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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 21st Mar 2019, 16:23
  #2241 (permalink)  
 
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Originally Posted by BrandonSoMD View Post
Using flight-qualified software and hardware in a simulator can present some challenges, by the way. Aircraft FMC and navigation software generally doesn't like simulator freezes, resets, and repositions, which are common in training. If the FMC software doesn't provide "hooks" for telling it to play nice in a simulator, it can be necessary to simulate the software instead of implementing it directly. I've seen some pretty odd simulator behavior because the FMC didn't understand why it was suddenly 28,000 feet higher and 400 miles away from its last known position.
Generally you are spot on here, except some considerable work has been done to support the use of aircraft code directly within flight simulators - particularly with the adoption of ARINC standard 610 (currently at RevC) "GUIDANCE FOR DESIGN OF AIRCRAFT EQUIPMENT AND SOFTWARE FOR USE IN TRAINING DEVICES"

The latest commercial simulators for 'new' aircraft all use the aircraft binaries - this is for multiple reasons including accuracy (but I also suspect protection of IP rights is high on the list, as is being able to charge $8 million for a data package from Boeing or Airbus, but that's a different discussion).

- GY
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Old 21st Mar 2019, 16:37
  #2242 (permalink)  
 
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The original MCAS was designed for 0.5 degree changes. Test pilots found out this did not work, and it was changed to the 2 cycles of 2.5 degrees.

5 degrees nose down, repeatedly, at lower altitudes is far more significant than stab runaway, and look at those effects. Wonder what the trim wheel revolution speeds are under MCAS...that has to be inspiring!

So, the flight testing showed the ac was inherently unstable in the test conditions. It would be very helpful to see what the conditions are that trigger the MCAS.

Last edited by Smythe; 21st Mar 2019 at 16:57.
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Old 21st Mar 2019, 16:41
  #2243 (permalink)  
 
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Originally Posted by GarageYears View Post
Generally you are spot on here, except some considerable work has been done to support the use of aircraft code directly within flight simulators - particularly with the adoption of ARINC standard 610 (currently at RevC) "GUIDANCE FOR DESIGN OF AIRCRAFT EQUIPMENT AND SOFTWARE FOR USE IN TRAINING DEVICES"

The latest commercial simulators for 'new' aircraft all use the aircraft binaries - this is for multiple reasons including accuracy (but I also suspect protection of IP rights is high on the list, as is being able to charge $8 million for a data package from Boeing or Airbus, but that's a different discussion).

- GY
Also spot on, BUT. ...
These days, and for simulators representing Brand-B aircraft, starting with the MAX, it's not just the "aircraft binaries", it's the ENTIRE vehicle simulation INCLUDING malfunctions that is delivered to the sim manufacturers (essentially just integrators now) as a binary. To be fair, both Big Brands are now operating this way, Brand-A has been for several years already.

The "different story" as you put it is the main reason for this. You wanna train for Brand-X airplanes, you'll do it on a Brand-X sim, using Brand-X software, Brand-X training program in a Brand-X training centre. IP protection was the excuse used to launch the approach, but it's always been about the training $$$. Smaller manufactures are being Hoovered up rapidly to gain control of those markets too... Bombardier / Embraer. Wanna place bets about bizjets and helicopters for the future?
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Old 21st Mar 2019, 17:34
  #2244 (permalink)  
 
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Originally Posted by Smythe View Post
The original MCAS was designed for 0.5 degree changes. Test pilots found out this did not work, and it was changed to the 2 cycles of 2.5 degrees.

5 degrees nose down, repeatedly, at lower altitudes is far more significant than stab runaway, and look at those effects. Wonder what the trim wheel revolution speeds are under MCAS...that has to be inspiring!

So, the flight testing showed the ac was inherently unstable in the test conditions. It would be very helpful to see what the conditions are that trigger the MCAS.
Again, no. The aircraft is not, by any stretch of the imagination, "unstable", let alone "inherently unstable" (in what way is that different from "unstable"). It just does not provide enough adverse stick force to satisfy a very specific certification requirement. The situations in which this becomes relevant are rare, and should not normally be encountered in regular flight. However, if such a situation develops (high angle of attack), it is almost always in a high-workload situation, which is why the aircraft should make it harder for the pilot to venture further into the undesired flight regime, by increasing stick forces. If the aircraft does not do so to a sufficient degree by aerodynamic forces alone, it is quite common to add a little electronic assistance function to bring it back in line, and make it easier to handle, especially under stress.

