737 Stuck Manual Trim Technique
 

Inability to operate the manual trim on a 737 is a hot topic just now.

During my 737 type conversion (3-400 series, UK, 1998) we were shown a techniqe for trimming manually even when aerodynamic loads were too large to allow normal movement of the wheel.

A large out-of trim input was provided and an attempt to turn the wheel manually proved it to be immovable. Recovery was for both pilots to pull the column back to give an appreciable pitch up, if only a few degrees, and then relax the pull. The resulting controlled pitch down released enough load on the stab to allow a bit of trim - perhaps less than half a turn initially, to be achieved. The procedure was repeated and with each repetition more and more manual trim was achieveable until a point was reached where normal though very stiff operation became possible.

I seem to recall this was a demonstration that manual trim remained available even in out of trim conditions way beyond those anticipated even in the worst concieveable runaway.

Is this a standard part of 737 conversions or was it an add-on by our very punctilious trainer? I'd be most interested to know how widely this technique is known because once seen, it would never be forgotten. I suspect the Ethiopian pilots hadn't seen this or there would be signs of pulls and bunts on the data, and possibly no acident to discuss either.

737 pilots - over to you....

Covered here:
https://www.pprune.org/tech-log/6193...izer-trim.html

It appears they couldn't stop the aeroplane flying into the ground, let alone get the nose high enough to do that...

The wording in the FCTM, P 8.17 is rather different to the technique discussed, the nicest thing that can be said is that it is understated and leaves a great deal to the imagination. It may just be that we are all separated by a common language, but being kind, perhaps the FCTM leaves a great deal to the creativity of the TCI/TRI etc. The technique is great sport, not so sure it adds confidence in the strength provided by certification standards. Conceptually, both pilots needed on the controls to deal with a fault that is not impossible to occur seems to be untidy at best. Expecting the crew to undertake aerobatics without having a tail wheel and another set of wings over the top painted in chequers seems to be out of place. There is a silver lining however, that is that the operators should be able to charge more for the disneyland ride that is considered to be appropriate.

If a runaway trim event was about as remote as me winning the lottery, there wouldn't be a problem, it would be hypothetical, and the matter would be just a curious gedankenexperiment, but the recent events suggest it is not, and the 50 years that this has been accepted as a solution may speak loudly to the state of the art. Had Orville suggested to Lt Selfridge that one of the plans of recovery was to follow the wright flyers FCTM in such a manner, the selfless Lt would have probably stayed landside, after all, that was before the time of airline coffee, pretzels and peanuts being served airborne.

FAA Part 142, manual trim use, Yes, manual trim use post stabiliser runaway, No. Yo-yo? Nope. Jack stall from military training only.

If the trim cannot be brought to within operating range quickly enough, the next option is to roll the plane to invert it - after turning the seat belt signs on. :eek:

Pity, I thought I'd asked a straightforward question, I'll try again.

How many have and have not seen this demonstrated in the sim?

First bring the power back.... 94% power with the nose down will make it impossible to use manual trim, for unreliable airspeed 4deg nose up and 80% power will give you strait and level with flaps out 10deg/75%

meleagertoo, long time ago but yes i have used that technique. Not exactly taught it at the time but you were supposed to know about "unloading" the airframe. If I remember correctly it was really the only way to get the trim moving manually with the stab run to full down, without rupturing yourself.(737-300)

What are the flap limiting speeds..? Does the MCAS operate when the flaps are `UP`,or When the flap lever is moved to the `UP` POSITION...?

..and Boeing expects to carry passengers in these wretched things?

Well, your premise is ok, but your figures are not. Boeing's memory items are 4deg/75% (flaps up) and 10deg/80% (flaps extended).

And that won't give you level flight, it will give you a speed not below minimum, not above maximum, at any weight, and will give you a climb at low level and a descent at high level. In other words, it will give you safe flight without reference to other instruments.

For the OP, no, I've never been trained an unloading technique in the simulator. I've only read about it in my spare time.

For a UAS, you would do the UAS memory items, which include a pitch attitude and an N1, as pointed out by Derfred in his post above.

What is described is also a design that is not compliant with the requirements of Part 25. There is no justification that can be made that an aircraft needs to be handled in such a manner with the failure of a system that is both possible and part of the design requirement to have no adverse effects on failure... Forget about MCAS, how on earth is the procedure in the FCTM reasonable or acceptable. This is not an acro, it is a transport category aircraft.

If done properly and no doubt Boeing's test pilots did measured tests, then if it saves your life then it's acceptable..Competence as a pilot is preferable of course. But evidence suggests all pilots are not necessarily competent.

AFAIK checklists were introduced to standardise training, and avoid risky seat-of-the-pants flying. Pitch and power is rarely part of standard flying. Unfortunately those checklists don't cover multiple simultaneous warnings, let alone the underlying AOA faults. Ironically, a very short AOA disagree checklist would have helped a lot, but this output was not even included as standard on the flight display. Instead the pilots had to fall back on several half-baked checklists, emergency ADs, and intuitive diagnosis.

Thanks Bloggs.

So what N1 do you set on Boeing then?

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In mine, it's 80% in both cases, same deck angle.