Ethiopian airliner down in Africa
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cervo77 obviously a well thought out and accurate explanation of MCAS and why it exists. as a Captain on the 737 MAX and previous generation 737s I don't agree with this last statement of yours, the Ethiopian crew *was* trained about MCAS per their CEO as all 737 MAX pilots in the world were by emergency AD after the Lion Air accident. further while i fully admit that a great deal of confusion can exist if you aren't aware of MCAS because of yoke behavior etc. it doesn't prevent one important fact being true, if you have improper trimming occurring that is not being made by you, the pilot, the stab trim cutout switches are right next to you and have been for decades on this aircraft. they fix this. heck you can physically grasp and hold the trim wheel itself and it will prevent this. lots of blame to go around here and hopefully when it comes to MCAS the software fix coming shortly as Boeing describes is very comprehensive (as it should have been on day 1.)
If the engineers did not invent this MCAS system for the 737 max, and that the trim system remained 100% identical to what we have on the 737-800
question: what would be the result on the way of flying this 737 max ? a huge effort required to pull and push the yoke ?? I am curisous to know
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Have you met an airline bean counter that gets it? They tend to look at today’s costs an hope luck and low odds will work in their favour.
No, it's just PR management. Once grounding becomes inevitable Boeing will focus on damage limitation and try and claim some of the credit.
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I think that deserves some clarification. I don't fully agree.
I'm a 30-year flight test engineer and am currently helping to rewrite the handling qualities flight test manual for the US Navy Test Pilot School. We focus more on military than transport aircraft, but we do test and fly 737-derivative airplanes (P-8A Poseidon and the C-40 Clipper) and the test methods are universally applicable.
Windup turns are done with set thrust, yes. Power is set as required to maintain the specified airspeed. What is being compared is the response of the airframe to increasing AOA or g at a fixed airspeed, and throttles are fixed during the maneuver to avoid contaminating the results with another independent variable. Several things can be learned from WUTs, including control force or deflection as a function of load factor or AOA, buffet characteristics as a function of AOA, and structural characteristics as a function of g.
While each test point is conducted at a specific power setting, the tests are typically conducted at a range of power settings. This provides a chance to assess the effect of power setting on the various aforementioned characteristics.
MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines. As such, it is a handling qualities difference that is definitely related to thrust line changes. Those differences would typically be revealed by a series of WUT test points. In this case, a WUT at high thrust would be worse, because of the increased pitch-with-power tendencies.
I'm a 30-year flight test engineer and am currently helping to rewrite the handling qualities flight test manual for the US Navy Test Pilot School. We focus more on military than transport aircraft, but we do test and fly 737-derivative airplanes (P-8A Poseidon and the C-40 Clipper) and the test methods are universally applicable.
Windup turns are done with set thrust, yes. Power is set as required to maintain the specified airspeed. What is being compared is the response of the airframe to increasing AOA or g at a fixed airspeed, and throttles are fixed during the maneuver to avoid contaminating the results with another independent variable. Several things can be learned from WUTs, including control force or deflection as a function of load factor or AOA, buffet characteristics as a function of AOA, and structural characteristics as a function of g.
While each test point is conducted at a specific power setting, the tests are typically conducted at a range of power settings. This provides a chance to assess the effect of power setting on the various aforementioned characteristics.
MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines. As such, it is a handling qualities difference that is definitely related to thrust line changes. Those differences would typically be revealed by a series of WUT test points. In this case, a WUT at high thrust would be worse, because of the increased pitch-with-power tendencies.
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Have we ruled out the Max's FBW spoilers?! On the NG and previous the spoilers/ speed brake were cable/ hydraulic. On the MAX they are fly by wire. The change from cable/ hydraulic to fly by wire is a *HUGE* change in the flight control regime. The Max spoilers have various complicated automatic triggers that could have a complex interaction with other systems. On the NG and previous the symmetrical spoiler deployment could be overridden by stowing the speed brake handle. The automatic deployment is very difficult to override on the Max. One has to reach up and move a guarded switch. That motion is not a memory item nor is it intuitive. On the NG and previous, symmetrical deployment of the speed brakes / spoilers was indicated by motion of the speed brake handle. On the Max the spoilers deploy for various MCAS and non-normal scenarios without proportional movement of the speed brake handle. That means the pilots (1) are not aware of their deployment, and (2) cannot easily override their deployment. IMHO the precipitous and unrecoverable descent would be consistent with un-commanded spoiler deployment. The FDR will confirm or refute my opinion, but regardless, changing a major flight control from manual - cable/ hydraulic to fly by wire is very suspect. I don't know if there is any precedent for a derivative aircraft being introduced with a major flight control system being changed from manual control to fly by wire without a new type or at least difference training being required. The differences training between NG and Max was about 4 hours of CBT... I have NG pilot friends who were signed off to fly the MAX without so much as a sim session.
