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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 12:36
  #1321 (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
The FAA language is "a pilot of average skill".

However the first time such a pilot now gets behind the yoke is after the aircraft has been certificated, sold to an airline, built, delivered... Maybe they should involve FO Joe Average a bit earlier in the lifecycle.

Gone are the days when airline chief pilots would schlepp off to Seattle and throw the thing around the sky for a while before telling the executives whether it was suitable to buy. Now if it promises a 1% operational cost saving it is bought straight off the CAD screen.

Back in the 1960s there was even a BOAC inspection and flight-test team at Everett!

Last edited by El Bunto; 14th Mar 2019 at 12:46.
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Old 14th Mar 2019, 12:44
  #1322 (permalink)  
 
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Originally Posted by ManaAdaSystem View Post
With STS it will continue to trim up even if I need to apply quite a lot of forward pressure to keep the nose from rising. I thing the parameters for the trim cut out to function are very high. Or possibly it doesnít stop STS from operating.
ManaAdaSystem,
look at the diagram below ; the "control column stab trim cutout switches" only operate on the electric path of the electric trim buttons.
The STS is on the other electric path, the path of the autopilot system.


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Old 14th Mar 2019, 13:04
  #1323 (permalink)  
 
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Originally Posted by EternalNY1 View Post
Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".
Yep personally I would pull the thing out and design the airframe properly. Or, second best, properly integrate with existing stab trim/efs.

But the question was what will Boing do. And the answer is, whatever gets the fleet flying the quickest.
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Old 14th Mar 2019, 13:08
  #1324 (permalink)  
 
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Originally Posted by Luc Lion
Why adding a spring ?
There is already an Elevator Feel System (EFS) which is controlled by a calculator, the Elevator Feel Computer module, thus it is controlled by software.
The Elevator Feel Computer in all models of the B737 is a mechanical computer. It shown in the drawing you posted. It varies elevator feel by using pitot pressure to regulate hydraulic pressure to an actuator which tensions a spring. The faster you fly the stiffer the elevator feels to the pilot. No software involved!

Dave.

Last edited by dgordon42; 14th Mar 2019 at 16:22.
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Old 14th Mar 2019, 13:10
  #1325 (permalink)  
 
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Originally Posted by Ian W View Post
These were discussed before - they are not MCAS as they occurred with autopilot ON, A previous poster pointed out that this change of level happens on NG as well not only 'this aircraft' and is due to pressure setting mismatch.

The purpose of ASRS is to highlight issues that need attention without come back on crews that may have made errors. A common error (and pressure setting problems are VERY common around 2 a day reported) indicates that attention is needed in one or more areas. Unfortunately, journalists are not capable of reading these reports and understanding what is being reported indeed they do NOT want to understand they want things to be as inflammatory as possible so readers click on their headlines. This is not really useful to the industry.
Ian I assume you read all of the narratives.

A few quick points from memory
Pilots not being able to usual scan and see what they are looking for
Pilots not familiar with new displays
Pilots not Knowing what the "Maint" msg means and unable to find it in pilots notes
Pilots not knowing what a particular switch labelled SEL was for.

That is abysmal conversion training (classroom and sim) , abysmal documentation and DANGEROUS


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Old 14th Mar 2019, 13:16
  #1326 (permalink)  
 
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Choose : You just got airborne and cleaned up in IMC;

2 Warnings come up, screaming and flashing, ringing and tinkling.
- Overspeed
- STALL

Choose what you will do because : Some failing sensors, or some twisted code lines, are giving you and your co-pilot conflicting information and warnings.

Then, like in most modern airframes where ( willing or not) some parts of the flight control management system are ALWAYS ON, the airplane itself starts trimming itself.

But to what information IS the airplane trimming itself? ? ? ? ?
Do you know?
Does it know?


Food for thought.
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Old 14th Mar 2019, 13:17
  #1327 (permalink)  
 
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Originally Posted by Sailvi767 View Post


I am going to assume you donít fly for a living. There is no way you would not recognize a stab out of trim condition while hand flying the aircraft. In addition the aircraft would only accelerate like you portray if the pilot failed to adjust power to maintain the desired airspeed.
Sure about that? Someone new to the aircraft, captain average, and a bit tired.

At 3,000 ft, the stick shaker starts going like mad, causing a hell of a racket, and you think you have an airspeed problem and might be stalling. Sure, the controls are getting heavier and heavier, and you trim a bit for that, but this is caused by the aircraft stalling - isnít it? (You cannot hear the trimmer, over the din of the stick-shaker.) So you have to let the nose drop, untill you are sure you have enough airspeed.

