is it mandatory to go missed following full scale CDI deflection?

texts:
In the USA, AIM 5-5-5 paragraph a1 specifies when a missed approach is required. I have also heard that a missed approach is required if the aircraft reaches full scale CDI deflection on a localizer course (this old CFI test standards doc from 2001 says it’s recommended in paragraph b).
Where is this requirement written? Is it true for all types of approaches, or only ILS and LOC?


texts: How comes lift is less than weight on take-off?

texts:
If $$lift=weight * cos(angle)$$ this means that lift is less than weight during takeoff.

Could someone please explain me why it is so


texts: What safety features prevent jets sucking in ground staff or equipment?

texts: There have been some gruesome deaths involving ground staff being sucked into jet engines, presumably because the engine thrust was set well above idle. Are there safety features (besides prudence on the flight deck) that are designed to mitigate this risk?


texts: What is this loose object above the flap fairing?

texts:
During my flight, I noticed a loose object above one of the flap fairings. You can see it in this video: https://imgur.com/wCPSEem.

Is it normal or should I notify the airline?

People pointed out to a similar question, but A) I'm not sure it's the same rubber; B) it's a different airplane model, C) the behavior of that rubber (if my footage shows a rubber indeed) is not the same, D) the other question asked what that rubber is, whereas my question is specifically about it being loose. I'm no aviation expert nor an engineer, but it doesn't feel right to me that it's loose.


texts: Does electrical usage contribute to fuel consumption?

texts:
I know that while in-flight the electricity is produced by the engines.

What happens if every possible system requiring electricity is in the on state? This should require extra electricity.

Does this usage of electricity increase the fuel consumption by any means?

*Edit to include the additional question from the comments section:

Given that the engines require fuel to produce electricity how big is the impact on fuel consumption, speaking of "mainstream" airliners like the A320?


texts: Why do delta wings generate less lift at a particular angle of attack compared to straight wings?

texts: I simulated a delta wing and a straight wing in xflr5 with the same profile, wing area and airspeed (very low airspeed. around 10 m/s. it's for a model aircraft). The straight wing was operating at nearly the lift coefficient of the 2d airfoil at a particular angle of attack, but the delta wing was operating at a lift coefficient far below the 2d airfoil coefficient. Why is this so? The wing has a medium sweep of 25 degrees. Will the lift improve with a higher sweep angle?


texts: What is the aerodynamic purpose of an Acorn?

texts: This is an IL-62. On the tail of the aircraft,  there is a large cone, protruding out of the vertical and horizontal stabilizer which is called acorn. I am trying to figure out what is the aerodynamic explanation for its presence over there.


texts: Is high propeller pitch inherently inefficient?

texts:
For an airfoil, in general, the aerodynamic force is more or less perpendicular to the chord line.
A low-pitched propeller blade has it's chord line more perpendicular to the direction of flight, therefore, more of the force acting on it can have a greater component parallel to the direction of notion, and less perpendicular. If this force is acting forward, then this is efficient. But this may not be possible at high speeds and low rotation velocities. Thus:
A high-pitched blade has it's chord line more parallel to the direction of flight than the above. Therefore, the aerodynamic force acting on it is likely to have a greater component perpendicular and lesser component parallel to the direction of motion. This is always inefficient.
The above manifests itself in the higher-pitched propeller producing more energetic swirl than the lower pitched propeller.
So my conclusion would be that all else being equal, high-pitched propellers are inherently inefficient. Is this correct? Is this what is observed in practice?


texts: Why do airplanes not have manual transmission?

texts:
I have limited experience with flight simulators but I have never bumped into a plane with manual transmission while, on the contrary, it's very common for other means of transportation (like cars and bikes) that rely on engine with some form of transmission control.

First of all, I'd like to know if it's actually true that no airplane have (or had) manual transmission and, secondly, why that is so.


texts: Why do gusts change the airspeed during landing, but turning (which changes where the wind is coming from) does not?

texts:
As we know it, aircraft are extremely sensitive to gust during its final landing stage. They can lose airspeed if the wind changes to tail, ad thus loose lift or need to adjust their thrust in order o regain the lost speed. On the other side, the opposite happens when encountering a headwind.

On the contrary, we don't take that into account when we consider a fighter jet. When a jet fly's at 20,000 with headwind of 50 knots, turns 90 degrees to the left and has the wind from the right- is it considered to be a change in wind direction or because the whole system is moving along with the plane and the change is more gradual- the aircraft feels no change in actual lift which is derived from the true speed it feels?


texts: Where can I find canonical examples of radio communications at non-towered airports?

texts: I'm trying to find any canonical examples of radio communication patterns at non-towered airports. The FAR/AIM has very little in terms of sample announcements, etc. The AC-90-66B (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-66B.pdf) doesn't offer much either. The best resource I could find so far is the "Say Again, Please" book by Bob Gardner, but I'm trying to find the guidelines from the "FAA's mouth."


texts:
Why are there curved propellers on some aircraft, what is there advantage?

If these are worthwhile advantages why aren't there curved blades on turbo fans?


texts: I've noticed that there isn't any type of hatch/plug door near the canopy of the B-1B Lancer. How do pilots enter and exit the aircraft?


texts: Can lasers be used for weather detection along an aircraft's flight path?

texts:
Aircraft use RADAR for weather detection such as storm clouds, rain, etc. Why don't they use LASER instead to measure the density of the weather ahead?

RADAR has been known to return false signals of weather ahead (i.e. clear cloud, low density).

Would LASER be a more accurate application as LASER has been used in many other areas such as measuring terrain topography, density of some materials, temperature, etc.

P.S  Please forgive my ignorance if this technology is already in use for this application.


texts: Will 1090 Mhz band become too congested in the future?

texts:
1090 Mhz is currently used for SSR Mode A/C replies and Mode S communication(ELS-EHS replies and ADS-B broadcasts) by civilian aircraft and some of military IFF modes.

With the infamous 2020 ADS-B Mandate about ADS-B usage in certain airspaces(Mandate) , it is expected that this frequency will be very crowded in future.

There are certain methods/precautions to prevent congestion like randomized broadcast timing(between 0.4 s and 0.6 s for Airborne Position for example). F.R.U.I.T. and garble problems are also not new to this frequency.

Are there any discussions in the aviation circles about precautions in anticipation to congested 1090 Mhz band for certain airspaces?


texts: How are composite aircraft canopies constructed that sit flush with the fuselage?

texts: More specifically, how is the composite frame of the canopy manufactured? Attached picture as an example.


texts: What is the difference between RNAV and RNP?  I know that RNAV doesn't need monitoring and alerting, but RNP does.


texts: Are airliner flight plans/routes preset?

texts:
KLM has 3 flights daily from BLQ to AMS.

How do all of the crews handle the flight plans? Do the make a plan for every flight every day or do they have a database in which preset and stored flight plans are available and are ready to be extracted?


texts: Which modern day prop (piston) engines allow for inverted flight?

texts: A buddy of mine is looking to buy an airplane with an old radial engine because he says radial engines can fly inverted in aerobatic flying.  What modern day engines (engines that you can buy today), are capable of flying in inverted flight?


texts: Why am I not getting the "TO" VOR flag as I think I should?

texts:
I would appreciate some insight as to what I’m doing wrong or missing.
I just completed a XC flight practicing VOR/GPS Navigation. I was inbound to KLOL from KRNO with the lovelock VOR frequency (116.5, 040 Radial) dialed in. I was southwest of the VOR on a heading of 030 and at an altitude of 9500.
The issue is, I could not get the VOR to designate a  “TO” flag unless I turned the OBS to the reciprocal of around 220. This radial should indicate a “FROM” flag.
This is so confusing because I’ve cross-checked this on multiple simulators just to make sure I wasn’t going nuts. Dialing 220 should indicate “FROM” but it indicates “TO”.
Can anyone help me figure out what I did wrong?


texts: Do pilots really wear "pilot's watches"?

texts:
High-end mechanical wristwatches from Swiss and German manufacturers (e.g. Breitling, Rolex etc.) are often marketed as "pilot's watches", and have chronometer features to supposedly help pilots perform flight-related computations.

While I know next to nothing about aviation, I find it difficult to imagine that such a mechanical watch (which, for example, simply stops working if it is not moved for a few days) would be preferable to a modern quartz and/or digital watch, which keeps running for years on a single battery, self-adjusts with millisecond precision based on radio signals and even without that signal maintains time an order of magnitude more accurately than any mechanical watch.

To summarize: What kind of watches do modern commercial pilots actually wear? Or do they nowadays just use their cellphones for timekeeping tasks like everyone else?


texts: How do turbofan internals handle the load from the thrust?

texts:
To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%.

