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

MAX’s 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.

MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 25th Sep 2019, 13:36
  #2601 (permalink)  
 
Join Date: Jul 2002
Location: Ireland
Posts: 595
Originally Posted by Tomaski View Post

Nowadays the answer is more likely to be, "Because that is how the procedure is written!" I suspect in some training environments, that last answer is deemed sufficient and thus further investigation is discouraged.
Difficult because of the authority gradient between instructor and trainee I know, but at this point a good student should ask “Yes, but what if .........?”, especially if they are armed with the knowledge that manufacturers and regulators have accepted for decades that you can’t write a procedure for everything.

A pilot with good flying skills and excellent systems knowledge will have something to do (options) right down to a smoking hole in the ground whereas a ‘procedure-only’ trained pilot could ultimately reach a point when they simply don’t know what to do anymore and with no one to tell them if paired with a similarly trained pilot.

Sadly in some cases, this will be in largely serviceable aircraft where a safe outcome is possible.
Speed of Sound is offline  
Old 25th Sep 2019, 13:51
  #2602 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by Speed of Sound View Post


Difficult because of the authority gradient between instructor and trainee I know......
In some cases, it is not only the instructor-trainee relationship that one is dealing with. In some areas of the world, respect and deference for authority and a "face-saving" nature to personal interactions are simply part of the underlying culture. While I hold no strong opinion as to whether these cultural tendencies are good or bad in and of themselves, they can be significant obstacles to effective training and crew resource management.
Tomaski is offline  
Old 25th Sep 2019, 14:31
  #2603 (permalink)  
 
Join Date: Sep 2019
Location: leftcoast
Posts: 3
Originally Posted by Icarus2001 View Post
Why not use the electric trim which halts MCAS trim input?
I had assumed that the use of the term WIND IN referred to using the Trim Wheel- AFTER using cutout switch ( PRI and/or BKU ) leaving only hand crank. I recall that in an earlier issue of AV week. such was tried in an actual flight starting at 14 to 20 K AGL by pilot(s) who knew what to expect and why and how. The loss of altitude was about 8000 feet to get to level flight.

And from memory, at no time did lion or ethopia get over 5K AGL

Please correct me with links- AV week was in april or may I believe

Point is pilots did not know of HAL or that it would/could repeat.

Grebe is offline  
Old 25th Sep 2019, 15:45
  #2604 (permalink)  
 
Join Date: Dec 2002
Location: UK
Posts: 1,981
Boeing Adding Safety Oversight, Will Examine Flight Deck Design

https://aviationweek.com/commercial-...ht-deck-design

“… expected to create a centralized safety-centric organization, and plans to examine how flight-deck design and pilot training can change to better serve operators.”

“While most changes would be within Boeing, the most visible ones to industry are likely to stem from the recommendation to “re-examine flight deck design and operation.” The committee examined global flight crew certification training requirements, and “what we saw is that they vary significantly,” … partnering with airlines and others in the industry to re-examine assumptions around flight deck design and operation.’


“Boeing’s work would extend into training, both a key element for the safe operation of its products and, through its growing services business, a promising revenue-generator.”

The ‘airline approach’ indicates that it will still be US centric, opposed to a more worldly view (ex Southwest pilot).
Renewed interest in training, but commerce before safety.

The flight deck design / operational issues relate to human factors, particularly differences between ‘theory’ and practice. Assumptions … ^
safetypee is online now  
Old 25th Sep 2019, 18:26
  #2605 (permalink)  
 
Join Date: Sep 2019
Location: leftcoast
Posts: 3
RE cockpit management- many many years ago (1980-82 ) I spent many hours over a year riding on bus with an employee- engineer who was directly involved in the cockpit displays for the 767 re a two person cockpit. he had spent several years in Airforce flying F-111 - he was adamant that the displays and cockpit should be " quiet" that is absolute minimum to NO flashing lights and bells UNLESS something significant needing attention.

