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CockpitBuilders.com - Main => General Discusion Board. => Topic started by: FredK on March 13, 2019, 04:32:38 PM

Title: 737 MAX
Post by: FredK on March 13, 2019, 04:32:38 PM
I was seriously starting to think about upgrading my 737NG to the MAX MIP format, but now I do not know if I want to risk death on takeoff.

Fred K
Title: Re: 737 MAX
Post by: Joe Lavery on March 13, 2019, 07:37:41 PM
Very sad day for the passengers and crew of both of these aircraft. Also I was shocked when the CAA took the unprecedented decision to ban all flights to and from the UK by 737 Max aircraft.
So quite a difficult time for Boeing also until the cause of the crashes is determined.
Title: Re: 737 MAX
Post by: bernard S on March 14, 2019, 10:30:19 AM
my 2 cents   if pilots do not have 100 percent operation control then ground it    ..Boeing going to fix it   software and training ..they fixed the battery issue in 78 and bounced back
Title: Re: 737 MAX
Post by: navymustang on March 14, 2019, 11:13:49 AM
I'm getting a bit frustrated when the news folks don't gather correct data and start trying to blame Boeing for this entire mess. A runaway trim condition has several escape routes that most of you know. Why hasn't there been more discussion of poor piloting skills during these failures? Even with a control system that is not behaving - you can still get around the issue with proper emergency procedures.

Seems like airline training in the sim has been terribly miss-managed. I guess we need to sit back and see what evidence comes from the cockpit recorders.
Title: Re: 737 MAX
Post by: jfuenmayor on March 14, 2019, 11:51:13 PM
Well, from what I have gathered so far, it seems that there are some issues with the
actual frame design  and the CG as a result of moving the engines forward, up an closer in the  old 737 fuselage type, in order be able to to place them them and clear the terrain. Increasing the height of the landing gear was an option but it would have also introduced major changes in the fuselage and wing to make room for the main gear wells.

The net effect of this modification seems to have been the tendency for the airplane to pitch up in an unusual way at full throttle, ergo, enter MCAS. It was developed precisely to correct for this and avoid stall situations. Some experts may think it is not a good idea to use software to compensate for native design. The  MCAS system does not fully deactivate when the autopilot is disconnected, and reactivates itself every 10 seconds despite repeated pilot commands to do so, and will continue to trim down to avoid what the computer thinks is an imminent stall condition. The fact that it seems to only use two AOA vanes as data feed for error checking seems puzzling. It is quite hard for me to believe that, but that is what is out there. Critics claim that other parameters should be used for cross checking.
I am sure the millions of lines of code involved in the software for these airplanes have been audited to exhaustion but, as I said, to compensate for an air frame design flaw with  software seems a bit far fetched.

It is also speculated that the reason why the MAX was not designed from the ground up to accommodate the newer bigger engines,  was not only to transition the crews from the NG to the MAX with minimum training, but also to avoid a full re certification process of the new air frame which, also meant time and money. I do not think the engineers did not foresee this scenario which could result in a very dangerous situation. This is quite hard for me to fathom, since their job entitles to think about the unthinkable and solve it. Quite hard to do actually, and that is why they have my admiration.

So picture yourselves at low altitude, confronted with a situation for which you are not prepared and which is totally contrary to what you would expect. An AA pilot related that his training in the MAX consisted of an iPad video of one hour. No sim time. As a matter of fact AA does not have a Sim for the MAX, so claims this pilot.

It would appear to me  that the Ethiopian crew should have been fully aware of the MCAS behavior, hell I was, and I do not fly for a living. Also, the scenario of a runaway stabilizer trim must have crossed their minds, if they had time. The purpose of training in general,  is to learn to react naturally and swiftly  to a situation, and not to have to come up with an elaborate solution when there is no time for that, such as in this case, may I observe. The shock would come if the  Ethiopian crew did indeed flip those switches to deactivate the trim motors, and yet they ended up crashing. It seems they got up to only 1400 feet above terrain. Note a heck of a lot.

I hope Boeing is able to get to the bottom of this and correct what seems to be a real issue. Two brand new planes crashing in similar circumstances.

A passenger airplane is not a fighter, and although pilots must fly the damned thing, they do not have to fight it.

My two cents.


Title: Re: 737 MAX
Post by: KyleH on March 15, 2019, 11:05:51 AM
Ok we need to get some facts straight on this so we are not spreading additional miss information.

The MCAS system was required due to the change in placement of the engine, further forward from the wing on the pylon.
The 737 could not pass certification without the MCAS system because of a requirement that as you pull the yoke back the force on the yoke must not get lighter as you approach the end of it's travel, especially as you approach a stall. With the placement of the engines on the MAX, at high angles of attack and no flaps, the engines nacelles will begin to contribute some amount of lift, forcing the aircraft to continue pitching up, which resulted in the force required on the yoke to decrease as it approached a stall.

Imagine your a pilot, pulling back on the yoke approaching a stall with the control forces getting harder as they should, then the forces required get lighter resulting in you pulling it even faster into a stall.

The FAA would not certify the plane in this state. The MCAS system was designed to run the stab trim forward in this flight regime only, in order to maintain the same required control force on the column throughout the stall maneuver.
The system is supposed to only engage in the specific situation of: autopilot off, flaps up, and high angle of attack.
The FAA certified the plane with this system installed.