Forward movement is achieved by utilizing Newtons 3rd law - by moving masses of air backwards and thereby moving the aircraft forward.

The thrust will first push the engine forward, and then the engine mounting, and then the wing and the aircraft as a whole - but how exactly is the load from the fast moving thrust air taken up by the engine internals?

As wings generate lift, they bend to a varying degree. Do the fan and engine internals, e.g compressor and turbine blades bend as well? I can imagine the fan taking up a tremendous amount of thrust load and wants to leave the engine and travel forward out the housing.

How much of this is true? Any input or suggested reading on this is highly appreciated!


texts: How should night time be calculated when it is not night during the entire flight?

texts:
I am B777 rated pilot and software developer. Nowadays I am working on an application about flights and this app has to calculate night time. Still I am trying to figure out how to calculate night time correctly for logging purposes. As you know night definition is easy,

Night means the time between the end of evening civil twilight and the
beginning of morning civil twilight, as published in the Air Almanac,
converted to local time.

But calculating a flight's night time is a little bit confusing.

Is this just related about being day or night at takeoff and landing airports?
Or whole the route should be considered if it is day or night at that time while flying?

I searched a lot but couldn't find any formula or detailed explanation about this. Just found some sites and apps can calculate night time; but interestingly every app gives different result; and still it is unclear for me that how they calculate night time.
Example:
Departure : KMIA
Destination : LTBA
Block Off Time : 03:03Z
Block On Time : 13:36Z
Block Time : 10:33

If you calculate this flight's night time via http://www.crewlogbook.com/utilities/night_calculator.php you will get:
Night Time : 01:47

I wonder how this calculation was made?


texts: How does this test flight escape aparatus work?

texts:
I was watching this video about the test flight escape systems on a Bombardier flight. In the video, this machine is shown:

The yellow box moves up and down in the video. Does it move up and flip the airman over, mashing their feet? Or does it shoot down out of the airplane and create a hole to jump out of? If it's the latter, why are they sitting instead of standing?


texts: Is a mode C transponder required underneath Class C airspace?

texts:
FAR 91.215 states that a mode C transponder is required for...

  all aircraft in all airspace above the ceiling and within the lateral
  boundaries of a Class B or Class C airspace area designated for an
  airport upward to 10,000 feet MSL

My flight instructor and I disagree on how this regulation is interpreted. He says that I need a transponder to fly underneath class C. I understand it to mean that I only need and transponder if I am both above and within the lateral boundaries (i.e. overflying the airspace).

Which is the correct interpretation?


texts:
What is the feasibility of solar powered drones? From my understanding, solar panels are becoming more and more efficient, in terms of weight vs energy captured, and in terms of surface area vs energy captured.

What I am interested in is whether solar panels could be placed on different sized drones (small civilian quadcopter and MQ-9 Reaper), and provide enough solar power to keep the aircraft aloft indefinitely (under a theoretical condition of an "endless sunny day").

If this is not possible, are there are realistic changes that can be made to make it possible, while still keeping the core functionality of these two different drones intact?

For the purposes of this question, instead of focusing on a 100% solar powered drone, we can assume that fuel can be carried for takeoff/climb to loitering altitude, at which point is can switch to 100% loiter.


texts: What is the pressure in a civil aircraft fuselage at flight ceiling?

texts:
What is the pressure (in bar) in the fuselage at flight ceiling of large passenger airliners?
Is this pressure the reason for the difficulty in having large windows? If so, how can the window size be increased?


texts: What are some drawbacks to having a wingtip propeller on an aircraft?

texts:
I was reading about aircraft concepts that involved wingtip propeller design and was wondering what the drawbacks of such a technology would be. I could not access the full paper but came across this: https://arc.aiaa.org/doi/pdf/10.2514/3.44076

For me, one of my concerns is that if the propeller fails, feathering would be very difficult on the wingtip prop. I am also trying to decide on optimal placement for aircraft propellers in general. Would the drawbacks from having a wingtip propeller outweigh the benefits in high-lift generation and drag reduction?


texts: How can I calculate the force on the nose gear at landing?

texts:
How can I calculate the force applied on nose gear during landing as nose gear touches the runway little after the landing gear?
I understand force calculations in this question but I think it applies on main gear. How is the force on the nose gear calculated?


texts: When Airplane is reducing altitude from flight level (cruise), which one is more efficient

texts:
When an airplane is reducing altitude, say due to preparation for landing, the nose is tilted down. That I got from a video on Youtube which explains the way an airplane is going down until it reaches a certain altitude and until the nose is revert to tilt up. Then my question:

Is that explanation true that during reducing altitude the nose is tilted down?
Which one is more efficient compare to if the airplane is tilted up as the position of an airplane when it landing. "Efficient" here is about which one faster, more fuel efficiency.
What is the allowed maximum angle tilt down nose?


texts: Protocol for emergency evacuation of atc tower

texts: What is the protocol if the ATC tower needs to be evacuated for some emergency, for example a fire? How can operations continue if there aren't any controllers?


texts: Are there any civilian planes with seating arranged in a round area?

texts: Recently, I heard Airbus want to make an aircraft that looks like a UFO.  Is there currently any civilian passenger plane designed with the seating in a round area rather than the traditional design with a long aisle?


texts: How much was the engine moved in the B737 Max w.r.t. older versions?

texts:
In the wake of the sad crash of ET-302, I am reading on multiple sources that

  the 737 Max's "engine is a bit further forward and a bit higher in relation to the wing, compared to the previous version of the plane. That affects the balance of the plane"

(from the BBC)

Is there data available on how much these "bit further forward" and "bit higher" amount to?

In particular, to minimize misunderstandings, it would be ideal to know how much the CoG of the engines has moved w.r.t. the neutral point.


texts: What are these "lines" on the A319 flaps, are they damaged?

texts:
I've noticed a grey line on the flaps of the A319:

What is that?
Source


texts: Can the four-engined Lockheed JetStar II fly on one engine?

texts:
As we know, there are no four-engined business/private jets currently in production. Some Dassault Falcon models are actually trijets, but this is not the case. The only four-engined business jet in serial production was Lockheed JetStar line.

I'm wondering, in case of extremely rare emergency event, when 3 out of 4 16.5kN TFE7313 engines shutdown, could JetStar constantly fly on some flight level without loss of altitude using only one engine?


texts: Why/how is a downplane parachute configuration aerodynamically stable?

texts:
One of the most dangerous situations possible in skydiving is a so-called downplane, where both the main and reserve chutes deploy, and they shift outwards to the sides of the parachutist until essentially side-on, like so:

(Image by the United States Navy, via Wikimedia Commons; this is actually a simulation of a downplane, with two parachutists and only one parachute per parachutist, rather than the real deal, which would involve both parachutes deploying from a single parachutist, but it illustrates the configuration very nicely.)

This reduces the total cross-sectional area (as seen by the airflow) of the parachutist-parachutes assembly, causing said assembly to accelerate downwards to greater-than-optimal speeds, which is why a downplane situation is dangerous.

However, it is far from obvious how a downplane would be aerodynamically stable; even when virtually edge-on, each of the open parachutes still has a very high drag coefficient,1 a fairly low mass, and (as a result) a very low ballistic coefficient,2 while the skydiver attached to the parachutes has a fairly low drag coefficient, a much higher mass (relative to their parachutes), and, consequently, a very high ballistic coefficient.  As such, the parachutist should tend to trail ahead of the two parachutes, with the aerodynamic forces on the latter wrenching them up towards top dead3 center, unless the whole shebang is spinning rapidly enough about its vertical axis for the outwards centrifugal force on the parachute canopies to overcome the upwards drag force on said canopies, which would require a spin rate high enough to be lethal even without taking parachute malfunctions into account.

What is it that overcomes these aerodynamic forces on the parachutes and renders a downplane aerodynamically stable?

1: Albeit much lower than when face-on.

2: A measure of the relative unaffectedness by aerodynamic drag of an object moving through an atmosphere of given composition.

3: No pun intended.


texts:
Banners are towed with a single line trailing from the plane.

source: © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons)

How can they guarantee the banner is vertical and not upside down?


texts: Why do airports have to close in bad weather?

texts:
Shouldn't aircraft be able to withstand winds of up to 100 mph? When flying the wind is at a much higher speed than that.
Shouldn't they be able to take-off through fog using instruments alone?
Shouldn't they be able to take-off on a slippery runway, since the wheels are not powered.


texts: Is the Brodie landing system still in use somewhere?

texts:
The Brodie system was a method for taking off and landing without a runway, circa 1945. The landing or taking off aircraft was hung on a wire held at the appropriate height:

From PhotoBucket, Duggy009

It could be used on a ship too:

From Youtube: Brodie Landing System

Two advantages of this system: Easy to conceal and capacity to operate to/from areas unsuitable for an airstrip.

