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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 08:27
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Originally Posted by KRUSTY 34


One big read button on the yoke that disables ALL automatic functions, including MCAS!

I donít fly the 737, but the regional airliner I have flown for the last 20 years gives total control to the pilot once this button is pushed. Not even the yaw damper is retained. I mean Jesus H Christ! What the hell has happened to simple common sense in design?
I agree, but from the comments on this forum, the aircraft is not capable of flying to normal parameters without MCAS. I.e. the trim adjustment required as AOA increases due to the engine cowling lift. Does that mean it should never have been certified in the first place? Itís not exactly inherently unstable like a fighter, but Boeing have used automation to counteract problems with the design.
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Old 13th Mar 2019, 08:31
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Originally Posted by TacomaSailor
59-seconds after beginning the takeoff roll - the plane was at 200-knots and had gained NO altitude above the runway (based on elevation at 105-knots). Is that possible?
The aircraft was approximately 125' AAL (7750' AMSL) at the 59 second point (05:38:59Z). See the profile I posted a couple of days ago, where the altitudes are drawn to scale.
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Old 13th Mar 2019, 08:33
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FCeng84, thanks for the very useful aerodynamics lessons. Joining others, we may be jumping ahead somewhat in our assumptions about the Ethiopian and indeed Lion crash but I personally believe that having now turned-over the MCAS stone the issue must be addressed, regardless of it's (non) role in recent accidents. Some (random) questions/observations:

Before the pilot world knew about MCAS, how would an MCAS failure have been manifested? Should it have been an 'MEL' Item? In other words, if it was not visible/known to pilots, how would anyone have known the system was working? Consequently, was it just looked upon as a sticking plaster necessary to get over a certification requirement and something that didn't need to be monitored or even in place for real world operations? I'm reminded of VW diesel engines and emission tests.

What was the rationale behind only using a single data source to the MCAS?

I think it has already been addressed but, does the flight regime mean that MCAS will activate at/before/about the same time as the stick shaker?

How did Boeing come to the conclusion that a 5 second pause after pilot trim inputs was the MCAS reset period?

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Old 13th Mar 2019, 08:34
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Sorry for the thread drift, but as it is mentioned very often in this thread for obvious reasons and I can't find the original thread, can I ask - was the cause of the Lion Air crash actually determined or are definitive answers still awaited? Apologies again.
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Old 13th Mar 2019, 08:34
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Last night's Rachel Maddow show on MSNBC quoted reports on the Aviation Safety Reporting System, with US pilots reporting uncommanded nose-down problems with the MAX just after take-off, solved by switching off AP.

It's been happening in the US too.

Edited to add: she reports that there was a five-week delay in implementing the software fix...because of Trump's government shutdown. Also, there's still an 'acting' head of the FAA, because that's yet another role that Trump hasn't filled. He wanted his personal pilot to get the job, but didn't get his way. The FAA seems to have issues.

"NEW: https://twitter.com/Boeing CEO Dennis Muilenburg spoke by phone with TRUMP this a.m., urging him not to ground 737 Max 8s after Sunday’s crash. * Muilenburg has tried to cultivate Trump. He visited Mar-a-Lago after AF1 dust-up, & Boeing donated $1M to Trump inaugural.'

Last edited by PaxBritannica; 13th Mar 2019 at 09:08.
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Old 13th Mar 2019, 08:39
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Once bitten, twice shy... or NOT?


We pointed earlier ( post no 899 ) that Amsterdam and Lion Air accidents were in part due to single channel/sensor.

In fact on 31 July 2009, Boeing informed airlines about a future Service Bulletin that they are going to rectify the situation in regard to Amsterdam rad alt problem by a comparator function between the measured heights of the left and right radio altimeter systems.

https://books.google.com.tr/books?id...terdam&f=false

P.S. related page 130 bottom part.

Last edited by wetbehindear; 14th Mar 2019 at 05:32. Reason: wrong page number
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Old 13th Mar 2019, 08:53
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Originally Posted by TacomaSailor
11 seconds with 00' elevation gain (to 7,225') and acceleration from 105 to 154 knots
11 seconds with 25' elevation LOSS (to 7,200') and acceleration from 154 to 183 knots (did ETH-402 try to lift off runway and then settle back on to it?)
Bear in mind that ADS-B altitude granularity is 25ft, you won't see smaller increments than that. So it may only have dropped by a few feet but that is rounded to -25ft.

