Ethiopian plane crash

[George Smiley]

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

Do it cannot fly without mcas ?

[Cupramax]

George Smiley said:

Do it cannot fly without mcas ?

more haste, less speed, something Boeing could learn from.

[coanda]

George Smiley said:

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

Do it cannot fly without mcas ?

There may be areas of the flight envelope with less than desirable control qualities due to an increased pitch up moment caused by the engines being larger and further forward than other 737s.

The wiki page for MCAS has quotes from the flight test pilot who was unhappy with the aircraft control in some flight regimes with MCAS switched off. If the 737MAX could get in to an uncontrollable situation without MCAS activated, no one outside Boeing and the regulators know.

The following link gives an overview to the source of the need for MCAS - that the aircraft experiences uncommanded pitch-up in some situations (i.e. reported as the control column going slack - theres no force being fed from the horizontal stabiliser but the aircraft pitches up). This is unlike all previous versions of the 737. The MCAS system was intended to mask this pitch-up issue such that the pilots would not experience any control differences compare to the 737NG.

https://www.seattletimes.com/seattle-news/times-wa...

There are some very sensitive issues for all major airframe manufacturers in this so really can't go in to it much more in case it comes back to bite me.

Edited by coanda on Saturday 15th August 04:25

[dvs_dave]

coanda said:

There are some very sensitive issues for all major airframe manufacturers in this so really can't go in to it much more in case it comes back to bite me.

Presumably that means that they’re all at it to some extent. It’s just that Boeing got caught. Dieselgate style.

So its squeaky bum behind the scenes firmware updates and vague CYA service bulletin publications time I imagine.

[George Smiley]

I can’t recalll airbus shovibg engines on a near 70 year old airframe and using software to counteract the situation

[Teddy Lop]

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

my understanding is MCAS isn't there to correct flight characteristics because they're that undesirable, it simply adjusts them to mimic a handling package that the flight crew are already type rated for.

[eliot]

Teddy Lop said:

my understanding is MCAS isn't there to correct flight characteristics because they're that undesirable, it simply adjusts them to mimic a handling package that the flight crew are already type rated for.

Yes.
Perhaps akin to using software to make a BMW handle like a 1970’s Marina

[hutchst]

eliot said:

Yes.
Perhaps akin to using software to make a BMW handle like a 1970’s Marina

.... and then randomly disconnecting the brakes and activating the steering lock when you're doing 80 on the motorway.

[Teddy Lop]

hutchst said:

eliot said:

Yes.
Perhaps akin to using software to make a BMW handle like a 1970’s Marina

.... and then randomly disconnecting the brakes and activating the steering lock when you're doing 80 on the motorway.

perhaps, having a solitary steering angle sensor which fails, mis reads and then the computer wrestles control from the driver?

[coanda]

George Smiley said:

I can’t recalll airbus shovibg engines on a near 70 year old airframe and using software to counteract the situation

I didn't say that was the sensitive issue.

[coanda]

Teddy Lop said:

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

my understanding is MCAS isn't there to correct flight characteristics because they're that undesirable, it simply adjusts them to mimic a handling package that the flight crew are already type rated for.

Because the aircraft responded differently to the existing NG type, yes. The handling qualities appear to have been negatively impacted by the changes to the aircraft configuration. The fact this was found in wind tunnel testing, and concerns were raised at that point is telling.

[Teddy Lop]

coanda said:

Teddy Lop said:

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

my understanding is MCAS isn't there to correct flight characteristics because they're that undesirable, it simply adjusts them to mimic a handling package that the flight crew are already type rated for.

Because the aircraft responded differently to the existing NG type, yes. The handling qualities appear to have been negatively impacted by the changes to the aircraft configuration. The fact this was found in wind tunnel testing, and concerns were raised at that point is telling.

yes but the ultimate reason was the $ cost savings of not needing flight crew retraining for those handling qualities.

[coanda]

Teddy Lop said:

coanda said:

Teddy Lop said:

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

my understanding is MCAS isn't there to correct flight characteristics because they're that undesirable, it simply adjusts them to mimic a handling package that the flight crew are already type rated for.

Because the aircraft responded differently to the existing NG type, yes. The handling qualities appear to have been negatively impacted by the changes to the aircraft configuration. The fact this was found in wind tunnel testing, and concerns were raised at that point is telling.

yes but the ultimate reason was the $ cost savings of not needing flight crew retraining for those handling qualities.

Sure, ok, lets go with that.

[captain_cynic]

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

This is completely right.

Ultimately, you cant develop a software solution for a hardware problem.

A hardware issue will continue to emerge as more esoteric and unexpected problems that cannot be expected by software until the hardware problem is fixed.

[PRTVR]

captain_cynic said:

coanda said:

Lemming Train said:

There was an article a while back saying that EASA wanted to do rigorous testing of the handling characteristics with MCAS fully disabled before even considering recertifying it. Boeing refused. Could get interesting..

The aircraft could well exhibit divergent flight characteristics that cannot be controlled outside of the defined MCAS boundaries.

This is completely right.

Ultimately, you cant develop a software solution for a hardware problem.

A hardware issue will continue to emerge as more esoteric and unexpected problems that cannot be expected by software until the hardware problem is fixed.

But surely we are past the stage that software can limit problems ? Military aircraft are now running that would not fly without computer control, to utilise systems to protect the aircraft in a small part of the flight envelope doesn't appear unreasonable,

the problem arises when the system fails, as in the B2 bomber where reportedly three sensors fail,

for me the main problem has always been the single sensor, two sensors and an input from another source should have been a minimum, along with training if it fails.

[Starfighter]

Military aircraft have higher acceptable risk levels, higher levels of pilot training and additional safety systems in the event of failure.

[wisbech]

Plus the military aircraft that are deliberately unstable are combat aircraft with ejector seats for the one or two crew. Don’t think anyone has been silly enough to build an unstable transport military aircraft- which are the closest in concept to a passenger aircraft

[PRTVR]

but don't modern aircraft have systems to limit the action's of the pilot to maintain the flight envelope? Are we not talking about an addition to to the specifications,
My point about the likes of the B2 was what at the extreme end of the spectrum what was possible not that civilian aircraft are the same.

[hidetheelephants]

There's no chance of there being an intrinsically dynamically unstable airliner any time soon, no regulator would touch the idea with a barge pole.

[George Smiley]

PRTVR said:

but don't modern aircraft have systems to limit the action's of the pilot to maintain the flight envelope? Are we not talking about an addition to to the specifications,
My point about the likes of the B2 was what at the extreme end of the spectrum what was possible not that civilian aircraft are the same.

Not the same.

They have laws which protect from the pilot doing something that would put the flight in danger.

Mcas is about using software to control the pitch of the aircraft to overcome lift due to the engines being too big, too low and too far forward.