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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 11th Mar 2019, 04:01
  #241 (permalink)  
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Originally Posted by Capt Kremin View Post
China has grounded its fleet of 737 MAX aircraft and Boeing has cancelled all media and social events related to the rollout of the 777X next week.

There will be a chain reaction most likely. Surely EASA will do the same, if its not too busy with Brexit.. You wouldn't think that in modern day age the manufacturer like Boeing can make such a big error with a crucial system of a not so new aircraft. Imho they should have started from clean sheet, instead of modding 737.
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Old 11th Mar 2019, 04:04
  #242 (permalink)  
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Originally Posted by CONSO View Post
Simple question - WHO and WHY did anyone allow a SINGLE flight critical sensor to override all previous methods of recognizing and controlling the aircraft and NOT document it ??

Shades of HAL !
The pilot has complete control. In the event of a trim runaway you simple disconnect the trim via the provided switch, trim manually and continue the flight. The 737 provides far better indications of a trim issue than any current airliner via the trim wheels.
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Old 11th Mar 2019, 04:19
  #243 (permalink)  
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It was discussed early on about the ground elevation and it does appear that the crash location is on bit of a hill

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Old 11th Mar 2019, 04:29
  #244 (permalink)  
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Originally Posted by J J Carter View Post
It's absurd that flight telemetry and data is not transmitted in real time to satellites and sent back to the aircraft manufacturer.rather than being recorded on FDRs that are lost at sea or destroyed
It may appear 'absurd', but remember that the CVR/FDR provisions that exist in FAR 25 aircraft are there by regulation. Yes, technology has advanced since those regulations were first enacted, however, it would be an interesting exercise to review the regulations to see if the off-board real-time transmission of the FDR/CVR data would satisfy the current regulations, or a case could be made in respect of an equivalent safety finding. A great idea. Another fail-safe avionics subsystem for the major airframers to develop and certify means someone is going to have to pay for it. I wonder if the commercial airlines are going to push for this ? You'd think it would be a 'no brainer' ?
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Old 11th Mar 2019, 04:34
  #245 (permalink)  
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It is not to say that 737 Max pilots don’t know how to disconnect the trim. It is NOT a new procedure, and has been around since the NG.(maybe longer)
Time, to stop a trim issue, is not your friend when all the other issues are taking place at the same time. Even worse that the reason for MCAS is during higher AOA, when the engine nacelles on the Max are producing lift, which would be more prevalent during takeoff and arrival.(slower speeds, but still in a clean config)

Here are 2 links to some interesting reading, imo

1. https://leehamnews.com/2018/11/14/bo...to-the-pilots/

2. https://leehamnews.com/2018/11/07/bo...-air-accident/

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Old 11th Mar 2019, 05:06
  #246 (permalink)  
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Originally Posted by EI-mech View Post
If it's true that the MCAS only becomes active after flap retraction then I doubt it was involved in this instance. Acceleration (and thus flap retraction) doesn't happen until at least 1500' AGL, and it looks like this flight never even attained that height.
That is only based on the ADS B data online which may be inaccurate so only time will tell.
On a clear blue day like yesterday here in Addis, acceleration and flap retraction is routinely performed reaching 1000 AGL
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Old 11th Mar 2019, 05:14
  #247 (permalink)  
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Originally Posted by silverstrata View Post

Plus you go for the stab-trim cutout switches, and you forget they are down for off, while all the other switches on the 737 are up for off. (Why is Boeing so stupid...?) So you shout to the f/o, above the noise of the shaker and the trimmer, 'did you turn the stab-tim switches off', to which he-she replies 'yes' - meaning he placed the switches upwards. But this turns the trim on, not off.

Are you kidding me? Are you flying a 737?
I think that all 737 pilots know this switch goes down instead of up to turn it off.
We are not a bunch of monkey’s. Pilots that dont know the direction a switch goes should not be allowed to fly.

Perhaps Boeing also should change the direction of the Engine Start levers. We might do it wrong.

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Old 11th Mar 2019, 05:23
  #248 (permalink)  
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The underlying issue here seems to me that regardless of whether the MCAS is a good system, it's not going to cause a problem unless there's a sensor failure. If this crash turns out to have the same cause as the first, then that means two bad sensors, on virtually new aircraft belonging to two different airlines. Wouldn't this be an abnormally high failure rate on a critical part?
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Old 11th Mar 2019, 05:39
  #249 (permalink)  
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Who makes these sensors?
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Old 11th Mar 2019, 05:53
  #250 (permalink)  
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After the Lion Air crash I posted that the B737 Max has undesirable flight characteristics and Boeing weren’t keen to advertise this to potential buyers or certification authorities. The MCAS is a quick and cheap patch job to avoid a complete redesign of the flight control system or a new stall avoidance system which may have required a new type certificate.

