| V1 is the speed at which you can still stop the plane before the end of the runway. (It is computed for each takeoff based on runway length, aircraft mass, takeoff engine power setting, flaps, wind, runway condition, etc.) When the plane reaches V1, pilots take the hand off the throttle: they're committed to takeoff, even if an engine fails. It is better to take off and fix the problem or land again, than to smash into whatever is beyond the end of the runway. |
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| ▲ | t0mas88 a day ago | parent | next [-] | | There is some margin in the calculations. But the training is very very clear, before V1 you must abort and after V1 you must continue. No discussion, no decision to make. You call V1, hands go off the throttles and no matter what you're going to fly. The margin is for example that the plane must not just be able to fly, but also reach a minimum climb gradient to clear obstacles with a bit of safety margin. There is also an allowance for the time it takes from calling abort to actually hitting the brakes. And for example headwind is part of the calculation (it makes the takeoff distance shorter) but only 50% of the headwind is used in the calculations. But all of those margins are not for the crew to use, the crew must just execute the procedure exactly as trained which means at V1 you're committed to continue the takeoff. And before V1 in case of an engine failure you have to hit the brakes to make sure you can stop before the end of the runway. | | |
| ▲ | panxyh 21 hours ago | parent [-] | | [flagged] | | |
| ▲ | akerl_ 20 hours ago | parent | next [-] | | What an intensely rude thing to say to someone who has been providing specialist knowledge in a very deep technical field up and down this page. | | |
| ▲ | panxyh 19 hours ago | parent [-] | | [flagged] | | |
| ▲ | kelnos 13 hours ago | parent | next [-] | | Maybe we should just stop commenting about whether or not something is AI generated. It doesn't add anything to the discussion, and is a waste of time. An apology (in advance or afterward) doesn't absolve you of responsibility. And if you feel the need to apologize for something in advance, that's a huge clue that maybe you should stop yourself from doing the thing you've just apologized for. | | |
| ▲ | panxyh 9 hours ago | parent [-] | | > Maybe we should just stop commenting about whether or not something is AI generated. It doesn't add anything to the discussion, and is a waste of time. Ok, sure! As for the rest, "excuse me if I'm wrong" is a very common and valid phrase, though a bit ruined by sarcastic misuse I attempted to show with it that I don't assume anything or default to hostility, though on a different occasion you'd yourself probably argue that others feelings are not my responsibility. I'm not sorry for asking the question, unless t0mas88 got offended by it. | | |
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| ▲ | dxdm 18 hours ago | parent | prev | next [-] | | Finding oneself with the need to apologize in advance is an excellent hint to examine extra hard if you really should do what you're apologizing for. Apologizing when necessary is good, not having to apologize is much better. It's a great level-up for characters of most alignments. | |
| ▲ | akerl_ 19 hours ago | parent | prev [-] | | I’d recommend giving your own goodwill in the future instead of accusing commenters and then asking for goodwill in response. | | |
| ▲ | panxyh 18 hours ago | parent [-] | | I did. By apologising and making a question, not accusation. The commenter himself didn't seem hurt by it. I'd recommend raising your outrage threshold.
I clearly am keeping this light hearted, while you go into fight mode because you saw the word "offence". Loosen up a bit :) |
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| ▲ | crazygringo 21 hours ago | parent | prev | next [-] | | Nothing about it reads as AI to me. I'm not even the commenter and I take offense when people suggest that knowledgeable, helpful HN comments are AI. | | |
| ▲ | panxyh 20 hours ago | parent | next [-] | | I see now that it probably wasn't, but "nothing" is an overstatement. And knowledgeable and helpful responses can be AI, so there might be a fallacy somewhere in your offence-taking.
Are you offended when people do that in general, or only when they are wrong? I do appreciate the effort put into writing a good comment. | | |
| ▲ | crazygringo 17 hours ago | parent | next [-] | | > it probably wasn't, but "nothing" is an overstatement. No, "nothing" seems perfectly accurate to me. I don't see even a single indication in tone, phrasing or punctuation that is a classic LLM giveaway. It's offensive to standards of decency to question the authenticity of someone's speech, and it doesn't matter if you phrase it as a question or preface it with "excuse me if not". Unless there is really a strong reason to suspect something, which is absolutely not the case here. It's offensive when it's not warranted. | |
| ▲ | throwaway150 13 hours ago | parent | prev [-] | | > but "nothing" is an overstatement Absolutely not. There was genuinely nothing in their thoughtful and informative reply that seemed AI generated to me. Have you never seen people on HN write detailed, articulate answers? This was one of them. Asking a question, getting a helpful response, and then implying it was written by AI is quite rude. Saying, "Excuse me if not, $SOMETHING_VERY_OFFENSIVE" does not make "$SOMETHING_VERY_OFFENSIVE" any less offensive! It's disheartening to see someone take the time to write a great answer only to be met with such a rude question. Please don't do that here. It's frustrating and discourages genuine contributors. | | |
| ▲ | panxyh 10 hours ago | parent [-] | | > to me If it's absolute, then why add that?
