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

MAXís Return Delayed by FAA Reevaluation of 737 Safety Procedures

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

MAXís Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 26th Aug 2019, 01:27
  #2041 (permalink)  
 
Join Date: Dec 2018
Location: 8th floor
Posts: 0
Originally Posted by Takwis View Post
Quite a few votes for "It's an unreliable airspeed problem." Also quite a few votes for "It's a stab trim runaway problem." I haven't kept track of which has more votes, but I will note that at one time or another, Boeing has made both of those statements.
Still, even with the aircraft severely out of trim, with unreliable airspeed and altitude information, the airspeed around VMO, stick shaker and other distractions, the pilots managed too keep the aircraft in the air, fly it, and even gain significant altitude. The preliminary report for the Ethiopian flight mentioned reaching 13400 feet, so more than 5000 feet AGL.

At this point they decided to re-enable electric trim and they made two ANU adjustments. Until today I assumed that, since they found it impossible to trim manually with the trim wheels, their plan was to slowly bring the aircraft back into trim using the thumb switches, then disable electric trim again, which doesn't sound like such a bad idea.

However, when looking today at the DFDR traces, I noticed that, immediately after re-enabling electric trim and making the two manual ANU adjustments with the thumb switches, there is a blip on the AP Warn Capt. trace.

So it seems that their plan was actually to re-enable electric trim, then test if it works for a bit using the thumb switches, then re-enable the auto-pilot. Unfortunately the auto-pilot failed to activate, and instead MCAS made the final AND trim adjustment dooming the flight.

If that was indeed their plan and that's what they did, it sounds like a really bad idea.

Later edit: from what I'm reading the A/P can't be engaged while there is force applied to the control wheel or column, which makes this even stranger. Because I don't see anything indicating they released the pressure on the column around the time of that blip. The column remained in the aft position according to the DFDR trace from the preliminary report.

Last edited by MemberBerry; 26th Aug 2019 at 04:44.
MemberBerry is offline  
Old 26th Aug 2019, 01:34
  #2042 (permalink)  
 
Join Date: Mar 2015
Location: antipodies
Posts: 62
Originally Posted by MemberBerry View Post
I realized how confusing the situation would have been for the Ethiopian captain after working on my comment comparing the differences between the pressure altitudes computed on the left side and the right side.

The broken AOA indicator messed up the computed pressure altitude on the captain side so severely that it was showing the aircraft much lower than it actually was, more than 1000 feet lower as the speed increased, reaching almost 3000 feet difference during the final dive. At some point after the MCAS activation the aircraft was slightly climbing, but the captain pressure altitude was showing the aircraft as failing to climb, despite the increasing speed. Also the indicated airspeed was lower on the left side than on the right side by up to 25 knots.

So overall the instruments were presenting to the captain a situation much worse than it actually was. It's not the same thing if you are at 1500 feet, you lose 250 feet of altitude, and then the aircraft slowly starts climbing, compared with what the captain was actually seeing: being at around 950 feet and losing 450 feet of altitude, then the aircraft not climbing at all, despite the increasing speed.

With that in mind, even ignoring other factors, it becomes more understandable why the captain didn't reduce thrust. And I think determining quickly which side had the unreliable airspeed and altitude information, and using the information from the other side, is one thing that could have prevented the accident.
If your scenario is correct , perhaps the captain became aware that his instruments could not be correct and this is why he handed control to the first officer?
phylosocopter is offline  
Old 26th Aug 2019, 01:47
  #2043 (permalink)  
 
Join Date: Dec 2018
Location: 8th floor
Posts: 0
Originally Posted by phylosocopter View Post
If your scenario is correct , perhaps the captain became aware that his instruments could not be correct and this is why he handed control to the first officer?
I might be wrong, but I don't remember anything suggesting the Ethiopian captain handed the controls over to the first officer. According to the preliminary report the captain asked the FO to help trim up and pull up, and that they were both pulling up.

There might be a confusion here between the Ethiopian accident and the Indonesian Lion air accident, where the FDR traces suggest the captain handed control to the FO before the crash.
MemberBerry is offline  
Old 26th Aug 2019, 08:04
  #2044 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by Takwis View Post
Quite a few votes for "It's an unreliable airspeed problem." Also quite a few votes for "It's a stab trim runaway problem." I haven't kept track of which has more votes, but I will note that at one time or another, Boeing has made both of those statements.
Until the flaps were retracted, the AOA failure presents as an "Unreliable Airspeed" malfunction. Both Lion Air flight crews recognized the airspeed issue right off, while it appears the Ethiopian crew did not. The Unreliable Airspeed NNC basically calls for the flying pilot to turn off any automation and fly pitch and power settings until such time as reliable instruments can be identified.

