8 ms·

I'm annoyed that the top answer is basically saying "well that wouldn't happen". So what? The question wasn't about how likely a thing is, it's what happens sho

• sorahn 8y ago
  This is why my favorite coffee table book is the “XKCD What If”. He only spends a few seconds on “why it probably wouldn’t happen”, then fully digs into what would happen if it did.
  • everdev 8y ago
    I think I have this book, it is wonderful. It talks about the nuclear explosion that would result of you tried to hiy a baseball traveling at the speed of light.
    • dotancohen 8y ago
      Yes, that's the first What-If in the book. If I remember correctly, the nuclear explosion is from the fusion of the atoms in the air molecules building up in front of baseball, before it even gets to the bat!
      • buzer 8y ago
        https://what-if.xkcd.com/1/ https://what-if.xkcd.com/1/ > Everything within roughly a mile of the park is leveled, and a firestorm engulfs the surrounding city. The baseball diamond is now a sizable crater, centered a few hundred feet behind the former location of the backstop. > A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered "hit by pitch", and would be eligible to advance to first base.
• jsight 8y ago
  But isn't the answer kind of the same? Undefined behavior will result.
  • mabbo 8y ago
    And that's a fine answer. "Nobody has a plan for that because it's so unlikely, so the outcome is kind of unknown", then maybe some examples that come close.
  • aeternus 8y ago
    I doubt it is even undefined in this case. Ejected vs. not-ejected is very likely not even an input variable to the autopilot. So the answer would be: Autopilot will attempt to do exactly what it was doing before the pilot ejected.
    • derefr 8y ago
      Ejecting presumably shoves the plane downward in recoil from the pilot shooting upward. The autopilot would notice that. Also, the plane would be lighter after the ejection. And perhaps—I'm just guessing—the cockpit window or ceiling might now be gone? In which case there'd suddenly be a lot of drag from air swirling down into the cockpit. So no, I don't expect the autopilot would continue to do exactly what it was doing before. It'd have to do a bunch of corrections, and then it would return to what it was doing before :) (Or those corrections might be enough to make it decide "the pilot" should take over. What happens when there's no pilot and no autopilot? I'm guessing that's down to the way avionics hardware reads out when nobody's touching it.)
      • viraptor 8y ago
        The first two options are for acceleration and weight. The first one changes enough while the plane is flying to be measured in Gs. There's also air turbulence. You wouldn't want to rely on secondary things like that. The second one can change for a number of reasons in a military plane. If you can even measure it, considering the changing acceleration. The cockpit can be broken or sensors may be malfunctioning as well, so "cockpit missing" is not a great signal.
• nv-vn 8y ago
  It's literally not something that gets programmed though. It's like asking "if Microsoft Word stops responding and I press the close button, is it programmed to auto-save my file?" It could not possibly get to that point where it could execute such instructions, so it makes no sense to program that behavior in.
• ChuckMcM 8y ago
  My experience with aircraft autopilots is limited. I've used them in small planes (altitude hold, heading hold types). I have read about them on commercial and military jets, in order to simulate them for a flight simulator. With that caveat, every autopilot system I've studied turns itself off if the plane is outside its flight regime. So for example, if you pull a plane straight up and do a tail stall and try to turn on the autopilot, the autopilot would refuse to engage as the plane isn't in a "flyable" regime. What is more, the autopilots I've seen were explicitly programmed to be pilot activated, so even if the plane went from one regime where the autopilot kicked itself off automatically, back to one where the plane could be flown by the autopilot, the autopilot would not automatically re-engage. If the pilot ejects because they cannot control the plane, neither can the autopilot so it won't be on. If the pilot put the plane on autopilot and then ejected, the ejection would most likely force the autopilot to disengage. If a pilot put a plane on autopilot, walked into the back of the plane and opened a door and parachuted out, the plane would continue flying on autopilot until it ran out of gas and then the autopilot would disengage and the plane would crash.
  • Boulth 8y ago
    Excellent answer and it's a lot better than the one on stack exchange. (by the way Chuck, your important section on your profile is really impressive, I've never seen anything like it but it makes total sense).
    • HeyLaughingBoy 8y ago
      A bit OT, but over 20 years ago, I asked Chuck a n00b question on comp.robotics.misc with my flamesuit on and ready since that was often the tone of responses on some of those newsgroups. He carefully considered my dumb question and gave me a polite, reasoned response. If only the majority of Usenet was like that. So, yeah. I think he means it :-) I was pleasantly surprised when I saw that username pop up here a few years ago.
