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The only way to have MCAS active right after rotation alongside stick shaker is to take off flaps up which is not authorized. If you had stick shaker on rotation in the normal configuration, I don’t know why you would raise the flaps.
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NEWS 737MAX
- Thread starter ChuckMK23
- Start date
The only way to have MCAS active right after rotation alongside stick shaker is to take off flaps up which is not authorized. If you had stick shaker on rotation in the normal configuration, I don’t know why you would raise the flaps.
I think that is why people are raising eyebrows and investigations ensuing.
All AA and SWA 737 MAX aircraft have the optional disagree lite and additional sensor. AA has always had an AOA indicator in the HUD and PFDs on 737-800s and MAX. I heard SWA has recently added AOA indicators.
Yes and no. The existing procedure was for runaway trim. The stab trim cutout switches would have stopped the problem but it wasn’t runaway trim.
The trim system was trimming the aircraft, running, opposite the pitch direction for continued flight. That is the very definition of runaway trim. In the end it doesn't matter if it is in 10 second runs or not. The trim system is pointing your nose into the ground. What else would you do? Whatever happened to fly the plane first. Make it do what you want it to do.
I confessed to a high altitude event here not too long ago. We had no idea how we got into the low speed situation we were in, but it was clear that wasn't where we needed to be if we were going to avoid upset. Without any idea what was going on, the immediate actions were obvious. Only at a safe altitude and speed did we pondered what had happened. And it turned out to be something we could never have imagined, not unlike the MCAS failures.
No argument that the correct action was to use the trim cutout. It’s just not as simple as many are making it seem. With bad AoA input, they were likely getting a lot of erroneous warnings like stick shaker. Combine with the fact that MCAS just isn’t the same as a runaway trim scenario they may have experienced in the sim, and the existing speed trim system that desensitizes pilots to uncommanded nose down trim on climb out, plus the startle factor...
Yes. They should have been able to recover. But it wasn’t as simple as many armchair quarterbacks are making it seem. Just the ability to trim against MCAS and stop it makes it very different than runaway trim. The insidious part is that it starts again and again, and a heavy nose with stick shaker will make a lot of pilots think it’s not a good idea to trim nose up.
We have had 2 crews at this point show that they were unable to diagnose this MCAS issue as a runaway trim issue. It is worth asking and then understanding why.
Trying not to arm chair quarterback these specific incidents. We can't even be sure what kind of training they got. This is hangar flying.
We have had guys at my airline fly the entire return to landing with stick shaker from lift off to shut down back at the gate. They couldn't make it stop. They didn't know why it was happening. They just flew the plane. It was making power and climbing. Things like stick shaker can be very annoying and distracting. I get that. But remember, if VMC, as these poor souls were, does something like stick shaker convey accurate useful info to you when you can look out the window. Pitch/Power, anyone? You don't even need an AI if you are distrustful of instruments. You have a horizon.
For the yung'uns out there, don't ever let a plane do as it pleases (sez the guy who is bidding onto FiFi). Or as Bob Hoover said, "Fly the son of a bitch all the way into the crash."
Because it's not runaway trim. The aircraft responds to normal nose up trim inputs.
With how hard the training center at 121 operators emphasizes methodical QRC/QRH based troubleshooting for non-memory item issues, I could see how a relatively experienced CA with an ab-initio FO who was basically useless could end up stuck wrestling a plane, dealing with multiple strange sensory inputs, and trying to convince the FO to go to maybe the right checklist wouldn't work out so well.
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Well that is not going to go well...
So you are saying because if you can overpower the UNCOMMANDED nose down trim with nose up trim from the yoke, it isn't runaway trim? I have reviewed my 737 QRH ( been off too long to recall it ) . I fail to see how one would not think Runaway Stab Trim was anything but the logical way to go in a MCAS abnormal. No other procedure comes close to applying.
3 crews actually. A jumpseater apparently saved the day in the mishap jet the day before the Lion Air crash.
If you wrote a repeat gripe about a flight control malfunction in a Navy aircraft (that as PIC you weren’t able to wrangle with and needed a third party to help with) and then Maintenance signed it off and that aircraft was involved in a fatal mishap the next day...would you blame the plane itself or do you think there may be a bigger issue?
Wasn’t it a problem with the AOA probe? Surely they’d seen one of those before. That malfunctioning AOA probe caused MCAS to do what it was designed to do.
Also, if Lion Air mechanics didn’t understand how to fix the problem or have the parts necessary to fix it, then the mechanics should have said so and that plane shouldn’t have been flying again.
I believe the software fix isn’t to remove MCAS, it’s to limit how the degree to which it moves the pitch trim. The crews could have been alerted to the AOA disagree, but the airline elected to not have it installed.