Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Boeing admits flaw in 737 Max flight simulator

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Boeing admits flaw in 737 Max flight simulator

Old 22nd May 2019, 00:25
  #61 (permalink)  
 
Join Date: May 2010
Location: Boston
Age: 68
Posts: 401
Originally Posted by tdracer View Post
Posted about this on one of the countless other MAX threads, but it probably bears repeating.
Not too long ago I was at special event at the Museum of Flight - not only was I seated at a table with a bunch of current and retired Alaska Air pilots, during the cocktail hour I ran into a flight test pilot friend who'd been involved in the MAX development (Alaska is an all 737 operator - classics and NGs). To a man, they all agreed that if the stab tirm started doing something you didn't understand or like, the very first thing they'd do is turn it off and trim it manually. Hence the reason Boeing didn't treat MCAS as a flight critical system. However these were all older, high time experienced pilots
That being said, they also all agreed that no sim training for MCAS (or any of the other MAX differences) was a huge miss...
My bolding in above.
One of the criticisms I see of the ET crew is that they did not first trim with electric trim before using cutouts as hinted at in the Lion Air triggered emergency AD.

It is not clear whether lack of manual trim after cutout was due to lack of familiarity with the flip out handles or aero loads or both.
Something had to be happening in the period while electric trim was disabled, we don't know what since the CVR transcript has not been released.

Last edited by MurphyWasRight; 22nd May 2019 at 00:28. Reason: typo
MurphyWasRight is offline  
Old 22nd May 2019, 02:44
  #62 (permalink)  
 
Join Date: Aug 2008
Location: Vendee
Posts: 138
Originally Posted by tdracer View Post
Tak, that's NOT why the strake is there, The reason for the strake is is engine out approach - basically if the engine is not running, at higher angles of attack all that airflow spilling out of the inlet can cause flow separation on the wing - the strake acts as a big vortex generator to re-energize the flow and keep it attached over the wing. That's why you'll see strakes on the inboard side of the nacelles of most wing mounted big turbofan engines. Not to say they may not help in the way you're suggesting, but that's not why we put them there.

As for the wings being hung below the wings instead of out front - there are two main reasons for that unrelated to ground clearance (granted, the MAX is a pretty extreme case due to ground clearance). One is rotorburst - sticking the engine out front limits the amount of wing (and associated systems) that are exposed to damage due to a rotorburst. The other is that it's aerodynamically better - if the engine is too close to the wing, at cruise speeds and power settings you get interference drag due to the interaction of the fan flow with the free stream airflow. The drag penalty can be substantial - as much as 2% fuel burn. On the 747-8, they couldn't mount the engines as far forward as they wanted due to flutter issues and had to pay a not insignificant drag penalty as a result.
Nice explanation TD. I have to admit that in my flying years, that go back to the late 80's , I did not know that. In general yes, but not specifically like that. Always appreciate your insights from the engineering side.

Uncle Fred is offline  
Old 22nd May 2019, 11:17
  #63 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,272
Originally Posted by MurphyWasRight View Post
My bolding in above.
One of the criticisms I see of the ET crew is that they did not first trim with electric trim before using cutouts as hinted at in the Lion Air triggered emergency AD.

It is not clear whether lack of manual trim after cutout was due to lack of familiarity with the flip out handles or aero loads or both.
Something had to be happening in the period while electric trim was disabled, we don't know what since the CVR transcript has not been released.
The implication of your post is that the 737 pilot is happy to accept a significantly out of trim aircraft.
What was being assumed is that an experienced pilot would not let the automatics whatever they were put the trim where they didn't want it.- so when the Stab Trim cutout occurred there would not be a large out of trim condition to wind back.

There is also a lot of confusion between 'manual trim' with the column electric trim switch and manual trim with the non-powered trim wheel.
Ian W is offline  
Old 22nd May 2019, 12:04
  #64 (permalink)  
 
Join Date: Nov 2004
Location: UK
Posts: 436
Originally Posted by tdracer View Post
Not too long ago I was at special event at the Museum of Flight - not only was I seated at a table with a bunch of current and retired Alaska Air pilots, during the cocktail hour....
And there's the rub - anyone can spout off about what they'd do from the comfort of a chair at a table during cocktail hour, loaded with a beverage or 2.

