8 ms·

If a pilot ejects, what is the autopilot programmed to do? (2018)

88 points by avestura 11mo ago

ortusdux 11mo ago
I recently learned about the Green Ramp disaster, where the crew ejected from an F-16 under full afterburner, and the jet continued on to collide with several parked airplanes, resulting in 24 fatalities. "As of 2025, this incident has the largest number of ground fatalities for an accidental crash of an aircraft on U.S. soil. It was also the worst peacetime loss of life suffered by the division since the end of World War II." https://en.wikipedia.org/wiki/Green_Ramp_disaster https://en.wikipedia.org/wiki/Green_Ramp_disaster
tekla 11mo ago
TLDR: It does nothing and it should never do anything
darkhorn 11mo ago
I think the most proper thing for the jet should be to destroy itself. In a war enviornment I would not like my enemy to gain intel about my military jets.
- yjftsjthsd-h 11mo ago
  Not my wheelhouse, but doesn't that involve packing the aircraft with explosives, and wouldn't that involve risk of blowing up if someone else shoots you? Or is there some better way to self-destruct?
  - klysm 11mo ago
    Assuming there is an autopilot present, nose diving at max afterburner straight down is probably going to yield a similar result
  - SoftTalker 11mo ago
    Impacting the ground usually does it.
  - DonHopkins 11mo ago
    Jets are usually full of jet fuel that can blow up if someone else shoots you, or they run into the ground.
  - estimator7292 11mo ago
    One could calculate the amount of energy in a given amount of explosive and smashing into the ground at high velocity. I'm too lazy to do so, but I can tell you they're on the same scale. A heavy object moving fast has a shocking amount of energy. When such an object impacts the ground, all that energy has to go somewhere.
  - cosmicgadget 11mo ago
    There are probably a number of clever and failsafe ways to divert jet fuel somewhere that would destroy the plane on command.
  - miki123211 11mo ago
    You could self-destruct just the software / computers by encrypting everything with a few keys that are easy to destroy. This is a standard technique for quick and secure data wipes, particularly on e.g. modern SSD drives where a traditional wipe might be incomplete due to wear leveling algorithms.
- jojobas 11mo ago
  Would you go near a plane that's an electronic signal away from blowing itself up? Even if mechanical, warplanes get combat damage, and having a system like that could make a difference between survivable and sure death.
  - dylan604 11mo ago
    Maybe bring some strong jamming equipment to prevent the electronic signal from being received?
    - jojobas 11mo ago
      The signal can originate on the plane itself due to a software glitch, stray currents in the grounding skin or whatever. If anything, jammers tend to interfere with the carrier's electronics itself.
- crazygringo 11mo ago
  I think its high-speed collision with the ground or ocean generally takes care of destroying it. Especially with no pilot attempting to keep it level and slow it down and minimize damage.
- mikkupikku 11mo ago
  You could erase computer memory, but blowing up the plane won't stop them from gaining intel about the materials, mechanism, and whatnot that make up the plane. An explosion won't vaporize the airplane, just break it into smallish pieces. Those can be collected and analyzed to reconstruct most any detail about the construction of the airplane. They even do this with missiles and bombs. Even shell fragments. When artillery shells packed full of high explosives go off, their intricate fuse mechanisms are left remarkably intact.
the__alchemist 11mo ago
If it's a controlled ejection scenario, you try to fly to a specific location, airspeed, heading, and altitude, then pull. It will be in your local-area in-flight guide. The intent is, the plane ends up somewhere away from civilization. This if, of course, only suitable for scenarios where you have this luxury.
hex4def6 11mo ago
It seems like the sensible thing to do would be to fry / erase any IFF and encryption related stuff, but otherwise continue as before. E.g, if it's already been programmed to fly straight and level, continue to do that. If it's deactivated, stay deactivated. Just seems like a whole 'nother set of characteristics to test otherwise, as well as adding extra unpredictability. The aircraft is probably damaged / on fire, so its flight characteristics are already going to be extremely different to normal. The best thing in the moment may be to let the aircraft lawn-dart in a field, rather than attempt to get straight and level, and in the process potentially fly over inhabited area or towards a friendly set of aircraft / buildings / vehicles.
- pdonis 11mo ago
  If the autopilot is engaged, the pilot won't be ejecting, because the aircraft will be in some kind of controlled flight. Autopilots will be disengaging and lighting up a big red light in the cockpit well before the aircraft gets to the point where the pilot would consider ejecting. Remember that ejecting is an absolute last resort, since the pilot is quite likely to be injured and runs a significant risk of being killed in the process of ejecting.
  - cluckindan 11mo ago
    About one in 20 ejections results in death, usually due to low altitude, or being hit/crushed by the seat. Compare to 20 in 20 jet airplane crashes resulting in death and suddenly pulling that lever might seem a worthwhile risk to take
    - pdonis 11mo ago
      > About one in 20 ejections results in death But more than that result in injury. The possible injuries are pretty severe. > Compare to 20 in 20 jet airplane crashes resulting in death Crashes if the plane is totally uncontrollable, probably yes. But there's a lot of gray area in between "totally uncontrollable" and "controllable enough that an autopilot can fly the plane". There are plenty of cases where a pilot was able to make a controlled enough crash that they walked away from it, even though the plane itself was totalled. And once we get to the point of "controllable enough that an autopilot can fly the plane", the pilot would have no reason to eject--because the plane is controllable enough that the autopilot can fly it. Which means whatever problems exist can't be very severe--or the autopilot would be disengaging, because it needs things to be working pretty well to fly the plane at all. That was the point of my response in the GP to this post.
