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 12th Jun 2019, 19:51
  #361 (permalink)  
 
Join Date: Nov 2000
Location: Canada
Posts: 335

FAA says has no timetable for Boeing 737 Max's return to service

The Federal Aviation Administration said on Wednesday it does not have a specific timetable on when Boeing Co's troubled 737 Max jet would return to service after two fatal crashes led to the airplane's worldwide grounding in March.

Troubled aircraft has been grounded since March following 2 fatal crashes

Thomson Reuters · Posted: Jun 12, 2019 12:21 PM ET Last Updated: 2 hours agoThe Federal Aviation Administration said on Wednesday it does not have a specific timetable on when Boeing Co's troubled 737 Max jet would return to service after two fatal crashes led to the airplane's worldwide grounding in March.

FAA spokesman Greg Martin said the agency has "no timetable" for allowing the 737 Max to resume flying and will act "only when it is safe to return to service."

Bloomberg reported earlier that the troubled 737 Max aircraft will be back in the air by December, citing a top Federal Aviation Administration safety official.

Boeing did not immediately respond to a request for comment, and has not given a timeline on when the planes would be back in service.

Boeing is not expected to submit its formal software fix to the FAA this week or conduct a certification test flight that is required before it can submit the fix and training upgrade for approval, two people briefed on the matter told Reuters.
Grounded WestJet Boeing 737 Max aircraft are shown at the airline's facilities in Calgary on May 7. WestJet's schedule is adjusted through August 3 to accommodate the grounding and a spokesperson said Wednesday the airline was in close touch with regulators. (Jeff McIntosh/The Canadian Press)
A battered aviation industry has been speculating on when Boeing will win regulators' approval to put the plane back in the air along with a batch of software upgrades and training.A spokesperson for WestJet told CBC News that its schedule is adjusted through August 3. "We continue to monitor the situation and will adjust our schedule as required," said Morgan Bell.

"WestJet remains closely in contact with our partners at Boeing, Transport Canada and other regulators to understand how and when to safely reintroduce the Max aircraft into service."

Air Canada spokesperson Peter Fitzpatrick said that because the timeline for the plane's return to service is unknown, the airline has removed all 737 Max aircraft from its schedule until at least September 2.

"Through various measures we have maintained enough capacity to operate 96 per cent of previous planned flights and customers can plan and book their travel with Air Canada with full confidence."

American Airlines Group Inc. said on Sunday it was extending cancellations of about 115 daily flights into September due to the grounding.

Last edited by Longtimer; 12th Jun 2019 at 20:06.
Longtimer is offline  
Old 12th Jun 2019, 20:24
  #362 (permalink)  
 
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,113
Originally Posted by bill fly View Post
- although using a pseudonym - ...
In that context, note the warning about post anonymity stickied at the top of the forum. None of us are REALLY anonymous.

And if "we" can "guess" someone's general work role, someone who KNOWS THAT PERSON and knows how they tend to write and what they tend to be opinionated on can certainly make a damned good guess. (And what typos they make in their normal typing, even...says he, correcting a typo)

Add to that the ability of companies to monitor PC and 'net usage at a pretty deep level if they wanted to ... anything you post that remotely related to your work, you'd better have been willing to put in an formal memo and send to your boss, frankly.
Mad (Flt) Scientist is offline  
Old 12th Jun 2019, 20:53
  #363 (permalink)  
 
Join Date: Dec 2018
Location: Florida
Posts: 58
Paris, France - A Norwegian Boeing 737 MAX 8 had to land at the Paris-Vatry airport while it was en route from Malaga to Stockholm.The aircraft registered SE-RTB was conducting a repositioning flight from Malaga, Spain to its home base in Sweeden when German authorities refused permission for the use of German airspace.The aircraft took off from Malaga, Spain, on June 11 and began touring near German Airspace before it was forced to change its route by the German authorities.The Boeing 737MAXs have been grounded after the second fatal crash of the type in Ethiopia on March 10. The aircraft is not allowed to fly by international regulators since then except ferry flights.According to the company, Norwegian's Boeing 737 MAX 8 had been authorized by the European Aviation Safety Agency (EASA) to carry out a repositioning flight to join the airline's fleet in Stockholm.However, this authorization does not guarantee the use of airspace of other European countries. They have the right to refuse any access to their airspace.
Lake1952 is offline  
Old 12th Jun 2019, 21:43
  #364 (permalink)  
 
Join Date: Jun 2009
Location: florida
Age: 76
Posts: 1,079
Salute Mad !!

