Originally Posted by
Bend alot
The aircraft is certified if an AoA fails the stick shaker goes off, possible a requirement to get certification - the aircraft still operates the same regardless of where you are in the envelope.
The difference is in the MAX you get more than the stick shaker with an AoA failure you get a change of aircraft characteristics in certain areas. That change is "unknown in quantity" close to a stall and that change is known to be outside certifiable limits.
I expect it is very easy to get certification with a MCAS U/S, but I very much doubt it can be done without detailed training best done in the simulator - so there is a reduced startle factor with less experienced pilots.
Keep in mind where MCAS is actually required is in a small window of variable conditions and to NEED to be there, it is probably not a walk in the park day. So best not to have more surprises and start learning along the way when workload is already high.
Example - above 1,000 ft flaps up AP on - Birds! pull up, AP disengages miss birds, Another flock of birds again pull up in MCAS area now and it trims. You then trim to level as birds seem gone (MCAS deactivated) yet another flock of birds - pull back, this time the coulomb just comes right back aft into your crouch just like a cable has broken. Startle factor for more than a fraction of a second and it is in a stall, at best a few thousand feet AGL.
So you have just done two avoidance's in a B737, then third was in a fighter jet. Best to have some fighter jet training if that is what can happen.
Even if the MCAS was disabled the STS would still be operational and this works to increase column force required in the event of a high pitch up at low speed.
once the MCAS is disabled any erroneous data can be eliminated using memory items followed by check lists for unreliable airspeed, AP off AT off F/D off pitch either 10-80% with flaps extended ( in this instance MCAS is not active anyway) or 4-75% clean, if MCAS has been disabled due to erroneous signals then at 4 degrees NUA and 75% you are going nowhere near the stall environment, moreover you are in control and not some sub system putting in NDA stab inputs, of course the system has to ensure controlled flight in all phases of flight, the only problem is that we know that at full column deflection the airflow load over the stab can exceed the electric or manual trim capability and Boeing recommends reducing these loads by momentarily releasing back or forward pressure and using the electrical or manual trim, not so easy to do this when you are hurtling towards the ground.
what we really need to know is why these aircraft had erroneous data in the first instance, was this a build fault, manufacturing fault, poor system maintainance, bird strike or other?
Ive been flying the Classic, NG & MAX since 2005 through to a week before it’s grounding and have never once needed to use the trim cut out switches, the MAX is a beautiful bit of kit to fly albeit with a now discovered fatal flaw.
Just how we rebuild passenger trust is going to be a real challenge especially if like us we have mixed fleet where we might be rostered an NG and then for operational requirements change to the MAX.
Even now given the publicity surrounding the MAX grounding we have a number of passengers on nearly every flight asking if this is a MAX, not helped by the fact that the briefing card says 737-8/ MAX, I think many people will either avoid airlines flying the 737 MAX or avoid Boeing aircraft, then of course every time there is an incident involving a 737 ( MAX or otherwise) the media spotlight will focus again on MCAS.
If i were Boeing I would be starting design on a clean sheet replacement for the 737 rather than the middle of the market replacement. I have total faith that Boeing will get this right? maybe continue with NG production along side the MAX giving customers an option at a heavily discounted price.
They are probably going to have to discount the MAX unit price in any event.