The solution floated here, which may be close to the truth, seems to be to use both AoA values as inputs to MCAS (they are physically available anyway), and only to act if both values consistently read high, and close to each other. If they disagree sufficiently, MCAS will disable itself. When the probability of getting into a real high-AoA situation (where MCAS would actually be required) and getting an AoA disagree event at the same time (the result of which would be that MCAS were unavailable when needed) is shown to be sufficiently low, such a solution can be certified.

Since the failure mode has now been demonstrated to be of "catastrophic" severity, "sufficiently low" would be less than 1 in 10^9 flight hours),

Bernd
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Old 21st Mar 2019, 17:43
  #2245 (permalink)  
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Originally Posted by Smythe View Post
5 degrees nose down, repeatedly, at lower altitudes is far more significant than stab runaway, and look at those effects. Wonder what the trim wheel revolution speeds are under MCAS...that has to be inspiring!
From memory:
MCAS - 0.27/s
Normal trim flaps up - 0.2/s
Normal trim flaps extended - 0.4/s

I'd rather have an MCAS do what it did than a runaway with flaps extended at low level.

Last edited by Chesty Morgan; 21st Mar 2019 at 18:04.
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Old 21st Mar 2019, 17:51
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Think you meant 0.4/s
4 units per second would be a feat to behold.
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Old 21st Mar 2019, 17:51
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Again, no. The aircraft is not, by any stretch of the imagination, "unstable", let alone "inherently unstable" (in what way is that different from "unstable"). It just does not provide enough adverse stick force to satisfy a very specific certification requirement.
When it gets to a certain angle of attack, the engines, given the size and the forward/upward mounting, provide an unexpected amount of lift. This is the reason MCAS was developed, to push the nose down.

Poor design of the engine/wing configuration 'fixed' (so far not successfully) with software... the other fix, to turn off the AP, really? That to me is unstable design.

4 units per second would be a feat to behold.
Exactly, and likely at full speed!
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Old 21st Mar 2019, 17:59
  #2248 (permalink)  
 
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Salute!

After the Lion crash, and many affirmations of the MCAS rationale, I see this comment today
I don't get your comment "not certified". A 737 can fly with no computers or indeed no pretty much anything working, and this is demanded on the FAA test flights which I have conducted to make sure it works.
Ahem....... Guess the test pilot here flew the MAX at high AoA to help evaluate the FAR requirements for control force approaching the stall. Maybe not read all the posts bout the new engines and their mounting adding nose up pitch moments. If not, then maybe the test hops in the previous models did not include evaluating the STS with the trim motor turned off. You know, the thing that helps meet FAR requirements for speed stability when flying "trimmed". The tricky test point is that one up high to ensure that HAL tweaks the elevator without you doing anything when approaching a certain mach threshold. That's a good one, cause you might get aileron reversal and some flutter that really strains your control surfaes and wing.
But no problem, As another pilot here has stated over and over - " any competent crew/pilot could handle that".

And then I continue the quote;
If this has changed on the MAX then that is something to ponder most seriously. But I doubt it.
Well, sir, IT HAS CHANGED!!!!! And that has been the crux of most discussion on our various threads since early November. So DOUBT IT !!! Sheesh, .............................beam me up.
-----------------------------------------
I am trying to follow the ROE for our forum, but it's getting hard. I do not mean to diminish the length and breadth of experience that many pilots here have contributed to the discussion. But somethimes I get a little testy.

My fear is that some lurking here will think that we lost two planes and 300 passengers because incompetent crews did not simply turn off two switches within seconds of raising flaps at normal altitude and speed with the stall warning system telling them they were stalling and their airspeed was FUBAR.

The primary contributing factor to loss of control in the Lion crash and likely the Ethiopian one ,is gonna be the MCAS and its implementatio without fairly documenting it for the crews and not considering its activation at a corner of the envelope it was not intended for.

Gums...