This system seemed promising, especially for armies, but I never heard of subsequent use. Why was it discarded? or if it wasn't, what application do/did exist following this WW2 experimentation?.


texts: Comparison of pitching moment at different locations

texts:
I've conducted some numerical simulations of a pitching airfoil at three different locations of the pitching axis along the airfoil. The locations (from the leading edge of the airfoil) are: $0.25c$, $0.4c$, and $0.75c$. where  $c$ is the chord length of the airfoil.

Each simulation computes the pitching moment coefficient using the pitching axis itself as the reference point. That is, In, the first simulation the pitching moment is computed about $0.25c$ axis, and in the second simulation the pitching moment coefficient is calculated about $0.4c$, etc.
My questions are:

Is it OK to compare all three moment coefficient together given that the reference points are different?
Do I have to change the reference point to $0.25c$ for the two last results? if so, how can I achieve that without restarting the simulations and specifying the $0.25c$ as reference point?

Your help is greatly appreciated.


texts: Why would a turboprop rev down just before going full throttle during takeoff?

texts: The only turbprop I've travelled is the ATR 72. I've noticed that the props' rev go down (for like a second, the sound also goes down) just before engaging full throttle in order to takeoff. I've included a video (video is not mine), this thing happens at 1:40. Why the RPM drops for a sec? Or is this just the sound?


texts: Is there a specific purpose for the silver "swoosh" on Air Force One?

texts:
Air Force One, just ahead of where the wing joins, has a silver "swoosh" on the bottom of the fuselage:

Air Force Two, or other congressional aircraft painted with the blue/white livery that I was able to find do not have that same feature:

What is the purpose of this "Silver Swoosh"? I was bale to identify the following two paths of reasoning, which raise additional questions:

Option 1: Part of the Paint Job

If the silver is just part of the paint job, why don't other congressional aircraft have that same feature?
If it is part of the paint job, what does it signify or what drives its inclusion?

Option 2: It fulfills a defensive function

What defensive purpose does it fulfill?
Since it seems to be highly reflective, does it potentially serve as a mirror for missiles with certain seeker heads?


texts: When a plane flies faster than the speed of sound, does the distance between plane and sound increase?

texts:
I had this discussion with my dad about a question he had asked. Basically he said:

  If a plane flies faster than the speed of sound, will he be able to overtake his own sound and hear itself?

(let's leave behind the fact that he can run out of fuel or that the sound finishes before he hears it)

I disagreed because it seemed illogical to me, but we never actually found hard evidence to determine if the statement is true or false.

Can a plane actually do this?


texts: Why did the dividing wall separating the engine intakes of early twin-engine Westland Wessexes cause difficulties with intake anti-icing?

texts:
The Rolls-Royce1 Gnome-engined variants of the Westland Wessex helicopter family (i.e., the twin-engined versions)2 draw air for both engines from a common intake (having been designed prior to the advent of requirements for physical separation of helicopter engine intakes), meaning that a destructive failure of one engine can potentially throw debris into the intake for the opposite engine, potentially disabling it as well; this was considered as one possible contributing factor (among many other possibilities) to the total loss of power that culminated in a fatal 1981 crash of a Gnome-engined Wessex 60, and had definitely occurred on four instances before the 1981 crash (although, in each of these four prior cases, the second engine, although damaged, continued to operate).

Early Gnome-engined Wessexes had a dividing wall separating the left and right engine intakes; however, this was removed after some time, due to difficulties it apparently caused with anti-icing the intakes:

  However, in the event of compressor damage it is possible for the Gnome engine to eject debris forward out of the compressor which, in the Wessex 60, may be ingested by the other engine since the intakes are not separated.  Rolls Royce (RRL) were aware of four cases in which both engines in a Wessex had been damaged in this way, although in none of the cases was the power remaining available insufficient for continued flight.  Whilst the original design incorporated a dividing wall which achieved separation of the compressor intakes difficulties in achieving a satisfactory anti-icing standard led to its removal in a modification approved by the CAA but not by RRL.  The possibility therefore exists that a failure in one engine could, by cross ingestion, lead to a complete loss of power.  Since the Wessex 60 was certificated BCARs have been revised, and now require engine intakes to be independent of each other.  [AIB3 Aircraft Accident Report 4/83, pages 21-22 (pages 25-26 of the PDF file of the report); my emphasis.]

Why did the original dividing wall cause anti-icing difficulties?  Was it too thin to accommodate the wires or bleed ducts required to anti-ice it?

1: Formerly de Havilland.

2: Very early Wessexes instead used a single Napier Gazelle engine.

3: Not a typo - the AIB didn’t become the AAIB until November 1987.


texts: How should the pack flow knob be set on an Airbus A320?

texts:
On the Airbus A320 there is a pack flow knob and you can select LO(80%), NORM (100%), or HI(120%) according to the number of passengers and ambient conditions. Someone told me you select LO if there is less than 115 passengers HI if it is abnormally hot and NORM if everything is casual.

Do both numbers of passengers and ambient conditions have to be met to select LO,HI, or NORM?

For example, obviously if it is above 100 degrees Fahrenheit you would select HI, but what if it is in the 90s or high 80s? Is there a specific temperature or is it option based?


texts: What's the UX in modern airliner avionics for diversion choices, and does it integrate to autopilot?

texts:
This question mentions a flight that had to divert, in that case to Iqaluit (YFB).

I was wondering: in modern large airliners, what is the user interface like when diverting? How is the case of "what is the nearest airport/runway we can divert to now?" handled in the avionics displays?

Does the computer system know at all times what the nearest runway or airport is? Does that information appear when needed, or perhaps it's just continually displayed and updated at all times?

Does the system understand subtleties such as which one is best based on your current heading, altitude and so on? Or do pilots just have to quickly look up the nearest one with no special help from the avionics?

Or, is it figured out for each stage, as part of the preflight planning? Do they have it written down as part of a flight plan? Or does the crew have to program in a list of suitable diversion airports along the coming route, and if the worst happens the system will tell you which one (of that set) is nearest now?

In fact, is there just a big red button marked "Divert Now", and the plane immediately changes course to whatever it decides is the nearest and/or best diversion prospect at that moment?

To be clear, I'm talking about how it works in this sort of cockpit:

(To a civilian, most modern airplane controls look like that: touchscreens with some sort of graphical user interface.)


texts: How is V_S0 calculated for anything less than maximum weight?

texts: Is there a way to (safely) calculate the stall speed of an aircraft ($V_{S0}$) for anything below maximum weight? All the tables in the POH are valid for maximum weight only, and stall speed can drop significantly with a light load. As a consequence, if you're flying the published (max weight) $V_{ref}$ on final, you'll actually be carrying a significant amount of extra speed and thus increase the required landing distance, possibly in quite a dramatic fashion.


texts:
The mach 2.7 capable Boeing 2707 has an interesting design. I'm curious if there has been any studies done that concluded that this aircraft would simply not have worked, given the way it was initially designed, even if sufficient funding existed.

If so, what was the problem with the design? By problems, I don't mean it being financially feasible or sustainable, I mean technical limitations and restrictions imposed by physics. Could this sort of aircraft ever have achieved a sustained mach 2.7, and carry 277 passengers?

I'm personally inclined to believe it might have worked, considering other notable aircraft of the time, such as the military planes; the XB-70, the SR-71, or the civilian Concorde, and Tu-144. The civilian planes mentioned here are somewhat slower, but the military planes are somewhat faster, and puts the 2707 right in the middle.

However, it would be nice to see an actual evaluation of its design, if such a thing exists.


texts: Do Diesel engines have a mixture option?

texts: Consider the DA-42, it has no mixture control. Is that because it is run on Jet-A/diesel? Or is the mixture control automated?


texts: Is DAL-A required for twin-engine helicopters with FADEC?

texts: When operating Twin Engine helicopter with FADEC controls, is is necessary to certify at DAL-A?  If so, why? Is it related to the FADEC certification or is this required for an aircraft potentially roling into a military platform?


texts: I want to know how aileron reversal takes place when control reversal velocity is higher than divergence speed  and operating speed is in between them (for conventional wing)


texts: How was the 747 in the China Airlines Flight 006 affected by the wing damage it sustained?

texts:
The passengers on China Airlines Flight 006 had a very memorable flight when the crew lost control and the aeroplane went into a high-speed dive.

Various pieces of the aircraft were torn off. The plane was repaired and returned to service, with its wings bent permanently upwards by 5cm.