Boeing need to realise the limitations of the basic airframe and should have stopped with the 800 series. A complete new 21st century design is required which incorporates all modern safety features and allows for foreseeable improvements rather than bolting on ad hoc to a fuselage which has its roots in the 1950s.
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Old 11th Mar 2019, 05:55
  #251 (permalink)  
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Originally Posted by jugofpropwash View Post
The underlying issue here seems to me that regardless of whether the MCAS is a good system, it's not going to cause a problem unless there's a sensor failure. If this crash turns out to have the same cause as the first, then that means two bad sensors, on virtually new aircraft belonging to two different airlines. Wouldn't this be an abnormally high failure rate on a critical part?
One thing that was I wondering after the Lionair accident, was what are failure rates of the AoA vanes in general. Are they more or less reliable than the pitot-static systems they complement? This is fairly critical when a single vane in the MAX can provide the input to move the stab in MCAS.

My understanding is on the NG, a single vane failure indicating high alpha will generate indications only, i.e a stick shaker on one side and a probable IAS disagree due to an AoA input to IAS calculation. This is somewhat confusing with no AoA disagree annunciation (it certainly seemed to confuse Lionair maintenance who paid attention to to the working pitot-static system and not the failed AoA vane prior to the accident flight.

For any 737 pilots present, would an erroneous stick shaker activation due to faulty AoA data be something not incredible within a career?
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Old 11th Mar 2019, 06:05
  #252 (permalink)  
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Quote from the BBC-:
But following the horrific Lion Air crash, Boeing warned airlines of a potential fault in the new feature, which, under “unusual conditions, can push (the plane’s nose) down unexpectedly and so strongly that flight crews can’t pull it back up”.

This should have been enough to have the aircraft grounded immediately. Surprised to see the Chinese take the lead in grounding this model.
FAA, Boeing have a lot to answer for.
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Old 11th Mar 2019, 06:13
  #253 (permalink)  
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Undesirable flight characteristics were an unavoidable feature of early jet transports, the B707 was know to be marginal on 3 engines. As long as no secret is made of them and appropriate training given to a skilled pilot then they are manageable.

Problems arise when a child of the magenta line has to cope with something outside of his training, skill or experience.
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Old 11th Mar 2019, 06:20
  #254 (permalink)  
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So who knew?

Well, according to an article in Air Current titled “What is the Boeing 737 Max Maneuvering Characteristics Augmentation System?, (can’t do url’s yet), there was a redesign to accommodate the larger engines – they were pushed forward and upward, the (nose only?) undercarriage was lengthens.

While these changes seemed small, there was a change in handling in that the nose would start lifting (under certain conditions) that might bamboozle a pilot;

There is also some contention as to whether the airlines were fully briefed as to the use of MCAS, re-assuring them that it is was transparent, engaging when required automatically, when the angle of attack increase to beyond a certain threshold.

So you could see how a pilot, having exceeded the threshold angle of attack (as in climbing) and seeing the nose dip with the MCAS doing its specified job, (as well as being puzzled) might take corrective action, pulling up, that actually exacerbated the stall conditions. So, with the pilot fighting the MCAS, the plane might well change attitude and cycle through changes in altitude and speed in response to the pilot’s inputs.
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Old 11th Mar 2019, 06:21
  #255 (permalink)  
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Where is the evidence that AoA sensor failed?
Where is the evidence that the crew were fighting input from the MCAS?
Why has a simple failure of a pitot static system , such as would be caused by a bird strike, not being considered by all the space-cadets on this thread?
Why didnt the crew fly an attitude and thrust setting as per Non Normal checklist?
Or disconnect the Stab. trim as per the checklist, if in fact that was the problem ?
Didnt they read the Boeing memo?
Time for everyone to take a deep breath.
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Old 11th Mar 2019, 06:28
  #256 (permalink)  
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Originally Posted by Ccjung View Post
I’m not a pilot. Just a mechanical engineer who’s an armchair quarterback.

I come here when I need facts on air incidents.

A 14% increase in fuel efficiency from a simple move like that indicates vastly different aerodynamic performance. How much does bypass ratio add? How much does adding an extra row of compressor blades increase performance?

this indicates that there are some interesting boundary layer effects happening to this aircraft. I’m curious if somehow there are vortexes being generated at higher AoAs that somehow interfere with the pitot tubes.

Bring the wrath. I know I’m just an observer.
Read the article that describes how the 14% improvement was achieved. As a summary, New engines, bigger fan, needs more clearance so raised 8 inches. New engines plus various aerodynamic improvements creates increased fuel efficiency to match Airbus 320.
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Old 11th Mar 2019, 06:28
  #257 (permalink)  
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Despite the problem, I think the mood at Boeing is far from good. 2 hull losses in 5 months doest do your stock any good I guess.

And if it is the unreliable airspeed again.
Oh My.
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Old 11th Mar 2019, 07:04
  #258 (permalink)  
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The 737 Is a 60's project. Should have been ditched many years ago. But Boeing stretched it, reengined it multiple times making of it a Frankenstein airplane kept at. the limit of airworthiness by digital tricks.
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Old 11th Mar 2019, 07:12
  #259 (permalink)  
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Early days but it does sound more like a pitot problem to me.
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Old 11th Mar 2019, 07:15
  #260 (permalink)  
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China has this morning grounded all B737-MAX8 being flown by Chinese airlines - some 97 airframes.

Ethiopian (perhaps with different motivation) have also withdrawn their MAX8 from service

tick tock FAA, tick tock
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