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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 15:05
  #1341 (permalink)  
 
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Originally Posted by cervo77 View Post
By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.
Almost, but not quite. The Max has typically 2-3 inches less ground clearance under the engines than the NG.

Otherwise, an excellent summary of the issues, though you might want to delete your other copy of the same post in the Software Fixes thread as the mods tend not to like cross-posting the same thing twice.
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Old 14th Mar 2019, 15:06
  #1342 (permalink)  
 
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Originally Posted by Speed of Sound View Post

Journalists tend not to involve themselves in discussions but prefer to just lift chunks of it, often out of context, and don't even have to register as this is a public site.
Some of us Journalists are Engineers who try to write clear explanations of complex situations with unknown variables, that the average reader will understand.

The last 2 days of articles I've read sure could use a LOT more of that approach.

How would you (guys) react to a serious, well-stated question that could clarify some of the complexities of THIS situation, from an admitted Journalist?
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Old 14th Mar 2019, 15:07
  #1343 (permalink)  
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Previous 737 groundings 1989

Just recalled this from 1989 - 30 years ago...

Most of the world's 46 new Boeing 737-400 jetliners have been grounded in recent days after an engine type that has become increasingly suspect failed twice in the last week.
The airplanes affected are the 28 foreign 737-400's that are powered by that engine and 5 more planes, all flown by Piedmont Airlines, which use a similar engine.
The groundings followed an advisory, issued by Boeing on Tuesday, that urged airlines not to fly the planes until engine parts were replaced and power output was restricted. A Boeing 737-400 using the same engine crashed in Britain in January, killing 47 people a British Midland Airways 737-400 G-OBME

The Boeing advisory was followed by an emergency airworthiness directive issued yesterday by the Federal Aviation Administration. That directive officially grounded the Piedmont planes, which, having already been taken out of service and repaired, according to the Boeing advisory, were expected to resume flying today.
The engines involved are the CFM56-3C in the foreign planes and the CFM56-3B in the Piedmont planes.

In its emergency order, the F.A.A. warned that without the modifications the engine's fan blades might fracture, causing ''a complete loss of engine power.'' Engines that had failed on British 737-400's this past week showed signs of such fractures. In the Air Europe, BMA, Dan Air and Air UK Leisure fleets.

The most recent problems with the engine developed last Friday, when a Dan Air 737-400 carrying 100 passengers from London to Menorca returned to London after developing severe vibration in one engine. On Sunday, a Boeing 737-400 flown by British Midland Airways also had to return to London after developing engine trouble.
Piedmont Airlines, whose parent company is USAir Inc., is the sole operator of the 737-400 in this country. Although the Piedmont planes are powered by a different model engine, they had been flown at the higher power levels while being tested by Boeing and therefore fell under the F.A.A.'s emergency order.
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Old 14th Mar 2019, 15:09
  #1344 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Almost, but not quite. The Max has typically 2-3 inches less ground clearance under the engines than the NG.

Otherwise, an excellent summary of the issues, though you might want to delete your other copy of the same post in the Software Fixes thread as the mods tend not to like cross-posting the same thing twice.
okay
done!
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Old 14th Mar 2019, 15:11
  #1345 (permalink)  
 
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FDR printout of Lionair flight is now on “US grounds all Max’s “ thread
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Old 14th Mar 2019, 15:38
  #1346 (permalink)  
 
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Originally Posted by cervo77 View Post
Unfortunately the lion and Ethiopian's pilots have not had this chance
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.)
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Old 14th Mar 2019, 15:44
  #1347 (permalink)  
 
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The perils of posting something without attributing it.
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Old 14th Mar 2019, 16:03
  #1348 (permalink)  
 
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Originally Posted by Maninthebar View Post
They will almost certainly be able to divert resources budgeted to the MAX towards other airframes
Yes, but the lead times of some of the arts needed to build NG engines are not short, even if money is thrown at the problem.
To go from low rate production mostly for spares back up to more than 100 a month won’t be quick.
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Old 14th Mar 2019, 16:16
  #1349 (permalink)  
 
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Originally Posted by canyonblue737 View Post
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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Old 14th Mar 2019, 16:18
  #1350 (permalink)  
 
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Originally Posted by helimutt View Post
As has been said many times before, if you think training is expensive, try having a serious airliner accident
What you say is completely true.
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.
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Old 14th Mar 2019, 16:25
  #1351 (permalink)  
 
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Originally Posted by Rated De View Post
Does anybody find it odd, that Boeing's public statement is attempting to suggest they the company 'ordered' the grounding?
Isn't that Cart before the Horse?
Or is it evidence of regulatory capture??
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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Old 14th Mar 2019, 16:27
  #1352 (permalink)  
 
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Originally Posted by BrandonSoMD View Post
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.
MCAS is there to increase, not decrease, stick force. That stick force either becomes non linear or reverses (need to ask Boeing) at high AOA due to the aero effect of the new engines nacelles. I'm not sure there are any thrust line changes to the handling of the Max. The engines were re-positioned forward and UP.
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Old 14th Mar 2019, 16:29
  #1353 (permalink)  
 
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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.
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Old 14th Mar 2019, 16:42
  #1354 (permalink)  

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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.
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Old 14th Mar 2019, 17:22
  #1355 (permalink)  
 
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Originally Posted by cervo77 View Post
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
Just guessing. 1. You're in a clean hold off autopilot and you let your speed decay, but not to stick shaker, while rolling into a bank and you pull to maintain altitude and either you have to let off the pull or actually push to keep the nose from rising more than you want.
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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Old 14th Mar 2019, 17:26
  #1356 (permalink)  
 
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Originally Posted by boxmover View Post
What you say is completely true.
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.
...and their customers are exactly the same
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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Old 14th Mar 2019, 17:29
  #1357 (permalink)  
 
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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.
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Old 14th Mar 2019, 17:38
  #1358 (permalink)  
 
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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.....










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Old 14th Mar 2019, 17:56
  #1359 (permalink)  
 
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Originally Posted by SLFinAZ View Post
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?
Most probably not in this case but here it is:

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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Old 14th Mar 2019, 18:21
  #1360 (permalink)  
 
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Originally Posted by Aloha_KSA View Post
Have we ruled out the Max's FBW spoilers?! IMHO the precipitous and unrecoverable descent would be consistent with un-commanded spoiler deployment.
Nope, it barely descends with full boards...



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