Now, the failure mode in the Lyon Air case is that the AOA sensor failed and the system thought it needed to run to prevent a stall, resulting in the stab trim to run forwards pitching the nose down.

My opinion;

I agree with Jim. This is a training issue that we are now dealing with due to the pilot shortage and having low time crews in these airplanes.

I feel it's important to note, that there are other failures that can cause the trim to runaway that have nothing to do with MCAS system, and could occur on any airplane with powered trim, not just the MAX. In fact the Lyon Air aircraft flew 3 times previously with the fault, and those crews successfully recovered the airplane.
The procedure to recover from this is the same no matter the cause of the failure. Those that have a motorized 737 throttle quadrant should know, it's hard to miss the indications of a trim runaway with those massive wheels running right beside your knee. Proper training and procedures is required to overcome these situations.

As far as the simulators go, there are very few MAX simulators in the world due to the common type ratting granted by the FAA. Only airlines that were not flying the NG have them.

And for the Ethiopian flight, all we have at this time is flight path data that shows a similar profile. We don't have any data yet to determine what went on in the cockpit. It could have been something unrelated to MCAS. I only hope that FAA and Transport Canada decisions to ground the MAX have some valid evidence that has not been released yet and not just giving into hysteria generated by the media on a complex issue that most are not capable of understanding.

Publishing a revised software 'fix' is not going to get to the root of the problem which is pilot skills, training and proficiency.
Title: Re: 737 MAX
Post by: KyleH on March 15, 2019, 02:03:35 PM
For anyone interested, a summary of the events on the flight previous to the Lyon Air accident:

Quote
"About 400 feet, the PIC noticed on the Primary Flight Display (PFD)13 that the IAS DISAGREE warning appeared and the stick shaker activated. The FDR showed the stick shaker activated during the rotation. Following that indication, the PIC maintained a pitch of 15° and the existing takeoff thrust setting. The stick shaker remained active throughout the flight.

 The PIC handed over control to the SIC and announced “memory item airspeed unreliable”. After the transfer of control, the PIC cross checked the PFDs with the standby instrument and determined that the left PFD had the problem. The PIC then switched on the right flight director (FD) so the SIC would have a normal display.

 While handling the problem, the PIC instructed the SIC to continue acceleration and flap retraction as normal. The PIC commanded the SIC to follow FD command and re-trim the aircraft as required. The PIC noticed that as soon the SIC stopped trim input, the aircraft was automatically trimming aircraft nose down (AND).

 After three automatic AND trim occurrences, the SIC commented that the control column was too heavy to hold back. At 14:25:46 UTC, the PIC declared “PAN PAN” to the Denpasar Approach controller due to instrument failure and requested to maintain runway heading. The Denpasar Approach controller acknowledged the message and approved the pilot request. A few second later, the Denpasar Approach controller asked the LNI043 whether he wanted to return to Denpasar and the pilot responded “standby”.

At 14:28:28 UTC, the PIC moved the STAB TRIM switches to CUT OUT. The PIC re-engaged the STAB TRIM switches to NORMAL, but almost immediately the problem re-appeared. The PIC then moved the STAB TRIM switches back to CUT OUT and continued with manual trim without auto-pilot until the end of the flight.
Title: Re: 737 MAX
Post by: FredK on March 15, 2019, 04:06:49 PM
Kyle and Joaquin

I believe that both of you have valid points, and it will be interesting to see how this develops for Boeing in general.

Yes, the 737 is an aging air frame design...engine placement has evolved a long way since those original small engine pods were tucked right under the wings.  So to minimize developmental and pilot training costs Boeing implements an MCAS system to deal with CG balance issues.  Not necessarily a bad thing for sure, but not as eloquent a solution as designing a whole new air frame.  Then, to again minimize pilot training costs Boeing mentions little of MCAS with minimal overall training requirements defined.

So...Has the quest "to minimize costs" breeched a proper safety certification process for these planes?  Where is Boeing on all this with regards to safety?  Where is the FAA oversight on all this with regards to safety?  Where are the airlines on all this with regards to safety.  It seems totally unfathomable to me that in this day and age there would be two catastrophic incidents involved in the process of introducing a new aircraft.  So something is very wrong somewhere.

It seems also unfathomable to me that the airlines do not even have a simulator for training even to this point....almost two years since the first introduction of the MAX. It seems to me that there are enough changes in the MIP layout of things (and with new systems like MCAS) that you would want to educate all that in a simulator environment that challenges you with potential failures.  Can you really learn all that from an IPAD?  I cannot judge that from my own background, but my commercial pilot friends say you can absolutely not.

This raises some issues for Boeing of course....The Airbus 320 NEO employs similarly sized engines but there is more room under the wing to accommodate since the Airbus sits higher off the ground.  I have not heard that there is a similar MCAS system implemented there, but I do not know that for sure.

And what about the Dreamliner?  The wing profile on that plane also sits as similarly low as the 737 and the engines are similarly set on pylons out front.  So clearly Boeing did not think it necessary to raise things off the ground there in a complete new design.  Is there a similar (or identical) MCAS sysytem on the Dreamliner?  Or are there other design features that obviate the need?

It will be interesting to see how all this plays out.  Regarding the MCAS system...it seems that the issue in the Lion Air case is one of bad data inputs rather than with the MCAS system itself.  Perhaps the same for the Ethiopian incident.   Boeing claims to be working on a software fix for MCAS, but that could get pretty convoluted if (1) you absolutely require MCAS operational in certain instances and (2) you absolutely require reliable inputs commensurately.