Once the flaps are retracted, the AOA malfunction triggers MCAS which then looks like a Runaway Stab Trim problem. As previously discussed, the aircraft was controllable if the flying pilot was using aggressive electric trim inputs (first Lion Air flight Captain and First Officer, Captain of the second Lion Air flight) and not so much if the primary response was with elevator (second Lion Air First Officer, Ethiopian Captain). Setting aside the issue of the delay or inability to connect the malfunction with the Runaway Stab Trim NNC, an open question is why three of the flying pilots were able to maintain aircraft control and two were not. This outcome is possibly related to training issues, automation policy (comfort with hand-flying, etc.).

BTW, reference some previous comments about stopping the moving trim wheel manually, 1) not really a problem given proper technique, and 2) I know of no historical case where this actually became necessary.
Tomaski is offline  
Old 26th Aug 2019, 11:47
  #2045 (permalink)  
 
Join Date: Apr 2009
Location: A place in the sun
Age: 78
Posts: 768
Simple questions. How many of you would retract the flaps when a stall warning is sounding off? Why would you do something which will raise the stall speed? Surely, the best thing to do would be to maintain the configuration and fly pitch and power while you try to sort out the multiple warnings.
Bergerie1 is online now  
Old 26th Aug 2019, 18:40
  #2046 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by Bergerie1 View Post
Simple questions. How many of you would retract the flaps when a stall warning is sounding off? Why would you do something which will raise the stall speed? Surely, the best thing to do would be to maintain the configuration and fly pitch and power while you try to sort out the multiple warnings.
A very reasonable question depending on your frame of reference. I have previously suggested that one of the things that we may be seeing play out in these events is a flight crew response that reflects the way in which they were trained and managed. In particular, if the pilots' training and operational environment placed a high degree of emphasis on following procedures as written rather than stepping back and looking at the "big picture" to determine if the procedure was appropriate at that time, then I would think that flap retraction would be a normal and expected step. Why? Because the crew is essentially running two procedures at the same time - the "After Takeoff" checklist and the "Airspeed Unreliable" checklist (and if they haven't identified the unreliable airspeed, they are still doing the After Takeoff checklist anyway). Since the "Airspeed Unreliable" checklist does not literally say to leave the flaps where they are until the reliable instruments have been determined, it may have been completely natural for the crew to continue to run the "After Takeoff" checklist which would mandate retracting the flaps.

I found it very interesting just after MCAS activated during the second Lion Air flight, the crew actually extended the flaps after having retracted them. The MCAS input stopped, although the stick shaker was still going. After a short time they retracted them again setting the stage for MCAS again. I would really love to know what they were thinking. Perhaps we will find out when the full CVR transcript is published with the final report.

I've mentioned before that the FCOM states quite clearly that the manufacturer cannot write a procedure for every possible set of circumstances, but some airlines give this concept very little consideration. If one's training and background includes a "big picture" emphasis, then I suspect then that there would be some hesitation to retract flaps with an active stall warning. If one's training emphasized following the written procedure without modification, then the flaps are probably going to come up - as we saw in all three of the incident/accident flights.
Tomaski is offline  
Old 26th Aug 2019, 21:45
  #2047 (permalink)  
 
Join Date: Mar 2019
Location: On the Ground
Posts: 109
You know that MCAS only works with the flaps up...they most certainly did not. With everything else going on, I doubt they ever made the connection.

"Hey look! Some system that we don't know exists quits doing some function that we don't understand when we put the flaps down! At least for the moment. Wish that stick shaker would quit, though."
Takwis is offline  
Old 27th Aug 2019, 02:44
  #2048 (permalink)  
 
Join Date: Jul 2010
Location: Asia
Posts: 550
If you've extended the flaps due to a stall warning then the instinct will be to raise them once out of that condition unless you are following a procedure which specifically tells you to leave them extended. Had the crews been aware of the MCAS and there been a laid down procedure to deal with its possible faults then they might have only had unreliable airspeed to cope with, rather than fighting an unknown system which was trying to spear them into the ground.

Unreliable airspeed has been known about for years, crews are trained in the simulator and there is a procedure to follow in the QRH. The crew of the Malaysia Airlines A330 in Brisbane last year which experienced unreliable airspeed were able to get back on the ground safely.
krismiler is online now  
Old 27th Aug 2019, 06:24
  #2049 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by Takwis View Post
You know that MCAS only works with the flaps up...they most certainly did not. With everything else going on, I doubt they ever made the connection.