Keeping Danny in Sandwiches
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As a retired oldie this problem seems to have similarities with the BAC1-11 deep stall problem during certification. The 1-11 and Trident had the problem of the wing shielding the T tailplane and the aircraft going into a deep stall with no aerodynamic flow over the tailplane and elevator. This issue was resolved by having both a stick shaker and finally a stick push, both being controlled by AOA vanes that shook the daylights out of the control column followed by a definite push down. Recovery from the stick shake was the same as the 737 200, relax the back pressure and apply power for minimum height loss.
If my understanding is correct there is only one AOA vane on the Max why isn't there a dispatch requirement for 3 and another for redundancy making 4 vanes. At least the MCAS software would then be operating with correct information. The original 737-200 had one AOA vane and there was an incident of an aircraft rotating on take off straight into a stick shake that remained on at all indicated airspeeds.
If my understanding is correct there is only one AOA vane on the Max why isn't there a dispatch requirement for 3 and another for redundancy making 4 vanes. At least the MCAS software would then be operating with correct information. The original 737-200 had one AOA vane and there was an incident of an aircraft rotating on take off straight into a stick shake that remained on at all indicated airspeeds.
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If the engineers did not invent this MCAS system for the 737 max, and that the trim system remained 100% identical to what we have on the 737-800
question: what would be the result on the way of flying this 737 max ? a huge effort required to pull and push the yoke ?? I am curisous to know
question: what would be the result on the way of flying this 737 max ? a huge effort required to pull and push the yoke ?? I am curisous to know
2. You are clean on long final with windshear in the vicinity when you get a windshear warning and perform the escape. When you click off the autopilot and pull the pull force has to decrease or reverse to a push to maintain the attitude you want.
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They know the low cost cheap flights risk a monumental mess up every now and then that leaves them stranded for XX hours in some ghastly place
But they also just hope the odds work in their favour and its not them that get caught.
Its the same everywhere: people complaining how some corporate is cutting services or not doing it "properly" while the same complainers are busy bodging up their electrics, roof, guttering whatever and hope the next purchaser does not notice.
So its circular - each side drives the next, and round and round we for ever lower costs taken from somewhere - 'cos you can have the most wonderful,ticketing,maintenance, backup whatever regime but if you have no customers as they have all gone to the next cheapest down the road you are going bust.
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Putting on one side the fundamental aerodynamic issues and the lack of clarity or coverage in the operating manual. There is no getting away from the fact that there is a major flaw in the MCAS system that allows automation to try to crash the aircraft. It is obvious from the FDR trace that is what has happened. It is true that the pilots could have averted the accident had they acted quickly and with sufficient knowledge, but that does not take away that Boeing and the FAA (and perhaps the Lion Air investigators) are culpable for allowing an unsafe aircraft into the air. The AoA sensor/s and the MCAS system is not fail safe and does not provide adequate notification to the pilots. The general guidelines and practice of duplication and redundancy were not followed for the MCAS system.
It is a sad day for the aircraft industry that it is likely to show that politics has apparently superseded the proud tradition of safety always coming first. It is unforgivable and should not be tolerated. For my part, I hope the matter is fully investigated and those that are culpable face the full force of the law.
Lastly, I would like to offer my condolences to those that have lost their lives and the families and friends they have left behind. It is shameful.
It is a sad day for the aircraft industry that it is likely to show that politics has apparently superseded the proud tradition of safety always coming first. It is unforgivable and should not be tolerated. For my part, I hope the matter is fully investigated and those that are culpable face the full force of the law.
Lastly, I would like to offer my condolences to those that have lost their lives and the families and friends they have left behind. It is shameful.
Salute!
you are wrong, sky9
There are two vanes.
The problem is the MCAS switches from one to the other upon reset. Had Lion crew MCAS been using the good vane all they would have had would have been unreliable something or other warnings and no flight control interference. And no stick shaker for left seat guy.
I am more scared by what Aloha hints. AoA inputs and who knows what other things for the spoiler What other things on the MAX that we do not know, nor the pilots?
Gums sends.....
you are wrong, sky9
There are two vanes.
The problem is the MCAS switches from one to the other upon reset. Had Lion crew MCAS been using the good vane all they would have had would have been unreliable something or other warnings and no flight control interference. And no stick shaker for left seat guy.
I am more scared by what Aloha hints. AoA inputs and who knows what other things for the spoiler What other things on the MAX that we do not know, nor the pilots?
Gums sends.....
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I'd love to know what your background and knowledge base is on this. To date my understanding is that MCAS is trim specific in function and adds incremental trim specific to certain criteria. Taken in a vacuum it's difficult to fathom how this by itself could lead to a loss of control by a qualified aviator. Under what possible circumstances would speed brakes be deployed except during landing??? Or are you confusing speed brakes with the leading edge flaps and slats on the 737?