How did this permanent damage affect it afterwards? Did it fly or perform noticeably differently? Did it require a special inspection regime for the rest of its operating life?


texts: Partial Serial numbers on Military Aircraft - what combination is unique?

texts:
Modern US military aircraft have partial serial numbers painted on their tails. Interestingly, it seems these serial numbers are actually not quite enough to be unique on their own, being comprised of only the year the aircraft was ordered, followed by the last 3 digits (usually) of the serial number. On occasionally this is not a unique combination by itself. Is there a specific combination of tail markings that is guaranteed to be unique? For example, if one combines the branch markings (such as 'AF' for Air Force) and/or the base code (such as 'AZ' for Arizona National Guard), would that be guaranteed to be unique?
Thanks so much for any insight.


texts: What are the various thrust modes in the Airbus A320?

texts: I was going through A320 AFM and came across Thrust modes. I was not able to understand why thrust is in thrust mode during climb and descent because we climb or descent with a constant speed. So according to me it should be in constant speed mode.


texts: On a large transport aircraft where exactly is the Forward pressure bulkhead?

texts: Is the Forward pressure bulkhead in front of the pilots.. I.e when you lift the Radome for maintenance is that the Forward pressure bulkhead you can see? Some images or a diagram would be great.


texts: How does MCAS compare to stall protection systems installed in other aircraft?

texts:
How is MCAS in 737 MAX 8 different from the stick pusher in MD80 or DHC8 and from the Airbus alpha protection, in terms of overall safety?

All these systems will push the nose down at high AoA and all of them rely on the AoA data, which can become corrupted?

If all of those systems perform a similar function, why is only MCAS currently under scrutiny?

(this is an operation safety question, not related to Boeing's apparent lack of proper disclosure and training)


texts: Why are visual approaches (in the US) preferred by US pilots, but not European pilots?

texts:
I listen to ATC a lot and often hear airliners cleared for visual approaches in the USA. Interestingly, if it's European airliner pilots they deny the visual approach and request ILS even if they are in an emergency and probably should land ASAP. Why is that? Are European pilots not used to hand flying? I assume pilots flying, for example, A380, should have extremely good piloting skills. What is the problem with doing a simple visual approach?

I also haven't heard yet from ATC to clear an airliner for a visual approach in Europe.

Here is the audio source (via YouTube): 30% of time is spent dealing with turning ILS on for 31L.


texts: Is it necessary to have my full name (including middle name) on my student pilot license?

texts:
So my student pilot license is missing a middle name, but my drivers license, written exam, and passport all have it printed.

I've spoken with the DPE, and he says it may be an issue, or it may not, and that he is going to look into it.

I've called FSDO, airmen certification branch, and other DMVesque organizations, and they all seem to say the same thing:

  Oh, you need to talk to (insert amorphous bureaucracy here)

Does anyone know who I actually need to talk to, or if this is even an issue? Do I just need to call FSDO and insist that they fix the issue, or what?

The DPE said that with the written exam being OK it may be a non-issue. Would love to hear from a DPE on here if possible.


texts: Why do Airbus aircraft typically have less wing flex than Boeing aircraft?

texts:
I was watching this video on YouTube about Boeing vs Airbus aircraft, and at around the 5:09 mark the female pilot stated that Airbus wings are much "stiffer" and "less aerodynamic" compared to Boeing's' more "aerodynamic" wings.

I looked at a few videos and it does appear that Airbus aircraft have some wingflex but not to the same extent as Boeing aircraft.

Taken from: this video

I gather that wing flex is mostly beneficial for aerodynamics so why then, do Airbus aircraft typically have less wing flex than Boeing aircraft?


texts: Why don't all aircraft use/need nacelle chines?

texts: Most modern commercial aircraft (e.g. 737, 767, 777, 787, 747-8, A380, etc.) feature inboard nacelle chines to improve flow over the upper surface of the wing at high angles of attack. However, many other similarly purposed aircraft (e.g. DC-8, L-1011, 757, 747-400) do not have nacelle chines. If these chines are so critical for optimum takeoff and landing performance, how are so many planes able to function just fine without them?


texts: Where can I find detailed steps on how to perform all ACS maneuvers?

texts:
All the maneuvers outlined in the Airman Certification Standards (slow flight, power on stalls, short field, etc.) have been taught by my instructor to me but on no occasion have I received reference material for each of these maneuvers. I find after long periods of not practicing these, it can sometimes become easy to interchange the order of operations of 2 steps in a given maneuver. I have my checkride scheduled and need to be able to reference these.

Where can I find the individual steps in each required maneuver?

Aircraft: PA-28-140 / Piper Cherokee

To be clear: I know that the ACS itself has bulleted items identifying required things the candidate must be able to demonstrate, but this still doesn't detail how to perform the maneuver.


texts:
I am wondering what turn coordination really means and what makes a turn uncoordinated?

I know that when the turn is coordinated, there is no slip and skid, an aircraft is flying a perfect circle etc. and that in one case there is too much rudder input or too little bank etc. etc. But I am interested about forces during the turn. Can someone tell me which force during an uncoordinated turn is too big or too small and literally what makes a turn uncoordinated in terms of forces?


texts: Were WW2 American fighters designed to operate from dirt airstrips?

texts:
Fighter or fighter-bomber planes built in America during WW2, such as the P-36, P-39, P-47, P-51. Were these designed to takeoff and land on dirt airstrips?

My impression, and correct me if I'm wrong, is the following: Most airbases inside USA/Canada at this time had paved runways. At least half the fighters were designed to takeoff and land on carriers. Also, I think every single photo in wikipedia I've seen of these planes on the ground, is on a paved runway.

Now there is of course the Western Front in Europe, and some American aircraft did get sent to the USSR in lend-lease. I do not know if Britain and France had the luxury of paved runways at the time, but in Russia, most certainly did not. So you would think at least some of them had to had the strong undercarriage required for dirt airstrips. But I am not sure if they came that way or had to be modified after arriving in Europe.

One way to investigate this is to start looking at the airfields America had during WW2. Wikipedia has a giant category page for this, but even tho most of those pages have a history section, sadly I could find nothing about paved/unpaved. However, this photo from Midway shows paved runways, and I'm pretty sure Wheeler Airfield during Pearl Harbor had a paved runway too. If they were doing that in the middle of the Pacific, my guess is that most airbases in the 48 states and east/west coast mainland also had paved runways.

The reason I ask is because a stronger undercarriage requires more weight. Dirt landings require bigger wheels which take up room in the fuselage that could otherwise be used for fuel or bombs. Therefore, if paved surfaces are available, it makes sense to take advantage of it in your design. But as I said above, I can't be sure if paved surfaces would be available everywhere they intended to use them.


texts: Which US airport historically has the most days in which VMC prevail?

texts: I live in a part of the country where VMC are starting to become increasingly uncommon, which has led me to wonder - which US airport historically has the most days in which VMC prevail per year?  What sources of information can be used to investigate VMC trends at a given airport?


texts: Why are there so many moving parts used in the landing gear?

texts:
This short clip of the landing gear on a Hawker 850XP being retracted seems extremely complex.

I'm curious to know why there are so many moving parts but as a layman I'm struggling to make sense of it all.

So what exactly is going on here and why?


texts: Who runs the Air Navigation System (air traffic control) in Canada?

texts: Who runs the Air Traffic Control system in Canada? Is it the government?


texts: How to define pitch angle for a passive variable pitch propeller?

texts:
This question is a continuation of the question How to calculate variable pitch propeller parameters? mentioned before.

Actually, the theory described as an answer on the question above is the exact one i am using at the moment.
However at the current stage, i want to make the calculations only for a 2D sectional symmetric airfoil, supposing a rectangular-shaped blade and not considering any twist.
Also i forgot to mention before that my idea is to attach a rod on the root of the blade, set in an offset of the aerodynamic centre Xa.c (variable) and place a gear on it to connect with the opposite blade and synchronizing it. Also counterweights will be attached on the rod for balancing purposes but this is for later studies.

In this case i have ended up with the following formula for the pitching moments:

dM = dMa.c - dL*Xa.c

As can be seen here dM and dL are correlated there are two unknown there which are the lift coefficient Cl and angle of attack α.

from literature i found that Cl can be expressed as Cl0 + Cla* α and then to 2π*α (from thin airfoil theory), as well as Cm = 0 for symmetric airfoils.

Using these assumptions and moment equilibrium  i end up on α=0 which doesn't make sense.


texts: If jet engines did leave chemtrails, wouldn't the chemicals cause adverse reactions in the engines?

texts:
Please note, this question does not call into question whether or not the conspiracy theory is true or untrue, but the feasibility of certain chemicals being used as fuel additives in order to make the theory viable.

