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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

Old 4th Apr 2019, 15:34
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I'm not a pilot in any shape or form but just watched Simon Calder on Sky News tell the world about what the software should do. So why didn't the software cut in on this demo flight at Farnborough or for that matter on the Lion Air and Ethopian flights?

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Old 4th Apr 2019, 15:56
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Originally Posted by crewmeal
I'm not a pilot in any shape or form but just watched Simon Calder on Sky News tell the world about what the software should do. So why didn't the software cut in on this demo flight at Farnborough or for that matter on the Lion Air and Ethopian flights?

737 Max demo

That example illustrates the difference between pitch and AOA. If an aircraft has sufficient speed, it can enter a very high pitch angle maneuver such as this one, while bleeding off speed, and then soon leveling off. At all points in this trajectory the AOA is within the normal range, and at no time is the aircraft approaching a stall. Neither stick shaker nor MCAS will activate, provided the pilot lowers the nose before the speed drops too much.
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Old 4th Apr 2019, 16:42
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Originally Posted by GordonR_Cape
If an aircraft has sufficient speed, it can enter a very high pitch angle maneuver such as this one
And, notwithstanding the "takeoff almost vertical" caption, the pitch attitude was only about 40°, so nowhere close to "vertical".
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Old 4th Apr 2019, 16:53
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, Yes the shot is taken from behind with a strong zoom distorting the angle. , plus the aircraft is empty with little fuel, so acceleration must be phenomenal . I wonder what is the thrust-to-weight ratio in this configuration compared to a first generation 1950-60 military jet ?
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Old 4th Apr 2019, 20:32
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Originally Posted by ATC Watcher
, Yes the shot is taken from behind with a strong zoom distorting the angle. , plus the aircraft is empty with little fuel, so acceleration must be phenomenal . I wonder what is the thrust-to-weight ratio in this configuration compared to a first generation 1950-60 military jet ?
3:1 ~ 5:1 at least !
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Old 4th Apr 2019, 21:14
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In this case, the MCAS may or may not have been in operation, it’s not an anti stall device, it just adjusts the handling characteristics in pitch to match that of the earlier models by subtly repositioning the stab as needed during high AoA manoevres.
The accident aircraft were suffering from erroneous AoA input which moved the stab continuously Airplane Nose Down. It would be safe to assume that the demo aircraft was fully serviceable and the MCAS if in operation was operating correctly.
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Old 4th Apr 2019, 22:07
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BREAKING: A Boeing-led review of a stall-prevention system suspected in the deadly crashes of two of the company’s new 737 Max jetliners has detected an additional software problem that the FAA has ordered fixed before the planes are cleared to fly again, the company acknowledged Thursday.

Additional software problem detected in Boeing 737 Max flight control system

the most concerning this from my perspective is the way Boeing is playing down the issues....

Boeing called the additional problem, which is unrelated to the stall-prevention system,“relatively minor.

Two officials familiar with the FAA investigation said the issue is nonetheless classified as critical to flight safety.
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Old 4th Apr 2019, 22:22
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Originally Posted by crewmeal
I'm not a pilot in any shape or form but just watched Simon Calder on Sky News tell the world about what the software should do. So why didn't the software cut in on this demo flight at Farnborough or for that matter on the Lion Air and Ethopian flights?
Because they were flying with flaps extended. MCAS does not engage with flaps extended.
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Old 4th Apr 2019, 22:35
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Take a glider pilot and put her/him into light single, stall it and their reaction will always be to point the nose at the ground before reaching for the throttle lever.
Surely not! Glider stall recovery requires the pilot to simultaneusly push forward on the spoiler lever while pitching nose down. The glider pilot - any pilot - in a light aircraft should be flying manoeuvres with one hand on the throttle - which works in exactly the same sense as the spoiler on a glider - and vv.
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Old 5th Apr 2019, 02:08
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Originally Posted by crewmeal
I'm not a pilot in any shape or form but just watched Simon Calder on Sky News tell the world about what the software should do. So why didn't the software cut in on this demo flight at Farnborough or for that matter on the Lion Air and Ethopian flights?


MCAS has probably activated multiple times already, but with a working AoA sensor. It would have trimmed down once then gone back to sleep.
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Old 5th Apr 2019, 03:27
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I am a glider pilot and we never use the spoilers in a stall. Point the nose down and then rase it before the airspeed increases excessively. You really need to anticipate the increased air speed. On landing yes the spoilers do behave like a throttle. They can give us a lot more range if it is needed.

At least that is what we do in a Schweitzer 2-33A.
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Old 5th Apr 2019, 04:14
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Originally Posted by Arydberg
I am a glider pilot and we never use the spoilers in a stall. Point the nose down and then rase it before the airspeed increases excessively. You really need to anticipate the increased air speed. On landing yes the spoilers do behave like a throttle. They can give us a lot more range if it is needed.