SoftTalker 11mo ago
A pilot would only eject if the aircraft was uncontrollable with no reasonable hope for recovery. Unlikely the autopilot can do anything deliberate at that point.
- quotemstr 11mo ago
  Yes, but the autopilot should have some kind of contingency programming in case the pilot is mistaken about the aircraft being unflyable.
  - appreciatorBus 11mo ago
    If this was possible it would just be part of regular flight control laws and would be used to avoid becoming uncontrollable in the first place.
    - quotemstr 11mo ago
      Huh? If I'm the human pilot, I can pull the ejection lever for multiple reasons, including my just being an idiot. The plane, after I eject, should do something reasonable. Maybe it * starts broadcasting a mayday? * crashes into the nearest large body of water? * attempts to fly itself back to base (we have the technology)? I mean, it has to do something and flying straight and level until it runs out of fuel is unlikely to be the optimal value of "something" Why would it be controversial to say "Look, guys, we should decide what the plane does after the pilot ejects. Maybe the best policy is just flying same course and speed until fuel exhaustion, but we should choose this policy, not default into it without consideration."
      - SoftTalker 11mo ago
        Ejecting for for no reason would end the pilot's flying career. Ejecting for any reason will result in an investigation, at minimum. Pilots are expected to fly the airplane until the last extremity. So while yes it's possible, it's unlikely, and the return on investment of making the plane able to do something like "return to base" in that circumstance would be a large negative number.
cosmicgadget 11mo ago
Thinking about this one (https://theaviationist.com/2025/02/12/ea-18g-growler-crashes-in-san-diego-bay/ https://theaviationist.com/2025/02/12/ea-18g-growler-crashes...), it seems like after ejection you'd want the plane to lawn dart whenever possible. It allows the pilot to know if it is an okay place to ditch and it minimizes the reverse engineering risk. I imagine there is a good reason this isn't the way things are though.
Spooky23 11mo ago
This thread is a great example of how engineers by nature are tempted to add complexity to nearly any scenario.
bragr 11mo ago
The analysis and conclusions of the responders here (2018) seem pretty invalidated by the 2024 F-35B ejection incident. Maybe more thought should be put into what the autopilot should do? https://www.marinecorpstimes.com/news/your-marine-corps/2024/10/31/marine-pilot-loses-command-after-ejecting-from-f-35b-that-kept-flying/ https://www.marinecorpstimes.com/news/your-marine-corps/2024...
- appreciatorBus 11mo ago
  A single incident doesn’t invalidate anything. No one has argued that it’s impossible for a fighter to fly on for a significant period of time in good shape after a pilot ejects, or the pilot has never ejected mistakenly out of an air worthy aircraft. Rather the argument is that this is a vanishing rare occurrence and the complexities of trying to implement an unmanned auto pilot of a potentially damaged aircraft are probably not worth the handful of times it might be used. One incident doesn’t disprove that it’s vanishingly rare.
ffb7c5 11mo ago
I think we should make an API call to an LLM with the current GPS location to decide what to do, bonus points if we can mount a forward facing camera and upload the picture as well
- latentsea 11mo ago
  > bonus points if we can mount a forward facing camera and upload the picture as well As an NFT of course.
jcul 11mo ago
> The only victim of the accident was Wim Delaere, a computer science student reported to have been either 18 or 19 years old.[4][5][1] He was sleeping alone after celebrating the end of his university exams the previous day when the MiG crashed and killed him at 10:30 am. His mother and brother were shopping for groceries in Kortrijk, and his father was working in Ypres.[4] From the linked Wikipedia article on one of the answers. What an unlucky kid. https://en.wikipedia.org/wiki/1989_Belgium_MiG-23_crash https://en.wikipedia.org/wiki/1989_Belgium_MiG-23_crash
- deadbabe 11mo ago
  His death later inspired the movie Donnie Darko, about a kid in 1988 who is killed by a jet engine in similar circumstances.
  - PNewling 11mo ago
    I can't find anything that would suggest this is true, but I would love if you were able to link me something proving me wrong, as I loved that movie growing up and like reading about it still.
    - HeyLaughingBoy 11mo ago
      You have no idea how old you saying "I loved that movie growing up" makes me feel :-)
  - HeyLaughingBoy 11mo ago
    /pedantic That's not at all what Donnie Darko is about, but a jet engine from an unaccounted-for airplane does land in his house.
ternus 11mo ago
I was astonished at the claim that pilots ejecting can lose half an inch of height due to spinal compression induced by the G-forces. Claims seem to be borne out: https://www.forcesnews.com/news/can-ejecting-aircraft-make-pilot-shorter https://www.forcesnews.com/news/can-ejecting-aircraft-make-p... https://www.quora.com/Do-pilots-lose-height-when-they-eject-1 https://www.quora.com/Do-pilots-lose-height-when-they-eject-...
- ern 11mo ago
  Making sure that the consequences are well-publicized also has the useful side-effect of making sure that ejection is regarded as a last resort.
  - varjag 11mo ago
    You don't really get a rando who would be unaware of that in the pilot seat of a fighter jet very often.
    - ern 11mo ago
      By "publicize" I meant making sure the consequences were well known within the fighter pilot community.
      - varjag 11mo ago
        They were well known in fighter pilot community. It's not an obscure fact, they undergo training for ejection seats. There is a specific ejection posture to minimize the risk of snapping your spine.
dang 11mo ago
Discussed at the time (of the article): If a pilot ejects, what is the autopilot programmed to do? - https://news.ycombinator.com/item?id=17391550 https://news.ycombinator.com/item?id=17391550 - June 2018 (76 comments)
jayd16 11mo ago
I wonder if dumping the fuel ASAP is a good idea or bad idea.
- euroderf 11mo ago
  Only good, I would think. It's pretty volatile stuff innit ? Dispersion.
1970-01-01 11mo ago
They did not address the fact that sometimes there's more than one soul onboard. So the answer is truly "it depends"
shadyKeystrokes 11mo ago
[dead]