Chemtrail conspiracy theorists believe that there are certain additives being put into jet fuel to spew out [nano-]particles that rain down on us, for means that are being kept secret.  The hypothesized reasons behind 'chemtrailing' range anywhere from weather modification, population reduction, and sunlight blocking to reduce the earths temperature hence combatting global warming.

Some popular agents that are called into speculation:

Aluminium based aerosols
Mono-atomic gold
Barium

My question is, wouldn't these additives, chemicals, etc, cause adverse reactions inside the jet engines, if the turbine is the actual catalyst supposedly spraying these things?


texts: Are these ballast bags for a hot air balloon?

texts:
While driving around on the back side of Aspen Mountain (so up around 10,000 feet altitude) we came upon these bags of ash.  They look like they could be opened up on the bottom to let the contents out, our best guess is that they are ballast bags for a hot air balloon.  You can see my brother's legs in the first picture for some kind of scale.

Were we right?


texts: How do fighter jets measure how high they are?

texts:
I know most of the commercial planes use altimeter to find how high they are. I was just curious in finding out what fighter jets use to to find their height and what are the other technologies that could be used other than pitot tubes to find speed of an aircraft or fighter jet.

2. What material are used to make pitot tubes in aeroplane?


texts: What would cause an abrupt increase in engine noise after takeoff on the Boeing 737-800?

texts:
I flew last week on a Boeing 737-800, I was in row 7, so just in-front of the wings.

I know from experience that there is a significant difference in engine noise from the front to the rear of the aircraft, up front you get more of the buzz, towards the back you get more "roar" engine exhaust noise.

However on this occasion the thing that struck me was an abrupt change in noise at about 1 minute from takeoff, not sure on altitude, but probably around 2000ft.

The takeoff (EMA) was 100% normal, straight climb no significant turn.

At this (estimated) 1 minute mark, the right-hand engine suddenly got louder, a harsher buzz, but seemingly no change in RPM (no pitch change). I would say inside the aircraft it almost doubled in volume.
There was no obvious added vibration to the airframe.

The flight went on as normal (4 hours to ACE Lanzarote) and the noise subsided as we reached cruise.

What could cause this?
A few things went through my mind: undercarriage retraction(?). Bird strike, blade damage, flame-out, resonance, internal changes in the engine such as guide vane angles, engine working loose!


texts: Can a protective mesh protect engines from bird strikes?

texts: Can a protective mesh be installed on the front of the engines to stop birds from entering the engine and causing damage?


texts: Why is the Mooney's signature tail profile different from most planes?

texts:
In another question, someone said everyone but Mooney has the vertical stabilizer on backward. (As a Cessna driver, this looks backwards to me). Is there an aerodynamic reason or some reason other than marketing?

(Note the slants of the leading and trailing edges.)


texts: What is the content of a Letter of Agreement between the Collaborative Decision Making participants?

texts:
Can you give a sample of a Letter of Agreement?
How to calculate average taxi time at airport?


texts: What counts as "runway in sight" when flying an IFR approach to minimums?

texts:
I've watched a few videos on youtube where the pilot flies an Instrument Landing System (ILS) approach to the minimum allowed altitude before establishing visibility of the runway (MDA or minimums).

What I'm wondering though is what constitutes "runway in sight"?  I mean, in some cases that's going to be obvious (ie., you can see the runway clear as day long before minimums.)  But what if the cloud base is right at minimum and you can kind of see outside, but not in every direction (ie. maybe it's slightly clearer just a bit to your left than to your right.)

What do you have to see to consider the runway in sight?  The whole runway?  Just the lights? Just the approach lights?  Just the VASI/PAPI?  Would it be considered enough if, perhaps, you could see a windsock that you know is close to the runway?  Or perhaps there's a cross street right before the runway that you're very familiar with, would that work?  What would be considered "runway in sight" so that you can continue the approach rather than going missed?

Note/Clarification: The general rule, of course, is "when in doubt, go missed".  So in a lot of ways this question is academic.  What I would love, though, is a two part answer, with one part that has the exact rules (per the FAA) and the other with some common sense guidance on when to continue and when to go missed.


texts: In calm winds, which runway should I select at an untowered airport?

texts:
In calm wind situations, approaching an uncontrolled airport with no other aircraft reporting on CTAF, which runway should I select that would cause the least safety hazard?

Especially at an airport with one runway, I don't want to set up to land head-on with an aircraft flying without a radio.


texts:
I'm trying to identify the filming location of this stock footage of an FAA building.
It was used in a 1984 episode of the "Falcon Crest" TV series, but it is stock footage that was bought from a film library to be used as a short establishing clip only.  Unfortunately, only a small part of the structure is visible in the segment.
Since the FAA changed its name from "Federal Aviation Agency" to "Federal Aviation Administration" effective April 1, 1967, I think this footage must be older.
Any ideas?  Thank you so much for taking a look.


texts: Restricted Area "popping up" around you -- can it happen, and what do you do about it?

texts: What happens if you are flying along through a Restricted Area (lets assume you're in a J-3 so you're VFR/no transponder, but you have a handheld radio to talk to ATC with) and  said restricted area is activated while you're still in it?  Would this be considered an operational failing on ATC's part, or would such a thing be blamed on the using agency (i.e. they ought to ask ATC "is anyone using this?" before they take it "hot")?  Are there procedures you should follow in this scenario, other than "fly out of the restricted airspace the fastest way possible and hope whatever hazard caused the R-area to go hot doesn't hit you?"


texts: How does the nose wheel lock on the Robin DR400 work?

texts:
I recently learned that there is a locking mechanism on the nose wheel of a Robin DR-400. This mechanism locks the nose wheel in place when there is no weight on the wheel.
In particular, the wheel will be locked when the plane is in the air. And at landing, when there is weight on the wheel again, it unlocks.
But the nose wheel can also become locked if the center of gravity of the plane is too far back, or may fail to unlock upon landing. In this case, the aircraft becomes uncontrollable, and this can cause a runway excursion.

So I am wondering a few things:

How does this mechanism work?
What is gained by having the nose wheel lock itself? Rather than for instance a spring-like mechanism that just keep the wheel aligned with the plane when the plane is in the air.
Are there other planes with a similar locking mechanism?
Are there planes with a different mechanism to keep the nose wheel from moving in flight?

Here is what the landing gear looks like. It is not retractable and there are fairings on the wheels for better aerodynamics:


texts:
I was doing research on control surfaces present on an aircraft and I noticed that some aircraft like the B2 Spirit does not have a vertical tail stabilizer and therefore no rudder either.

How do aircraft such as these perform turns and counteract adverse yaw in banked curves? Do they apply some sort of differential thrust system for turning?


texts: Why is Denver International Airport runway 16R/34L rarely used?

texts: From watching planes land at DIA on Flightradar24, none seem to ever land on 16R (longest runway in the US at a length of 16,000 ft), but instead land on a runway 4,000 ft shorter such as runway 16L (12,000ft). So why do even large planes like the 747 not land on the longer runway to have an easier landing?


texts:
There is not much information on the cockpit aspect of the Microwave Landing System. Apart from Wikipedia, there's this excellent 15-minute FAA video from 1974 on TRSB (time reference scanning beam) MLS.

  Similar to other precision landing systems, lateral and vertical guidance may be displayed on conventional course deviation indicators or incorporated into multipurpose cockpit displays. Range information can also be displayed by conventional DME indicators and also incorporated into multipurpose displays.

How do pilots fly a non-straight-in (curved path) MLS approach on a Course Deviation Indicator?

(Source) CDI instrument.

I'll offer an analogy for the simple way I understand MLS: If VOR/DME were to be magically very accurate and to have slant information, an airplane would have been able to perform accurate area navigation using a single VOR/DME station. Instead, this station is the MLS system which covers the approach segment.

(Source–PDF) MLS depiction from 1978.

With the ever changing track and glide-path, I understand even in the 70's an FMS-like system was installed for the preset approach waypoints—in the lateral and vertical.

Even when coupled to the Flight Director, is there a requirement for a multi-crew, i.e., the Pilot Not Flying would be calling out the upcoming changes? Is there a requirement for an operative (must be on) autopilot? From the FAA video starting at 11:55, I get the feeling that for anything but a straight-in approach an autopilot is a requirement.

It is still being used in Heathrow,* perhaps there's information based on an MLS-certified civilian plane?

Apologies for the mess above, it all boils down to:

From the aspect of instruments and procedures, how do pilots fly an MLS approach?