  • 21 8y ago
    Not an expert, but in military planes there are systems which kick in exactly when the plane is outside it's normal regime. Auto-GCAS Saves Unconscious F-16 Pilot: https://www.youtube.com/watch?v=WkZGL7RQBVw https://www.youtube.com/watch?v=WkZGL7RQBVw
• Merad 8y ago
  I don't think autopilot programs are anywhere close to that complex. All the ones I've seen had modes like "hold course and speed" or "follow a series of pre-programmed waypoints". Some military aircraft will have a radar guided terrain following mode as well. In the (highly unlikely) event that the autopilot is engaged when the pilot ejects, the autopilot is just going to continue following whatever mode it's set to.
  • luke0016 8y ago
    Some are that complex. There are commercial systems that can essentially land a plane all by itself, called CAT IIIb. The pilot takes over after the plane is completely on the ground. In the future the planes will probably be able to taxi without the pilot too. https://en.wikipedia.org/wiki/Autopilot#Autopilot_for_ILS_landings https://en.wikipedia.org/wiki/Autopilot#Autopilot_for_ILS_la... https://en.wikipedia.org/wiki/Instrument_landing_system#ILS_categories https://en.wikipedia.org/wiki/Instrument_landing_system#ILS_...
• everdev 8y ago
  My kids ask questions like this all the time. Them: What if a shark jumped into a volcano? Me: That wouldn't happen because sharks live in the ocean and can't jump high enough or far enough to reach land. Them: OK, but what if? Me: ... It would get burned and die... So yes, if a pilot ejects and the plane had auto-pilot on and the auto-pilot was programmed to try to land after a pilot ejection and the plane was still safe to fly, the plane would in fact attempt to land.
  • berns 8y ago
    But the question is what is it actually programmed to do. The answer seems to be that is scenario is not contemplated. But it isn't a childish what if type of question.
    • theoh 8y ago
      The ejection seat is a rocket device. If it's connected to the avionics in any way, that is another potential point of failure. Maybe, if the cockpit canopy is jettisoned rather than fragmented at the moment the seat is fired, the switch/action of jettisoning the canopy is connected with avionics. Seems more likely but still improbable. But we need an expert...
  • dotancohen 8y ago
    A few decades ago an F86 pilot ejected from a flat spin. The resulting changing in CG leveled off the aircraft and when his wingman saw the plane flying level and straight again, he radioed "You better get back in that plane". It landed in flyable condition in a corn field, engine running.
    • deleted 8y ago
      [deleted]
    • theoh 8y ago
      This is a similar story. (Maybe it is actually the incident to which you are referring?) https://en.wikipedia.org/wiki/Cornfield_Bomber https://en.wikipedia.org/wiki/Cornfield_Bomber
• ThenAsNow 8y ago
  The assumption inherent in the question is that there is some kind of autopilot mode or logic change based on whether ejection has occurred or not. It is pretty unlikely that such explicit logic exists. Also, ejection only makes sense in the context of a manned military aircraft. For the question to make sense as posed, the implication is that the pilot had engaged the autopilot and then ejected while the autopilot had meaningful control authority over the aircraft. That's not a scenario the airworthiness certification authorities probably consider as critical. Manned aircraft require deliberate human action to engage the autopilot. What the flight control computers do in general (e.g., limit control inputs to keep aircraft within acceleration/maneuvering limits, automatically enter a stable attitude when stick forces are not present) is not considered the "autopilot". You could ask the question, "If the pilot ejects, do flight control computers attempt to fly the aircraft in any particular way?" At least for U.S. aircraft, recent ejections (e.g. the Thunderbird ejection near the end of Obama's tenure), suggest the answer is "no". If an automated flight termination system is installed, when safety constraints are violated (e.g., heartbeat signal or veering outside of geographic limits) it usually takes action to put the aircraft into the ground as quickly as possible (e.g., cut power to actuators on an unstable aircraft). This is common with UAVs. I don't think this is the case with manned aircraft.
• Kenji 8y ago
  That's StackExchange for you. If they don't mark your question as irrelevant and off-topic, they write a smug reply that doesn't answer the question.
• Pica_soO 8y ago
  Welcome to stackoverflow- where avoiding the question is an art.