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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 09:28
  #961 (permalink)  
 
Join Date: Mar 2008
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Originally Posted by wetbehindear View Post
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
  #962 (permalink)  
 
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Originally Posted by PaxBritannica View Post
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
  #963 (permalink)  
 
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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
  #964 (permalink)  
 
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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
  #965 (permalink)  
 
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Originally Posted by Momoe View Post
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
  #966 (permalink)  
 
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Originally Posted by Less Hair View Post
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
  #967 (permalink)  
 
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Originally Posted by WHBM View Post
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
  #968 (permalink)  
 
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Originally Posted by PaxBritannica View Post
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
  #969 (permalink)  
 
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Originally Posted by Bravo Delta View Post
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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Old 13th Mar 2019, 10:21
  #970 (permalink)  
 
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Originally Posted by Bravo Delta View Post
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.

Unfortunately I think you are correct, Boeing have some rogue sensors on their new Aircraft, thatís all , they have a drill to counter this .
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Old 13th Mar 2019, 10:23
  #971 (permalink)  
 
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Originally Posted by acad_l View Post
True. But the Airbus planes are stable throughout their flying envelope. The Max alas is not. The FAA should have never allowed a software fix as a remedy for a basic design flaw. And there must have been engineers at Boeing who were very upset of having been overruled by bean counters and MBA types. Admittedly the MCAS as it is today is a remedy (to the symptoms) worse than the disease. But there should never have been an MCAS in the first place, the right thing to do was to redesign the horizontal stabilizer.

Only airliner I can think of that turned out to have a stability issue was the BAC-111. But that was found late in the game, not by design, and the remedy apparently worked.
By my understanding that's a bit of a simplification... and most T tailed aircraft tend to have that characteristic, as with the Comet and fatigue, the 1-11 just happened to be the first to fly in that regime.
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Old 13th Mar 2019, 10:25
  #972 (permalink)  
 
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why didn't Boeing develop the 757 instead
Well because the biggest market was airlines flying the 737 who pilots already had a 737 type rating like Southwest, Ryanair etc for starters.
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Old 13th Mar 2019, 10:30
  #973 (permalink)  
 
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Methinks our Antipodean mate has been on the XXXX.
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Old 13th Mar 2019, 10:31
  #974 (permalink)  
 
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I wonder if sometime ago, in a committee room in Chicago a conversation like this occurred:

"OK fellas, we are having some problems certifying our new jet. Apparently there is this ridiculous certification requirement that stick force must not decrease when approaching the stall. Clearly this situation won't happen in real life but we need a solution to keep the regulators happy. Since no ones ever going to use it and the regulators arn't too sharp these days it doesn't have to be too clever but it REALLY needs to be cheap. We have taken loads of orders for this jet and if we change too many things it will cost money"

Now then BUBBA, whats this MCAS you were thinking of............
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Old 13th Mar 2019, 10:32
  #975 (permalink)  
 
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If it's an AOA failure that's causing these problems does anyone know the failure rate of these vanes ?

And who makes them ?

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Old 13th Mar 2019, 10:36
  #976 (permalink)  
 
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Originally Posted by ASRAAMTOO View Post
I wonder if sometime ago, in a committee room in Chicago a conversation like this occurred:

"OK fellas, we are having some problems certifying our new jet. Apparently there is this ridiculous certification requirement that stick force must not decrease when approaching the stall. Clearly this situation won't happen in real life but we need a solution to keep the regulators happy. Since no ones ever going to use it and the regulators arn't too sharp these days it doesn't have to be too clever but it REALLY needs to be cheap. We have taken loads of orders for this jet and if we change too many things it will cost money"

Now then BUBBA, whats this MCAS you were thinking of............
I had a similar mischievous though. VW diesel engines and emission testing was my analogy.
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Old 13th Mar 2019, 11:09
  #977 (permalink)  
 
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Originally Posted by crosscust View Post
MCAS is operational with flaps up. Most (if not all) airlines do not start retracting flaps till 3000í AFE. According to reports, Ethiopian never achieved anything higher than about a 1,000í (not even close to 3k).

Most opinions on here are probably from media types baiting for info so they can self profess themselves for the cameras. Give it a rest till something concrete comes out from the FDR/CVR etc investigations.
not true, flap retracton at Addis is 1000 above airfield elevation, or 8625 amsl
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Old 13th Mar 2019, 11:09
  #978 (permalink)  
 
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So the Americans have had 5 cases of control issues after takeoff on the MAX. At least two happened when they engaged the auto pilot.
There appears to be several issue with the MAX.
Only time before itís grounded world wide.
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Old 13th Mar 2019, 11:20
  #979 (permalink)  
 
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Originally Posted by Sucram View Post
not true, flap retracton at Addis is 1000 above airfield elevation, or 8625 amsl
As far as I know, the 737 acc altitude is 1500' AAL, so flap retraction will be even higher up. I can't find any exemptions to NADP1/2 in the aerodrome information. Am I missing something?
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Old 13th Mar 2019, 11:25
  #980 (permalink)  
 
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all I have to say is that I will wait for the final report of the accident. please don't start blame the airplane or the manufactures. the MAX is not a new plane that fall from the stars and none know how to fly. is a 737ng with new engines and some new software for more efficiency and safety. all the others thing is the same and a pilot with a 737ng type rating can fly the airplane. as aviation experts said there is no only one thing ( MCAS ) that will cause a accident.
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