He had also spent a few hours in the F-111 in what was called TFM terrain following mode - low level high speed - almost completely controlled by computer and radar ( a sophisticated OTTO )

So in 30 years or so- we havent been able to control HAL ??

from wiki
The A-model's Mark I avionics suite included the General Electric AN/APQ-113 attack radar mated to a separate Texas Instruments AN/APQ-110 terrain-following radar lower in the nose and a Litton AJQ-20 inertial navigation and nav/attack system. The terrain-following radar (TFR) was integrated into the automatic flight control system, allowing for "hands-off" flight at high speeds and low levels (down to 200 ft).[87]

And early on two or three were lost due to issues with . . .. horiz stabilizer

And wing problems-cracks were dude to untempered martensite from drilling holes in wingbox at too high speed plus the use of a certain type of Tool Steel .

AS a result - the B1 wingbox was made of titanium- and EXTREME care-requiremets were imposed on hole drilling for regular bolts and specialized taper- loks

wuz there

Last edited by Grebe; 25th Sep 2019 at 22:22. Reason: added details of TFR ( not TFM )
Grebe is offline  
Old 26th Sep 2019, 03:24
  #2606 (permalink)  
 
Join Date: Sep 2019
Location: leftcoast
Posts: 3
RE ability of crew to recover from MCAS

Ethiopian MAX Crash Simulator Scenario Stuns Pilots

May 10, 2019

This was in Aviation daily on May 10, 2019


https://aviationweek.com/commercial-...o-stuns-pilots

And a partial extract

This is important because the test pilots had recreated the Ethiopian flight in a simulator and took the plane to an altitude of 10K and speed at 250kt before activating the malfunction. These test pilots were briefed about MCAS and were ready to try and regain control of the plane. Here are their findings under controlled conditions.
1) It took them 40 seconds and a loss of 8000ft before recovering. The two crashes did not reach 8000ft and their speed was over 300kt due to MCAS keep pushing the nose down. They did not have the height and with over speed using manual trim was difficult if not impossible
2) Neither crew nor the airlines were told of the MCAS system and their resulting effects if MCAS is activated.
3) MCAS should be on the MEL but it is not.
4) Data comes from one vane but should be two or more to make it double or triple redundant.

Based on the above findings, both crashes were non recoverable especially with MCAS working on a 10 seconds on and 5 seconds off cycle.
Grebe is offline  
Old 26th Sep 2019, 12:40
  #2607 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Not questioning that your excerpt is from some other article (or perhaps the comment section?), but your quote does not appear in the article you cited. The major takeaway from this particular Aviation Week article is the absolute necessity to respond to any 737 runaway stab trim problem quickly before it gets to an excessive out of trim state.

Complete article:

Ethiopian MAX Crash Simulator Scenario Stuns Pilots

Sean Broderick, Aviation Daily May 10, 2019

WASHINGTON—A simulator session flown by a U.S.-based Boeing 737 MAX crew that mimicked a key portion of the Ethiopian Airlines Flight 302 (ET302) accident sequence suggests that the Ethiopian crew faced a near-impossible task of getting their 737 MAX 8 back under control, and underscores the importance of pilots understanding severe runaway trim recovery procedures.

Details of the session, shared with Aviation Week, were flown voluntarily as part of routine, recurrent training. Its purpose: practice recovering from a scenario in which the aircraft was out of trim and wanting to descend while flying at a high rate of speed. This is what the ET302 crew faced when it toggled cutout switches to de-power the MAX’s automatic stabilizer trim motor, disabling the maneuvering characteristics augmentation system (MCAS) that was erroneously trimming the horizontal stabilizer nose-down.

In such a scenario, once the trim motor is de-powered, the pilots must use the hand-operated manual trim wheels to adjust the stabilizers. But they also must keep the aircraft from descending by pulling back on the control columns to deflect the elevator portions of the stabilizer upward. Aerodynamic forces from the nose-up elevator deflection make the entire stabilizer more difficult to move, and higher airspeed exacerbates the issue.

