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In the extremely scientifically accurate movie Airplane the Autopilot takes off with the gear up.

Has this ever happened? Could any commercial or 4+ passenger GA aircraft do this, say with a 1%+ chance of not crashing?

Maybe with a smooth, small ditch that would guide the body and/or grass it could doable. The belly would certainly be warm! (Or on fire)

Silly question, but didn't find anything about it online.

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    $\begingroup$ Yes sure, any flying boat does :) $\endgroup$
    – sophit
    Commented Dec 28, 2022 at 3:47
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    $\begingroup$ I don't have any authoritative evidence on this, but I expect the friction of the ground would prevent the aircraft reaching takeoff speed. There might also be some difficulties in raising the nose. $\endgroup$ Commented Dec 28, 2022 at 6:20
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    $\begingroup$ @RalphJ, I would could the skis as (a special kind of) landing gear though. $\endgroup$
    – Jan Hudec
    Commented Dec 28, 2022 at 12:54
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    $\begingroup$ @JanHudec If the skis are all that you've got (like photo in Mike Sowsun's post, or a pure airplane-on-skis), I'd entirely agree. On an LC-130, the wheels are still there, but they are extended/retracted thru the skis, so the case could be made that it's still a "gear up" takeoff -- especially since the skis can't be retracted. But this is an exercise in terminology more than in what the OP was asking about, so I'm not inclined to pursue this thought much further. $\endgroup$
    – Ralph J
    Commented Dec 28, 2022 at 18:22
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    $\begingroup$ the Autopilot Get it right. That's Otto Pilot. :-D $\endgroup$ Commented Dec 31, 2022 at 0:06

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Excluding planes that use something else than landing gear for take-off—seaplanes, using launch rails, or air-launched—there was one accident where a plane went around after landing gear up by mistake: Crash: PIA A320 at Karachi on May 22nd 2020, impacted residential area during final approach, both engines failed as result of a gear up touchdown. Two points to take from that accident:

  1. The plane was only able to lift off again because it still had way higher than normal take-off speed. Since sitting on the engines does not allow as high pitch attitude as normal rotation on gear, the angle of attack is lower and so higher speed is needed to get the same lift.
  2. The damage to the engines caused during the event caused them to both fail in a minute or so.

That shows it's unlikely it would be possible to take off this way from stand-still. Of course this does not show no plane could do that, but most commercial aircraft are similar in that regard. They are designed stay intact enough on a gear-up landing so the people on board won't be injured, but will be damaged enough that they won't be able to take off without repairs.

Side note: the autopilot can't start the engines on its own and the pilots would hopefully not be insane enough to do that with airplane sitting on its belly.

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    $\begingroup$ Comments on that link mention "a Tu-154 touching down with landing gear retracted, skidding a solid 650m on the runway while the engines spooled up, lifting off again for another approach and landing successfully." Another commenter points out that its tail-mounted engines will keep them out of harms way while scraping the belly, unlike the A320 accident aircraft. So this idea is a non-starter for an A320, but maybe not for other designs. $\endgroup$ Commented Dec 30, 2022 at 1:29
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    $\begingroup$ @PeterCordes … thanks; fortunately there is even a reference: Malév flight 262. While the tail-mounted engines would not be damaged, it really surprises me the plane was able to lift off again, because the bottom of the aircraft is flat so without gear it cannot raise the nose to get enough lift. $\endgroup$
    – Jan Hudec
    Commented Dec 31, 2022 at 15:24
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    $\begingroup$ The fuselage curves upward some distance ahead of the elevators; maybe at the speed they were going (with engines already spooling up before touchdown) that short lever arm was enough for the pitch authority the elevators could provide? (Compared to how far the center of mass was ahead of the centre of lift from the wings, which is what the tail would have to balance on the other end of that lever.) $\endgroup$ Commented Dec 31, 2022 at 15:31
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Just a raw estimation to be added to the other answers:

At takeoff, engine's thrust is used to accelerate the airplane and to overcome aerodynamic drag plus rolling resistance of the landing gears. Or, in the case of our sliding airplane, the sliding friction.

In order to understand if making the airplane slide on its belly instead of rolling on its tires is doable, let's ballpark estimate these four terms (acceleration, aerodynamic drag, rolling resistance and sliding friction). No worries, just a couple of simple multiplications.

  1. Acceleration: since the airplane has to reach the same takeoff speed within the same airfield's length both with and without landing gears, then it has to accelerate in the same way for both cases; from basic physics, acceleration is $a=V²/2L$ and for Newton's second law the relevant force to be applied is $F=ma=mV²/2L$ where $m$ is the airplane's mass, $V$ the takeoff speed and $L$ the field's length. Let's use a B747 to do the maths (SI units): $F=(370'000\times85²)/(2\times3'300)=405kN$

  2. Drag: let's evaluate it just before takeoff which is where the highest value is reached before (any kind of) landing gears become useless; we use the usual drag equation $D=½\rho V²SC_d$ at sea level with $C_d=0.02$ as given in the B747's polar: $D=½\times1.125 \times85² \times511 \times0.02=40kN$

  3. Rolling resistance; this is simply the weight times a coefficient which depends on the materials; for tire on asphalt this is some 0.03: $F_{roll}=370'000 \times 0.03=11kN$

  4. Sliding friction; also in this case it is simply the weight times a friction coefficient that for steel (I couldn't find aluminium) on asphalt is more or less 1: $F_{slide}=370'000 \times 1=370kN$

So, let's do the sum to get the needed thrust $T$ for the case with landing gears (1.+2.+3.) and without (1.+2.+4.) respectively:

$T=405+40+11=456kN$

vs.