* The link is now dead, it seems Heathrow no longer offers MLS approaches, but I can't confirm it.


texts: What is the relation between N1 and Wing anti-ice

texts: When wing anti-ice is selected, the N1 or EPR limit is automatically reduced, and the idle N1 or EPR is automatically increased. What does this statement mean ???


texts: If Floyd Bennett Field failed due to its remoteness and isolation, how has JFK been so successful?

texts:
Floyd Bennett Field was built at the end of the 1920s in order to give New York City its own airport and avoid having to rely on Newark; however, despite its superb airport facilities, Floyd Bennett Field was never a commercial success, being cursed by the relative remoteness and isolation (compared to Newark) of its location in far southeastern Brooklyn.  As a result, when the airlines and the airmail stayed at Newark, LaGuardia Airport was built in northern Queens, quickly becoming much more successful than Floyd Bennett ever was, and remaining New York’s primary airport until 1948, when Idlewild Airport (JFK from 1963) opened in far southeastern Queens.  Idlewild/JFK, in turn, quickly came to overshadow both LaGuardia and Newark, and has been the primary airport of the New York metropolis ever since.

But JFK is even more remote than Floyd Bennett!

If remoteness killed Floyd Bennett, why hasn’t it killed JFK?


texts: Can a jet engine be restarted after a catastrophic failure?

texts: I have a retired 747 pilot saying that a catastrophic jet engine failure could be restarted. I have little or no training, but I believe that the word "catastrophic" means that there is no recovery. My reference is the 747: The Jumbo Revolution documentary which is on youtube.com and cable TV.


texts: How to get the correct angle when doing a visual appoach before landing?

texts:
Before landing, without ILS, how can you get the correct vertical angle and know when you're too high or too low?
I think there are some red and white directionnal lights next to the runway that can tell you if your angle is correct, but I'd like to know precisely how a nice approach is done.
Do pilots sometime just figure it out because it's a habit? Is it more difficult if the runway is surrounded by an ocean?
I'm talking about commercial airliners as it seems more simple with small aircrafts.


texts: Is yelling "clear prop" required by FAA regulations?

texts: In general aviation, it's almost ubiquitous that pilots yell "clear" or "clear prop" before engaging the starter. Are there any regulatory requirements to take this action either in the form of 14 CFR or maybe in the Airman Certification Standards?


texts: How would an aircraft visually signal "in distress"?

texts:
A ship at sea would fly its flag upside down to signal it's in distress. How does a plane or airliner that has no radio or transponder visually signal that it is in distress?

This question: How do commercial pilots send distress signals? explains how it is done using a radio or transponder, but how could the message "please don't shoot me down" be relayed visually to a fighter pilot?


texts: How close to the White House did the Space Shuttle Discovery "fly"?

texts:
The CNN article For 747, transporting a shuttle is no heavy burden shows the shuttle Discovery on top of a "shuttle shuttle", a special 747 used to shuttle the space shuttles around.

How close to the White house did it fly? Did there need to be any special arrangements to fly so close to this highly sensitive airspace (especially post-9/11)?

Note: Presumably this is a NASA aircraft rather than a military aircraft (e.g. Marine 1) so the flight planning for this "fly-over" may not be exactly the same as those for landing a helicopter on the White House lawn.


texts: Why is engine No.2 started first, instead of No.1?

texts: I realized that some Boeing manuals recommend that the engine number 2 must be started first, is there any special reason for this?


texts: What is the relationship between the UH60 Blackhawk stabilator function lateral sideslip and pitch coupling?

texts:
I'm having a hard time understanding the correlation between the wind gusts (where are they coming from, what are they affecting) and why, in a nose left situation,  the stabilator is driven down.

I keep thinking it would make sense for it to go up (e.g. left pedal, more tail rotor torque, tail up, nose down.

  sideslip to pitch coupling to reduce susceptibility to gusts.    When the helicopter is out of trim in a slip or skid, pitch excursions > are also induced as a result of the canted tail rotor and downwash on the stabilator.

  Lateral accelerometers sense this out of trim condition and signal the stabilator amplifiers to compensate for the pitch attitude change (called lateral to sideslip to pitch coupling).

  Nose left (right slip) results in the trailing edge programming down.
  Nose right produces the opposite stabilator reaction.

If the stabilator drives down, this will make the nose go down further.

I know I'm missing something big here but can't put it together.


texts: Why do super sonic fighter jets have narrow waist?

texts:
Some of the supersonic fighter jets (such as F-4 Phantom and F-5) have narrow waist on their fuselage.

Why do these fighter jets have narrow waist?


texts:
Why isn't the APU a standard diesel generator? Jet-A and diesel are interchangeable (with the addition of a lubricant). So why not use a cheaper piston engine as opposed to a jet turbine?

V.S.


texts: What is the maximum G load a 747 can withstand during an emergency course reversal?

texts: In an emergency course reversal, passenger safety first priority, to avoid say, a column of ash from a new volcano, what it the most G a 747 can withstand with an average passenger complement?


texts: Can anyone find Putins Il-96-300PU july 17 flight map?

texts:
Can anyone find Putin's Il-96-300PU July 17 flight track?

Putin's flight path has not been publicized on the internet. The Russian media is claiming that his aircraft would be in danger of being shot down, but has not shown that he would be even over Ukraine.  Initial information indicated that he was flying through Poland.

Is there a flight track for Vladimir Putin's aircraft on July 17?


texts: Has any aircraft ever been designed such that it could descend safely with no control input?

texts:
Has there ever been any aircraft of any type that could glide safely with no control input simply based on the way the frame of the aircraft was designed?

I was trying to think of requirements for building an aircraft that would be accessible to the masses and the first thing I thought of was safe landing in the event of engine failure or other catastrophic mechanical breakdown.

It seems to me that it would be possible using modern composites to create some type of aircraft whose default flying configuration is a safe, slow descent. NOT including parachute equipped such as cirrus, has any such craft been designed/flown?


texts: Why did WWII prop aircraft have colored prop tips?

texts: Why do propeller aircraft from World War II and similar planes sometimes have the tips of the props colored? I see it on single engine planes like the P-51 as well as bigger, multi-engine planes such as the B-17.


texts: Is the seat-belt sign activation when a pilot goes to the lavatory standard procedure?

texts:
Yesterday, I took an inter-European commercial flight with a popular budget airline. Before take-off, the captain announced that the First Officer would be taking the entire flight today.

During the middle of the approximately 2 hour cruise, the seat-belt sign came on. The flight attendant, who was next to me at the time, quickly turned to look at the front of the cabin.

The captain came out of the cockpit, a flight attendant took his place and locked the door behind him, he spoke over the PA system and asked everyone to fasten their seat-belts. A couple of people stayed up and he firmly told them, again over the PA, to sit down and fasten their seat belts.

Despite largely overcoming my fear of flying recently, I was slightly alarmed at this point, so I asked the flight attendant if we were expecting some turbulence. He told me that no, we weren't and that the seat-belt was only because the captain needed to use the restroom.

Sure enough the captain used the restroom, came out, re-entered the cockpit and a few minutes later turned the light off.

My question -  is this standard procedure or is it likely the flight attendant was giving me the 'passenger friendly' version of the story? I have since wondered if it was the FOs first 'solo' flight and if that might have been related.


texts: Why are propellers de-iced before the engines are started, and does ice on the fuselage affect the flight characteristics of the plane?

texts:
I recently flew on a flight out of Montreal on a DHC8 turboprop.  The plane had been parked at the airport overnight during a winter storm, and as I walked out to the plane, there were visible icicles accumulated on the wings.  There was also a layer of ice completely covering the windows on one side of the plane, presumably because of the direction of the prevailing wind during the storm.

The plane was successfully de-iced and took off without a problem.  However, I had some questions about the de-icing process as I observed it from inside the plane.

The ground crew had to de-ice the propellers manually before the engines could be started.  Is this mainly because of the risk of ice ingestion in the engines, or is there a problem with the propeller being imbalanced because of uneven weight?  Or both?  Or neither?
The de-icing by the trucks seemed to focus on the wings, and it looked like there was still some ice left on the exterior windows when we left the de-icing pad. My understanding of icing is that ice on the wings is extra-bad (I remember a fatal crash happened near me due to wing ice when I was growing up), but does ice on the fuselage affect the flight characteristics of the plane?  Or is it not really a concern?


texts: Why are HUDs usually green instead of red?

texts:
Every HUD I've seen, whether photographs or in video games, uses green light to draw the lines and text.

Why green? I thought red was a better color for pilots' eyes so they can stay adjusted for night vision. Do HUD's allow you to switch colors at night?

Note: I'm interested in military aircraft only, especially fighter jets. But if the reason happens to be the same across the military and civilian world, that's fine too of course.


texts: Could someone really die in the way that Goose did in the movie "Top Gun"?

texts:
Looking at this question I remembered a question I always wanted to ask:

In the movie "Top Gun" one of the main characters dies when trying to eject from the F-14. Here is the scene where this happens. Did an incident like this ever occur in real life, or is there at least a theoretical possibility that a pilot could be killed this way?