The U.S. crew tested this by setting up a 737-Next Generation simulator at 10,000 ft., 250 kt. and 2 deg. nose up stabilizer trim. This is slightly higher altitude but otherwise similar to what the ET302 crew faced as it de-powered the trim motors 3 min. into the 6 min. flight, and about 1 min. after the first uncommanded MCAS input. Leading up to the scenario, the Ethiopian crew used column-mounted manual electric trim to counter some of the MCAS inputs, but did not get the aircraft back to level trim, as the 737 manual instructs before de-powering the stabilizer trim motor. The crew also did not reduce their unusually high speed.

What the U.S. crew found was eye-opening. Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn. They resorted to a little-known procedure to regain control.

The crew repeatedly executed a three-step process known as the roller coaster. First, let the aircraft’s nose drop, removing elevator nose-down force. Second, crank the trim wheel, inputting nose-up stabilizer, as the aircraft descends. Third, pull back on the yokes to raise the nose and slow the descent. The excessive descent rates during the first two steps meant the crew got as low as 2,000 ft. during the recovery.

The Ethiopian Ministry of Transport preliminary report on the Mar. 10 ET302 accident suggests the crew attempted to use manual trim after de-powering the stabilizer motors, but determined it “was not working,” the report said. A constant trust setting at 94% N1 meant ET302’s airspeed increased to the 737 MAX’s maximum (Vmo), 340 kt., soon after the stabilizer trim motors were cut off, and did not drop below that level for the remainder of the flight. The pilots, struggling to keep the aircraft from descending, also maintained steady to strong aft control-column inputs from the time MCAS first fired through the end of the flight.

The U.S. crew’s session and a video posted recently by YouTube’s Mentour Pilot that shows a similar scenario inside a simulator suggest that the resulting forces on ET302’s stabilizer would have made it nearly impossible to move by hand.

Neither the current 737 flight manual nor any MCAS-related guidance issued by Boeing in the wake of the October 2018 crash of Lion Air Flight 610 (JT610), when MCAS first came to light for most pilots, discuss the roller-coaster procedure for recovering from severe out-of-trim conditions. The 737 manual explains that “effort required to manually rotate the stabilizer trim wheels may be higher under certain flight conditions,” but does not provide details.

The pilot who shared the scenario said he learned the roller coaster procedure from excerpts of a 737-200 manual posted in an online pilot forum in the wake of the MAX accidents. It is not taught at his airline.

Boeing’s assumption was that erroneous stabilizer nose-down inputs by MCAS, such as those experienced by both the JT610 and ET302 crews, would be diagnosed as runaway stabilizer. The checklist to counter runaway stabilizer includes using the cutout switches to de-power the stabilizer trim motor. The ET302 crew followed this, but not until the aircraft was severely out of trim following the MCAS inputs triggered by faulty angle-of-attack (AOA) data that told the system the aircraft’s nose was too high.

Unable to move the stabilizer manually, the ET302 crew moved the cutout switches to power the stabilizer trim motors—something the runaway stabilizer checklist states should not be done. While this enabled their column-mounted electric trim input switches, it also re-activated MCAS, which again received the faulty AOA data and trimmed the stabilizer nose down, leading to a fatal dive.

The simulator session underscored the importance of reacting quickly to uncommanded stabilizer movements and avoiding a severe out-of-trim condition, one of the pilots involved said. “I don’t think the situation would be survivable at 350 kt. and below 5,000 ft,” this pilot noted.

The ET302 crew climbed through 5,000 ft. shortly after de-powering the trim motors, and got to about 8,000 ft.—the same amount of altitude the U.S. crew used up during the roller-coaster maneuvers—before the final dive. A second pilot not involved in the session but who reviewed the scenario’s details said it highlighted several training opportunities.

“This is the sort of simulator experience airline crews need to gain an understanding of how runaway trim can make the aircraft very difficult to control, and how important it is to rehearse use of manual trim inputs,” this pilot said.

While Boeing’s runaway stabilizer checklist does not specify it, the second pilot recommended a maximum thrust of 75% N1 and a 4 deg. nose-up pitch to keep airspeed under control.

