If the elevators failed?

Question

Just out of interest. If the elevators locked them selves in a neutral position on a large airliner, and this airliner hypothetically had a couple of hundred passengers with no seats or obstructions.... Could the pilot control pitch by ordering the passengers to run back and forth, moving the Cof G foward and Aft?

Answer 1

since elevator is a primary flight control it has usually a back-up operation if I remember my 737 it has even a manual reversion in case of lock out or failure. you only have to break torque or exert a force to overcome the locking mech.

But since you hypothetically says so, so perhaps it can, even with seats, but perhaps a little CG effect only. I say perhaps cause in the A340 where it  has a fuel tank in the elevator called "trim tank" In flight during climb the CG becomes more FWD, during cruise  when the fuel is going forward meaning from trim tank to the center tank the CG becomes more AFT.

Fuel  consumption is trim tank must be finish first then center tank then wing tank.

Answer 2

Theoretically....maybe.  But it's obviously kind of impractical to be able to coordinate that type of thing.  "Okay, time to flare....RUN!".  Also would depend on how big the aircraft was.

Answer 3

I take stairs... lol

Answer 4

Yes - hypothetically he could move the passengers back and forth (not necessarily make them run) to adjust the CG position. Perhaps, even this may make it possible to control the aircraft on its longitudinal axis, and even approach and land safely.

A more effective method, however, would be to use his power to control the pitch. This has happened in the case of the ill-fated Japanese 747 many years ago when the aircraft lost its rear empennage. Also, as stated earlier, the trim tabs may help marginally.

Answer 5

It might make sense to re-position the passengers once to get a more neutral CG, but I can't anyone attempting to reposition the passengers multiple times. It would make more sense to use engine power to control pitch. Also, if you still have elevator trim, that could be used to control the descent. Same for things like flaps and slats.

Answer 6

I saw a project in a NASA lab (on TV documentary) where they've programmed the flight computer to automatically control the ailerons to produce lift in the same effect the malfunctioning elevators would have. The pilot would use the control column as normal but the ailerons would be working a lot harder than you think.

Answer 7

Actually, the entire stabilizer is moved for trim by a device called the 'horizontal stabilizer jackscrew.'  Pilots are trained for the condition of jammed elevator to control the airplane by operating stab trim.  As long as inputs are slow and gentle this works fine.

Answer 8

The whole, running back and forth is a negative. but in 1989 , United 232 a DC 10's number 2 engine failed resulting in  severed hydraulic lines, and with no hydraulics you cant use the elevator, but they where able to control the plane by  variable thrust on each engine. so your answer would be Yes

Answer 9

There is a story of a Russain military cargo plane that was carrying a bunch of troops.  They had bottles of vodka that they helped themselves to, got wasted and started running back and forth inside the plane.  The center of gravity of the aircraft got all out of wack, the plane went into and unrecoverable stall and they ended up a smoking crater in the earth.  In the military they have loadmasters that have to calculate weight and balance so that doesn't happen.  You start playing with CG, you can get into serious trouble on those big aircraft, just ask those russian troops.

Answer 10

The plane that crashed at Sioux City lost elevators trim and rudder control when the rear engine blew pieces through the hydraulics to these control surfaces. The pilots were able to get the plane to Sioux City and make it to the runway using the two wing mounted engines. They used up down throttle to control pitch and differential throttle to control turns.

Unfortunately they did crash land on approach but there were survivors.

Answer 11

No, because if they aren't strapped in their seats when the airplane crashed, it'll make it harder to find the bodies. Shifting the C of G like that would create many more problems than just having the elevator in neutral.