Top Gun was filmed in the mid 80s, which is quite a while ago. If there were incidents, did they do something to fix that issue? And this question goes not only for F-14s but also other aircraft with ejection seats.


texts: Tail numbers not starting with N, with domestic US carriers?

texts:
I'm looking at some of the on-time performance data made public by the US Bureau of Tranport Statistics, e.g. through here. These have the tail numbers of the aircraft used in commercial intra-US flights over the years.
I'm seeing that, occasionally, tail numbers are missing. But in some cases they're actually garbled (e.g. N105@@) - or just perhaps uncommon. Specifically, I'm seeing, among others, tail numbers such as:
89869E
91469E
9149E
A367NW
EI-BWD
HZO
M67153

Can some of these be "legit"? That is, could the above (and similar) strings be actual tail numbers of aircraft which were used in commercial domestic US flights?

Note that we're talking about entries from years between 2001 and 2008.


texts: Can a 777X legally be ferried with one or both wingtips folded?

texts:
The 777X family (777-8/-9/-10) features wingtips that fold up on the ground to let the aircraft fit in tight spaces. These have to be extended and locked in place before a revenue flight can take place, but can a 777X legally be ferried with one or both wingtips in the folded position - for instance, if one of the wingtips is jammed in the up position while at some backcountry airport that doesn't have maintenance facilities for a 777?

For the purposes of this question, I'm assuming that it's physically possible to operate the aircraft. The non-folding part is the same length as the wing of a regular 777, so it would still be able to take off safely, just with considerable performance penalties compared to normal, wingtips-folded-down flight. Ferry flights for maintenance purposes can get away with a lot that wouldn't be allowed during line operations (for instance, multi-engine jetliners can be ferried with one engine - or, for quadjets, two - inoperative, and the 747-400 can be ferried with one of its winglets broken off).


texts: Is there less vertical space for an engine under the wing of a 737 Max than for an A320neo?

texts:
The source of this question is the understanding that the LEAP-1B couldn't fit under the wing of a 737 without changing its longitudinal position. But this wasn't the case with the design of the LEAP-1A/A320neo. For lack of ground clearance?

What is the height under the wing of a B737 Max at the point where the engine is attached? Under the wing of an A320neo?

Regarding question duplicity: This is about wing ground clearance, not engine ground clearance.


texts: Can aircraft stall at low speed during final landing?

texts: Is it possible for an aircraft to stall when it turns multiple times before landing and its airspeed is below 200mph? And if it does, is there any way to recover at such low height and speed? I always get nervous looking out the window and feeling that 1.5g in my seat during landing.


texts: What would happen when a pilot receives a message about Dead Reckoning Fault?

texts: Dead Reckoning Fault will lead to some restrictions of the flight. What will happen after receiving this message?


texts: Estimating the fuel required in terms of flying distance and total weight

texts:
I am looking for a mathematical model to estimate trip fuel required. I have searched the internet but not found any specific mathematical model as such. The question is formulated as follows:

Let $W_0$ be the weight of a particular aircraft with a given fixed set of technical specifications (say Boeing 737-800) without any fuel, passenger or cargo, $W_c$ be combined the weight of the passengers, their baggage and all additional cargo and $x$ be the flying distance (take off to touch down).

Question:

What are the best known mathematical models or algorithms to predict or estimate the minimum amount of fuel required $W_{f_{min}}$ in terms of $W_0, W_c$ and $x$ for this aircraft?

Assumptions: For simplicity, let us assume that the following conditions are true

Weather is perfect i.e. no additional fuel required due to bad weather
There is no air traffic due to which additional fuel is burned
The pilot is good and flies tries to minimize fuel consumption
In case any addition information is required or missing, please
assume    them in your answer and proceed.


texts: Do Airbus avionics give good deadstick landing outcomes?

texts:
We have recently had a second good outcome, in Russia, of a no power landing of an Airbus aircraft. The first was the "miracle on the Hudson".

It appears to me that the avionics of this aircraft are very good at handling the stall v. low speed nose up approach problem.

Does anybody have any insight into this programming?


texts: What would the altitude profile for a typical airline flight look like?

texts:
It's hard to appreciate an aircraft's rates of change in altitude, in particular with respect to its travel through the mass of air, rather than over the ground, since the latter is affected significantly by wind-speed (the distance an aircraft travels with respect to the ground is highly variable, compared to the distance it travels with respect to the air around it).

Then, when climb profiles are plotted, it's always on a graph with a hugely compressed horizontal axis (naturally, because it's hard to discern much information when one axis is a thousand times longer than the other).

Finally, when climb/descent rates are given they are usually in vertical distance/minutes, which is useful from an aviation point of view, but hard to compare with a vertical distance/horizontal distance measurement, or for example the familiar gradient figure that would be used to describe the slope of a road.

So, assuming absolutely still air throughout a flight, what might the altitude profile as plotted against distance look like, for a typical airliner on a flight long enough to be at cruising altitude for a few hours?

And, what sort of gradients would be represented for its climb after take-off and its descent towards its destination?


texts: What is the climb/descent rate that triggers the TCAS up/down arrow?

texts:
If Aircraft One is maintaining a low rate of climb/ descent, is there a minimum descent or climb rate threshold below which the up/down arrow will not show up on the TCAS of the Aircraft Two?

I have heard figures of 400 fpm and 500 fpm.

Is there an industry standard, do standards depend on aircraft performance / weight class?


texts: What does ATC do when a VFR flight in the mode C veil has a malfunctioning altitude encoder or transponder?

texts:
Recently I replaced the altitude encoder in my airplane because ATC could not receive my altitude during VFR flight following. Up to that point I had been flying VFR under the class B shelf for some time, and I assume my transponder wasn't transmitting the altitude to ATC. It may have been non-functional for several months.
Was I causing panic in the control tower because my plane wasn't reporting the altitude, and I wasn't on any ATC frequencies for them to contact me? Can ATC determine my altitude from their ground based radar? Is ATC able to contact VFR airplanes when their transponders/encoders are off, or tuned to the wrong squawk code, or malfunctioning? The transponder is tested every two years, so that is a lot of time for something to go wrong.


texts: Why are longer wings with foldable wingtips used on the B777X instead of lighter ones with original size?

texts:
The new Boeing 777X has longer wings to improve efficiency, but has to adopt foldable wingtips to "fit" into all original airports that host its predecessor.
Tendentially, longer wings would have an higher weight and foldable mechanism surely add extra weight too, but thanks to new materials, new wings should be almost as heavy as previous ones.
For me, in absence of further information and comparisons, it's not so easy to understand why this solution is surely better of simply have lighter wings with original length, that would allow benefits too.


texts: Are Boeing 737 winglets adjustable from the cockpit?

texts: As I taxied past some Southwest 737s during a recent trip I saw what appeared to be different angles of the winglets relative to the wing. Are winglets adjustable, are they arranged differently from Port to Starboard, or is it an optical illusion?


texts:
On a 13-hour flight all shades were ordered closed (entire flight—not cool), same airline on a 3-hour route, same thing.

Both flights took off in the morning, around 8 AM.

Only reason I can think of is to keep the cabin cool, lower the demand on the engine bleed, and burn less fuel?

I ruled out the minimize jet-lag reason as sleeping masks were handed out and same thing happened on the shorter flight.


texts: What is the role of the flight dispatcher? How do the dispatcher and the flight crew interact?

texts:
The flight dispatcher is known as the ground pilot.

Air Canada flight dispatcher (source: On the job: Flight Dispatch)

It's not clear to me what is their role related to a given flight, or where are they working from, how the interactions occur between the flight dispatcher and the flight crew, or the maintenance team.


texts: Are gliders susceptible to bird strikes?

texts:
Gliders don't travel at the high speeds that make bird strikes so devastating in airliners. However, they are also smaller, lighter and softer, and can still move pretty swiftly.

Are they also vulnerable to bird strikes? What happens when a large bird collides with a glider?


texts: How does the IAS stall speed vary with increasing altitude?

texts:
First of all, we all know what IAS is and if not for some people you can follow this link to read the basics about stall and the differents speeds. So we also know that our TAS/ Mach number will increase with increasing altitude.

Let's assume that our IAS stall speed is 100kts at sea level, what will be our IAS stall speed at 30 000 feet with exactly the same aircraft ? (Assume ISA atmosphere)

Everyone would be tempted to answer that it doesn't change, right? but what about the low speed buffet in this picture ?

We agree in saying that the low speed buffet here is not the same as the one at sea level but look, our IAS/CAS stall speed has a higher value now. Maybe that it's a representative value of IAS/CAS calculated by the Air Data Computer from an EAS but still, our IAS stall speed has rised.

