F4E Mx

The high-speed nose-down attitude froze the manual trim wheel and the aero force on the elevators made it impossible to maintain full back pressure on the control column to maintain full up elevator travel manually so, yes, that is what I am saying.

JohnBurke

What do you think moves the elevators now?

Do you understand what trim does, and what it moves?

F4E Mx

The pitch TRIM function on the 737 is made by the movable stabilizer that is normally positioned by trim switches on the control column, the autopilot, or by the manual trim wheel in the cockpit. The elevators, the primary pitch control, are positioned by the control column.

Firefighter

I’m sorry you feel that way, not sure what I’ve done to come across as a reporter. I’m just generally curious. So I asked. I thought if anybody would fully understand it would be pilots, and would be a better source than CNN or New York Times.

JohnBurke

Do you understand what powers the elevators?

aviatorhi

I don't think he does or that in a stabilizer vs elevator contest the stabilizer always wins.

ShyGuy

Right, wrong, or indifferent, Boeing will settle both crashes and maybe even the FAA. It's the only play left to clean up the messy public image.

JohnBurke

This is guiding him back to answer his own question. He stated that Boeing should have boosted the elevator. He needs to understand that the flight controls have always been hydraulically boosted.

What he doesn't understand is that the out of trim condition was flyable and could have been landed, had the crew not allowed airspeed to exceed the certification envelope for the airplane and crash. It was the crew's failure to fly the airplane that so exascerbated the out of trim condition that the crew continued to paint themselves into an unrecoverable corner. What would have been manageable at the speedof occurrence was not salvageable at the speed to which they accelerated.

The 737 elevators are small; the horizontal stab is big, and while sufficient elevator existed to control the airplane at the time of the stab motion, at higher speeds the forces from nose down trim eventually exceeded control authority, thanks to flying at excessively high airspeed and creating pitch forces from the stab position, rather than elevator position. Had the speed been kept in check, sufficient elevator was available.

Whether or not the crew could trim is largely immaterial; they didn't run out of elevator until they pushed the airplane so far beyond the flight envelope that the problem became fatal. X amount of trim at X airspeed...a little effort to control, but controllable. X amount of trim at a much higher airspeed (in excess of 500 knots), not controllable. Boosting flight controls was not the problem...the controls were already boosted, as they are in all 737's. Too high an airspeed was the problem: ultimately a failure to fly the airplane.

It's also important to understand that with all the hype and mania surrounding the MCAS system, there already exist multiple functions in the 737 that trim the stab, from the existing stall warning system that uses the elevator feel shift module to provide a nose down moment at four times the normal feel input to the speed trim system to mach trim...which, incidentally, is also approached as one pushes the speed envelope for the airplane by accelerating to and beyond. MCAS was only one such function, and one that moved slowly and in small increments. Other systems did the same, and ultimately while using the stab trim motor cutoff switches was required by procedure, the crew could also have interrupted the trim motor action with control wheel switches or the manual trim wheels (which apply brakes to the trim). Multiple options existed for control, and multiple functions that were a part of the 737 (all 737's from the NG upward) existed to trim the stab without pilot input. MCAS was a bit player in the grand scheme, and what was most needed was flying the airplane. Keeping the speed in check would have saved the day.

Again, fly the damn airplane.

aviatorhi

Yeah I think we pretty much agree on that.

Both accidents were pilot error. A silly and (probably) unnecessary system contributed due to improper systems design philosophy, but for me the buck stops at the fact that this was basically runaway trim and they handled the whole thing wrong on every single count.

rickair7777

FAA won't be settling anything, if you're talking about lawsuits.