Fred K
Title: Re: 737 MAX
Post by: 757Simulator on March 16, 2019, 04:06:54 AM
Kyle and Joaquin

I believe that both of you have valid points, and it will be interesting to see how this develops for Boeing in general.

Yes, the 737 is an aging air frame design...engine placement has evolved a long way since those original small engine pods were tucked right under the wings.  So to minimize developmental and pilot training costs Boeing implements an MCAS system to deal with CG balance issues.  Not necessarily a bad thing for sure, but not as eloquent a solution as designing a whole new air frame.  Then, to again minimize pilot training costs Boeing mentions little of MCAS with minimal overall training requirements defined.

So...Has the quest "to minimize costs" breeched a proper safety certification process for these planes?  Where is Boeing on all this with regards to safety?  Where is the FAA oversight on all this with regards to safety?  Where are the airlines on all this with regards to safety.  It seems totally unfathomable to me that in this day and age there would be two catastrophic incidents involved in the process of introducing a new aircraft.  So something is very wrong somewhere.

It seems also unfathomable to me that the airlines do not even have a simulator for training even to this point....almost two years since the first introduction of the MAX. It seems to me that there are enough changes in the MIP layout of things (and with new systems like MCAS) that you would want to educate all that in a simulator environment that challenges you with potential failures.  Can you really learn all that from an IPAD?  I cannot judge that from my own background, but my commercial pilot friends say you can absolutely not.

This raises some issues for Boeing of course....The Airbus 320 NEO employs similarly sized engines but there is more room under the wing to accommodate since the Airbus sits higher off the ground.  I have not heard that there is a similar MCAS system implemented there, but I do not know that for sure.

And what about the Dreamliner?  The wing profile on that plane also sits as similarly low as the 737 and the engines are similarly set on pylons out front.  So clearly Boeing did not think it necessary to raise things off the ground there in a complete new design.  Is there a similar (or identical) MCAS sysytem on the Dreamliner?  Or are there other design features that obviate the need?

It will be interesting to see how all this plays out.  Regarding the MCAS system...it seems that the issue in the Lion Air case is one of bad data inputs rather than with the MCAS system itself.  Perhaps the same for the Ethiopian incident.   Boeing claims to be working on a software fix for MCAS, but that could get pretty convoluted if (1) you absolutely require MCAS operational in certain instances and (2) you absolutely require reliable inputs commensurately.

Fred K


Are you a aeronautical engineer? Not being mean. Just curious because your tossing out a lot of unfounded and presumptive speculation.

All the best,

Mike
Title: Re: 737 MAX
Post by: blueskydriver on March 16, 2019, 04:19:31 AM
Here is a nice YouTuber and B737NG Pilot that discusses many topics, including the 737 MAX and it's MCAS. He has also posted about the two recent accidents... :idiot:

https://www.youtube.com/watch?v=TlinocVHpzk (https://www.youtube.com/watch?v=TlinocVHpzk)

John
Title: Re: 737 MAX
Post by: KyleH on March 16, 2019, 11:23:03 AM
Fred,

With those other aircraft you mention, they were all designed aerodynamically to operate with the engines they have on them no augmentation system needed. When the NG was created, it got a new wing that again is designed to accommodate the engines that were given to it. This is not the case with the MAX, which resulted in them finding this issue at flight test, requiring the MCAS system.

It is also not a simple matter of training the flight characteristics for the MAX to eliminate the need for MCAS. It is the fact that the regulations do not allow for the control forces to get lighter as you pull back on the yoke. If the MAX doesn't have MCAS - it will not meet certification requirements and not be allowed to fly. The FAA appeared to be satisfied with the solution rather than requiring an aerodynamic fix.

Sim's for the MAX do exist, I've been in one of them. I have no idea if they have the MCAS system simulated. As to weather or not an airline should require a full simulator if they already have an NG one, when the differences in the cockpit are relatively minor I don't know. The engineering side of me says the cost benefit might not be there, an FTD device may be enough. Would be better than videos only.

I'm not saying that there isn't a problem that needs to be dealt with on the MAX, but unlike the DC-10 cargo door, this on the surface looks like an issue that should be able to be safely dealt with by the pilots. Similar to the A330 pitot probe issue that was a contributing factor to the AF447 crash.

I have my suspicions on what the accident sequence for the Lyon Air flight will turn out to be, but will have to wait for the report.

I know for myself that if I was manually flying the aircraft, and those big trim wheels were turning without me commanding it from the switches, I'd be going for the stab trim runaway procedures after checking that the autopilot was indeed off. Now with the stick shaker going off at the same time, it might take longer to notice.


Title: Re: 737 MAX
Post by: FredK on March 16, 2019, 12:15:11 PM
Quote
Are you a aeronautical engineer? Not being mean. Just curious because your tossing out a lot of unfounded and presumptive speculation.

All the best,

Mike

For sure....I am not any kind of of trained aeronautical engineer.  I am not even a trained pilot. I certainly do not profess to have a correct understanding of what exactly happened in the two incidents (the official reports of what exactly happened and why have not even been published yet).

That said, I do have a deep interest in aviation and the 737 in particular to the extent that I have invested in a fairly sophisticated 737 cockpit in my home.

That is the extent of any qualifications I have.