You are right about privacy, and unlike 95% or more here, my life story is on the profile link by my callsign. It has been since early 2004 or so, maybe longer.

FC eng sounds like an honest aviation enthusiast plus real engineer, and has posted super tech data devoid of "there I was' or "if it were me".

Oh well, we post and we tke our chances.

Gums sends...
gums is offline  
Old 12th Jun 2019, 22:03
  #365 (permalink)  
 
Join Date: May 2019
Location: Somewhere over the rainbow...
Posts: 0
Originally Posted by bill fly View Post


Well it’s a shame that knowledgeable people can get warned off - although using a pseudonym - whether I agree with them or not (I didn’t always).

It starves a thread of funded info and opens it to repetition and lay questions.

Maybe the solution would be a new pseudonym - although I guess it would become clear in time...
You could always PM the guy and ask if he's still there and if he's willing to comment.
yoko1 is offline  
Old 13th Jun 2019, 00:12
  #366 (permalink)  
 
Join Date: Mar 2015
Location: Washington state
Posts: 149
]737MAX back in July?

The three U.S. operators of the Max have dropped the jet from their flight schedules through at least early August, in line with the timeframe cited by De Juniac. Meanwhile, SpiceJet Ltd. said Boeing representatives told it the 737 Max should be back in the air by July, signaling a quicker return for the plane.

“The timeline communicated to us based on their experience is July -- end of June basically,” SpiceJet’s Chief Financial Officer Kiran Koteshwar said in an interview. “We are expecting it to be July.”

Representatives for Boeing in India didn’t comment.
If the FAA actually has no timeline and doesn't even have software to look at while Boeing is communicating to its customers that the plane will be back in July then an SEC investigation should be forthcoming. Elon Musk got in severe trouble for making up information that could affect the stock price.

Fear of the SEC may also may explain why some posters have "gone dark."
Water pilot is offline  
Old 13th Jun 2019, 01:44
  #367 (permalink)  
 
Join Date: Dec 2001
Location: Brisvegas
Posts: 2,721
In that context, note the warning about post anonymity stickied at the top of the forum. None of us are REALLY anonymous.
well you can track an IP to a physical address but tell me how you prove who was on the keyboard or device. Use wifi somewhere and the device ID is logged but again who was using it. Is there some legal case history to show this stands in court?
Icarus2001 is offline  
Old 13th Jun 2019, 02:14
  #368 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 571
Originally Posted by Water pilot View Post
]737MAX back in July?
Elon Musk got in severe trouble for making up information that could affect the stock price.

Fear of the SEC may also may explain why some posters have "gone dark."
Did Elon really get into trouble, what actual penalty or consequence of genuine note has he actually suffered? Who has been imprisoned for financial crimes and misdemeanors in the last decade? Bernie Madoff (podcast of his story). White collar crime has been decriminalised.

Boeing executives are in all probability safe from the SEC. That's precisely why this financial Frankenstein aircraft was produced, executives get to keep their bonuses if it all worked out, and if it doesn't, oh well someone else will pay.
On the other hand, if I were a mid level engineering manager I would be extremely concerned. Someone had to ultimately sign off on the MCAS safety analysis, that person is likely to be the scapegoat in all this.

Seattle Times: Current and former engineers directly involved with the evaluations or familiar with the document shared details of Boeing’s “System Safety Analysis” of MCAS, which The Seattle Times confirmed.
The safety analysis:
  • Understated the power of the new flight control system, which was designed to swivel the horizontal tail to push the nose of the plane down to avert a stall. When the planes later entered service, MCAS was capable of moving the tail more than four times farther than was stated in the initial safety analysis document.
  • Failed to account for how the system could reset itself each time a pilot responded, thereby missing the potential impact of the system repeatedly pushing the airplane’s nose downward.
  • Assessed a failure of the system as one level below “catastrophic.” But even that “hazardous” danger level should have precluded activation of the system based on input from a single sensor — and yet that’s how it was designed..
CurtainTwitcher is offline  
Old 13th Jun 2019, 03:35
  #369 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 64
Posts: 2,381
Originally Posted by Icarus2001 View Post
well you can track an IP to a physical address but tell me how you prove who was on the keyboard or device. Use wifi somewhere and the device ID is logged but again who was using it. Is there some legal case history to show this stands in court?
Would you be willing to bet your job and livelihood on that, just to make a social media post? Even if you don't get fired, it's the very definition of career limiting - and if you do get fired for cause, your chances of working in the industry again are not good. I don't know about FC, but in my case my handle is such that anyone who really wanted to know could figure out who I am in short order.
I started posting before I retired, but I was really careful about what I posted (I dearly wanted to call out a certain member for some BS he wrote about the 747-8 fuel burn, but couldn't because the data I had access to was considered proprietary. Then I saw exactly what I wanted to post in the Everett Herald newspaper - I didn't hold back after that).
Now that I'm retired (out of the game for about 30 months) I'm not as concerned, but I still have to be a bit careful since I still know stuff that's considered proprietary.
tdracer is offline  
Old 13th Jun 2019, 05:21
  #370 (permalink)  
 
