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If someone is jumping up and down in the bedroom of a private jet will the pilot be able to tell without listening? In other words, will the plane noticeably move?

Peter Mortensen
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    If you jump up and down in my piper archer ill know.... – Dave Nov 15 '20 at 00:17
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    ...jumping up and down, in the bedroom? So that's what the young people call it nowadays? – jvb Nov 15 '20 at 20:55
  • Finally, Suggestive Smut arrives on Aviation SE ! – Fattie Nov 16 '20 at 20:46
  • @Dave I think you mean jump and down *"ON"* my Piper Archer, not *"IN"*! :) – End Anti-Semitic Hate Nov 17 '20 at 00:24
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    @RockPaperLz-MaskitorCasket i guess it depends how tall you are... – Dave Nov 17 '20 at 01:02
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    @RockPaperLz-MaskitorCasket id say you jump up and down in a plane although you can jump up and down on a plane – Dave Nov 17 '20 at 01:04
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    @Dave I was teasing you a little because the last time I flew a Piper Archer, there was more room to jump "on" it than "in" it! :) – End Anti-Semitic Hate Nov 17 '20 at 01:26
  • @Dave Great photo! Notice how no one is brave enough (or stupid enough) to stand on the wingtips (and most of the heavier people are seated towards the fuselage)! – End Anti-Semitic Hate Nov 17 '20 at 01:28
  • a random google result said a small private plane is ~7,650lbs, so if two 180lb people jumped two feet up at exactly the same time, the plan would, as a rough order of magnitude, jostle (180*2)/(7,650+180*3)*24 = 1.0 inch – Mooing Duck Nov 17 '20 at 02:22
  • @MooingDuck Would that calculation depend on the altitude and/or atmospheric pressure? – End Anti-Semitic Hate Nov 17 '20 at 02:44
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    @MooingDuck - Well, 7650lbs still doesn’t have a bedroom. And, at over 6 feet tall, I might be able to jump forward and backward. But, definitely not up and down. For comparison, MTOW on a Light Sport Aircraft is 1320. A 4-seater trainer is twice that. A Pilatus-12 is four times that. A Phenom 300 is almost twice that. And still, no bedroom or headroom for jumping. So, to be realistic, at a bare minimum, you have to start at 20,000lbs. Five times that for a Gulfstream 650. – Dean F. Nov 17 '20 at 05:00
  • @RockPaperLz-MaskitorCasket: My back of the envelope math assumes that the planes and people are identical in every way except mass. Very back of the envelope. The idea is to show that the motion is going to be very very small. – Mooing Duck Nov 17 '20 at 18:04
  • @MooingDuck Thanks. I'm wondering, if you wanted to compute it more accurately, if you would have to take altitude and/or atmospheric pressure into account? (Not looking for the exact equation, but knowledge of whether those factors would play a role.) – End Anti-Semitic Hate Nov 17 '20 at 22:35

3 Answers3

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If an aircraft is large enough to have a “bedroom”, it will be too large for the movement of an average sized person in the bedroom to be noticed in the cockpit.

Dean F.
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    Now, if the plane is small enough.... A friend of mine was flying a PC-12 for a fractional ownership company one day and the part-owner customer and his girlfriend closed the cockpit door for some privacy, and he swears he could detect some "shaggin wagon" motion in the smooth air at cruise. At the end of the trip he was terrified to look the customer in the face because he was afraid he'd crack a smile, the wrong kind of smile, and it could have cost him his job. – John K Nov 15 '20 at 00:07
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    Oh that was sort of the scenario I was wondering about/ –  Nov 15 '20 at 04:25
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    @DeanF - but what about TWO average-sized persons..? :-) – Bob Jarvis - Слава Україні Nov 15 '20 at 21:01
  • @BobJarvis-ReinstateMonica - If the pilot can feel two people “jumping up and down” in an aircraft the size of a private jet, I would be highly impressed. – Dean F. Nov 16 '20 at 03:51
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    @DeanF. - alright, forget "jumping up and down". How about "swinging from a chandelier"? How about "going for a walk and a talk", eh? Listen -- strange women lying in ponds distributing swords is no basis for a system of government! Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony! You can't expect to wield supreme executive power just 'cause some watery tart threw a sword at you! I mean, if I went round sayin' I was an emperor just because some moistened bint had lobbed a scimitar at me, they'd put me away! – Bob Jarvis - Слава Україні Nov 16 '20 at 04:20
  • @BobJarvis-ReinstateMonica - And, now for something completely different. A plane with two bedrooms. But, seriously. No. – Dean F. Nov 16 '20 at 22:06
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    OP said nothing about the pilot actually being in the cockpit. – Mark Nov 17 '20 at 00:12
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    @Mark - Well, in that case, the pilot really can feel the passengers... – Dean F. Nov 17 '20 at 04:23
  • @Mark - ...jumping up and down. – Dean F. Nov 17 '20 at 04:24
  • Help! Help! I'm being repressed! – user33214 Nov 18 '20 at 10:10
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That depends on how much the weight of that person force shifting (as a result of changing the center of gravity (CG)) as a ratio to the total weight force of the aircraft. If it's a tiny ratio then it will not affect the CG and thus will not change the aircraft attitude.

Peter Mortensen
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Mohamed Sayed
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Depends very much on the size of the plane and the position of the jumping passenger.

For example, a Cirrus SF50 has a maximum takeoff weight of 2722kg. An overweight passenger (let's take 150kg for the example) jumping really hard can probably exert a force similar to 300kg upon landing. That's more than 10% of the gross weight of the plane. If the plane is not fully loaded, the ratio will be even bigger. So, especially if the passenger is not jumping close to the Center of Gravity of the plane, this is definitively feelable.

Take the other extreme, an Airbus Airbus A380-800. This one has a maximum takeoff weight of 575 000kg. Here the 300kg of the passenger only represents around 0.05% of the weight of the plane. The only way the pilot might feel that is if the passenger is jumping directly onto the rudder and even then I'd be doubtful.

For the sake of the argument, let's say all passengers in an A380 jump at the same time (and in a coordinated fashion, since random jumping would equal out). The plane is certified for 853 passengers. Say, every one of them weights an average of 100kg, which is a lot, then we would have 85300kg of passengers. Double that weight to get a rough estimate for the jumping impulse and now you have 170600kg, which would come close to 30% of the gross weight. Again, very feelable.

Dakkaron
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  • This answer brings me back to the question of scale. A smaller aircraft and a larger individual may have the respective mass in proportion to make the aircraft move in unexpected ways. But, an aircraft that small does not have the room required for a person that large to really jump up and down. Stomping up and down would be the most they could manage. – Dean F. Nov 17 '20 at 09:51
  • @DeanF. jumping from a squatting position and not straightening up fully could be quite effective. If they really wanted to cause trouble they could slam their feet down on landing, like breaking a plank by jumping on it. Of course I'm getting further from the OP's idea of "jumping up and down" – Chris H Nov 17 '20 at 11:18