Boeing is developing modifications to MCAS, as well as additional training. Simulator sessions are expected to be integrated into recurrent training, and may be required by some regulators, and opted for by some airlines, before pilots are cleared to fly MAXs again. The MAX fleet has been grounded since mid-March, a direct result of the two accidents.
Also one (very minor) critique of whoever's quote you did cite:

MCAS should be on the MEL but it is not.
The Minimum Equipment List (MEL) is strictly for those components that the aircraft can be dispatched with in an inoperative or degraded condition. If it a component or system is NOT in the MEL, it is presumed necessary for dispatch. Thus there is a very good reason why MCAS is not in the MEL.

Last edited by Tomaski; 26th Sep 2019 at 12:58.
Tomaski is offline  
Old 26th Sep 2019, 14:17
  #2608 (permalink)  
 
Join Date: Sep 2019
Location: leftcoast
Posts: 3
Not questioning that your excerpt is from some other article (or perhaps the comment section?), but your quote does not appear in the article you cited. The major takeaway from this particular Aviation Week article is the absolute necessity to respond to any 737 runaway stab trim problem quickly before it gets to an excessive out of trim state.
Yep I must have screwed up copying notes from a few thousand posts in this thread and those in the Tech section that were/are locked as a sticky
But IMHO the point is the same
A) above some 'reasonable' speed, the use of the manual trim wheel to correct anything other than a minor change in angle is essentially impossible.
B) This same issue applies AFIK to NG
C) The yo-yo game was dropped from training and manuals over two decades ago
D) How fast a response is needed depends on AGL and how fast the stabilizer is driven.
Grebe is offline  
Old 26th Sep 2019, 16:42
  #2609 (permalink)  
 
Join Date: May 2000
Location: SV Marie Celeste
Posts: 580
A) above some 'reasonable' speed, the use of the manual trim wheel to correct anything other than a minor change in angle is essentially impossible.
Simply not true. Manual trim is used regularly while conducting air tests. I have used it, it works fine. Obviously if you allow ANY trim to go to the stops you have a serious problem in your hands. Speed trim, aileron trim or rudder trim..... in a 737 or in most other aircraft.
calypso is online now  
Old 26th Sep 2019, 17:10
  #2610 (permalink)  
 
Join Date: Jan 2008
Location: Reading, UK
Posts: 11,600
Originally Posted by Grebe View Post
above some 'reasonable' speed, the use of the manual trim wheel to correct anything other than a minor change in angle is essentially impossible
Are you saying that the "roller-coaster" technique works by reducing airspeed significantly to the point where manual trim wheel forces are manageable where they weren't previously ?
DaveReidUK is offline  
Old 26th Sep 2019, 17:58
  #2611 (permalink)  
 
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 58
Posts: 424
Worth reading some of the detailed NTSB safety analysis, as part of the recommendations to the FAA: https://www.ntsb.gov/investigations/...ts/ASR1901.pdf

I found the following about MCAS failure and AOA-related warnings to be relevant to this thread:
The NTSB reviewed sections of Boeing’s system safety analysis for stabilizer trim control that pertained to MCAS on the 737 MAX. Boeing’s analysis included a summary of the functional hazard assessment findings for the 737 MAX stabilizer trim control system. For the normal flight envelope, Boeing identified and classified two hazards associated with “uncommanded MCAS” activation as “major.” One of these hazards, applicable to the MCAS function seen in these accidents, included uncommanded MCAS operation to maximum authority. Boeing indicated that, as part of the functional hazard assessment development, pilot assessments of MCAS-related hazards were conducted in an engineering flight simulator, including the uncommanded MCAS operation (stabilizer runaway) to the MCAS maximum authority.