Ok, you are getting a bit low now, time to pull back. Ahh, but the aircraft will not respond - pull as hard as you like, but the stick feels jammed (you need 60 kg of force to counter full stab-trim). You shout to the f/o to help pull, but the ground is coming up fast.... End of short story...

Silver
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Old 14th Mar 2019, 13:22
  #1328 (permalink)  
 
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Originally Posted by jimtx View Post
The handling differences due to thrust line may have been tuned out but it wasn't by MCAS. Windup turns are done with set thrust.
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.
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Old 14th Mar 2019, 13:32
  #1329 (permalink)  
 
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Originally Posted by Brandon
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.
I thought the MCAS increases the (lightening) stick force required to keep pulling back as AOA increases (so pilots have less tendency to pull thru into a stall), the more pronounced nose-up pitch occurring because of the aerodynamic lift generated by the bigger, more forward-positioned engine cowls.

In any case, the mention of wind up turns in the context of pax 737s is a bit of a furphy, IMO. The main issue is high AOA and reducing stick force, however you arrive at the high AOA.
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Old 14th Mar 2019, 13:33
  #1330 (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.
That is all good and well, and always works when all sensors are giving you and the systems the correct information.

AF447 => An iced over AOA probe gives false info, and it does not matter what happened the next minutes, they never figured out in time what the actual problem was.
The B-2 crash => See? With failing sensors there simply is NO TIME.
The X-31 crash => (Where pitot anti-ice was not connected) => The plane goes out of control SO FAST, the only way out is to eject.

When given false information from failing sensors, (and not knowing it) or the failure codes redraw so fast on screen that you simply can not keep track of all of them => It is game over.

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Old 14th Mar 2019, 13:37
  #1331 (permalink)  
 
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Originally Posted by silverstrata View Post
Sure about that? Someone new to the aircraft, captain average, and a bit tired.

At 3,000 ft, the stick shaker starts going like mad, causing a hell of a racket, and you think you have an airspeed problem and might be stalling. Sure, the controls are getting heavier and heavier, and you trim a bit for that, but this is caused by the aircraft stalling - isnít it? (You cannot hear the trimmer, over the din of the stick-shaker.) So you have to let the nose drop, untill you are sure you have enough airspeed.

Ok, you are getting a bit low now, time to pull back. Ahh, but the aircraft will not respond - pull as hard as you like, but the stick feels jammed (you need 60 kg of force to counter full stab-trim). You shout to the f/o to help pull, but the ground is coming up fast.... End of short story...


This is one of the better comments in this discussion. As a long-time flight test engineer with personal experience flying jumpseat aboard Boeing commercial-class airplanes during many test flights, and many hundreds of hours in the related simulators both testing and flying the simulators, I have personally witnessed aircrew in simulated emergency situations with all four feet standing on the bottom of the forward display panel to gain enough leverage to pull with >100 lb on the yoke to control the airplane (and specifically in runaway stab trim and hyd-fail situations). Nobody had a hand free to fiddle with manual trim or deal with the stab trim cutout switch and its guard (at least on the aircraft types I've tested).

Yes, these things are addressed in pilot training. But I've also watched extremely-intelligent and supremely-trained flight test pilots miss very obvious things due to the confusion surrounding automation (I helped test a major glass-cockpit upgrade to a Boeing 707-derived military jet, which included adding modern-day Honeywell autopilot systems). I've personally sat behind them in the jump seat and watched them completely miss what was going on outside the window, as two pilots and a flight engineer got wrapped up trying to figure out some stupid aspect of VNAV operation, to the point where a safety "knock it off" call had to be made to get them to break their "target fixation" on the troubleshooting.

Watch the video of the recreation of the cockpit troubleshooting in the AeroPeru crash due to tape covering the Pitot-static ports... two well-trained pilots so confounded by an airplane acting differently than they expected, that some very basic hand-flying principles and alternate information sources were missed for nearly an hour.

It's easy to armchair-quarterback a situation after the fact - but I've seen it all happen enough times to recognize the reality of the man-machine interfaces.
Ultimately, if a design is such that a pilot can get confused enough to lose all situational awareness, the problem fundamentally is a poor design, not just pilot training or problem-fixation.
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Old 14th Mar 2019, 13:38
  #1332 (permalink)  
 
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Originally Posted by Vilters View Post
That is all good and well, and always works when all sensors are giving you and the systems the correct information.

