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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 14:36
  #1341 (permalink)  
 
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Originally Posted by dead_pan View Post
Another SLFie who may be stating the obvious, but surely the goal of any airframer is to produce an aircraft that even the minimum standard of pilot can fly and have a decent chance of successfully troubleshooting in the event of something going awry? Not prejudging anything BTW
Therein lies the problem. What would be your minimum standard? Aviation authorities have different standards. Do you happen to know what the FO had for total flight time? And what was the Captain's total time in airframe? If you take the time to discover these significant facts, then that should scare you.

I'm not letting Boeing off the hook for such a poor design, but there's a reason that several other crews have documented this very issue and landed safely.
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Old 14th Mar 2019, 14:42
  #1342 (permalink)  
 
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NTSB to France

NTSB Sends Additional Investigators to Assist in Ethiopian Investigation
3/14/2019​

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.
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Old 14th Mar 2019, 14:45
  #1343 (permalink)  
 
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Originally Posted by CRayner View Post
If the first officer has just got his licence I want the captain to be a senior trainer, and if the captain has just been promoted then please may his co-pilot be of considerable experience on the type.
Amazingly enough in many realities in EASA as well as a few others jurisdictions worldwide, You will find that a newly promoted Captain with 100 hours (yes one hundred) PIC time is considered "experienced" and can hence fly with any newly 250 hours released FO. Forget Senior Trainers flying with released FOs, hence non training flights, that's "not efficient" or having experienced (and skilled, which is not always the same) FOs to fly with newly promoted Capts as well. Let's enjoy the deregulation.
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Old 14th Mar 2019, 14:54
  #1344 (permalink)  
 
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If the airframe/sensors are feeding the pilots/systems with wrong information, it does not matter if they have 20.000 or 200 hrs PIC.
If at high speed and low altitude as in this case, there is NO time.
If error codes refresh so fast on screen that you can not follow them visually? You have no time to fall back on experience and evaluate and have mere minutes/seconds till impact.
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Old 14th Mar 2019, 14:56
  #1345 (permalink)  
 
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For those who want to understand how we came to this amateur job:

It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines. The nacelles for the MAX are larger and placed higher and further forward of the wing,

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.

The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity will contribute to destabilize the aircraft in pitch.

The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft’s natural tendency to Dutch Roll = Wagging its tail).

Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described l which assisted the pilot to exit the stall.

The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt.

The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings.

But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the manoeuvre has a high pitch ratio. The aircraft’s inertia can then provoke an over-swing into stall AOA.

To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.

It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.

It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.

How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.

They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.

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

Unfortunately the lion and Ethiopian's pilots have not had this chance

Last edited by cervo77; 14th Mar 2019 at 15:27.
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Old 14th Mar 2019, 15:05
  #1346 (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
  #1347 (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
  #1348 (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
  #1349 (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
  #1350 (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
  #1351 (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
  #1352 (permalink)  
 
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The perils of posting something without attributing it.
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Old 14th Mar 2019, 16:03
  #1353 (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
  #1354 (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
  #1355 (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
  #1356 (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
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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
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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
  #1359 (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
  #1360 (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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