Also the altitude reported in ADS-B depends on the message type being parsed; some use the barometric pressure from the Mode-C source to calculate altitude per 1013hPa*, whereas others use the GNSS height corrected to WGS84. There's no AMSL data from ADS-B.

* aircraft at my local airport regularly land at -200ft per message type 7

Last edited by El Bunto; 13th Mar 2019 at 09:11.
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Old 13th Mar 2019, 09:14
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Originally Posted by yellowtriumph
Sorry for the thread drift, but as it is mentioned very often in this thread for obvious reasons and I can't find the original thread, can I ask - was the cause of the Lion Air crash actually determined or are definitive answers still awaited? Apologies again.

From the preliminairy report can be found that one of the AOA sensors gave a wrong reading leading to the aircraft trimming nose down, as well as a stickshaker and a multiple of fail flags related to speed and altitude.

Boeing also issued a bulletin where MCAS is blamed.

So there is no final report yet, but MCAS almost certainly was the root cause for the Lion Air crash.
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Old 13th Mar 2019, 09:16
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Now those with long memories may recall another overstretched aircraft, the MD-11. That, too, got a "clever" bit of software to overcome design aspects. LSAS. Longitudinal Stability Augmentation System. Even the name sounds similar to MCAS. Did one of the onetime McDD engineers who stayed on after the Boeing takeover have anything to do with the more recent concept.

And again, those with long memories will recall that the MD-11 had a hull loss rate substantially out of kilter with norms, and was well known for ending up on its back and burned out alongside the runway on landing, exactly at the point where LSAS had been designed to kick in.

There were even discussions about it on PPRuNe at the time. One who seemed to understand its technicalities wrote "I seriously wonder if the FAA would be as accommodating now". Hmmm ...

Md-11 Lsas
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Old 13th Mar 2019, 09:21
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Originally Posted by El Bunto
Also the altitude reported in ADS-B depends on the message type being parsed; some use the barometric pressure from the Mode-C source to calculate altitude per 1013hPa*, whereas others use the GNSS height corrected to WGS84. There's no AMSL data from ADS-B.
Yes, although AFAIK the altitudes on FR24 always come from Airborne Position messages, which in turn always contain baro alt.

And of course if you know the QNH and altitude, as we do in this case, it's straightforward to apply the appropriate pressure correction to work out AMSL.
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Old 13th Mar 2019, 09:22
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I think I remember forgetting this before... but as it appears that some of the problems with the 737 Max 8 seem to stem from overextending/overevolving an old-ish plane with short legs, why didn't Boeing develop the 757 instead. More modern plane, longer legs (taller u/c) etc?
Genuine question.
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Old 13th Mar 2019, 09:28
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Originally Posted by wetbehindear
Once bitten, twice shy... or NOT?


We pointed earlier that Amsterdam and Lion Air accidents were in part due to single channel/sensor.

In fact on 31 July 2009, Boeing informed airlines about a future Service Bulletin that they are going to rectify the situation in regard to Amsterdam rad alt problem by a comparator function between the measured heights of the left and right radio altimeter systems.

https://books.google.com.tr/books?id...terdam&f=false



I will post related Service Bulletin when I find it.

P.S. related page 130 bottom part.
I wasn't thinking about the Amsterdam crash (which had a lot of other factors) but had a similar train of thought, given that a failed AoA sensor appears to cause serious trim issues, why not have a comparator between left and right AoA. If values are outside parameters, set trim to neutral, maintain AT (Reducing thrust will reduce nose up moment but pilots are familiar with this on 737) and climb which isn't perfect but seems to be a damn sight better than the current situation.
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Old 13th Mar 2019, 09:35
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Originally Posted by PaxBritannica
Last night's Rwchel Maddow msnbc quoted reports on the Aviation Safety Reporting System, with US pilots reporting uncommanded nose-down problems with the MAX just after take-off, solved by switching off AP.