The speculative considerations I mentioned are just that.....speculations.....about the debate going as to whether these two incidents are due to design flaw and/or training. From my layman's perspective I simply conclude (speculate) that there were at least serious training deficiencies involved.  I also conclude (speculate) that there was some design or software flaw involved...only because it is really hard for me to fathom that the well experienced pilots on board in both cases could not have successfully handled the situations otherwise.  But yes, those are my opinions.....so challenge away!

I also have curiosities about MCAS and whether such a system exists on other similar aircraft...and if so, why or why not related to design engineering.  But clearly I have raised these as questions, and I also invite comments from those in the know.

Kyle...Thanks you for your insights.

Fred K

Title: Re: 737 MAX
Post by: jackpilot on March 16, 2019, 01:41:08 PM
As usual, once the analysis/reports are available, we all will be in a better position to comment based on documented facts. :D
Title: Re: 737 MAX
Post by: Joe Lavery on March 16, 2019, 03:09:13 PM
More speculation  8)

I am a qualified pilot, but only on GA aircraft, the biggest thong I've ever flown is a Norman Islander, (co-pilot only); which to be fair gives me no qualification to speculate on the cause of these two 737 MAX crashes.

However there has recently been a suggestion that there was something wrong with the scew-jack, but again I have not seen this corroborated anywhere.

Yet after the loss of the MD-83 in 2000 through the failure of the Screw-jack, I would have thought that the idea of fail safe would have been the byword for aircraft designers. Not perhaps "this doesn't work properly how can we design around it".

I also have a 737 cockpit, but that doesn't give me any insight at all as to the issue we've all, (very interestingly) been discussing.

 :2cw:
Title: Re: 737 MAX
Post by: navymustang on March 16, 2019, 03:46:07 PM
I love the news - they have several times reported screw jack issues as mentioned by Joe. Last night the national news said they found the elevator section and the screw jack was in an unusual position. What the heck does that mean? Shame on the news for reporting such things.
Title: Re: 737 MAX
Post by: Joe Lavery on March 16, 2019, 03:52:22 PM
I have to admit a smile when I read that comment on the news... do you think the crash might have had some hand in the unusual attitude on the screw jack.... maybe!

Incidentally I'm not making light of what was a tragedy for all those who boarded those aircraft, never to see their loved ones again. I cannot imagine the anguish and pain their relatives are feeling right now.

Joe.
Title: Re: 737 MAX
Post by: blueskydriver on March 16, 2019, 06:31:09 PM
Surprised the news media has not said "both aircraft had the MCAS or Makes Crashing Airplanes Simple in use..."! You know how they love a good run on story; especially, now that the weather is getting better...lol!  :idiot:

John
Title: Re: 737 MAX
Post by: 757Simulator on March 17, 2019, 04:24:06 AM
Quote
Are you a aeronautical engineer? Not being mean. Just curious because your tossing out a lot of unfounded and presumptive speculation.

All the best,

Mike

For sure....I am not any kind of of trained aeronautical engineer.  I am not even a trained pilot. I certainly do not profess to have a correct understanding of what exactly happened in the two incidents (the official reports of what exactly happened and why have not even been published yet).

That said, I do have a deep interest in aviation and the 737 in particular to the extent that I have invested in a fairly sophisticated 737 cockpit in my home.

That is the extent of any qualifications I have.

The speculative considerations I mentioned are just that.....speculations.....about the debate going as to whether these two incidents are due to design flaw and/or training. From my layman's perspective I simply conclude (speculate) that there were at least serious training deficiencies involved.  I also conclude (speculate) that there was some design or software flaw involved...only because it is really hard for me to fathom that the well experienced pilots on board in both cases could not have successfully handled the situations otherwise.  But yes, those are my opinions.....so challenge away!

I also have curiosities about MCAS and whether such a system exists on other similar aircraft...and if so, why or why not related to design engineering.  But clearly I have raised these as questions, and I also invite comments from those in the know.

Kyle...Thanks you for your insights.

Fred K


Thank you Fred. Great post!

Mike
Title: Re: 737 MAX
Post by: jfuenmayor on March 18, 2019, 02:02:20 PM
Hi guys, I have read with interest all the posts by Kyle Fred and the rest of the crew, and certainly, the points are valid. My simple question is, should software correct for inherent misbehavior of the air frame due the introduction of some modifications that induce said behavior ?.

The Airbus depends heavily on automatic systems and the basic tenet is, if there is enough conflicting information coming from the sensors the autopilot disengages and goes to alternate law since direct law is only possible at or below 250 Kts. and gear down, at least that is what I recall from my 8 hour experience in both the 330 and 320 Level D sims. (lucky me). The similarities between the case of the AF flight and these, other than pilot's inexperience is not applicable. The crew of the AF flight were baffled with a flood of ECAM warnings and what they saw did not make sense to them. The PF at one time  did push the stick forward with no results. I guess in a futile attempt to recover when below 10000 feet they kept the stick back.

There is no doubt that the pressures on the industry is forcing the entry of new pilots with relatively low air time, as low as one hundred and fifty hours. I have trusted information that some airlines send pilots  for type rating only with a Commercial, Instrument and Single Engine experience,  with say, 150 hours of air time, not simulator time. After that, they go to the jump seat and shortly after to the right seat. The reasoning being that the new systems can compensate for the lack of experience. I understand the Captain in the Ethiopian airliner  had 8000 hours and the FO 200 or so.