It is all rather removed from the confines of a flightdeck with the stick shaker rattling your vision, doubling your pulse rate, and drowning out any noise from the trim wheel which is highly likely to be doing exactly what you want and need it to be doing for you... until you realise that it is no longer your friend, and it has put you in an in-recoverable corner in a matter of seconds, while you're gathering your ***** together over the stick shaker and other unbelievable symptoms which just don't add up.

Pass me another bevvy, 'cos the alcohol is beginning to work its magic on me and I've got a few more views on how bad pilots are these days to get off my chest while I have an audience... now sit yourselves down, make yourselves comfortable, and recharge your glasses!
pilotmike is offline  
Old 22nd May 2019, 13:37
  #65 (permalink)  
 
Join Date: May 2010
Location: Boston
Age: 68
Posts: 401
Originally Posted by Ian W View Post
The implication of your post is that the 737 pilot is happy to accept a significantly out of trim aircraft.
What was being assumed is that an experienced pilot would not let the automatics whatever they were put the trim where they didn't want it.- so when the Stab Trim cutout occurred there would not be a large out of trim condition to wind back.

There is also a lot of confusion between 'manual trim' with the column electric trim switch and manual trim with the non-powered trim wheel.
What I was trying to point out is that the "greybeards" statement was that the first thing they would instinctively do when trim acted up for whatever reason was to hit the cutout switches then use the manual wheel to trim, not first attempt to correct the trim using thumb switches.

Up until MCAS probably the most likely cause of runaway trim was a HW failure of some sort such as stuck relay which the thumb switches might/might not override so would be logical to hit cutout as soon as possible before stab ran to the limits. Only takes seconds of runaway to get to a bad state.

An unanswered question is why the initial re-trim by ET pilot only removed about 1/2 of the MCAS trim, that and failure to manually trim after cutout are the final causes.
MurphyWasRight is offline  
Old 22nd May 2019, 13:41
  #66 (permalink)  
 
Join Date: Jun 2009
Location: VA, USA
Age: 53
Posts: 555
Originally Posted by pilotmike View Post
And there's the rub - anyone can spout off about what they'd do from the comfort of a chair at a table during cocktail hour, loaded with a beverage or 2.

It is all rather removed from the confines of a flightdeck with the stick shaker rattling your vision, doubling your pulse rate, and drowning out any noise from the trim wheel which is highly likely to be doing exactly what you want and need it to be doing for you... until you realise that it is no longer your friend, and it has put you in an in-recoverable corner in a matter of seconds, while you're gathering your ***** together over the stick shaker and other unbelievable symptoms which just don't add up.

Pass me another bevvy, 'cos the alcohol is beginning to work its magic on me and I've got a few more views on how bad pilots are these days to get off my chest while I have an audience... now sit yourselves down, make yourselves comfortable, and recharge your glasses!
I'm beginning to wonder if the pilot-less aircraft isn't really the answer then. Given that the folks up front apparently can't handle a real emergency, might as well not be there at all.

The "unbelievable symptoms" were discussed in great detail after the Lion Air loss, were they not? Stickshaker on one side, trim goes wonky after the flaps are retracted and the AP won't engage.... meanwhile let's leave the thrust at T/O and off we go.

- GY
GarageYears is offline  
Old 22nd May 2019, 14:02
  #67 (permalink)  
 
Join Date: Mar 2019
Location: French Alps
Posts: 119
Originally Posted by MurphyWasRight View Post
What I was trying to point out is that the "greybeards" statement was that the first thing they would instinctively do when trim acted up for whatever reason was to hit the cutout switches then use the manual wheel to trim, not first attempt to correct the trim using thumb switches.
Thank you for this clarification.
So, after all it appears that for some experienced US pilots, the first thing to do was throw the cutout switches ASAP and then use the manual trim wheel.

Last edited by Fly Aiprt; 22nd May 2019 at 14:03. Reason: Typo
Fly Aiprt is online now  
Old 22nd May 2019, 16:10
  #68 (permalink)  
 
Join Date: Jan 2008
Location: uk
Posts: 751
Originally Posted by MurphyWasRight View Post
What I was trying to point out is that the "greybeards" statement was that the first thing they would instinctively do when trim acted up for whatever reason was to hit the cutout switches then use the manual wheel to trim, not first attempt to correct the trim using thumb switches.
The greybeards may have another reason - in the "old" days it was specifically advised not to use main electric trim to counter a runaway.

Peter Lemme (satcom.guru) has tweeted parts of 727 manuals and found the procedure was to hit cutouts "immediately" with no mention of trimming in opposition (see image attached). He also shows other bits of the manual that were specifically advising against it.