It's been happening in the US too
Looks like another problem, not mcas/sts trim problem with autopilot off. Itís a auto throttle problem with autopilot on. Maybe airplane expert can comment & analyze this
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Old 13th Mar 2019, 09:39
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Whilst the cause of the most recent accident is still yet to be revealed and a long way off from being understood, it begs the question, what will it take to get the 737MAX airborne again? And how long will that take?

The potential for Aviation carnage is there...
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Old 13th Mar 2019, 09:43
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Where are the recorders at this very moment? Seems the US want them for their NTSB from AAIB?
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Old 13th Mar 2019, 09:57
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Originally Posted by Momoe
I wasn't thinking about the Amsterdam crash (which had a lot of other factors) but had a similar train of thought, given that a failed AoA sensor appears to cause serious trim issues, why not have a comparator between left and right AoA. If values are outside parameters, set trim to neutral, maintain AT (Reducing thrust will reduce nose up moment but pilots are familiar with this on 737) and climb which isn't perfect but seems to be a damn sight better than the current situation.
Because this means your total architecture needs to be different, with computers comparing signals and reverting to different flight laws with failures, as in FBW on Airbus and newer Boeing types (777, 787). This would require the entire system to have to be recertified and it no longer being type compatible with older 737's.
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Old 13th Mar 2019, 09:59
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Originally Posted by Less Hair
Where are the recorders at this very moment? Seems the US want them for their NTSB from AAIB?
My guess would be Paris. The NTSB will probably have someone there while recovering the data.
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Old 13th Mar 2019, 10:01
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Originally Posted by WHBM
Now those with long memories may recall another overstretched aircraft, the MD-11. That, too, got a "clever" bit of software to overcome design aspects. LSAS. Longitudinal Stability Augmentation System. Even the name sounds similar to MCAS. Did one of the onetime McDD engineers who stayed on after the Boeing takeover have anything to do with the more recent concept.

And again, those with long memories will recall that the MD-11 had a hull loss rate substantially out of kilter with norms, and was well known for ending up on its back and burned out alongside the runway on landing, exactly at the point where LSAS had been designed to kick in.

There were even discussions about it on PPRuNe at the time. One who seemed to understand its technicalities wrote "I seriously wonder if the FAA would be as accommodating now". Hmmm ...

Md-11 Lsas
Until the investigation is complete iím not presuming MCAS was the official cause, but regardless, worth keeping in mind that well known graph (amongst engineers), the bath tub curve - that graph shaped like a bathtub - worth googling if anyone is not aware of it. Question to the certifying folk - how many Ďreal world conditioní sectors does a new type have to fly before being approved for commercial operation? Is that even a requisite?

Have some questions about MCAS in general too, maybe someone here can answer?

One can only presume the engines were engineered in that position due to their increased aerodynamic lift profile. An economically motivated trade-off between; (being competitive, pushing the envelope, increasing system complexity), and, (cost, safety, simplicity, and reliability). I used to work on some 737-200ís - probably the first jet I was able to sit jump seat too. Thanks for reigniting some nostalgic memories with that post.

I have no visibility to the design spec, but if there is no vote comparison for sensors that provide critical data, essential to airworthiness, then my eyebrows are raised :/

Last edited by davionics; 13th Mar 2019 at 11:11.
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Old 13th Mar 2019, 10:05
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Originally Posted by PaxBritannica
Last night's Rachel Maddow show on MSNBC quoted reports on the Aviation Safety Reporting System, with US pilots reporting uncommanded nose-down problems with the MAX just after take-off, solved by switching off AP.

It's been happening in the US too
The public search engine on the ASRS is dire (hopefully airline safety departments have better access), so I've only been able to find one of those incidents so far:

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Old 13th Mar 2019, 10:20
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Originally Posted by Bravo Delta
This is absolutely incredible, Auto pilot on or off - who cares.
Boeing and the FAA say pilot error and the plane is certified to fly.
Please tell me how come the crew fell into the same trap as another third world crew did only months earlier.
You pilots are more interested in the stripes and image.
Know your systems Know your plane.

Just slow down there a minute.

íKnow your systemsí- The system that pilots werenít made aware of until after the Lion Air accident?
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