Originally Posted by Bend alot;[url=tel:10482520
10482520]Yoko.
One or several of the experienced 737 pilots that have posted along the line of pilots fault.
Said first thing is to hit the cut out switches - not trim to a neutral, them kill the switches.
I am also qualified on the 737, so I’m familiar with the system and procedures. Whoever said to use the cutout switches without regard to either a published procedure or before attempting to neutralize the trim was wrong - just plain wrong. Perhaps in the old days when pilots were expected to have a greater knowledge of the systems would such a divergence been acceptable. Not so much anymore.
I don’t really see the crew errors as being a case of the pilots personally being at fault, but rather continued evidence that airlines around the world (including, sadly, mine) continue to underinvest in their pilots, by some combination of accepting ridiculously low experience (i.e. the ET302 First Officer) and/or minimal training that is heavy on managing the automation and checking off boxes in the sim and light on managing the aircraft (to include proficiency in hand-flying) and preparation for unusual, out of the box situations.
As far as use of the trim cutout switches, we have to assume the ET crew was either following an established procedure or not. If they were attempting to accomplish the runaway stab procedure (the only one that I know of that uses the cutout switches), then they did it incorrectly leaving the aircraft in a grossly out of trim condition. If they were not following a published procedure and merely grasping at straws, then they were grasping at the wrong straw. The immediate remedy to the MCAS inputs was the yoke trim switch, not the trim cutout switch. Once the trim had been neutralized (or at least close), only then would it have been appropriate to disable all electric trim.
These comments were made before the simulator deficiencies were made. So these pilots also could have hit the switches and found that it was too far out of trim, for manual trim wheel operation. So what to do now when you expect the wheel to move but it will not move?
This is one of the ways in which pilot training has suffered. Even my own airline stopped teaching the runaway stab trim procedure in the sim in the past few years because they considered it so statistically improbable. We’ve had quite a few pilots here get a rude awakening with these accidents. That being said, the only thing really required of the flying pilot was to trim the stab and (in the case of ET302) set a normal power setting. As I have mentioned before, three of the five pilots who actually operated the aircraft with an ongoing MCAS malfunction did exactly that. It was only the second Lion Air First Officer and the Ethiopian Captain who failed to trim effectively against MCAS. So it seems that some of these pilots actually did know how to keep the plane flying. Unfortunately, two of them did not.
You need to maintain power and pitch and your out of trim - with a frozen trim wheel and a few distractions going on. Do you start the "Yo-Yo" procedure at what is a low altitude or turn the switches on to try the trim?
Well, my first answer would be that you would try not to get in this situation in the first place (see above). I mean it is entirely possible to put any aircraft in a position where a recovery is no longer possible, so it is best to avoid not doing that in the first place. The last few minutes of AF447 comes to mind here.
Question - If the column trim switch is held trim up THEN the cut outs are turned back on, would it trim or does the column switch need to be "reset" to neutral then back to nose up?
Why would you turn the cut out trim switches back on, if you were not intending to trim?
I am not aware of any “reset” function for the yoke trim switches. MCAS and Speed Trim will pause for 5 seconds if the pilot trim is used. If they had held the yoke trim switches in the nose up position before turning on the cutout switches, I believe they would have gotten an immediate response. However, by this time they had exceeded Vmo, so there is a real question as to how the stab behaves in this region. A while back there was an article on a blog called (I think) Bjorn’s Corner in which he speculates that the pitch forces were so sensitive at this speed that when the pilots tried to use the yoke trim switches after restoring power, the resulting g-forces were startling that they did not apply sufficient nose up trim before MCAS (which doesn’t care about g-forces) made its final, fatal input. Perhaps if one of the pilots had set an appropriate power setting to keep the aircraft within its certified envelope then they would not have had this issue.