Of course the greybeards also had the rollercoaster technique in their manuals and were possibly in their training too. It is possible that everything changed at the same point between classic and NG:

1. "Control airplane pitch attitude manually with control column and main electric trim as needed" added to procedure
2. trim wheel made smaller so manual trim less likely to work if mistrimmed
3. rollercoaster taken out of manuals
EDIT: and quite possibly related: 4. Stab trim actuators combined - classic had AP servo and main trim motor, NG has just single motor driven by AP or main elec trim

Then the MAX removed the separate autopilot-trim cutout too.
Attached Images
File Type: png
runaway.png (195.1 KB, 10 views)

Last edited by infrequentflyer789; 22nd May 2019 at 16:28.
infrequentflyer789 is offline  
Old 22nd May 2019, 16:18
  #69 (permalink)  
 
Join Date: Mar 2019
Location: French Alps
Posts: 119
Originally Posted by GarageYears View Post
I'm beginning to wonder if the pilot-less aircraft isn't really the answer then. Given that the folks up front apparently can't handle a real emergency, might as well not be there at all.

- GY
Not sure of what would have happened of the Lion Air and Ethiopian flights had there be no pilots on board ?
Maybe the flights might have ended sooner, so the people on board would have had less time to get bounced around before the crash ?

The "unbelievable symptoms" were discussed in great detail after the Lion Air loss, were they not? Stickshaker on one side, trim goes wonky after the flaps are retracted and the AP won't engage.... meanwhile let's leave the thrust at T/O and off we go.

Not sure of what procedure you are referring to with "Stickshaker on one side".
What would it look like ?
"In case stickshaker activation, first reach over to the other yoke to make sure only one shaker motor is running.
If so, then stickshaker alarm is spurious, ignore it and consider MCAS .
If not, then do stickshaker memory items"
Are you sure you would be able to diagnose the number of shaker motors running before running memory items ?
Really ?

Last edited by Fly Aiprt; 22nd May 2019 at 16:32. Reason: Typo
Fly Aiprt is online now  
Old 22nd May 2019, 20:05
  #70 (permalink)  
 
Join Date: Nov 2004
Location: UK
Posts: 436
Originally Posted by GarageYears View Post
I'm beginning to wonder if the pilot-less aircraft isn't really the answer then. Given that the folks up front apparently can't handle a real emergency, might as well not be there at all.

The "unbelievable symptoms" were discussed in great detail after the Lion Air loss, were they not? Stickshaker on one side, trim goes wonky after the flaps are retracted and the AP won't engage.... meanwhile let's leave the thrust at T/O and off we go.

- GY
Seriously? Your conclusion is that pilotless is better? So when the Lion Air 737Max was doing its best to kill everybody on board the day before the Lion Air crash directly caused by MCAS, what - or rather WHO - do you believe saved the day and the lives of all those souls on board?

Was it the aircraft?
Was it automation?
Was it MCAS?
Was it a computer?

Wrong, wrong, wrong and WRONG again! The automation was going beserk and was trying to kill them all. The correct answer is, it was....

...

...

a pilot!

Yes, a pilot saved everyone from the unthinking actions of an ill-conceived and very badly implemented computerised system.

Pilots 1, automated system gone wrong NIL on that occasion.

Unfortunately, MCAS equalised very soon after. And then MCAS went on to score the decider some months later, against Ethiopian. Finally, the ref has called FOUL, and has had the good sense to stop the match. But your solution is to remove the pilot? Incredible, given all the evidence!
pilotmike is offline  
Old 22nd May 2019, 20:27
  #71 (permalink)  
 
Join Date: Apr 2008
Location: back of beyond
Posts: 93
Originally Posted by pilotmike View Post
The automation was going beserk and was trying to kill them all.
...

Yes, a pilot saved everyone from the unthinking actions of an ill-conceived and very badly implemented computerised system.
Rather poor choice of example seeing that MCAS is not active during automatic flight. In fact the sole reason for MCAS is to provide pilot-friendly handling characteristics, and would not have been necessary in a pilotless aircraft
fizz57 is offline  
Old 22nd May 2019, 22:48
  #72 (permalink)  
 
Join Date: Mar 2019
Location: French Alps
Posts: 119
Originally Posted by fizz57 View Post
Rather poor choice of example seeing that MCAS is not active during automatic flight.
Hmm, automatic flight ?
With a faulty AOA sensor ?
Really ?