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Old 21st Mar 2019, 18:03
  #2249 (permalink)  
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Originally Posted by flyingchanges View Post
Think you meant 0.4/s
4 units per second would be a feat to behold.
Ha. Yes, typo. I'll amend.
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Old 21st Mar 2019, 18:05
  #2250 (permalink)  
 
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Originally Posted by Smythe View Post
When it gets to a certain angle of attack, the engines, given the size and the forward/upward mounting, provide an unexpected amount of lift. This is the reason MCAS was developed, to push the nose down.

Poor design of the engine/wing configuration 'fixed' (so far not successfully) with software... the other fix, to turn off the AP, really? That to me is unstable design.



Exactly, and likely at full speed!
No, 4 units per second is not physically possible, it only trims at .4 units per second with the flaps out.
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Old 21st Mar 2019, 18:24
  #2251 (permalink)  
 
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Wot Gums says. ^^^^^^
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Old 21st Mar 2019, 18:55
  #2252 (permalink)  
 
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March 21, 2019 / 8:34 AM / Updated an hour ago

Boeing to add extra safety alarm in 737 MAX jets: FT

(Reuters) - Boeing Co will install an extra safety alarm in the cockpits of all its 737 MAX aircraft after intense criticism in the wake of two fatal crashes, the Financial Times reported on Thursday.
The planemaker will include a warning light in the new 737 Max planes and retrofit all existing ones, according to the report. The light will tell pilots if two key sensors do not agree, the FT reported, citing a person familiar with the situation.

Boeing did not immediately respond to a request for comment.

Shares of the company were down about 1 percent at $372.49 in morning trade

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Old 21st Mar 2019, 18:58
  #2253 (permalink)  
 
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Originally Posted by Cows getting bigger View Post
Wot Gums says. ^^^^^^
Yes. Exactly that.
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Old 21st Mar 2019, 19:07
  #2254 (permalink)  
 
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Originally Posted by Longtimer View Post
". . . The planemaker will include a warning light in the new 737 Max planes and retrofit all existing ones, according to the report."
But an AoA indicator will continue to be an option:

Doomed Boeing Jets Lacked 2 Safety Features That Company Sold Only as Extras

From the above article:

The angle of attack indicator will remain an option that airlines can buy. Neither feature was mandated by the Federal Aviation Administration. All 737 Max jets have been grounded.

“They’re critical, and cost almost nothing for the airlines to install,” said Bjorn Fehrm, an analyst at the aviation consultancy Leeham. “Boeing charges for them because it can. But they’re vital for safety.”
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Old 21st Mar 2019, 19:08
  #2255 (permalink)  
 
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Originally Posted by Longtimer View Post
March 21, 2019 / 8:34 AM / Updated an hour ago

Boeing to add extra safety alarm in 737 MAX jets: FT

(Reuters) - Boeing Co will install an extra safety alarm in the cockpits of all its 737 MAX aircraft after intense criticism in the wake of two fatal crashes, the Financial Times reported on Thursday.
The planemaker will include a warning light in the new 737 Max planes and retrofit all existing ones, according to the report.The light will tell pilots if two key sensors do not agree, the FT reported, citing a person familiar with the situation.

Boeing did not immediately respond to a request for comment.

Shares of the company were down about 1 percent at $372.49 in morning trade

Yea, so that's going to work, so at point of rotation, we get a vane split, and MCAS will still do its stuff while the crew are fumbling for the checklist.
But hey, we're Boeing and we've given you guys a little light.
From what others before have described, its still a sub-system reliant on its on-side sensor only, with no automatic cut out if the off-side sensor is in disagreement.

Ttfn
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Old 21st Mar 2019, 19:13
  #2256 (permalink)  
 
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[QUOTE=Tunkurman;10425639]Have you seen this 737 runaway stabilizer training on YouTube? OMG when that stab wheel is running there is not much time to react. Very scary. Look at the first officer trainee's reaction when the warning signals turn on and the plane dips. After seeing this I am so sad to see that these easy to access STAB TRIM switches could have saved both planes.