88 points by avestura 11mo ago

I recently learned about the Green Ramp disaster, where the crew ejected from an F-16 under full afterburner, and the jet continued on to collide with several parked airplanes, resulting in 24 fatalities. "As of 2025, this incident has the largest number of ground fatalities for an accidental crash of an aircraft on U.S. soil. It was also the worst peacetime loss of life suffered by the division since the end of World War II." https://en.wikipedia.org/wiki/Green_Ramp_disaster https://en.wikipedia.org/wiki/Green_Ramp_disaster

tekla 11mo ago

TLDR: It does nothing and it should never do anything

darkhorn 11mo ago

I think the most proper thing for the jet should be to destroy itself. In a war enviornment I would not like my enemy to gain intel about my military jets.

yjftsjthsd-h 11mo ago
Not my wheelhouse, but doesn't that involve packing the aircraft with explosives, and wouldn't that involve risk of blowing up if someone else shoots you? Or is there some better way to self-destruct?
- klysm 11mo ago
  Assuming there is an autopilot present, nose diving at max afterburner straight down is probably going to yield a similar result
- SoftTalker 11mo ago
  Impacting the ground usually does it.
- DonHopkins 11mo ago
  Jets are usually full of jet fuel that can blow up if someone else shoots you, or they run into the ground.
- estimator7292 11mo ago
  One could calculate the amount of energy in a given amount of explosive and smashing into the ground at high velocity. I'm too lazy to do so, but I can tell you they're on the same scale. A heavy object moving fast has a shocking amount of energy. When such an object impacts the ground, all that energy has to go somewhere.
- cosmicgadget 11mo ago
  There are probably a number of clever and failsafe ways to divert jet fuel somewhere that would destroy the plane on command.
- miki123211 11mo ago
  You could self-destruct just the software / computers by encrypting everything with a few keys that are easy to destroy. This is a standard technique for quick and secure data wipes, particularly on e.g. modern SSD drives where a traditional wipe might be incomplete due to wear leveling algorithms.
jojobas 11mo ago
Would you go near a plane that's an electronic signal away from blowing itself up? Even if mechanical, warplanes get combat damage, and having a system like that could make a difference between survivable and sure death.
- dylan604 11mo ago
  Maybe bring some strong jamming equipment to prevent the electronic signal from being received?
  - jojobas 11mo ago
    The signal can originate on the plane itself due to a software glitch, stray currents in the grounding skin or whatever. If anything, jammers tend to interfere with the carrier's electronics itself.
crazygringo 11mo ago
I think its high-speed collision with the ground or ocean generally takes care of destroying it. Especially with no pilot attempting to keep it level and slow it down and minimize damage.
mikkupikku 11mo ago
You could erase computer memory, but blowing up the plane won't stop them from gaining intel about the materials, mechanism, and whatnot that make up the plane. An explosion won't vaporize the airplane, just break it into smallish pieces. Those can be collected and analyzed to reconstruct most any detail about the construction of the airplane. They even do this with missiles and bombs. Even shell fragments. When artillery shells packed full of high explosives go off, their intricate fuse mechanisms are left remarkably intact.

