During the final flight of Alaska Airlines Flight 261:

The CVR transcript reveals the pilots' continuous attempts for the duration of the dive to regain control of the aircraft. At one point, unable to raise the nose, they attempted to fly the aircraft upside-down.

I was wondering what the actual procedure is, if the horizontal stabilizer has a complete failure like this? Do commercial pilots ever simulate such scenarios?

  • Thanks @ymb1 , I had a look at the question but that scenario is not as extreme as the one referenced here. :) – Cloud Jun 5 at 9:44
  • Only a comment instead of an answer, because it refers to small sport planes and gliders: You can land with a complete loss of elevator control, by using the elevator trim. However (on the model I was flying), it is recommended in the instructions manual to jump out with the parachute, as this procedure is extremely difficult. My instructor did land it once only with the trim. I once did it in a simulator, although on a different model. So there are aircraft where it is possible. – vsz Jun 5 at 11:25
  • @vsz Landing with complete loss of elevator is a documented procedure in transport aircraft and is practiced in sim. It's an issue on FBW aircraft when you have loss of certain combinations of hydraulics and electrical/computers at the same time. – user71659 Jun 5 at 18:32
up vote 14 down vote accepted

This would fall under catastrophic failure and theres not much that can be done. You may as well ask what will happen if a wing falls off.

but..

UA232 Sioux City. The #2 engine (in tail) blew up and took out the hydraulic lines rendering all tail control surfaces (horizontal and vertical) inoperative. The crew found they could regain limited control of the attitude of the aircraft by varying the thrust on the wing engines, increasing thrust gave some pitch up, decreasing thrust-pitch down. This was due to the line-of-thrust being below the wing. The crew did a great job of getting the airplane back to the airport and heading down the runway. Even though it cartwheeled and burned, a lot of passengers survived, thanks to the crew's action.

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  • @RonBeyer Read the article. Still don't understand how lift can be generated through engine intake without a wing. Amazing. – Cloud Jun 5 at 14:07
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    @Cloud The F15’s body is similar enough in general shape to a wing so that given enough speed and the right attitude relative to airflow, it generates some lift (same as any other flat-ish body). – Cpt Reynolds Jun 5 at 15:18
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    @CptReynolds, the F-15's high thrust-to-weight ratio (greater than 1 under some circumstances) certainly helps. – Mark Jun 5 at 19:40
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    @Mark Agreed. Or, as one of my propulsion instructors used to say: “With sufficient thrust, anything flies!” – Cpt Reynolds Jun 5 at 21:10

Yes it is done regularly on recurrent sim training, but not to full travel because it is normally treated as a control system fault that can be stopped before it becomes totally uncontrollable, and the Alaska Airlines incident was a mechanical failure of the acme threads on the screw jack where the stab was free to tilt up as far as it could go and they were doomed.

In sim training usually the instructor will generate a stab runaway while you're in some settled down situation minding your own business, and you have to recognize it (there is usually a clacker sound that goes off after it has run for more than say 5 seconds if you don't notice the indication moving), hit the stab trim DISC button on the wheel to disengage the trim channels, and do what ya gotta do. If the autopilot was on in ALT hold mode it would have disengaged itself at some point also when the elevator force required to hold altitude got too high and exceeded the torque limit on the autopilot servo.

What you are now faced with is an airplane that is now trimmed for a single speed, wherever the stab stopped at, and to fly at any other speed requires you to displace the elevator and hold it there, against the springs in the pitch feel system wanting to return it to neutral. So it all depends on how far the stab moved before you cut it off.

Nose down runaways are generally worse than nose up runaways, because it's easier to push and hold then pull and hold, because you can jam your leg against the column to give your arms a rest on a nose up runaway. Stab runaways are one of the more unpleasant training scenarios especially because if you get a nose down runaway (which depends on the evilness quotient of your instructor) your arms are going to be really sore when you're done.

Most airplanes have significant trim change with flap extension and flaps can be deployed to help with controlability depending on the airplane's response to flap deployement, so that's a case where knowing your airplane can really help.

Although the AA261 incident did absolve the jackscrew grease as a root cause, it did cause a review and testing of grease intermix practices (the jackscrew had both lithium grease and clay base grease on it and the grease was degraded), where it was found that mixing lithium base and clay base greases caused premature breakdown, and an industry wide campaign was done. Most maintenance manuals have admonishments against mixing clay and lithium grease.

Problem is, there isn't a separate mil-spec for clay and lithium, only between moly and non-moly grease, and greases may only be called for by the mil-spec not brand name, so the situation, to this day, can be bit of a mess. For example, Aeroshell 33 (lithium) and Aeroshell 7 (clay) are the same mil-spec, but are not supposed to be intermixed. Clear as mud?

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    I was wondering after reading your answer... why don't the controls feature a 'lock' option... i.e. you could pull up as far as possible and then click a lock mechanism to hold it there so your arms don't fatigue? – Cloud Sep 13 at 10:39
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    That that would be like having a steering lock option so you could let go of the wheel on off ramps because you have to manhandle it after the power steering crapped out. The probability you will end up in the weeds is pretty high. – John K Sep 13 at 13:03

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