"Hey look! Some system that we don't know exists quits doing some function that we don't understand when we put the flaps down! At least for the moment. Wish that stick shaker would quit, though."
Obviously the crew couldn't have been aware of MCAS. It's more the ability to make the high-level observation "hey, the plane is misbehaving, but it is misbehaving WORSE when the flaps are retracted" kind of thing that might have led them to do things differently. That in turn would require some outside the box thinking that may have been strongly discouraged within their training and operational culture. As I said, we don't currently know what led the crew to extend the flaps and retract them again. Perhaps we will know more when the final is released.
Tomaski is offline  
Old 27th Aug 2019, 06:38
  #2050 (permalink)  
 
Join Date: Jul 2008
Location: Australia
Posts: 149
High level observation and the ability to correlate an aircraft manouvre to a previous configuration is what test pilots do. They have extensive education, experience and training in order to test new aeroplanes. The average line pilot is simply not equipped to deal with an out of the box situation that has been built into the aircraft.
Lookleft is offline  
Old 27th Aug 2019, 06:54
  #2051 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by krismiler View Post

Unreliable airspeed has been known about for years, crews are trained in the simulator and there is a procedure to follow in the QRH. The crew of the Malaysia Airlines A330 in Brisbane last year which experienced unreliable airspeed were able to get back on the ground safely.
I can't really speak for other aircraft, but I feel that the Airspeed Unreliable procedure for the 737 has some weaknesses, especially when it comes to applying it to the takeoff phase. I think some guidance should have been included as to when to make the initial power reduction (think terrain avoidance) and when to retract flaps. BTW, even though this procedure has been around for years, I have never seen it demonstrated in the sim as part of a takeoff or landing procedure. It has always been done at altitude and only for as long as it took to executed the initial steps and identify the reliable instruments (I suspect this will change in the wake of the MAX accidents). If you look through the procedure, it can actually get pretty involved. I also take issue with the fact that it does not advise the crew to maintain VMC if possible and land at the nearest suitable airport. Hopefully some of this will be looked at and changed.
Tomaski is offline  
Old 27th Aug 2019, 07:24
  #2052 (permalink)  
 
Join Date: May 2008
Location: Europe
Age: 40
Posts: 565
Der Spiegel

Renowned German publication, Der Spiegel, has produced a through piece of journalism on Boeing and the 737. It paints a picture of Boeing so damaging, it makes one consider the future viability of the company. It's the underhand way they're doing business, where their actions are 180 degrees opposite to their rhetoric, that's really scary.

It's in 3 pieces, the first piece is here https://www.spiegel.de/international...a-1282869.html

It also paints a scathing image of the collusion between the FAA and Boeing, to the point where FAA has completely lost all creditability, and makes you wonder what will happen in the rest of the world when the FAA, once again, rubber stamps the Max and clears it for a return to service.
SMT Member is offline  
Old 27th Aug 2019, 07:26
  #2053 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by Lookleft View Post
High level observation and the ability to correlate an aircraft manouvre to a previous configuration is what test pilots do. They have extensive education, experience and training in order to test new aeroplanes. The average line pilot is simply not equipped to deal with an out of the box situation that has been built into the aircraft.
You are of course correct, yet we should also acknowledge that not all malfunctions are clearly annunciated (particularly of the flight control variety), and there are some times when the crew must recognize that something doesn't "feel" right even if they can't immediately identify the problem. Depending on their background, different pilots will have different views on whether the flaps should have been extended or retracted while the stick shaker/unreliable airspeed problem was resolved. I would agree that "out of the box" thinking really isn't taught anymore, and probably highly discouraged in some places. That state of affairs, however, runs completely afoul of the manufacturer's disclaimer that they cannot come up with procedures to fit every situation. So basically if an airline's training and operational culture takes the position that crew must adhere to the written procedures at all times and not improvise, then they must accept that every once in awhile a situation will arise for which theirs crew will be ill-equipped to handle.
Tomaski is offline  
Old 27th Aug 2019, 11:55
  #2054 (permalink)  
 
Join Date: Jul 2002
Location: Ireland
Posts: 595
Originally Posted by Lookleft View Post

They have extensive education, experience and training in order to test new aeroplanes.
And most importantly, are fully informed of the individual systems they are flight testing.
Speed of Sound is offline  
Old 27th Aug 2019, 14:20
  #2055 (permalink)  
 
Join Date: Apr 2008
Location: Paris
Age: 69
Posts: 256
Originally Posted by SMT Member View Post
Der Spiegel

Renowned German publication, Der Spiegel, has produced a through piece of journalism on Boeing and the 737. It paints a picture of Boeing so damaging, it makes one consider the future viability of the company. It's the underhand way they're doing business, where their actions are 180 degrees opposite to their rhetoric, that's really scary.

It's in 3 pieces, the first piece is here https://www.spiegel.de/international...a-1282869.html

It also paints a scathing image of the collusion between the FAA and Boeing, to the point where FAA has completely lost all creditability, and makes you wonder what will happen in the rest of the world when the FAA, once again, rubber stamps the Max and clears it for a return to service.
The politicians on both sides of the atlantic are smart: rather than pressure Boeing or get in trouble with the US they will say nothing and just wait until the next crash. At that point Boeing will not be able to buy themselves out of trouble, and the public will pay to have the FAA resume a major check role.