The problem exists and is very real, two planes have been lost. They just need to get to the bottom of it so the public can regain its confidence . Just for  little a bit of recalling, the Comet's original design flaws,  which led the catastrophic failure of the fuselage after pressurization  were corrected ,but the public never regained their trust in the airplane. The last nail in the coffin was a new kid in town, the 707.

In the case at hand, we do need a heck of a lot more information before drawing any firm conclusions, and true, we are speculating but with some basis. Thinking is not a flaw, but data is king and so, I think that in this instance,  reasonable, reliable information, provided it does not hinder the investigation itself,  has to be made crystal clear to the layman as well as the people in the industry as it is obtained, if we are to regain confidence. A full  report of the probable causes may take over a year, sometime more. Tough situation for Boeing.

Joaquin.
Title: Re: 737 MAX
Post by: Joe Lavery on March 18, 2019, 06:57:10 PM
Well said Sir....  :)

Joe.
Title: Re: 737 MAX
Post by: tennyson on March 18, 2019, 09:48:58 PM
To answer the original question by Fred, yes, I am in the process of upgrading to the MAX, from my 737-800NG.

As far as speculation goes about on-going incidents, I will defer my comments, as the major contributors above seem to have a good handle on the guts of it.

I am very concerned at the way we all interpret these events, and I'm not just talking about the Boeing incidents.
The general Media, in it's holier than thou attitudes hangs draws and quarters individuals, businesses and Corporations prior to any hard evidence on mere supposition.

Boeing have taken stock losses in the billions over an incident that may eventually find them completely non-culpable.

I appreciate the level of knowledge and skill that most of us have in the aviation field, but without the true facts and all the facts, all the supposition in the world amounts to nought.

I, in my upgrade path have done and continue to do lots of study on the MAX. I believe that in the following months and years we will see the facts emerge, life will go on and with the eventual enormous savings in fuel and training, the MAX will go on to supersede the 738 and 739's that it was designed for.



Frank 
Title: Re: 737 MAX
Post by: jackpilot on March 18, 2019, 10:01:21 PM
Wise words Frank.
Title: Re: 737 MAX
Post by: Trevor Hale on March 19, 2019, 03:46:03 PM
To answer the original question by Fred, yes, I am in the process of upgrading to the MAX, from my 737-800NG.

As far as speculation goes about on-going incidents, I will defer my comments, as the major contributors above seem to have a good handle on the guts of it.

I am very concerned at the way we all interpret these events, and I'm not just talking about the Boeing incidents.
The general Media, in it's holier than thou attitudes hangs draws and quarters individuals, businesses and Corporations prior to any hard evidence on mere supposition.

Boeing have taken stock losses in the billions over an incident that may eventually find them completely non-culpable.

I appreciate the level of knowledge and skill that most of us have in the aviation field, but without the true facts and all the facts, all the supposition in the world amounts to nought.

I, in my upgrade path have done and continue to do lots of study on the MAX. I believe that in the following months and years we will see the facts emerge, life will go on and with the eventual enormous savings in fuel and training, the MAX will go on to supersede the 738 and 739's that it was designed for.



Frank
I couldn't have said any of the above better myself. Frank.
Thank you!

 


Title: Re: 737 MAX
Post by: FredK on March 19, 2019, 11:07:27 PM
Keep in mind also that there had been very significant debate within Boeing as to whether to scrap the 737 completely and to develop a wholly new air frame design in its place.  Up to this point the MAX upgrade decision was very clearly the right decision, but only time will tell if that was the right decision longer term.

The bigger challenge perhaps on the horizon for both Boeing and Airbus is China's C919 which is aimed squarely at the MAX/NEO market (under certification now with 800 orders).  Also the CR929 China/Russia joint venture wide body development. Both are planned to utilize engines sourced from GE and/or Rolls to start. The expanding market is China and the rest of the Far East, and rest assured the Chinese airlines will overlook a lot regarding operating cost and quality issues with respect to sourcing from within there own country....that is just how it works there.

Interesting and challenging times ahead for the aviation industry no matter what!

Fred K
Title: Re: 737 MAX
Post by: jfuenmayor on April 06, 2019, 07:06:23 AM

Preliminary report om Ethiopian crash.
Draw your own conclusions.

http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+,(ET-AVJ).pdf (http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+,(ET-AVJ).pdf)
Title: Re: 737 MAX
Post by: FredK on April 06, 2019, 03:39:49 PM
That is an interesting read.....

Certainly there are plenty of facts in this case that are crystal clear. 

However only Boeing can decipher all that to determine the root of the problem. Boeing has acknowledged responsibility and says that they have a handle on it all.  Hopefully for them that is the case.  Another accident would sink the 737 ship.  That has to be a lot of pressure on the people involved right now.

Fred K
Title: Re: 737 MAX
Post by: jfuenmayor on April 06, 2019, 05:45:08 PM
Sure thing Fred. It is sad in all aspects. The industry will surly learn a lot from this.

An additional piece of information is the fact that Airbus had similar problems with
AOA vane malfunctioning and feeding erroneous data, and they solved it years ago. Also, the press has stated that the pilots disconnected the MCAS. This is not true. The preliminary report is clear. The system cannot be disconnected by either turning the AP or the electric trim switches off, the CND (Command Nose Down) was active with the switches off. Really scary.

BTW.  The link that i submitted link is public record. I can see that the rest of the thread has been removed. Interesting.