My bet is, as soon as the AOA vane/synchro/whatever would have failed, the autopilot would have called it a day, and another mode of auto flight would have taken place : free fall...

Fly Aiprt is online now  
Old 22nd May 2019, 23:06
  #73 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 64
Posts: 2,314
Pilot Mike and Fly Aiprt, you're rather missing the point. MCAS (and countless other systems) are less than 100% robust because it's assumed that if they do something stupid, the carbon based life forms sitting in row zero will take over and fly the aircraft. However, it's been repeatedly demonstrated that at least some of those carbon based life forms - otherwise known as pilots - are not completely up to the task (forget MCAS, think AF 447). If the designers have to design all the systems on the aircraft assuming the pilots won't take over and do the right thing when something fails, then why have pilots?
Of course this would take a complete re-think of how aircraft and automatics/avionics are designed, with many levels of redundancy and backups. The 'we must have pilots' side keeps pointing to cases where the pilots stepped in and saved the day when the automatics went south - but that's how the system is designed, assuming that when things go wrong the pilots will step in and save the day. The designers would not design the automatics that way if they couldn't count on the pilots to step in.
Now, I'm not suggesting we're to the point where we can design the aircraft so we don't need pilots - that's still decades away. But when pilots become completely overwhelmed and demonstrate the inability to even remember to pull the throttles back so they don't overspeed when something goes wrong, it moves us one more step in that direction.
tdracer is offline  
Old 23rd May 2019, 00:25
  #74 (permalink)  
 
Join Date: Mar 2019
Location: French Alps
Posts: 119
My experience in designing aircraft systems (not for Boeing ;-) is, the key is research for graceful failure.
If when your system fails, average crews get overwhelmed, then something is wrong with the system, not the crew...

That is, provided you actually test your system in real life in real airplanes, which we are not sure Boeing actually did.
And there is no need to this day, to resort to full autonomous commercial flight the technology is not mature to envisage yet.

As a designer, just do your homework, do study ergonomics and human factors, and you'll be the guy up to the task.

As to considering the crews being overwhelmed as not being "up to the task", well the people I know of, that have actually encountered life threatening situations with complex multiple alarms/failures, are far more tolerant than you are.
Because they know that they also have been overwhelmed, like anyone of us would have been, whatever our abilities, real or supposed.
Fly Aiprt is online now  
Old 23rd May 2019, 00:40
  #75 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 542
Originally Posted by Fly Aiprt View Post
My experience in designing aircraft systems (not for Boeing ;-) is, the key is research for graceful failure.
If when your system fails, average crews get overwhelmed, then something is wrong with the system, not the crew...

That is, provided you actually test your system in real life in real airplanes, which we are not sure Boeing actually did.
And there is no need to this day, to resort to full autonomous commercial flight the technology is not mature to envisage yet.

As a designer, just do your homework, do study ergonomics and human factors, and you'll be the guy up to the task.

As to considering the crews being overwhelmed as not being "up to the task", well the people I know of, that have actually encountered life threatening situations with complex multiple alarms/failures, are far more tolerant than you are.
Because they know that they also have been overwhelmed, like anyone of us would have been, whatever our abilities, real or supposed.
An A330 crew recently had a major electrical failure that generated 62 ECAM's (if my sources are correct) and landed in the the middle of nowhere at 0345 am body clock time on a short runway. I suspect when the facts come out about this it will be seen as one of the remarkable aviation achievements in spite of the automaton, bells & whistles.

Computers, automating & system design have a long long way to go before we can even begin to think eliminating carbon based pilots.
CurtainTwitcher is online now  
Old 23rd May 2019, 00:44
  #76 (permalink)  
 
Join Date: Mar 2019
Location: French Alps
Posts: 119
Originally Posted by tdracer View Post
But when pilots become completely overwhelmed and demonstrate the inability to even remember to pull the throttles back so they don't overspeed when something goes wrong, it moves us one more step in that direction.
As an aerobatics instructor, I can say with confidence that confronted with a difficult upset, every trainee WILL not even remember to pull the throttle back unless specifically trained for that.
We're talking of flying real airplanes, experiencing real spinning, gees, etc. not calibrated sim exercices with a warned crew.
And my trainees ranged from low time students to multi kilo-hour F117 pilots or airline captains. So...

Besides, confronted with a stickshaker alarm and severe AND trim at low altitude, retarding the throttles seems a rather odd idea... But I may be wrong.

