106 votes
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Why is Python used on aircraft although it may not be certifiable?

Just because aviation developers use Python, does not mean that Python actually goes flying. Lots of aviation development is about testing, stressing, validating, analyzing, and documenting the code ...
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77 votes

Why do aircraft use hydraulics instead of pneumatics?

The big disadvantage here is the loss of precision due to the high compressibility of gas compared to liquid. Because gases are highly compressible, they provide a buffer to changes in pressure ...
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69 votes
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Why does the mixture knob spin?

It's called a Vernier Control. It has an internal screw that is part of the fixed housing, with threaded jaws that engage the threads around the outside and are part of the knob. When you turn the ...
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61 votes
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How does an Airbus aircraft connect to the Internet?

There are three different ways that aircraft can give internet access to its passengers, which will most likely be on at around 38,000 feet. First off, to have Inflight wifi, there needs to be a ...
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60 votes
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What does this plus (cross) sign on this electrical panel mean?

(airliners.net) Above I marked five similar plus signs on the 737 (there are more). Beneath the +'s are the contacts for the backlighting of each panel. If it acts up then pressing on the sign will ...
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58 votes
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What is the technique or procedure to disable/disengage the MCAS on Boeing 737 Max 8 & 9 Aircraft?

MCAS doesn't have its own on/off switch It is a fly-by-wire feature designed to account for a particular flight regime that would not (or was not expected to be) encountered very often in normal ...
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52 votes
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Are fighter jets designed to be so inherently unstable that a human can't fly one unassisted?

My short answer: Stability is reduced by shifting the center of gravity aft. Shifting it past the neutral point makes the airplane unstable, so movements away from the trimmed state are accelerated. ...
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49 votes
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How do aircraft stall warning systems work?

Audible Warning On light aircraft there is a reed (much like used on a musical wind instrument) mounted on one wing root, which is angled such that at the Angle of Attack which would cause a stall, ...
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49 votes

Is this opinion on personal computer flight simulators too strict or is it actually true?

It isn't true, not as an indictment of the simulator software community as a whole anyway. It may be that your pilot friend doesn't have experience with modern simulators, let's take X-Plane for ...
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49 votes
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Why does the B-29 have eight oil needles?

Each of the four engines is represented by two needles, one in each row. The top gauges are for the nose oil; the bottom gauges are for the rear oil. Nose and rear here refer to two sections (remember ...
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  • 119k
47 votes

Why do flight control cables not slacken during the cold temperatures at cruise?

If you look closely at your drawing you will see the cables are not really simple pull cables but really act like steel belts. That is, there is a pulley at each end and when you actuate the control ...
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44 votes

Does a Boeing 737-800 Have a Ram Air Turbine (RAT)?

No it does not, it does not need one, there is a mechanical connection to the flight controls that can be used if all else fails. The B737 flight controls are hydraulically powered. There are three ...
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43 votes
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Do safety-critical avionics systems run Linux?

None of the avionics systems I've worked on have used Linux or any consumer-type operating system. There are a few main issues. First is the practical. Most safety-critical avionics involve a ...
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39 votes
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How does WiFi work on an aircraft?

The small bulb houses the antenna that provides the satellite communications for the internet link. Inside the aircraft several wireless access points provide a WIFI signal to the passenger's ...
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37 votes
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Which external instruments are visible on the A350's nose section?

Here's a better picture showing all probes, and labeled: Link to original, high-resolution, unnumbered picture They are: Ice detector Multi-function probe 1 Static port TAT probe Side-slip vane ...
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35 votes
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What is a "Flight Director"?

The flight director is related to the autopilot system. It displays a guide on the artificial horizon, which shows the attitude of the airplane, but does nothing to control the plane. The guide ...
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35 votes
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Is there a landing gear system that extends automatically to prevent belly landing?

The simple fact is that an unintended gear deployment could be catastrophic, as it has a profound impact on the flight dynamics of the aircraft (one of the reasons there are warnings for both ...
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35 votes

Why is Python used on aircraft although it may not be certifiable?

As a software engineer who works at a defence company that develops and sells mission critical (but not safety critical) systems, I can confirm that there's a pretty even split between development in ...
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  • 451
35 votes
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Is Doppler navigation still in use for civilian aircraft?

Only in military applications nowadays, primarily helicopters as the system doesn't require the alignment process of the INS system, is not subject to GPS jamming, is very accurate when flying low (as ...
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  • 119k
34 votes
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Would a wireless fly by wire system be practical?

The fly-by-wire is absolutely vital for control of the aircraft, and the three dominating factors here are safety, safety and safety. Weight is not one of them. The fly-by-wire system is triple or ...
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33 votes

Do safety-critical avionics systems run Linux?

The short answer is that no safety-critical avionics systems that I'm aware of use Linux, and the highest criticality systems often don't use a commercial operating system at all. However, Linux is ...
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  • 6,325
32 votes

Do aircraft have siren to warn public in case of a crash over land?

I understand where you are at with this, I'm going to start off with a bit of math to show how it's not workable. Commercial airliners move quickly, even in a controlled glide one is going close to 3 ...
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32 votes

How do aircraft stall warning systems work?

Large commercial aircraft typically rely on either Angle of Attack (AoA) Vanes or Differential Pitot Tubes (Smart Probes (PDF)) to supply input to flight computers for the purpose of calculating AoA. ...
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  • 3,113
32 votes
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How do aircraft differentiate between missile locks?

Non-holographic radar systems such as those used in fighter aircraft and active guided missiles only point in one direction at a time. Normally, when the radar is in search mode, a mechanism inside ...
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31 votes

How is fuel dumped in aircraft?

Commercial aircraft have fuel dump nozzles located under the wings for dumping fuel. Fuel is gravity jettisoned from the tanks located in the wings and the fuselage. Large commercial aircraft such as ...
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  • 3,946
31 votes

Is there a landing gear system that extends automatically to prevent belly landing?

It has been tried before. Piper's PA-28R and PA-32R aircraft were equipped with an automatic landing gear extension system which would automatically extend the landing gear below 85kts regardless of ...
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31 votes
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Does the Antonov An-225 have an Auxiliary Power Unit (APU)?

No. It doesn't have an APU — it has two of them. They are located close to the main landing gears. From An-225 Mriya is the world’s largest aircraft (English version): Auxiliary power plant ...
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  • 3,116
29 votes
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Can a Boeing 777 be hacked?

As of currently, the answer to this question is in principle no for commercial aircraft, at least not remotely. There are two parts to this: From a system perspective: Aircraft systems could ...
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29 votes

What happens to the spinning wheels of the landing gear after takeoff, before retraction?

In most common passenger aircraft brakes are automatically applied when the gear is retracted. The wheels stop spinning before they enter the wheel well. This is particularly important because a ...
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29 votes
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Why do aircraft use 400 Hz AC instead of the 50 or 60 Hz of wall outlets?

Induction motors turn at a speed proportional to frequency, so a high frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are ...
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