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This question already has an answer here:

During my PPL training, We practiced some emergency procedure on Piper cherokee and simulated flight controls failure.

My instructor asked me to sit on one hand and place the other on the trimmer.

I had to fly the aircraft using only rudder and trimmer, using trimmer and power for pitching and rudder for direction until short final.

My question is... Can the same procedure be exercised on big aircraft like Boeing?

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marked as duplicate by Jan Hudec, Ralph J, feetwet, fooot♦, Pondlife Dec 7 '15 at 3:12

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To some extent, yes. There was United Airlines Flight 232 in which catastrophic failure in the tail engine destroyed all the hydraulic lines. The plane was crash-landed in Sioux City, Iowa after the pilots controlled the aircraft using only the two intact wing engines. The trimmer might not produce as large as an effect on larger aircraft as on smaller ones; control of the engines would be enough because they affect the aircraft more than the trimmer due to their thrust.

However, if the damage is so severe that a control surface is destroyed or locked into a certain position, the engines might not be able to counteract that.

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  • $\begingroup$ The trimmer must produce larger effect on a jet than it does on a small plane, because the range of operating speeds is larger. Jets usually trim by moving the whole horizontal stabilizer rather than trim tabs to get sufficient trim authority and less drag. $\endgroup$ – Jan Hudec Dec 6 '15 at 23:16
  • $\begingroup$ @JanHudec The effect is not as much as the effect by the engines. $\endgroup$ – SMS von der Tann Dec 7 '15 at 2:39
  • $\begingroup$ The effect is different than the effect of the engines. The main problem with it is that on most aircraft the trim is actuated by the same hydraulic circuits as the elevator, so if you have a total hydraulic failure, you've lost both elevator and horizontal stabilizer trim. $\endgroup$ – Jan Hudec Dec 7 '15 at 5:52

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