Last edited by Fly Aiprt; 23rd May 2019 at 00:49. Reason: Typo
Fly Aiprt is online now  
Old 23rd May 2019, 06:09
  #77 (permalink)  
 
Join Date: Oct 2017
Location: Vienna
Posts: 80
Originally Posted by Fly Aiprt View Post
My experience in designing aircraft systems (not for Boeing ;-) is, the key is research for graceful failure.
If when your system fails, average crews get overwhelmed, then something is wrong with the system, not the crew...
This is a very important point, and people should really understand it. To simplify, if we assume "piloting skill" is something we can measure with a single number, pilots would still have a different level of skill. Normal distribution is defined by the mean and standard deviation, the latter simply telling us how big is the difference between "top guns" and "barely passed the certification".


Standard deviation


Lots of posters here assume they themselves are, and everybody else should also be nothing but a "top gun" (the blue graph above). Does that reflect reality? I'll let yourself answer that.

But of course the reality is even more complex. Top guns have bad days. Could be a headache, could be a divorce. That stuff will kick you out of your best, within the magenta graph. In essence, even a top gan is only top gun on their best days. Then of course we'd need to measure different parameters. Somebody might be an ace pilot, but will miss a detail, like say trim spinning in the wrong direction (while somebody else might suck at hand flying but would thought, "hmm, this is weird").

So what can you do? Two things:
- stringent certification requirements which measure not only the knowledge and skill, but also "soft skills*" like "ability to keep calm while overspeeding 1000 feet AGL with severe trim down"; in essence making sure nobody by say level 90 on the magenta graph passes (which would run the industry crazy due to "shortage**" of pilots)
- design the systems so that not an average crew can handle it, but any certified crew can handle it. There is a big difference between the two, but I'm sure everyone can agree a certified crew should be able to handle a plane, or there is a problem.

*not really skills as those can't be learned.
**perhaps a big part of a problem - HR market requirements allow subpar pilots to be certified?
derjodel is offline  
Old 23rd May 2019, 06:37
  #78 (permalink)  
 
Join Date: Nov 2004
Location: UK
Posts: 436
Originally Posted by fizz57 View Post
Rather poor choice of example... In fact the sole reason for MCAS is to provide pilot-friendly handling characteristics,
And an unbelievably inappropriate choice of words by you. MCAS turned out to be anything but "pilot-friendly" when it went rogue on 3 occasions. The results speak for themselves. Nothing friendly about that, at all.

The fact is, MCAS was an ill-considered and very badly bodged attempt to fix another much more serious problem, purely for financial reasons, and the un-intended consequences had horrific results. If it was anything other than a totally unsafe and unsatisfactory system, why would the aircraft be banned by every administration, with no satisfactory fix or end to the desperately sorry saga in sight?

It was nothing whatsoever about being "pilot-friendly" - rather it was a cynical, cheapskate fix for a bigger problem, which was pushed through the regulatory system inappropriately, many would say, and it has killed far too many people.
pilotmike is offline  
Old 23rd May 2019, 09:39
  #79 (permalink)  
 
Join Date: Jan 2012
Location: Welsh Marches
Posts: 58
Originally Posted by pilotmike View Post
It was nothing whatsoever about being "pilot-friendly" - rather it was a cynical, cheapskate fix for a bigger problem, which was pushed through the regulatory system inappropriately, many would say, and it has killed far too many people.
Absolutely, sums it up in a nutshell. This could well be the prosecution closing argument.

Regards

Alchad
Alchad is offline  
Old 23rd May 2019, 09:52
  #80 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 2
Right person for the job

Hi Jodel,
I think we should distinguish between average folk and average professional pilots in this argument.
Pilots only get (and stay) where they are after stringent selection, training and repeated checking. They are a small part of the community.
That doesn’t mean they have to be especially clever or elite - but just ideal people for their job. Other people are ideally suited to other professions, at which many pilots may fail.
A professional pilot should be well up on your scale - if that scale applies to flying skills/aptitude as applied to the general community. The bad ones get found out with very few exceptions.
A doctor or an architect doesn’t go through this process - has to prove him(her)self to stay in business in other ways...
So an aircraft designer has the right to expect a certain level of skill. I seem to remember in my manual, that Boeing were pretty clear on the skill tests their pilots were expected to pass. That needs to be borne in mind when using terms like “average”.
On the other hand, a professional pilot has the right to expect a level of skill from the manufacturer. This includes honest self criticism such as is required of a professional pilot.
B
bill fly is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.