Trev, let me know if there is an issue with it. I am aware of your previous post regarding the decision made by the EU.

Joaquin.
Title: Re: 737 MAX
Post by: jfuenmayor on April 06, 2019, 05:48:04 PM
Oops, the rest of the the thread is in the archives...sorry :)
Title: Re: 737 MAX
Post by: Garys on April 06, 2019, 06:41:55 PM
Not scary really. The system worked exactly as it should.

05:39:45 = The system is designed to work with flaps up
05:39:55 = The system is designed to work with AP off.
05:40:35 the stab trim was confirmed cutout
05:40:41 = The system is designed to make the input. The output to the Hstab didn't happen because the cutout switches were at cutout. At this point in time they had effectively disabled the MCAS system from making any  flight control surface changes.

Its easy to be a monday morning quarter back, so I"m not going to speculate to the crews actions but I do know that they had the system beat at 05:40:35 
Title: Re: 737 MAX
Post by: Trevor Hale on April 07, 2019, 08:55:12 AM

Trev, let me know if there is an issue with it. I am aware of your previous post regarding the decision made by the EU.

Actually, I did more digging and that's why my post was removed.  We don't get over a million unique users a month.  the rules don't apply to us :)
Trev
Title: Re: 737 MAX
Post by: KyleH on April 07, 2019, 12:59:58 PM
Interesting read.
Just a factual report at this point so no conclusions, but some items I noticed:

The MCAS was disabled when the cut out switches were selected:
Quote
At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position

The crew didn't seem to understand that they couldn't now use the trim switches on the yoke:
Quote
At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

According to this, there was 8 seconds between the captain asking the question and the FO declaring it not working. I don't know if this is a long enough time to trim a 737 manually before much pressure would be relieved from the yoke when its been put into a nose down state.

In addition, this statement makes me wonder if the FO was actually manually trimming the aircraft in the wrong direction:
Quote
From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position....

They then put the trim cut-out switched back to the normal position!
Quote
At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.

Now this part of the report I do find scary :
Quote
1.5.2 FIRST-OFFICER
According to Ethiopian Airlines records, the First-Officer has the following flight experience:
? Total hours: 361
? Total hours in B737: 207
? Total hours in B737-8 MAX: 56
? Flight time in previous 90 days: 207 hours and 26 minutes
? Flight time in previous 7 days: 10 hours and 57 minutes
? Flight time in previous 72 hours: 5 hours and 25 minutes

The FO started flying a 737 with only 154 hours total time. In this country that doesn't even allow me to fly a C172 for hire with only myself on board let alone a jet that can seat almost 200 passengers.



..... Also, the press has stated that the pilots disconnected the MCAS. This is not true. The preliminary report is clear. The system cannot be disconnected by either turning the AP or the electric trim switches off, the CND (Command Nose Down) was active with the switches off. Really scary.
...
Joaquin.

No.
1) As stated before; MCAS only functions with the autopilot off.
2) The report shows that the system was disabled with the trim cut-off switches in the cut-off position at 5:40.
3) The events towards the end lead me to believe that the crew put the cut-off switched back to the normal position, which would have re-engaged the electric trim and by extension MCAS system.

We can't say anything clearly until we have a final report with expert analysis.
Title: Re: 737 MAX
Post by: Garys on April 07, 2019, 01:33:45 PM
"3) The events towards the end lead me to believe that the crew put the cut-off switched back to the normal position, which would have re-engaged the electric trim and by extension MCAS system"

Definitely 100% the switches were moved back to normal position. Not every switch has a feed into the FDR. We know from the prelim report that they disconnected as the voice recorder had verbal confirmation with no horizontal stab movement from the MCAS input thereafter.


05:43:11 Electric trim movement came immediately after the captain said pitch is not enough. It may be in the final report that the cut out switches were heard being moved to the normal position by the cockpit area microphone, but with the stick shaker and overspeed clacker going off, it is possible that this event will go undocumented.


Title: Re: 737 MAX
Post by: jfuenmayor on April 07, 2019, 08:53:12 PM

Well, I do not think that anyone here knows how the MCAS system was really  written unless there is a software engineer among us that is involved with the project and has seen the source code , but, it would seem that the crew re activated the switches in order to have access to electric trimming in a futile effort to trim faster, which of course returned the trim control to the MCAS which was already active due to the false readings.

If any of you has tried to move the trim wheel manually, in a real Level D B737 sim, I am sure you would agree that even in level flight, the number of turns and effort required is significant. Let alone in the real plane on a dive where the forces are higher.

When I say that you turn the MCAS off, I mean that there is a way to make the system inactive. The A/P was engaged at 400 ft RA, and it was so, when the MCAS system  commanded the nose down. So condition No. 1 was bypassed. Turning off the Autopilot is standard procedure when you are faced with a control problem. Automatic systems, including auto throttles  must be turned off and control returned to the crew so they can maneuver out of the situation manually.

The FO had a very low time but not the Captain (8000 hs.), who was the pilot flying.

Getting from 1.5 Units to 4.0, requires significant effort. That is what they were up against.  If the actions taken by the crew, as recommended by the manufacturer, did not correct the problem, in such a dire situation and the lack of time, they had to try something else, I would. We still have to see more information, but I am sure that out of this tragedy, many lessons will be learned. Pointing fingers is an exercise of futility, and hubris has no place.

In the mean time, the planes are still grounded, for a reason.


