Originally Posted by
Hugh Jars
Hi John. It does't really matter how many hours I have, but since you asked - I've done 25 years in airlines, with around 6000 hrs on the B737 NG... Nevertheless, I don't feel I have superior knowledge to anyone, just sharing my insight and understanding of the type I fly everyday.
I did watch the videos, and most of the info he discusses I had already touched on before the videos were produced. Some info he presented was incorrect (part of which he corrected in subsequent videos, some not). Nevertheless, overall they're quite informative.
He has some experience on the B737, but flies the tripler. He's not current on type (B737). I'm current (for what that's worth [smilebigeye]). He describes and demonstrates the difficulty of manually trimming at high speed. There's no evidence to suggest that both pilots had a go at the same time to trim. The 200hr FO just said "it's not working", and they moved on and switched the Stab Trim Cutout switches back on). Whether the trim wheels were recovered (and the position of the manual knobs known) may give some insight as to whether they both had a go. Once again, a crew coordination issue (see below).
The MCAS (in its present iteration) did't ignore the other side Alpha Vane - it was designed to only use one side (once powered up), with no redundancy(!). It does switch between L and R FCC's on alternating flights (and following a power-down), but essentially if the Alpha vane data the MCAS is currently using becomes corrupt, there's nothing you can do to revert to a valid source.
The whole system was poorly designed and implemented in the first place. Other posts here reflect the underhandedness and systemic issues of Boeing. They will pay dearly...
The other John (JDNSW)
Indeed, John. They absolutely should have slowed down. Reducing thrust and/or deploy the speed brakes may have helped. You're right about the thrust/pitch couple, but remember that slowing down would have:
a) made it easier to trim out the nose-down stab and regain some elevator authority, and;
b) moved the CP forward, possibly mitigating some of the pitching moment (remember, at that speed they were in test pilot territory).
It's noted in the report that the thrust was left at either the takeoff or climb thrust setting. There are two possibilities:
1) They took off without the autothrottle engaged (no biggie. Sometimes it's not available due to an MEL, and we do it semi-regularly), or;
2) They disengaged the autothrottle as part of the Runaway Stabilizer checklist (most likely).
The catch is that with autothrottle disengaged, you lose Vmo speed protection (and other protections), and have to operate the thrust levers manually to ensure your speed remains where you want it. This is probably a crew coordination issue that in the heat of the moment, it appears nobody was in full control of the aircraft. Having a 200hr pilot in the right seat even under normal operations can be quite a challenge (from experience).
That's absolutely the reason they should have reduced thrust (see above).
Excellent point, John. None of the 737NG's on the civil register in OZ have either the AoA gauge or AoA Disagree monitoring installed, as far as I'm aware. The RAAF may have it on their variants (unsure).
I think the human factors aspect has played a bigger part in the prangs than we know (at the moment). Experience, cockpit gradient, personalities, fatigue, health etc will take some time to be established.
Another John. [smilebigeye]
