106 votes
Accepted

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 ...
abelenky's user avatar
  • 30.7k
71 votes
Accepted

How dissimilar are redundant flight control computers?

As far as Airbus is concerned: Each unit is composed of two dissimilar boards, one driving the output and the other checking it. Dissimilar means both different CPUs and chipsets (A320 uses i386 (...
Jan Hudec's user avatar
  • 56.2k
53 votes
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Why are on-board computers allowed to change controls without notifying the pilots?

There is a general design principle, that some, but not all, of the behavior of the flight guidance system or autopilot should be visible to the pilot. Usually automatic engagement or disengagement ...
Cody P's user avatar
  • 6,775
50 votes
Accepted

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 ...
Gerry's user avatar
  • 19.7k
48 votes
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How does TACAN work?

How is TACAN different from the VHF Omnidirectional Range (VOR) system? A very short question, but the answer calls for describing several techniques which are by themselves difficult to summarize ...
mins's user avatar
  • 71.8k
40 votes

How dissimilar are redundant flight control computers?

Redundancy is not only achieved by multiplying the computers, but also by diversifying them. On Airbus airliners, two different computers are used (one with Intel chips, the other with Motorola chips ...
Peter Kämpf's user avatar
38 votes
Accepted

What exactly did this mechanic sabotage on the American Airlines 737, and how dangerous was it?

It's a serious crime, but what that guy did, only affecting one system out of three, would be unlikely to cause a crash if the pilots were half way reasonably competent. The take-off would be ...
John K's user avatar
  • 130k
37 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 ...
Cody P's user avatar
  • 6,775
37 votes
Accepted

How is varying modulation depth achieved by localizer ground transmitters?

The beam strength decreases as you move away from it's own centreline, so is it actually that the entire modulated signal strength decreases which when de-modulated is effectively a difference in ...
mins's user avatar
  • 71.8k
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 ...
T. Archer's user avatar
  • 451
32 votes

Why is the input power of an ADS-B Transponder much lower than its rated transmission output power?

The rated TX power is the maximum power emitted while transmitting. The electrical input power is much lower, because the design of the transponder is such that it accumulates energy from the input at ...
DeltaLima's user avatar
  • 83.1k
32 votes

Why is the 5G rollout a problem in the USA but apparently nowhere else?

If you read the FAA’s statements (not media reports) closely, you will find their complaint is merely that it hasn’t been proven not to be a problem, not that they actually expect a problem or have ...
StephenS's user avatar
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26 votes
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How does the ADF null positions find where the NDB is?

Short answer Do you find the null position, then assume it's 90 degrees from the beacon? That's correct. For the antenna pattern shown in the question, the angle between direction of nulls and peaks ...
mins's user avatar
  • 71.8k
25 votes
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Why didn't the A330neo and A320neo share the cockpit of the A350?

The short answer is that it's what the market wanted. There is always a lot of discussions between the airlines and manufacturer's before Airbus or Boeing commits to building a new aircraft. In ...
Gerry's user avatar
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25 votes
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What kind of delay does the A320's fly-by-wire system add?

Yes there will be a delay, but the delay caused by the control loop is really tiny. I've seen position control loops run successfully and stable at a couple of hundred Hz for simulator motion systems, ...
Koyovis's user avatar
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25 votes
Accepted

What CPU does the F-16 use?

MIL-STD-1760A is simply the standard that a processor must conform to, and is not an actual model of CPU. There are actually a lot of independent computers in a military aircraft, each with specific ...
aerobot's user avatar
  • 855
25 votes
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What is the difference between autopilot and fly-by-wire system?

An autopilot can fly the aircraft based on pilot selected modes. The autopilot therefore reduces the pilot's workload by replacing manual inputs via the yoke or sidestick. A fly-by-wire (FBW) system ...
Bianfable's user avatar
  • 55.5k
25 votes
Accepted

Why is the 5G rollout a problem in the USA but apparently nowhere else?

Since you are asking specifically about the 3.7–3.98 GHz band, the answer is that most of the world uses the 3.3–3.8 GHz band. The 3.7–3.98 GHz band was seen as much less important until US operators (...
Jörg W Mittag's user avatar
22 votes
Accepted

Are there any accident reports that mention hacked/compromised avionics as a factor?

Searching the NTSB Accident Database which also covers some international commercial flights for the key words "hack", "hacked" do not provide any results related to hacked avionics. Likewise using ...
Ron Beyer's user avatar
  • 36.2k
19 votes

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

There are a few options for this and it depends on the type of plane you are in, for the most part it looks like the information must at least be proactively navigated to in what ever NAV system you ...
Dave's user avatar
  • 101k
18 votes
Accepted

What causes the phase to change in a VOR?

The latest decades VOR are Doppler VOR (DVOR) where the bearing signal is produced by a 14 m diameter circular array of fixed Alford loops antennas. An additional central antenna radiates the ...
mins's user avatar
  • 71.8k
18 votes
Accepted

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

On a Boeing 777, the pilot can select to have nearby airports displayed on their navigation display (ND). It's the quickest way to get the info IMHO. Of course this data needs to be corroborated with ...
HenryJohn's user avatar
  • 466
18 votes

Why are on-board computers allowed to change controls without notifying the pilots?

There are two types of autopilots, one for the behaviour around the CoG and one for control of the CoG, as mentioned in this answer. Also sometimes called Inner Loop and Outer Loop. In short: The F-...
Koyovis's user avatar
  • 61.6k
18 votes

If you were to fly an ILS in a knife edge would you receve GS and LOC be flipped?

No, the directional part of ILS is located at the ground. (Ground) transmitter creates lobes with specified frequency and modulation to mark the high, low, right and left areas. LOC and GS signals ...
Martin's user avatar
  • 2,766
18 votes

What do the letters "h" and "i" next to TCAS ND symbols mean?

They mean the simulator or mockup is buggy and Wingdings 3 was missing / broken / not selected. There should be trend arrows there instead. First smoking gun: this appears to be a photo of either a ...
TypeIA's user avatar
  • 14.2k
18 votes
Accepted

At what point is the input data to glass cockpit PFDs converted to digital?

Glass cockpits are modular systems, and not all of them are exactly the same. But many/most include a module called an Air Data Computer (ADC) which performs the digitalization function for the ...
TypeIA's user avatar
  • 14.2k
17 votes
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Are there common standards for aviation graphical user interfaces?

I think your best bet might be going through the Instrument Flying Handbook (PDF, 68 MB) by the Federal Aviation Administration. It has plenty of nice graphics, if you're fine with a lot of other ...
Thunderstrike's user avatar

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