At least that is what we do in a Schweitzer 2-33A.
Spoilers full open on a 233 will dump you in like a brick. Tried that once.
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Old 5th Apr 2019, 06:20
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Unbelievably shocking information drip feeding out now. Lawyers for the families of the deceased are going to have a field day, several different groups of defendants potentially emerging:

https://www.reuters.com/article/us-e...-idUSKCN1RA0DP
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Old 5th Apr 2019, 09:04
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Originally Posted by QuagmireAirlines
Is there any way to bring the "yoke jerk" back to the Max? Maybe with a harder pull, so normal MCAS response isn't affected?

AoA vanes keep failing, https://www.heraldnet.com/nation-wor...-had-problems/ Got to handle that in Fault Detection & Isolation software well. Even when 2 AoA vanes freeze up to about the same AoA reading! --> 2014 Lufthansa 1829 - Bilbao.

Looking at several accidents like these Max ones, incidents including Qantas 72 ( https://www.youtube.com/watch?v=H3q5S9PCoJA ), etc., what's needed is an easy, quick, one-button (shielded) way to tell the airplane: Turn off all automatic movements of any aero control surface and throttles. Pilot only, proportional control, direct and quickly done.
There is, usually big and red on the control yoke, called Instinctive Cut Out button, or autopilot disengage button. Trouble is, here is a sub system, that is not routed via the ICO

Ttfn
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Old 5th Apr 2019, 10:25
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Originally Posted by meleagertoo
Surely not! Glider stall recovery requires the pilot to simultaneusly push forward on the spoiler lever while pitching nose down. The glider pilot - any pilot - in a light aircraft should be flying manoeuvres with one hand on the throttle - which works in exactly the same sense as the spoiler on a glider - and vv.
Glider air brakes/spoilers are locked closed normally. No reason to touch them in a stall unless they're already open.
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Old 5th Apr 2019, 13:14
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Ralph Nader calls for an appliance style total product recall. His logic is effectively that an undesired byproduct of the plane's design (over pitch up) should've never left the design sheet. I.e. if a kitchen appliance had a tendency to over-heat, the manufacturer wouldn't be able to get away with installing fire-protection material to combat a fire, but would be forced to redesign the appliance to not over-heat in the first place.

https://www.npr.org/2019/04/04/70999...=1554469797383
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Old 5th Apr 2019, 13:17
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A second software problem

But later Thursday, Boeing confirmed to The Washington Post that it had found a second software problem that the Federal Aviation Administration has ordered fixed —
One of the officials familiar with the investigation said that everyone wants a thorough review now, as the worst outcome would be to have another problem emerge later. “You don’t want to be in a situation where there was one contributing factor to an accident, and then three weeks later you find another” problem that could impact a flight.
In a statement, Boeing called the additional problem “relatively minor” but did not offer details of how it affects the plane’s flight-control system. “We are taking steps to thoroughly address this relatively minor issue and already have the solution in work to do that,” it said.
Washington Post.

Whatever this problem is, it does not improve confidence in the design and certification checking process, and probably indicates limitations in system simulation and evaluation, which apart from flight testing ‘real’ failure conditions and validating crew procedures may leave gaps in the understanding.

One speculative item is slat signalling / inhibition, which diagrammatically appears related to AoA. This was identified in Pprune threads (tech log?) in the technical discussions after the Lion accident (FDR evidence).
If so, then the new problem could be how to limit the extent of AoA failure for some systems, but not others.
MCAS (and slats) to be limited, but the full (failed) range of AoA used in ‘the highest one wins’ logic required to meet ‘fail safe’ (misnomer) approval in other systems such as stick shake - and the interaction with low seed awareness etc.

This again identifies the inherent problems of only having two sensors.
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Old 5th Apr 2019, 16:02
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Originally Posted by CW247
Ralph Nader calls for an appliance style total product recall. His logic is effectively that an undesired byproduct of the plane's design (over pitch up) should've never left the design sheet. I.e. if a kitchen appliance had a tendency to over-heat, the manufacturer wouldn't be able to get away with installing fire-protection material to combat a fire, but would be forced to redesign the appliance to not over-heat in the first place.

https://www.npr.org/2019/04/04/70999...=1554469797383
With all due respect, Ralph Nader starts his argument with an assertion unsupported by any facts, and makes multiple false statements in many sentences. Not a very useful way to convince us of the merits of his advocacy. I found it nauseating, even though one should feel sympathy for his loss.
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Old 5th Apr 2019, 16:15
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CW427's point re adding fire protection material to to flaky kitchen appliance is spot on. However, it seems not to apply to Boeing. Batteries overheating/bursting into flames? No problem. Put them in a fire resistant box. Job jobbed! Never mind fixing the bursting into flames issue!
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Old 5th Apr 2019, 16:30
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Boeing boss: http://news.sky.com/video/share-11684695

Trust is broken. CEOs legally crafted statement rings too little too late.

Need to get back to how they conducted initial testing, and it's thoroughness, and how this airframe received it's CoA. A lot of key questions need investigation.
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