Title: Re: 737 MAX
Post by: Garys on April 07, 2019, 11:02:12 PM
Boeing aircraft logic uses and/or gates. knowing the source code is irrelevant. For MCAS to work Autopilot must be off AND flaps must be up. There is no OR. I think you may be confusing the Flight Director, which is not an autopilot mode, so its incorrect that condition 1 was bypassed. The 1st MCAS nose down command came almost immediately after the autopilot was disengaged.

Again I"m not going to comment on the actions of the crew, but the recommendation from the manufacturer is to trim the aircraft manually into the green band  before using the cutout switches, ( MCAS is disabled during manual trim and for a further 5 seconds) disconnecting autothrottle and leaving the cutout switches in disable position. I will let you draw your own conclusions on whether that was followed.

There is so much crap in the media about the MCAS system.

From a systems standpoint, MCAS worked as it should. I'm glad to see that system is being updated. I think from a design standpoint it was absurd to only use the input from only 1 AOA and that the disagree annunciation was a customer option.

I'm only looking at these two accidents from a systems standpoint. That is all I care about. Im more concerned about the issues with the AOA.

Title: Re: 737 MAX
Post by: jfuenmayor on April 08, 2019, 12:54:26 PM

A Flight director is a guidance system for reference, and no, it is not the A/P, as a matter of fact, the FD is engaged normally before any flight during cockpit preparation and is an item in the checklist. And yes, the source code is important, because even though you may think  that you coded for a certain condition, in the field, it may not be so. It is called a BUG, and it is so when the code results in an unwanted action. If the possibility of a failure of one of the AOA vanes, giving conflicting information back to the MCAS subsystem was not tested for its reactions, that would be very serious indeed. At any rate, the problem has occurred twice, under similar circumstances. Now,  how do you fix it ?, you audit the source code line by line. Now, that said, as I mentioned before, the AP which is activated with the CMD  push button and shown on the  in the PFD, was activated by the FO on the CAPT's command (flying pilot), again, standard procedure. The pilot flying does not have to divert his attention to pushing a button while actively flying the aircraft, this was done at 400 ft AGL. The disturbance occurred under those conditions. In normal flight, once you engage the AP and VNAV and LNAV are active, the crew just monitors  the flight. Also, the oscillations that were noted should draw attention. Now, I do not know if it is the MCAS system that disengages the AP, in that case, it takes over, and the results are there to see.  Boeing has not yet come with the patch over six months after the first accident. They are looking at the code, of course, and this is not as easy as people may think. They cannot afford to screw up again, that would be disastrous for the MAX.
Title: Re: 737 MAX
Post by: navymustang on April 08, 2019, 04:44:07 PM
Somebody correct me if I am wrong - but hasn't this occurred with U.S. airlines twice with the Max and in both cases the pilots were able to make corrective actions and fly the aircraft safely back to the airport or alternate?
Title: Re: 737 MAX
Post by: KyleH on April 08, 2019, 07:38:56 PM
Joaquin you seem to be interpreting data that isn't there. There is nothing in that report that leads me to believe that MCAS wasn't working as designed. The data profile looks like a functioning MCAS system with an AOA failure.

Well, I do not think that anyone here knows how the MCAS system was really  written unless there is a software engineer among us that is involved with the project and has seen the source code , but, it would seem that the crew re activated the switches in order to have access to electric trimming in a futile effort to trim faster, which of course returned the trim control to the MCAS which was already active due to the false readings.

I'm certain no one here worked on this project and if they did they wouldn't be able to talk about it.
I have done software/circuit design in safety critical systems and do have understanding about how this kind of development is done.

Quote
When I say that you turn the MCAS off, I mean that there is a way to make the system inactive. The A/P was engaged at 400 ft RA, and it was so, when the MCAS system  commanded the nose down. So condition No. 1 was bypassed. ....
Quote
The pilot flying does not have to divert his attention to pushing a button while actively flying the aircraft, this was done at 400 ft AGL. The disturbance occurred under those conditions. In normal flight, once you engage the AP and VNAV and LNAV are active, the crew just monitors  the flight. Also, the oscillations that were noted should draw attention. Now, I do not know if it is the MCAS system that disengages the AP, in that case, it takes over, and the results are there to see.

This is not true, you cannot claim that information from the report. The report shows the MCAS system applying nose down trim at the proper time, autopilot off and Flaps up.
The very short trim down commands you can see on the chart are consistent with the autopilot commands for that phase of flight, acceleration after take-off. Then as the flaps come up slight nose up trim to maintain speed. The oscillations could simply be turbulence.

The autopilot disconnecting could have been because of the associated AOA sensor failure, or someone moving the control column. Gary would probably have a better list of the item's that could cause that.

We have to remember that these events have multiple contributing causes and we can't focus on one system to the exclusion of all the others. The MCAS may have commanded the nose down attitude, but it is only one link in the chain.

We need proper NTSB analysis to determine the probably causes of what went on.


Boeing has not yet come with the patch over six months after the first accident. They are looking at the code, of course, and this is not as easy as people may think. They cannot afford to screw up again, that would be disastrous for the MAX.
Reportedly, Boeing did have a release ready in January, however due to the FAA shutdown, could not have it reviewed. Where the process is right now, I don't know.


