Reply to post: Re: Appalling software, it seems

Re: Appalling software, it seems

because if you have two of anything and they give different readings, which one do you trust?

In the MCAS case, you'd disable MCAS if you were warned that the AoA sensors are disagreeing and that one may be faulty. That is, you'd ignore the AoA sensors entirely. MCAS isn't required to fly the aircraft, it's a system to make the aircraft behave more like the previous 737 models, rather than a system necessary for general flight safety.

Therefore if all the following were true then 2 AoA sensors are sufficient:

1) There is a way for the pilots to know that there is something wrong with the AoA sensor suite;

2) The pilots know MCAS exists;

3) The pilots know that MCAS depends on the AoA sensors;

4) The pilots know the failure mode symptoms of MCAS;

5) The pilots know how to disable MCAS;

6) The pilots have been trained to fly the aircraft without MCAS assist (in which case MCAS wouldn't be necessary at all, as its primary purpose was to make the plane fly like the old 737 and thus not require any additional flight training, thus if the pilots were going to be trained how to fly the plane without MCAS, there'd be no reason for it).

In the Lion Air case, it appears that none of the above were in place.

Point one is enabled by an optional, at extra cost, "AoA sensor disagreement warning light" I think it was described as. That is, a light that turns on (or a status on the MFDs) that just tell the pilots the AoA sensors disagree. If you want to know the actual AoA readings are, that is the actual angle of attack angle the sensors are reading the plane as being at, as opposed to just a warning light, that is yet another extra cost option on top of the warning light cost.

And as is apparently the case, the other points were not clearly laid out in the flight manual or the conversion "training", which is apparently all of 1 or 2 hours.