www.youtube.com/watch?v=3pPRuFHR1co

Thanks Tunkurman. Sort of proves what I have been saying all along. Notice that within 12 seconds the stabiliser is disabled by STAB OFF switches. The runaway STAB drill which is a memory checklist says
Condition "STAB TRIM RUNS CONTINUOUSLY" but if you note in this video, if is off after 12 seconds and before the plane can even begin to become unstable. The guys did not even spill their coffee and the remainder of the flight was very calm.
The word "CONTINUOUSLY" has always meant to me and I am sure thousands of 737 pilots to mean running in a manner not expected because in normal use it just moves in small increments either up or down. The moment it runs for more than a few seconds, that is a runaway.
If we are to start analysing every word in the Boeing QRH for its hidden meaning then the whole thing becomes a farce. During training we are shown that a stabiliser running is a very dangerous situation that needs instant memory action. It is this training that instills the knowledge of how to react - not a single word in a checklist.
There is a difference in the Lion Air in that there may have been stick shaker activity as well but multiple failures are a fact of life when flying and then QRH makes this very clear. "This document does not cover multiple failures.........." which must be dealt with by airmanship. No document could ever cover multiple failures.
Yanrair.


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Old 21st Mar 2019, 19:18
  #2257 (permalink)  
 
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BOEING QRH ADVICE ON NON NORMAL CHECKLISTS
Non–Normal Checklist Operation

Non–normal checklists start with steps to correct the situation. If needed, information for planning the rest of the flight is included. When special items are needed to configure the airplane for landing, the items are included in the Deferred Items section of the checklist. Flight patterns for some non–normal situations are located in the Maneuvers chapter and show the sequence of configuration changes.

While every attempt is made to supply needed non–normal checklists, it is not possible to develop checklists for all conceivable situations. In some smoke, fire or fumes situations, the flight crew may need to move between the Smoke, Fire or Fumes checklist and the Smoke or Fumes Removal checklist. In some multiple failure situations, the flight crew may need to combine the elements of more than one checklist. In all situations, the captain must assess the situation and use good judgment to determine the safest course of action.
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Old 21st Mar 2019, 19:25
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yanrair, you're really not getting it. By your line of argument, everything should be flying again in the morning, no changes and life moves on - "Nothing to see here". So, when the next crew creates another smoking hole are we just going to roll-out 'airmanship' again or are we going to do the SENSIBLE thing and identify/remove/mitigate the risk?
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Old 21st Mar 2019, 19:31
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[QUOTE=yanrair;10425972]
Originally Posted by Tunkurman View Post
Have you seen this 737 runaway stabilizer training on YouTube? OMG when that stab wheel is running there is not much time to react. Very scary. Look at the first officer trainee's reaction when the warning signals turn on and the plane dips. After seeing this I am so sad to see that these easy to access STAB TRIM switches could have saved both planes.

www.youtube.com/watch?v=3pPRuFHR1co

Thanks Tunkurman. Sort of proves what I have been saying all along. Notice that within 12 seconds the stabiliser is disabled by STAB OFF switches. The runaway STAB drill which is a memory checklist says
Condition "STAB TRIM RUNS CONTINUOUSLY" but if you note in this video, if is off after 12 seconds and before the plane can even begin to become unstable. The guys did not even spill their coffee and the remainder of the flight was very calm.
The word "CONTINUOUSLY" has always meant to me and I am sure thousands of 737 pilots to mean running in a manner not expected because in normal use it just moves in small increments either up or down. The moment it runs for more than a few seconds, that is a runaway.
If we are to start analysing every word in the Boeing QRH for its hidden meaning then the whole thing becomes a farce. During training we are shown that a stabiliser running is a very dangerous situation that needs instant memory action. It is this training that instills the knowledge of how to react - not a single word in a checklist.
There is a difference in the Lion Air in that there may have been stick shaker activity as well but multiple failures are a fact of life when flying and then QRH makes this very clear. "This document does not cover multiple failures.........." which must be dealt with by airmanship. No document could ever cover multiple failures.
Yanrair.
So to sum up. In the same situation with a Stab Trim repeatedly trimming nose down, you would NOT switch off the Stab Trim at the cut out switches because the NNC says 'continuous' and this is 'repeated' - really?
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Old 21st Mar 2019, 19:40
  #2260 (permalink)  
 
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Originally Posted by ivor toolbox View Post
Yea, so that's going to work, so at point of rotation, we get a vane split, and MCAS will still do its stuff while the crew are fumbling for the checklist.
But hey, we're Boeing and we've given you guys a little light.
From what others before have described, its still a sub-system reliant on its on-side sensor only, with no automatic cut out if the off-side sensor is in disagreement.

Ttfn
No. At rotation flaps would be extended. MCAS does not engage with the flaps extended.
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