Primarily for general aviation discussion, but other aviation topics are also welcome.
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#1821087
NigelC wrote:Begs the question if they hadn't fitted the system in the first place and just trained the pilots to recognise and recover from the over rotation handling characteristic would they have suffered the losses?

Not these ones - but would they would have suffered different ones - perhaps a nice stall?
#1821093
As I understand it, the whole problem arose because Boeing specifically did not want to make any additional pilot training necessary to fly the Max - thereby making it a much easier sell to airlines who would not need to get new ratings for their pilots.

So although it seems plausible/probable that proper pilot training could have made the Max as safe as any other commercial jetliner, that approach was ditched at a very fundamental level in favour of increasing control system complexity (and the MCAS was probably not the biggest control system change) to maintain apparent handling attributes which were close enough not to warrant any training.

Sadly, once they bought into that it looks like the FAA almost became complicit and joined Boeing in defending what in hindsight looks indefensible.

Any other commercially owned company than Boeing would have gone bust over this. But luckily they are also (one of or *the* ?) the world's largest arms manufacturer, so they get away with it.

Trebles all around :cheers:
#1821106
Morten wrote:As I understand it, the whole problem arose because Boeing specifically did not want to make any additional pilot training necessary to fly the Max - thereby making it a much easier sell to airlines who would not need to get new ratings for their pilots.


Which is why they kept sticking bigger and bigger engines (fan diameter) further and further forward of the wing - it was a successful trusted marque used by lots of airlines. Ive since read discussion of the 757 being a better design for the new generation engines if shrunk as a replacement rather than continuing with the old 737 design.

Regards, SD..
#1821153
NigelC wrote:Boeings fix after more than a year is to change the software so it requires both AOA sensors to detect an excessive nose up condition and signal the nose down trim and that it will only activate once not continually. So a single failure now disables the system.
Begs the question if they hadn't fitted the system in the first place and just trained the pilots to recognise and recover from the over rotation handling characteristic would they have suffered the losses?


This is the 1oo2 voting scheme of which I mentioned above, i.e., the sensors have to agree. If they don’t, the system is declared inoperative.

The reason why they didn’t just omit this system and leave it to the pilots is that it’s a certification requirement to have an automatic recovery system for such natural positive instability brought about by the nose-up couple introduced by the lower mounting of the engines. Having introduced the nose-up recovery system, they botched it royally!

Iceman 8)
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#1821157
Morten wrote:As I understand it, the whole problem arose because Boeing specifically did not want to make any additional pilot training necessary to fly the Max - thereby making it a much easier sell to airlines who would not need to get new ratings for their pilots.

A friend of mine used to work for Norwegian until the pandemic hit and he was the first PF (as first officer) with passengers on a regular route on one of the first B737Max they took delivery of. They didn't do any time in a simulator, only a couple of hours worth of reading. From what I can recall of what he told me, there was no specific mention of the recovery system.

While they did have 787s for the longest routes, much of Norwegian's strategies were focused on the 737: you don't need as many passengers on a given route. They even flew Oslo to Dubai with 737s, albeit with limited seats due to the fuel needed. So for them the B737Max must have seemed almost too good to be true. Alas, Norwegian recently went public with the decision to focus solely on short-distance flights. If they can find enough funds to go on, that is.
#1821183
Iceman wrote:
NigelC wrote:Boeings fix after more than a year is to change the software so it requires both AOA sensors to detect an excessive nose up condition and signal the nose down trim and that it will only activate once not continually. So a single failure now disables the system.
Begs the question if they hadn't fitted the system in the first place and just trained the pilots to recognise and recover from the over rotation handling characteristic would they have suffered the losses?


This is the 1oo2 voting scheme of which I mentioned above, i.e., the sensors have to agree. If they don’t, the system is declared inoperative.

The reason why they didn’t just omit this system and leave it to the pilots is that it’s a certification requirement to have an automatic recovery system for such natural positive instability brought about by the nose-up couple introduced by the lower mounting of the engines. Having introduced the nose-up recovery system, they botched it royally!

Iceman 8)

It was the illogical position I was trying to point out.
Either the handling without intervention is so compromised that a fail active system is required in which case the current "solution" isn't adequate ( the previous one being lethally dangerous)) or it isn't in which case the imposition by the FAA of the system and their subsequent acceptance of Boeing's lashup is, at the least, complicit in the hull losses.
Original system - Single failure in perfectly normal flight can result in hull loss.
New system - Single failure in over rotation no automatic recovery action occurs, it remains to be seen the result of that.

BTW It would be very interesting to know how often the system was triggered during normal line operations.
#1821190
http://www.b737.org.uk/flightcontrols.htm

Very informative site with full description of all 737 flight control systems and complete time line for all major regulators responses to accidents which highlight the loss of trust internationally in the FAA, eg EASA demanded to fly modified 737MAX before considering removing grounding in Europe rather than accept FAA clearance.
#1822131
There is a misconception as illustrated by some comments above that the MCAS is designed to operate routinely. This is not the case , it is designed to operate only when the aircraft approaches an angle of attack close to critical aoa where the pitch stability becomes undesirable. The aircraft would not be in a normal flight envelope for it to be needed. So in answer to the question about how often the system triggered, pretty close to zero other than the well known erroneous occurrences.
#1822142
There is a misconception as illustrated by some comments above that the MCAS is designed to operate routinely. This is not the case ,

True - but that in turn assumes that the on-board sensors correctly identify WHETHER the aircraft is operating routinely. The latest build-quality allegations suggest perhaps the sensors cannot always be trusted to be doing that!
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#1822144
dr107flyer wrote:There is a misconception as illustrated by some comments above that the MCAS is designed to operate routinely. This is not the case , it is designed to operate only when the aircraft approaches an angle of attack close to critical aoa where the pitch stability becomes undesirable. The aircraft would not be in a normal flight envelope for it to be needed. So in answer to the question about how often the system triggered, pretty close to zero other than the well known erroneous occurrences.


Presumably that is why Boeing took the decision not to even inform 737 Max pilots of the existence of MCAS until they were ‘forced’ to?

Nice.
#1822157
A4 Pacific wrote:
dr107flyer wrote:.. in answer to the question about how often the system triggered, pretty close to zero other than the well known erroneous occurrences.


Presumably that is why Boeing took the decision not to even inform 737 Max pilots of the existence of MCAS until they were ‘forced’ to?

Nice.


There are, AIUI, 2 AoA sensors on every Max, on each side of the nose; however, only one was routinely, by default, connected to the MCAS system. ISTR reading an account from a whistleblower who claimed that it would have been possible to connect both, compare the outputs by software, and either disable MCAS if they disagreed or alert the pilots to a disagreement allowing them to disable it (and follow a more constrained set of attitudes), or make it a no-go item if the disagreement existed before takeoff (when taxiing and into wind) or when rolling but well before Vr. But any of the latter would have involved extra training for pilots converting from other 737 variants, and Boeing's principal selling point to the customer airlines was that no such training (and costs thereof) would be necessary. For that reason the option to connect both was readily installable (software almost all that was needed), but was not proactively mentioned to customer airlines.

If that is true, combined with new story alleging poor workmanship which might have led to erroneous indications from 1 of the 2 AoA devices when the other might have been working, the initial decision not to use both seems even more culpable.

But I have no relevant expertise as engineer or ME pilot ..
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