Edmund
edmundronald is offline  
Old 27th Aug 2019, 16:32
  #2056 (permalink)  
 
Join Date: Jul 2007
Location: the City by the Bay
Posts: 508
If the Max is not fit to fly (which it isn't in it's current form as is obvious) and can not be made to fly safely (which currently is very much in doubt) then it must be put away. Boeing may face bankruptcy without the MAX (from which it CAN recover) but should the MAX have one more crash Boeing will face extinction.
armchairpilot94116 is offline  
Old 27th Aug 2019, 16:47
  #2057 (permalink)  
Thread Starter
 
Join Date: Apr 2015
Location: Under the radar, over the rainbow
Posts: 458
Originally Posted by SMT Member View Post
Der Spiegel

Renowned German publication, Der Spiegel, has produced a through piece of journalism on Boeing and the 737. It paints a picture of Boeing so damaging, it makes one consider the future viability of the company.
I just finished reading that three-parter. I think it paints a fairly reasonable picture, in broad terms, but (a) the tone is more that of an editorial than of an investigative piece; (b) there is very little, if any, information that has not been previously published (sometimes in more-accurate and better-sourced form); and (c) it is entirely clear that the authors and editors have little technical knowledge of aviation.

That said, I agree that it would be reasonable to wonder about Boeing's future viability -- if not for the fact that it's nearly impossible to believe that the government of the US, and the business and financial sectors together, won't do absolutely everything possible to maintain B as a going concern and world leader in aircraft manufacture.

OldnGrounded is offline  
Old 27th Aug 2019, 17:31
  #2058 (permalink)  
 
Join Date: Jul 2002
Location: Ireland
Posts: 595
Originally Posted by OldnGrounded View Post
it's nearly impossible to believe that the government of the US, and the business and financial sectors together, won't do absolutely everything possible to maintain B as a going concern and world leader in aircraft manufacture.
The problem with an international business like aviation is that you canít make people buy your aircraft, especially if there are safety concerns. Even if the idiot Trump threatens to economically punish any country which doesnít buy from Boeing, I doubt that many would, when their citizenís lives are at risk.

The only way the US government and financial sectors would be able to stop Boeing from going under after another crash, would be to so heavily subsidise its products, that airlines have no choice but to buy them. Boeing would then be effectively a state-aided nationalised company in all but name.
Speed of Sound is offline  
Old 27th Aug 2019, 17:51
  #2059 (permalink)  
Thread Starter
 
Join Date: Apr 2015
Location: Under the radar, over the rainbow
Posts: 458
Originally Posted by Speed of Sound View Post
The problem with an international business like aviation is that you canít make people buy your aircraft, especially if there are safety concerns. Even if the idiot Trump threatens to economically punish any country which doesnít buy from Boeing, I doubt that many would, when their citizenís lives are at risk.


The idiot Trump won't be around forever and, in any event, you are quite right that his threats wouldn't work to convince purchasers. Whatever happens, Boeing's commercial aircraft business depends upon the world believing that, going forward, its products are safe. I think that's an achievable goal, although it's going to require a significant change in corporate culture.

The only way the US government and financial sectors would be able to stop Boeing from going under after another crash, would be to so heavily subsidise its products, that airlines have no choice but to buy them. Boeing would then be effectively a state-aided nationalised company in all but name.
If that's what's necessary to keep Boeing going, I expect that's exactly what will happen. BA is the largest single US exporter and a key symbol of American industrial strength. If US carriers were forced to buy (mostly) only Airbus planes, trade deficits would be significantly worsened. And the defense side of the business is a key supplier to US and foreign armed forces. Even more than the auto manufacturers, that have been bailed out more than once, Boeing is too big too fail.
OldnGrounded is offline  
Old 27th Aug 2019, 18:03
  #2060 (permalink)  
 
Join Date: Dec 2018
Location: 8th floor
Posts: 0
The article from Der Spiegel pointed out something interesting: with all the outsourcing Boeing did for component manufacturing, it should now be easier for new aircraft manufacturers to emerge, since they could use the same component suppliers Boeing does. So in their rush to increase profits as much as possible, they may have jeopardized their future market share. Basically killing the goose laying the golden eggs. I'm not familiar with the situation on the Airbus side, do they have similar levels of outsourcing?

From Der Spiegel:
And this all comes at a time when the Airbus-Boeing duopoly has been developing cracks. The two may still be the world's undisputed aerospace leaders, but companies in China, Russia and Japan are in the process of grabbing a bigger piece of the pie. Furthermore, it has become easier to build airplanes because a highly specialized global market of suppliers has developed that can deliver almost any part in the desired quality at the desired moment in time. The times when airplane construction was a calling card of unattainable technological excellence are coming to an end. Things are becoming more difficult, especially for Boeing.
MemberBerry 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.