AF447 => An iced over AOA probe gives false info, and it does not matter what happened the next minutes, they never figured out in time what the actual problem was.
The B-2 crash => See? With failing sensors there simply is NO TIME.
The X-31 crash => (Where pitot anti-ice was not connected) => The plane goes out of control SO FAST, the only way out is to eject.

When given false information from failing sensors, (and not knowing it) or the failure codes redraw so fast on screen that you simply can not keep track of all of them => It is game over.
You will probably find a lot of things to learn and appreciate in this video of the AeroPeru crash due to Pitot-static port blockage.
https://www.dailymotion.com/video/x6m3uwb
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Old 14th Mar 2019, 13:42
  #1333 (permalink)  
 
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Originally Posted by bill fly View Post


Sure, but I bet there is plenty of motivation now we know how it works/fails.

See the teacup a few posts further up ďIf you think safety is expensive... etcĒ

I agree the decision making process that got to the current system and its certification will come under a lot of scrutiny in the next few weeks.
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Old 14th Mar 2019, 13:47
  #1334 (permalink)  
 
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Originally Posted by Less Hair View Post
How much longer could Boeing build new NGs?
If it had customers it could build them almost for ever.

The bigger question is how long would it take to spin up the production of NG engines and other parts. I suspect that getting back to building 100 plus NG engines per month would take 6 plus months to fully achieve.
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Old 14th Mar 2019, 13:49
  #1335 (permalink)  
 
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Originally Posted by boxmover View Post


If it had customers it could build them almost for ever.

The bigger question is how long would it take to spin up the production of NG engines and other parts. I suspect that getting back to building 100 plus NG engines per month would take 6 plus months to fully achieve.
They will almost certainly be able to divert resources budgeted to the MAX towards other airframes
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Old 14th Mar 2019, 13:56
  #1336 (permalink)  
 
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Originally Posted by WHBM View Post
Perfectly possible. Train the training captains first, let them have some real, non-sim experience of it on test flights, all to a plan, start revenue flights with two captains, then progressively have them train the FO's, starting with the experienced ones. It's not hard to come up with that. Isn't devising this sort of transition what the role of Chief Pilot is all about ?
These days the roll of the Chief Pilot is to get the program flown at minimum cost. The will design a program that meets the minimum legal standards and if they think it necessary a bit above that. Training Captains off line flying non revenue flights is way beyond whatís going to happen unless itís legally mandated.
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Old 14th Mar 2019, 13:59
  #1337 (permalink)  
 
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Originally Posted by El Bunto View Post
The FAA language is "a pilot of average skill".

However the first time such a pilot now gets behind the yoke is after the aircraft has been certificated, sold to an airline, built, delivered... Maybe they should involve FO Joe Average a bit earlier in the lifecycle.
This seems a poor FAA perspective. By definition, 50% of pilots will be below that average skill level.

Particularly when they only have 200 hours total.

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Old 14th Mar 2019, 14:09
  #1338 (permalink)  
 
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Originally Posted by Luc Lion View Post
ManaAdaSystem,
look at the diagram below ; the "control column stab trim cutout switches" only operate on the electric path of the electric trim buttons.
The STS is on the other electric path, the path of the autopilot system.
So this means the STS system will trim even if the column cut out switches are in the cut out position?
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Old 14th Mar 2019, 14:12
  #1339 (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 not odd, although the wording is slightly misleading.

My understanding is that, while regulators like the FAA, EASA, etc have imposed territorial bans on the Max flying through the airspace that they have jurisdiction over, Boeing has sought the grounding of the worldwide fleet (I don't know if that has actually happened yet).

The FAA, as well as being responsible for what is and isn't allowed in US airspace, is also the continuing airworthiness authority for the 737. It has the power to grant a request by Boeing to temporarily suspend the aircraft's Type Certificate (in respect of only the Max, obviously). If it did so, other airworthiness authorities (EASA, ANAC, etc) would have no option but to follow suit and the Max would be effectively grounded worldwide.
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Old 14th Mar 2019, 14:23
  #1340 (permalink)  
 
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Average

Originally Posted by WHBM View Post
This seems a poor FAA perspective. By definition, 50% of pilots will be below that average skill level.

Particularly when they only have 200 hours total.
The use of average here is sloppy. Leaving out of account the numerical quantification of skill, and its distribution among pilots, it is quite possible that a majority of them are below average. However, what I want is the aeroplanes I travel in to be manageable safely by pilots of minimum allowable skill. Not every flight deck will be occupied by superhero pilots. 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.
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