$T=405+40+370=815kN$

The latter represents an increase of some 80% in respect to a takeoff with landing gears... most probably not feasible.

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  • $\begingroup$ Wing moving through the air needs to be pushed with a force that is typically between 0.05 and 0.10 of the weight it is carrying. A bit more at the high angle of attack occurring at take-off. Since commercial aircraft have to be able to continue flying with one engine inoperative, with all engines it needs at least 0.2, but usually around 0.3 of its weight. If the coefficient of friction of aluminum on tarmac was just 0.1, the engines would have plenty of power to accelerate it. I don't think it's that low at the weights involved though. $\endgroup$
    – Jan Hudec
    Commented Dec 28, 2022 at 13:51
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    $\begingroup$ … remember, we are not talking about asphalt and aluminum ski sliding on it, we are talking about tarmac (asphalt-glued gravel) and normal forces under which the aluminum piece is abraded rapidly. $\endgroup$
    – Jan Hudec
    Commented Dec 28, 2022 at 13:52
  • $\begingroup$ @JanHudec: you're definitely right, I was just considering the very beginning of the takeoff. I'm going to update my answer with a more general approach. $\endgroup$
    – sophit
    Commented Dec 28, 2022 at 17:52
  • $\begingroup$ @JanHudec: done! $\endgroup$
    – sophit
    Commented Dec 28, 2022 at 22:30
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    $\begingroup$ If that is a "raw estimation" I'd hate to see a detailed one! Nice! $\endgroup$ Commented Dec 30, 2022 at 21:57
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Amphibious aircraft. These only have the gear down when taking off from the ground, not from the water. For instance, de Havilland Canada Twin Otter can be configured as amphibious, it was used by multiple airlines and with 19-20 passengers it is quite an airliner.

Rocket launched (Space Shuttle) or air dropped (X-15) aircraft also use the landing gear only for landing but the most known examples are not commercial. SpaceShipTwo however seems commercial at least in the plans.

While the unprepared land base aircraft may have enough engine power at least on ice, I cannot imagine how it could maintain the necessary orientation without the landing gear while taking off.

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Aside from the other answers, I think what you’re asking is whether an aircraft could or has taken off where undercarriage would normally be extended. I can’t say that this has never happened but it seems most unlikely. Propeller-driven aircraft would typically have the prop touch the ground with the wheels retracted, but that wouldn’t be the case for a jet, which would likely have a high enough thrust/weight ratio to overcome friction, especially on a wet runway. That raises the question of why any pilot would attempt this; if the undercarriage was inoperative then they would be faced with a wheels-up landing. If they were attempting to steal a plane then why not choose one with its undercarriage extended. There are more unlikely scenarios but I don’t need to list them here. The only definitive answer would be from someone who has seen/executed this manoeuvre, if it’s never happened then it’s unanswerable.

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  • $\begingroup$ I don't think any plane could take off like that, but one went around like that—and crashed due to the damage it caused. $\endgroup$
    – Jan Hudec
    Commented Dec 28, 2022 at 12:33
  • $\begingroup$ Note that wheels-up landing is not a huge deal—all planes are designed so that if they land wheel-up (on runway or other sufficiently flat ground), they remain sufficiently intact to avoid injury for the people on board. $\endgroup$
    – Jan Hudec
    Commented Dec 28, 2022 at 12:35
  • $\begingroup$ May happen if there is some danger on the ground so grave that attempting to take off with such an aircraft becomes an option. Like enemy advancing, for instance. $\endgroup$
    – h22
    Commented Dec 28, 2022 at 14:00
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    $\begingroup$ @Jan Hudec - a 737 has a thrust/weight ratio of about 0.3 so it would struggle to move on a dry surface but may do better on a wet runway. Once it started moving the left from the wings would reduce friction from the ground. $\endgroup$
    – Frog
    Commented Dec 28, 2022 at 18:40
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    $\begingroup$ The most likely case for a commercial airplane taking off "gear up" would be a large floatplane (eg. a float-equipped Twin Otter) taking off from a grass runway on the floats. $\endgroup$
    – Mark
    Commented Dec 29, 2022 at 2:09
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Float planes and flying boats have taken off from snow or ice in the past.

Here are two Videos of a Cessna float plane taking off from a frozen lake.

Cessna 185 taking off on the ice with floats - Red Lake, Ontario

Off the ice on floats, Red Lake

enter image description here

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Malév Flight 262 performed a gears-up touchdown, skidded on the runway for 650 meters, then took off again and flew for 16 minutes before making a second landing. https://en.wikipedia.org/wiki/Mal%C3%A9v_Flight_262

This was probably possible due to the Tu-154 landing gear pods, into which the wheels retract during flight, which acted as sleds and shielded the landing gear, wing and flaps, as well as the Tu-154's tail-mounted trijet engine configuration and high thrust-to-weight ratio.

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