To perform these simulator tests, Boeing induced a stabilizer trim input that would simulate the stabilizer moving at a rate and duration consistent with the MCAS function. Using this method to induce the hazard resulted in the following: motion of the stabilizer trim wheel, increased column forces, and indication that the airplane was moving nose down. Boeing indicated to the NTSB that this evaluation was focused on the pilot response to uncommanded MCAS operation, regardless of underlying cause. Thus, the specific failure modes that could lead to uncommanded MCAS activation (such as an erroneous high AOA input to the MCAS) were not simulated as part of these functional hazard assessment validation tests. As a result, additional flight deck effects (such as IAS DISAGREE and ALT DISAGREE alerts and stick shaker activation) resulting from the same underlying failure (for example, erroneous AOA) were not simulated and were not in the stabilizer trim safety assessment report reviewed by the NTSB.
GordonR_Cape is offline  
Old 26th Sep 2019, 22:17
  #2612 (permalink)  
fdr
 
Join Date: Jun 2001
Location: 3rd Rock, #29B
Posts: 789
Originally Posted by DaveReidUK View Post
Are you saying that the "roller-coaster" technique works by reducing airspeed significantly to the point where manual trim wheel forces are manageable where they weren't previously ?

There are two conditions where the manual trim force is reduced,
  1. When the aircraft is at the speed (AOA) as trimmed by the THS/Stab, where no deflection of the elevator is needed
  2. Approaching zero airspeed where the resultant force from the THS/Stab is reduced, being dependent on V.CL(stab-aoa)
Whenever the speed is considerable and the trim solution is not correct for the actual speed, then there is a need for a balancing force from the elevators. It is the elevator deflection that results in the excessive force on the stab screw jack which then may defeat the torque available from the pilot in manual application of trim.
fdr is offline  
Old 26th Sep 2019, 23:00
  #2613 (permalink)  
fdr
 
Join Date: Jun 2001
Location: 3rd Rock, #29B
Posts: 789
"Boeing assumed that an MCAS failure had a safety risk that was "major," which was less severe than the "catastrophic" category, the NTSB said. The company assumed pilots would easily recognise an MCAS failure and counteract it."

SMH https://www.smh.com.au/business/comp...27-p52vdf.html



How on earth did not disclosing the system being installed tie in with any assumption of recognition????

"..... wait, lo!, we have some problem with the airspeed indicator, and I see that is the altimeter too is bad.... ", "and I have a stall warning...." "so lemmethink in the cacophony of the cockpit here, hmmm, what would the manufacturer have done, I wonder, I should be able to work this out in the next 30 seconds, after all, the manufacturer only had 50 years to sort it out, and about 5,000 aerospace engineers, so this should be easy while I fight for control of the aircraft... which is now fighting me... it is doing something I have not ever seen before, but obviously I must be able to reverse engineer the system and determine what the problem is... is there too much weight in the tail, is there a failure of a control line, or did the manufacturer add a new device that can kill me and not bother to tell me about it? I wonder... clocks running, tick tock... " "aha, I have it, they must have installed a new system in the aircraft for a problem in the design, and told the FAA about that, and then they must have changed the system so it didn't have any of the safety protections of the original and they must have not bothered to tell the FAA about it or have done any meaningful safety analysis on it, and then they probably called it something innocuous like MCAS, it sounds better than USTKM (Unknown System Trying to Kill Me), and then, if I don't guess how this works, and I don't sort it out i the next 5 seconds, after the event I am going to be blamed for being substandard by the FAA, the manufacturer, the US Senate, and many opinionated people on chat rooms who are happy to demean my memory as being less than competent for not sorting the problem out in the remaining 2, ... 1 second".