the__alchemist 11mo ago

If it's a controlled ejection scenario, you try to fly to a specific location, airspeed, heading, and altitude, then pull. It will be in your local-area in-flight guide. The intent is, the plane ends up somewhere away from civilization. This if, of course, only suitable for scenarios where you have this luxury.

hex4def6 11mo ago

It seems like the sensible thing to do would be to fry / erase any IFF and encryption related stuff, but otherwise continue as before. E.g, if it's already been programmed to fly straight and level, continue to do that. If it's deactivated, stay deactivated. Just seems like a whole 'nother set of characteristics to test otherwise, as well as adding extra unpredictability. The aircraft is probably damaged / on fire, so its flight characteristics are already going to be extremely different to normal. The best thing in the moment may be to let the aircraft lawn-dart in a field, rather than attempt to get straight and level, and in the process potentially fly over inhabited area or towards a friendly set of aircraft / buildings / vehicles.

pdonis 11mo ago
If the autopilot is engaged, the pilot won't be ejecting, because the aircraft will be in some kind of controlled flight. Autopilots will be disengaging and lighting up a big red light in the cockpit well before the aircraft gets to the point where the pilot would consider ejecting. Remember that ejecting is an absolute last resort, since the pilot is quite likely to be injured and runs a significant risk of being killed in the process of ejecting.
- cluckindan 11mo ago
  About one in 20 ejections results in death, usually due to low altitude, or being hit/crushed by the seat. Compare to 20 in 20 jet airplane crashes resulting in death and suddenly pulling that lever might seem a worthwhile risk to take
  - pdonis 11mo ago
    > About one in 20 ejections results in death But more than that result in injury. The possible injuries are pretty severe. > Compare to 20 in 20 jet airplane crashes resulting in death Crashes if the plane is totally uncontrollable, probably yes. But there's a lot of gray area in between "totally uncontrollable" and "controllable enough that an autopilot can fly the plane". There are plenty of cases where a pilot was able to make a controlled enough crash that they walked away from it, even though the plane itself was totalled. And once we get to the point of "controllable enough that an autopilot can fly the plane", the pilot would have no reason to eject--because the plane is controllable enough that the autopilot can fly it. Which means whatever problems exist can't be very severe--or the autopilot would be disengaging, because it needs things to be working pretty well to fly the plane at all. That was the point of my response in the GP to this post.

SoftTalker 11mo ago

A pilot would only eject if the aircraft was uncontrollable with no reasonable hope for recovery. Unlikely the autopilot can do anything deliberate at that point.

quotemstr 11mo ago
Yes, but the autopilot should have some kind of contingency programming in case the pilot is mistaken about the aircraft being unflyable.
- appreciatorBus 11mo ago
  If this was possible it would just be part of regular flight control laws and would be used to avoid becoming uncontrollable in the first place.
  - quotemstr 11mo ago
    Huh? If I'm the human pilot, I can pull the ejection lever for multiple reasons, including my just being an idiot. The plane, after I eject, should do something reasonable. Maybe it * starts broadcasting a mayday? * crashes into the nearest large body of water? * attempts to fly itself back to base (we have the technology)? I mean, it has to do something and flying straight and level until it runs out of fuel is unlikely to be the optimal value of "something" Why would it be controversial to say "Look, guys, we should decide what the plane does after the pilot ejects. Maybe the best policy is just flying same course and speed until fuel exhaustion, but we should choose this policy, not default into it without consideration."
    - SoftTalker 11mo ago
      Ejecting for for no reason would end the pilot's flying career. Ejecting for any reason will result in an investigation, at minimum. Pilots are expected to fly the airplane until the last extremity. So while yes it's possible, it's unlikely, and the return on investment of making the plane able to do something like "return to base" in that circumstance would be a large negative number.

cosmicgadget 11mo ago

Thinking about this one (https://theaviationist.com/2025/02/12/ea-18g-growler-crashes-in-san-diego-bay/ https://theaviationist.com/2025/02/12/ea-18g-growler-crashes...), it seems like after ejection you'd want the plane to lawn dart whenever possible. It allows the pilot to know if it is an okay place to ditch and it minimizes the reverse engineering risk. I imagine there is a good reason this isn't the way things are though.

