Originally Posted by
Smythe
737, Sorry, but I am not in agreement here. I understand you are a pilot, and so are many of us. The parameters and the if/then scenario have never been properly detailed. We would not have 3 incidents and 2 crashes if it had been.
While MCAS is part of the Speed Trim System (STS), the parameters appear completely different.
I know the Boeing ac, but are not current like I am on Airbus ac..
From what I have seen on the STS system, STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero by Mach 0.68. 10 seconds after takeoff, 5 seconds following release of trim switches, and Autopilot not engaged.
What are the parameters that engage MCAS?
I really do not agree with 2 AoA sensors, and the pilot is not the 3rd sensor, especially if there is only one left for whatever reason (as in the Ethiopian crash). As I have stated before, the AoA's are always in disagreement in many conditions, such as climbout and short final ,and while you claim the pilot has a decision, well, where or what is that decision based?
Lose 1 out of 2 sensors, and what is your decision based on?
Those AoA vanes always have issues and you know it.
I can't quote chapter and verse the MCAS engagement parameters since that information has yet to be published. As a practical matter, however, pilots don't memorize all these numbers and then mentally cross-check what the STS/Mach Trim/MCAS is doing. The trim wheel is making adjustments all the time during a normal flight (probably the same on an Airbus), and the trim is either appropriate for the conditions or it isn't. If the trim isn't appropriate, then it should become apparent fairly quickly - again if someone is paying attention. And if someone is not paying attention, then there are much bigger potential issues than MCAS waiting in the wings.
Yes, it would be great if we had triple-redundancy on everything on the 737. However, I must point out that it has relied on double-redundancy with a pilot as tiebreaker for, well, ever since the plane has been flying. It is pretty much a fact of life on the 737, and it really hasn't been an issue. If I lose one of
anything, there is always a way to figure out which one is working and which one isn't.