Quote
If any of you has tried to move the trim wheel manually, in a real Level D B737 sim, I am sure you would agree that even in level flight, the number of turns and effort required is significant. Let alone in the real plane on a dive where the forces are higher.
This is what makes me wonder if 8 seconds is enough time for the FO to declare the manual trim 'not working'


Somebody correct me if I am wrong - but hasn't this occurred with U.S. airlines twice with the Max and in both cases the pilots were able to make corrective actions and fly the aircraft safely back to the airport or alternate?
Yes, there are NASA reports to that effect. The Lyon air accident aircraft flew a couple of times with the fault before the fatal flight, and those crews successfully recovered.
 
Title: Re: 737 MAX
Post by: jackpilot on April 09, 2019, 09:03:38 AM
May be a dumb point, but every comment, analysis, report etc is all about the MCAS and recovery procedures, no word about the original culprit IMHO which are faulty AOA probes.
Who manufactures them and what is their reliability record?
 Seems to me these are not ultra sophisticated .
Title: Re: 737 MAX
Post by: mickc on April 09, 2019, 09:44:33 AM
May be a dumb point, but every comment, analysis, report etc is all about the MCAS and recovery procedures, no word about the original culprit IMHO which are faulty AOA probes.
Who manufactures them and what is their reliability record?
 Seems to me these are not ultra sophisticated .

Indeed.  (although hopefully more complex than a bit of red string stick to a glider window  :D :D)

There were reports of the AOA sensor on the LionAir aircraft had recently been repaired at an MRO in Florida somehwere.  (again - unconfirmed etc.)
Title: Re: 737 MAX
Post by: Garys on April 09, 2019, 06:08:35 PM
Not usually a problem unless hit by lighning
Title: Re: 737 MAX
Post by: 727737Nut on April 10, 2019, 10:23:26 AM
Pilot Error................... Flying at or above VMO....failure to maintain control of aircraft.... Didn't follow proper procedures..............period!!

Now here is where the long investigation process comes into play,

Contributing Factors.................................................  Time will tell.  MCAS alone did not cause either crash by itself.  It is only a single chain link in the accident chain. 

add
Think about this for a moment, at one point in the middle of the FDR data, trim went to 0.4units ND!!  It didn't nose dive at that point........ then at the end when it did nose dive, trim was 0.8 - 1.1 units ND.  So why did it dive then and not when it was even more nose down earlier in the short flight????   My theory, They were flying at and above VMO for most of the short flight, they were pulling back on the yoke hard with the elevator deflected way more than normal at above VMO,  Something broke in that aft area!    Sad part was is this, all they had to do was throttle back and slow the F### down and put it to flaps 1 and turn trim back on and fly home........

I can't share my source as he is a current NG/MAX rated pilot in the US but folks, these were easily avoidable accidents
Title: Re: 737 MAX
Post by: Garys on April 10, 2019, 12:02:24 PM
Pretty much sums up my thoughts as well only except I think the design of the MCAS was too aggressive. 10 secs of trim is alot when only taking the input from one sensor.  Still shouldn't have crashed though.
Title: Re: 737 MAX
Post by: 727737Nut on April 10, 2019, 12:13:58 PM
Pretty much sums up my thoughts as well only except I think the design of the MCAS was too aggressive. 10 secs of trim is a lot when only taking the input from one sensor. Still shouldn't have crashed though.

I agree Gary but what people must realize is that the trim button on the yoke can be held longer  ;)  Trim the plane to fly by continuous pushing of the trim button then flip the cutoff buttons.  Head home for a beer.
Title: Re: 737 MAX
Post by: Garys on April 10, 2019, 12:19:11 PM
Here is the intended fix …. Interesting read.
https://www.pprune.org/10443754-post3824.html (https://www.pprune.org/10443754-post3824.html)
Title: Re: 737 MAX
Post by: Trevor Hale on April 10, 2019, 01:14:09 PM
If the System is going to work like it is written with the 3 layers of protection..  I am convinced this will make a difference, especially given the "Are you sure Option" LOL.

Title: Re: 737 MAX
Post by: tennyson on April 11, 2019, 09:28:27 AM
I gotta say that the comments here have been both enlightening and informative.

All judgements aside, and no matter whether you are a Boeing guy (or gal) or Airbus fan, there are no winners when an aircraft gets grounded.

Personally, for me, I'm glad that the fixes are out there and that Boeing can start the recovery process of what will certainly go down in history as the most prolific aircraft in history, the 737, that is.

I say that personally, as my own 737Max 8 build is reaching certain milestones. My MIP is very near completed and should be fully functional within a week or two. I have a MAX throttle builder who is chanting at the bit to finish the job and my overheads will undergo the upgrade treatment, as soon as my MIP is finalised.

I had moments of doubt (when the two MAX crashes happened) and wondered whether a powerhouse like Boeing could endure the storm, or had I jumped the gun and sunk a significant amount of money into a dead project.

Only time will tell, but without referring to the Chrystal ball, my gut tells me that it will take some time for the tarnish to wear off.
I think that 12 months down the track, with the savings in fuel and efficiency of the new MAX technology, the world will once again embrace the Boeing name and we will all move on.


Frank
Title: Re: 737 MAX
Post by: jackpilot on April 12, 2019, 10:33:41 AM
https://seekingalpha.com/instablog/398764-vaughn-cordle-cfa/5290930-boeing-737-max-8-crashes-case-pilot-error
Title: Re: 737 MAX
Post by: mickc on April 12, 2019, 07:20:35 PM
Great link Jack!