Originally Posted by
DYKWIA
Once it's overridden, it's down to brute strength to manually re-trim. As has been shown, this is impossible once a certain speed is reached.
In the memory items (completely quickly from memory) in both the UNRELIABLE AIRSPEED and STABILIZER RUNAWAY checklists are steps to disengage the autothrottles. This keeps you from getting into such a high-speed condition that you can't manually operate the stabilizer without unloading.
In the memory items for STABILIZER RUNAWAY is a step to use the stab trim cutout switches to stop the runaway. This stops the runaway before it gets to the full nose-down position that, coupled with excessive airspeed, puts you in a situation where unloading is needed to manual trim the stabilizer.
Neither of the accident crews properly applied the existing emergency procedures and their failure to do so made their situations much more difficult to handle.
The primary electric trim switches override MCAS activation and are fully functional for returning the stabilizer to a trimmed-state after each MCAS activation. The Ethiopian Captain did this through 21 MCAS activations which would have taken roughly 2:30 to 3:00 minutes. This isn't a "procedures", it is what a pilot does everytime the airplane he's flying becomes out of trim. It happens many dozens of times on every flight.
Your response will probably be "they should have reduced speed"... but that would also have pushed the nose down, and at about 1000 feet, that's not exactly what you want.
My response is that they never should have allowed the airspeed to reach 390 knots; about 140-180 knots faster than they should have been at that point.
The nose-down moment from the full nose-down stabilizer at 390 knots far outweighs the nose-up moment produced by the engines at climb power. You are much better off with low airspeed and low engine thrust.
Originally Posted by
Doddles
That sounds like an opinion presented as fact.
That is an opinion based on the facts that have been released up to this point. If new information is released then the opinion may change.
Certification standards are the minimums. Manufacturers exceed these minimums in most areas.
Aircraft systems are not only designed based on what crew *can* do - they're based on the human factors of what crew might *likely* do
Aircraft systems fail, sometimes in completely unexpected ways. When they do, us pilots have to find a way to address the problem and safely land the airplane.
Here's a question: If the Max is as safe as you say it definitely is, having passed all required certifications etc., and if safety is not regulated by emotion, why is the Max grounded and investigations ongoing about its safety?
The MAX was grounded (by the FAA) when the Ethiopian jackscrew was found in the full nose-down position. That established a strong link to the Lion Air accident before the unscheduled MCAS activation had been confirmed from DFDR data. Boeing had already sent information to operators, reminding crews of the proper existing procedures and describing additional accompanying symptoms, and started working on software changes.
The fact that Boeing had decided to make changes after the first accident does not mean that the original design did not meet certification standards. If it did not, the fleet would have been grounded months earlier. As of today, there still hasn't been any information released indicating that the original design failed to meet certification standards. Once the accident investigations are complete, a review of the certification standards may be undertaken.