Fade to black


This industry is morally bankrupt.
fdr is offline  
Old 27th Sep 2019, 01:39
  #2614 (permalink)  
 
Join Date: Dec 2001
Location: Brisvegas
Posts: 2,884
Or the thought process could be..."the controls are getting heavier I better trim back, that feels better, oh it is trimming forward again, I will trim back more than I require and then turn the trim off with those conveniently located trim switches. It may be a trim runaway. Memory items blogs..."
Icarus2001 is offline  
Old 27th Sep 2019, 02:43
  #2615 (permalink)  
 
Join Date: Mar 2015
Location: Washington state
Posts: 210
My understanding of this incredibly long thread is that "turn the trim off with those conveniently located trim switches" was exactly the wrong thing to do in this situation and was one of the reasons for the crash. The proper steps, as I understand this thread, are "use the electric trim to undo the nose down inputs from MCAS and then turn off the electric trim." How that would be the proper procedure for a true trim runaway is not something that I understand, if the electric trim is in fact misbehaving then you would want to disable it immediately rather than screw around on the off chance that there is something in the software logic that you don't understand.
Water pilot is offline  
Old 27th Sep 2019, 03:10
  #2616 (permalink)  
 
Join Date: Dec 2001
Location: Brisvegas
Posts: 2,884
Which is exactly what I wrote.
Icarus2001 is offline  
Old 27th Sep 2019, 03:36
  #2617 (permalink)  
 
Join Date: Feb 2015
Location: usa
Age: 33
Posts: 41
Originally Posted by Icarus2001 View Post
Or the thought process could be..."the controls are getting heavier I better trim back, that feels better, oh it is trimming forward again, I will trim back more than I require and then turn the trim off with those conveniently located trim switches. It may be a trim runaway. Memory items blogs..."
And you would prioritize that memory item ahead of the stick shaker memory item? And you wouldn't reduce thrust knowing all we know now? And you have super human strength to turn the trim wheel? Sounds like you would have had an outcome like the two crashes.
​​​​​​If it we're as simple as you claim the max would not be grounded this long.
Welcome to Aviation. The sooner you lose the pride and arrogance the longer you will endure.

Last edited by jdawg; 27th Sep 2019 at 03:46.
jdawg is offline  
Old 27th Sep 2019, 03:41
  #2618 (permalink)  
 
Join Date: Jun 2009
Location: florida
Age: 77
Posts: 1,200
Salute!

TNX, fdr and turbine and ski..,et al ...... Feel free to tell us what you really feel and opine and relate from actual stick time.Heh heh.

I must admit that having a new flight control mod on a model I had flown for 20 years and not telling me about it or knowing what it was supposed to do would " upset me". And you?

The "there I was" and actual stick time war stories and real technical discussions were cut off on the Tech Log.
So before they are cut off here we might get in some parting shots. Ya think?
++++++++++++++++++++++++
The official report on the Lion 610 crash is soon to be published.
It should provide plenty of grist for us to dissect.
So fading back for a while, but always there for the PM's and discussions.

Gums sends...
gums is offline  
Old 27th Sep 2019, 03:46
  #2619 (permalink)  
 
Join Date: Mar 2003
Location: The Dirty South
Posts: 406
Originally Posted by Icarus2001 View Post
Or the thought process could be..."the controls are getting heavier I better trim back, that feels better, oh it is trimming forward again, I will trim back more than I require and then turn the trim off with those conveniently located trim switches. It may be a trim runaway. Memory items blogs..."

Your F.O. Blogs would reply -

“Which memory items Captain Austronaut ? There haven’t been any STAB TRIM Runaway memory items for years. We do have IAS DISAGREE and ALT DISAGREE. Should we do the UAS items first ?”

Boom !

Maybe you should get together with JDawg. He doesn’t know there are no “stick shaker memory items”. You could both invent some new procedures for Boeing. God knows, it couldn’t hurt.

love the peanut gallery.
JPJP is offline  
Old 27th Sep 2019, 04:50
  #2620 (permalink)  
 
Join Date: Aug 2019
Location: Rocket City
Posts: 24
Originally Posted by fdr View Post
How on earth did not disclosing the system being installed tie in with any assumption of recognition????
"While Boeing considered the possibility of uncommanded MCAS operation as part of its functional hazard assessment, it did not evaluate all the potential alerts and indications that could accompany a failure that also resulted in uncommanded MCAS operation,"

It's a problem with how FHAs are done. And that's following the process for them. Go read ARP4754 and 4761.
ST Dog is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

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