We can also keep it simple and think about it for a non pressurized single engine aircraft. I don't need an exact value but I would love to have a logic and smart answer.

It seems to be very basic but when we correctly think about it we can find ourself a little bit confused.

For me, the answer is : The IAS stall speed will increases


texts: How do commercial pilots keep situational awareness of their current call sign?

texts:
Air transport pilots operate flights with a variety of flight numbers, often with multiple flights in the same day. This means, as a result, the callsign that they are using changes as well. Also, according to this answer, sometimes the callsign is completely different from the flight number.

Given that, how do pilots maintain keep track of what callsign that they are listening for at a given point in time? Are there conventions for posting the callsign somewhere in the cockpit?


texts: What happens to the pressure and density of air passing through shock waves?

texts: I understand that the pressure and density of air increase as the air gets closer to shock waves and the pressure and density of air that has escaped the shock waves increase as well. Then, what happens to the pressure and density of air passing through the shock waves? I guess the density of air would decrease due to the great heat produced by the shock waves (correct me if I'm wrong on this) but what about the pressure? Does it increase because of the heat?


texts: I'm supposed to fly from NYC to Jacksonville on Friday afternoon. If the forecast for Hurricane Florence holds, the storm should be somewhere over the Carolinas at that point. With neither NYC or Jax being directly impacted, can commercial airliners fly around the hurricane? Would it be likely that our flight would be cancelled/delayed because of a major hurricane being in the flight path? Thanks


texts:
What happens to a turbine engine from the time that a start is initiated until stable idle is achieved?

What can go wrong?


texts: How to calculate the force exerted by pressure on hot air balloon envelope fabric?

texts:
How to calculate the force of hot air balloon envelope fabric?
and how to select a fabric which can bear this force?
For example, a spherality balloon:

$r=10~m$
$T_1=100~°C$
$ρ_1=0.95~kg/m^3$
$T_2=20~°C$
$ρ_2=1.25~kg/m^3$
$m=1000~kg$

Where:

$r$ is the  radii of the balloon, in m
$T_1$ is the temperature of balloon inside atmosphere, in Celsius
$ρ_1$ is the density of the balloon inside atmosphere, in  kg/m3
$T_2$ is the temperature of balloon outside atmosphere, in Celsius
$ρ_2$ is the density of the balloon outside atmosphere, in  kg/m3
$m$ is the total weight of the balloon(including balloon all equipment and persons)


texts: Why has the European Union banned several airlines?

texts:
The European Union does not permit the entry of several airlines in any of its member states. It does so to ensure the safety of its own airfields, as it feels that management of several airlines is not caring enough. How is this justified?

No such ban is implemented by any Middle-East or American country, which have a very good safety record. What are the EU's views on banning airlines?


texts: Why wouldn't a helicopter ejection seat eject sideways? Or forwards?

texts:
This question got me thinking. Ejecting from a helicopter is necessarily more complicated than ejecting from a fighter jet or other fixed-wing aircraft. The answer to this question states that ejection-capable helicopters blow the blades first, then the canopy, then eject the passengers.

This seems to me like a lot of explosions above your head, which seems only slightly preferable. Why not eject the passengers either sideways or forwards?


texts: How long does it take for a propeller engine to spool-up?

texts:
To build further upon the question Why does a turboprop lag?, the following:

Assuming a propeller engine is running in idle and the throttle lever is switched to full thrust instantaneously at t = 0 seconds. How long does it take before the propeller delivers full thrust?

Exact times for a specific engine or range/order of magnitude for a generic one would be appreciated


texts: Do some light sport aircraft have clipped wings to lower their cruise speed?

texts:
Light sport aircraft may have a max airspeed in level flight at MCP of 120kts. I have heard that there are some light sport aircraft that have had their wings clipped in order to have a lower cruise speed.

But why do they clip the wings to reduce the cruise speed? Wouldn't that require a higher speed as less lift is produced at the same speed with less wing area?
Also, thinking about gliders having a big wing span and fighter jets having a short wing span I can not see why you would clip the wings? What am I missing?


texts: Are answers posted to the FAA Sample Knowledge Exams?

texts: I'm studying for the private pilot knowledge exam, and wondering if the answers to the sample test are posted anywhere. Here is the exam: https://www.faa.gov/training_testing/testing/test_questions/media/PARSampleExam.pdf


texts: What failure modes did Airbus seek to eliminate or mitigate when they changed the design of the A310/A300-600's rudder travel limiter?

texts:
In the NTSB report on the crash of American Airlines Flight 587, it is mentioned (in the context of the changes between the A300-B2/B4's rudder system, on the one hand, and the A310/A300-600's rudder system, on the other), that

Second, Airbus changed the rudder travel limiter system on the A300-600 from a variable ratio design, [...] which was used on the A300B2/B4, to a variable stop design. Airbus indicated that the variable stop design was chosen for the A300-600 over the variable ratio design because it was less complex and had less severe failure modes.  [Page 38 of the PDF, numbered as page 24.]

Some background:

An aircraft's rudder travel limiter (RTL) is, as the name suggests, a device that, if working correctly, limits the amount of rudder travel available at high indicated airspeeds in order to help keep the pilot's control inputs from breaking the aircraft.1
A variable-ratio RTL reduces the amount of rudder deflection per unit pedal travel as airspeed increases; it does not reduce the amount of pedal travel available, or the amount of pedal force needed to produce maximum rudder deflection.
With a variable-stop RTL, the amount of rudder deflection per unit pedal travel stays constant; instead, the amount of pedal travel available to the pilot decreases as airspeed increases (in the case of the A310 and A300-600, from 4 inches at 135 KIAS to just 1.2 inches at 250 KIAS), as does the amount of pedal force required to move the rudder to its travel limit.

With this in mind, I'm wondering what they meant by "less severe failure modes" - what failure mode(s) were they scared of with the variable-ratio design?  If anything, there's one severe failure mode that's present in the variable-stop design, but not in the variable-ratio design: if a pilot pushes the rudder to the stop while the aircraft's airspeed is rapidly increasing, this can negate the protections imposed by the RTL entirely, by physically preventing the RTL variable-stop arm from moving into position.  This scenario has actually occurred at least once (during an inflight loss of control in a different American Airlines A300-600 in May 1997); to quote the aforementioned report:

[...]  Testing of the rudder travel limiter determined that, if a pilot applied a sufficiently large pedal force when the pedal was at its travel limit, such a pedal force would further slow or stop the movement and, consequently, the effectiveness of the rudder travel limiter. The flight 903 event demonstrated that slowing or stopping the rudder travel limiter by application of large pedal forces could result in the rudder position substantially exceeding the designed travel limit. The Safety Board was concerned that such an increase in available rudder beyond its designed rudder travel limits could permit excessive rudder movements and possibly result in high loads on the vertical stabilizer.  [Page 134, numbered 120.]

This failure mode would not be present with a variable-ratio RTL, the proper operation of which is not dependent on mechanically restricting the amount of rudder pedal travel.
What failure mode(s) were Airbus trying to eliminate/mitigate when they switched from a variable-ratio RTL to a variable-stop RTL for the A310 and A300-600?

1: Obviously, it was not successful in this regard as concerns AA587, as the pilot of that flight was able to break off his aircraft's vertical stabiliser without going beyond the limits imposed by the RTL; however, the RTL was never designed or intended to protect the aircraft from the extremely high aerodynamic loads produced by a rapid series of pilot-commanded rudder doublets,2 as occurred in AA587's case.
2: A rudder doublet is when the rudder is rapidly slammed from stop to stop - i.e., when the pilot sends the rudder to its travel limit in one direction, then immediately to its travel limit in the other direction.


texts: Does an F/A-18 require a lot of rudder in turns?

texts: I am an aspiring Navy fighter pilot and I use an X-Plane add on for FA-18 Hornet as a fighter. It's made by a creator named Colimata. I think the turns are unrealistic. When I begin a bank a lot of rudder is required to keep coordinated. Does anyone know if this is realistic?


texts: Odd whining sound from planes passing over

texts: I'm trying to figure out what is causing the sounds that I'm hearing from planes passing over my house. I'm located approximately 60 miles NW of ATL. The noise I hear sounds like a turbine rapidly spinning up, and then back down approximately 5 seconds after. My theory is that this is from an initial descent, relieving some resistance on the turbine blades, but can't quite find the sound anywhere else. I have never heard this sound prior to moving here to GA a year ago and I have lived near major airports near Newark, Virginia Beach, and several military bases throughout my career. I do not have a recording yet as the planes are not quite visible when this occurs and I also don't hear the approach.