Mine "to me" gave me a different impression, but it being a "to me", I questioned, not accused. You perhaps recognize t0mas88 after all these years on HN. I don't. I'm relatively a new and infrequent user. So I hope that I would be criticised just as passionately if that'd be a random user whose comments indeed turned out to be AI. Because no matter what is the fact, the question is rude, nay, very offensive. Using AI isn't a tabu. It is fully debatable wether generating, reviewing and pasting helpful information on an informal forum is wrong, I just implied my own frustration with what I often experience. Of course I could've phrased it much better, and I suspect you guys wouldn't bat an eye. > Have you never seen people on HN write detailed, articulate answers? > It's frustrating and discourages genuine contributors. These are good points. |
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| ▲ | 20 hours ago | parent | prev [-] | | [deleted] |
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| ▲ | t0mas88 19 hours ago | parent | prev [-] | | Nope, AI would probably have written it nicer, I just typed it on my phone :) | | |
| ▲ | panxyh 19 hours ago | parent [-] | | Oh, cheers then :) But regarding flight ability, wouldn't that be V2?
I thought there exist conditions where V1 is well below rotation speed. Anyways, > to make sure you can stop before the end of the runway answers my main question, and makes sense from a procedural standpoint. But still, hard to believe that there is no room for in-situ evaluation if runway overrun is worse than likely crash.
Of course then again, those have to be split second decisions. |
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| ▲ | kelnos 13 hours ago | parent | prev | next [-] | | > Wouldn't veering into highway at 30 mph be weighted against certain, big loss of life? V1 for this plane in those conditions is nearly 200 mph. Even if they shut down all engines and applied full brakes (and assuming the brakes/tires didn't catch fire), they'd still run off the end of the runway with enough kinetic energy to kill themselves and anyone else in the way. | |
| ▲ | hugh-avherald a day ago | parent | prev | next [-] | | V1 is the decision speed with respect to a single engine failure in a multi-engine aircraft. It's the speed below rotation speed at which the decision to abort safely can no longer be made. Captains can make the decision to abort the takeoff in the case of absolute power loss or for 'failure to fly' (where the aircraft is clearly not going to fly, e.g. the elevator/pitch controls aren't responding). But the training is adamant: if you're uncertain what has happened after V1 you try to fly the plane away from the runway. | | |
| ▲ | panxyh 21 hours ago | parent [-] | | > abort safely That's what I'm getting at. I want to abort unsafely. Imagine 400 meters of grass field after the end of the runway, and a water body. I'm asking wether such factors are accounted for, or if plane on ground beyond runway does-not-compute. | | |
| ▲ | kelnos 12 hours ago | parent | next [-] | | > I want to abort unsafely I expect pilots are trained explicitly not to do that. If you can't abort safely, than it follows that the safer course of action is to try to fly. I'm sure there are exceptions to that, but a pilot has barely seconds in which to decide if any of those exceptions apply, so they're not going to abandon procedure unless the situation is clear. | |
| ▲ | HeyLaughingBoy 16 hours ago | parent | prev [-] | | You should never plan to use your safety margin! That "extra" 400m of grass? That's for all the other things that can still go wrong even when you follow procedure. e.g., you're below V1 so you abort takeoff, close throttles and hit the brakes. You should be able to safely stop on the runway. But now your brakes fail because maybe the reason you had to abort was a fire that also managed to burn through your brake lines, or it started to rain just as you were taking off, or... Now that's where the 400m of safety margin comes in to save your ass (hopefully). It's "extra", you don't plan on using it. | | |
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| ▲ | ExoticPearTree a day ago | parent | prev | next [-] | | After you reach V1, you take off. Between V1, Rotate and V2, there’s like a 2-3kts difference (between each of them). I am not familiar what the procedure is if you have dual-engine failure at or above V1. | |
| ▲ | kijin a day ago | parent | prev [-] | | A fully loaded plane is extremely likely to turn into a fireball if it hits anything on the ground, even at 30mph. It's just a thin shell of aluminum with tons of fuel sloshing inside. |
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