Elevator Jam Landing Assist
This will give limited changes to the vertical flight path from the spoilers to assist the approach and landing if the normal elevator system jams. The control panel is located on the Aft Overhead Panel, even if it is switched on it will only be active when the flaps are 1 or greater. When in use, the spoilers rise to a preset position; they then extend or retract as the elevator column is pushed or pulled to increase or decrease the rate of descent.
(737 MAX - FBW Spoiler System)
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The NTSB is sending investigators to France to help with the recorders:
NTSB Sends Additional Investigators to Assist in Ethiopian Investigation
WASHINGTON (March 14, 2019) —The U.S. National Transportation Safety Board is dispatching three investigators to France Thursday to assist with the downloading and analysis of flight recorders from the Boeing 737 MAX 8 that crashed Sunday near Addis Ababa, Ethiopia.
The NTSB investigators have expertise in recorders, flight crew operations and human factors. The French Bureau d'Enquêtes et d'Analyses (BEA) will be downloading the flight data recorder and cockpit voice recorder in support of the Ethiopian investigation.
The investigation is being led by the Ethiopian Aircraft Accident Investigations Bureau in accordance with the standards defined in International Civil Aviation Organization Annex 13. The NTSB appointed an accredited representative to the investigation under the ICAO standards because the airplane was manufactured in the United States. All investigative data regarding the investigation will be released by Ethiopian authorities.
For more information on NTSB participation in foreign investigations go to: https://go.usa.gov/xEswV.
The NTSB investigators dispatched to France will work in coordination with investigators on the ground in Addis Ababa. Those investigators were sent immediately after the accident and have been integral to the efforts underway in Ethiopia. They are being assisted by technical advisers from the Federal Aviation Administration, Boeing and GE/Safran, the manufacturer of the engines.
The NTSB is an independent U.S. federal agency charged with investigating transportation accidents and issuing recommendations to improve safety.
The NTSB investigators have expertise in recorders, flight crew operations and human factors. The French Bureau d'Enquêtes et d'Analyses (BEA) will be downloading the flight data recorder and cockpit voice recorder in support of the Ethiopian investigation.
The investigation is being led by the Ethiopian Aircraft Accident Investigations Bureau in accordance with the standards defined in International Civil Aviation Organization Annex 13. The NTSB appointed an accredited representative to the investigation under the ICAO standards because the airplane was manufactured in the United States. All investigative data regarding the investigation will be released by Ethiopian authorities.
For more information on NTSB participation in foreign investigations go to: https://go.usa.gov/xEswV.
The NTSB investigators dispatched to France will work in coordination with investigators on the ground in Addis Ababa. Those investigators were sent immediately after the accident and have been integral to the efforts underway in Ethiopia. They are being assisted by technical advisers from the Federal Aviation Administration, Boeing and GE/Safran, the manufacturer of the engines.
The NTSB is an independent U.S. federal agency charged with investigating transportation accidents and issuing recommendations to improve safety.
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https://www.ntsb.gov/investigations/...s/AAR9901.aspx
And sometimes an investigating agency tries to blame the pilots, especially when the aircraft is made in their country, like the French BEA when they blamed the pilots for American Eagle Flight 4184, October 31, 1994.
https://www.ntsb.gov/investigations/...s/AAR9601.aspx
https://www.ntsb.gov/investigations/...s/AAR9602.aspx
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As someone has recently posted on another Forum ..
Something is wrong, deep down in the system either at Boeing or the FAA.
Having TWO new types grounded in the space of 5-6 years is truly appalling by modern standards.
This will take an examination of culture at Boeing, particularly before and after 1997 to see the changes. Diane Vaughan examined NASA after the Challenger accident and issued "The Challenger Launch Decision: High Risk Technology, Culture and Deviance at NASA" in 1997, (revised 2016). The examination led to changes but not before Columbia was lost. I believe there is something similar here. Hopefully there is someone with the capacity, time and energy to do so because the question does at least need asking with regard to both organizations, (FAA & Boeing themselves, and also the relationship between the two).
Time was when the regulators were quite independent, and looked at things with true external oversight. They would need the knowledgeable personnel to work through everything. Then it slowly occurred to them that they might get the industry they were regulating to do certain of their jobs for them, particularly if this lessened their own costs. Instead of checking everything out from the outside, get the industry to bear the cost and write up a description of what they had done, which could then just be signed off. Increasing the industry did all the work, and the Regulator just said "OK then". Of course, they did not then need as many of their own knowledgeable technical staff now, it becomes just admin staff checking that a box ticking exercise has been completed. If they don't know what boxes to ask to be ticked in the first place, well, just ask the industry to devise the list for you ...
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PJ2 1396
would be good if they could get the same person to do it on FAA then boeing
would be good if they could get the same person to do it on FAA then boeing
Last edited by oldoberon; 14th Mar 2019 at 19:48. Reason: add post being responded to.