Spooky23 11mo ago

This thread is a great example of how engineers by nature are tempted to add complexity to nearly any scenario.

bragr 11mo ago

The analysis and conclusions of the responders here (2018) seem pretty invalidated by the 2024 F-35B ejection incident. Maybe more thought should be put into what the autopilot should do? https://www.marinecorpstimes.com/news/your-marine-corps/2024/10/31/marine-pilot-loses-command-after-ejecting-from-f-35b-that-kept-flying/ https://www.marinecorpstimes.com/news/your-marine-corps/2024...

appreciatorBus 11mo ago
A single incident doesn’t invalidate anything. No one has argued that it’s impossible for a fighter to fly on for a significant period of time in good shape after a pilot ejects, or the pilot has never ejected mistakenly out of an air worthy aircraft. Rather the argument is that this is a vanishing rare occurrence and the complexities of trying to implement an unmanned auto pilot of a potentially damaged aircraft are probably not worth the handful of times it might be used. One incident doesn’t disprove that it’s vanishingly rare.

ffb7c5 11mo ago

I think we should make an API call to an LLM with the current GPS location to decide what to do, bonus points if we can mount a forward facing camera and upload the picture as well

latentsea 11mo ago
> bonus points if we can mount a forward facing camera and upload the picture as well As an NFT of course.

jcul 11mo ago

> The only victim of the accident was Wim Delaere, a computer science student reported to have been either 18 or 19 years old.[4][5][1] He was sleeping alone after celebrating the end of his university exams the previous day when the MiG crashed and killed him at 10:30 am. His mother and brother were shopping for groceries in Kortrijk, and his father was working in Ypres.[4] From the linked Wikipedia article on one of the answers. What an unlucky kid. https://en.wikipedia.org/wiki/1989_Belgium_MiG-23_crash https://en.wikipedia.org/wiki/1989_Belgium_MiG-23_crash

deadbabe 11mo ago
His death later inspired the movie Donnie Darko, about a kid in 1988 who is killed by a jet engine in similar circumstances.
- PNewling 11mo ago
  I can't find anything that would suggest this is true, but I would love if you were able to link me something proving me wrong, as I loved that movie growing up and like reading about it still.
  - HeyLaughingBoy 11mo ago
    You have no idea how old you saying "I loved that movie growing up" makes me feel :-)
- HeyLaughingBoy 11mo ago
  /pedantic That's not at all what Donnie Darko is about, but a jet engine from an unaccounted-for airplane does land in his house.

ternus 11mo ago

I was astonished at the claim that pilots ejecting can lose half an inch of height due to spinal compression induced by the G-forces. Claims seem to be borne out: https://www.forcesnews.com/news/can-ejecting-aircraft-make-pilot-shorter https://www.forcesnews.com/news/can-ejecting-aircraft-make-p... https://www.quora.com/Do-pilots-lose-height-when-they-eject-1 https://www.quora.com/Do-pilots-lose-height-when-they-eject-...

ern 11mo ago
Making sure that the consequences are well-publicized also has the useful side-effect of making sure that ejection is regarded as a last resort.
- varjag 11mo ago
  You don't really get a rando who would be unaware of that in the pilot seat of a fighter jet very often.
  - ern 11mo ago
    By "publicize" I meant making sure the consequences were well known within the fighter pilot community.
    - varjag 11mo ago
      They were well known in fighter pilot community. It's not an obscure fact, they undergo training for ejection seats. There is a specific ejection posture to minimize the risk of snapping your spine.

dang 11mo ago

Discussed at the time (of the article): If a pilot ejects, what is the autopilot programmed to do? - https://news.ycombinator.com/item?id=17391550 https://news.ycombinator.com/item?id=17391550 - June 2018 (76 comments)

jayd16 11mo ago

I wonder if dumping the fuel ASAP is a good idea or bad idea.

euroderf 11mo ago
Only good, I would think. It's pretty volatile stuff innit ? Dispersion.

1970-01-01 11mo ago

They did not address the fact that sometimes there's more than one soul onboard. So the answer is truly "it depends"

shadyKeystrokes 11mo ago

[dead]