Join Date: May 2008
Location: denmark
Posts: 45
From Falcon 7X accident report: https://www.bea.aero/uploads/tx_elyd...0525.en_01.pdf
The highest design assurance level (DAL A) was assigned to THS ACMU modules and the HSECU. The highest verification and validation levels were therefore supposed to be in place throughout the design and safety analysis process. However they failed to identify the HSECU critical failure modes and did not anticipate THS runaway in normal law.
JAR 25.671: Control systems: General
The aeroplane must be shown by analysis, tests, or both, to be capable of continued safe flight within the normal flight envelope, without requiring exceptional piloting skill or strength after the following failures:
-A runaway of a flight control to an adverse position and jam must be accounted for if such runaway and subsequent jamming is not extremely improbable (Probability of 1 x 10-9 or less per flying hour )
From https://en.wikipedia.org/wiki/DO-178B
Level A, Catastrofic, is required for a failure rate better than 10E-9 pr. hour.

Ethiopian airliner down in Africa
So in sum, we have a non-DAL A system integrated with a secondary control system with no redundancy, monitoring, crew warnings or a dedicated means to disengage.
My own summary:
- MCAS is not the main problem. It just highlighted a latent design problem, present in all B737 versions.
-The B737 flight control system responsible for controlling the trim motors are not designed according to DO-178B level A.
- B737 does not have an extremely improbable improbable risk of a THS runaway, therefore it have been equipped with cutout switches as a memory item.
- B737 need to be capable of continued safe flight within the normal flight envelope, without requiring exceptional piloting skill even with the THS in the most unfavorable position.

So either:
- The system have to redesigned mechanically to allow the pilots to overcome the control forces on yoke, and manual trim throughout the envelope,
- Or the system have to be redesigned with a DAL A system including the chain from sensors, sensor voting, actuation, and monitoring of actuation to prevent a single fault form generating a runaway.
- Or the FAA (together with the aviation authorities in the rest of the world) somehow decide that it is safe based on operational statistics of the trim on the NG, grandfathering rights etc.

On the Falcon they were in a situation where the architecture supported DAL A, but the design process had failed to consider some failure modes, this made it an easier problem to solve than the MAX issue.
I can’t see how this can be solved by correcting some lines of code..
HighWind is offline  
Old 13th Jun 2019, 06:21
  #371 (permalink)  
 
Join Date: Aug 2000
Posts: 1,324
- B737 need to be capable of continued safe flight within the normal flight envelope, without requiring exceptional piloting skill even with the THS in the most unfavorable position.
I think most aircraft will have a problem with this.
All aircraft can get into situations where they are uncontrollable.
The NG can fly with the stab fully forward, but it’s really hard. And you can’t trim the aircraft manually out of that situation.
ManaAdaSystem is offline  
Old 13th Jun 2019, 08:03
  #372 (permalink)  
fdr
 
Join Date: Jun 2001
Location: 3rd Rock, #29B
Posts: 663
Originally Posted by HighWind View Post
From Falcon 7X accident report: https://www.bea.aero/uploads/tx_elyd...0525.en_01.pdf

JAR 25.671: Control systems: General

From https://en.wikipedia.org/wiki/DO-178B
Level A, Catastrofic, is required for a failure rate better than 10E-9 pr. hour.

Ethiopian airliner down in Africa


My own summary:
- MCAS is not the main problem. It just highlighted a latent design problem, present in all B737 versions.
-The B737 flight control system responsible for controlling the trim motors are not designed according to DO-178B level A.
- B737 does not have an extremely improbable improbable risk of a THS runaway, therefore it have been equipped with cutout switches as a memory item.
- B737 need to be capable of continued safe flight within the normal flight envelope, without requiring exceptional piloting skill even with the THS in the most unfavorable position.

So either:
- The system have to redesigned mechanically to allow the pilots to overcome the control forces on yoke, and manual trim throughout the envelope,
- Or the system have to be redesigned with a DAL A system including the chain from sensors, sensor voting, actuation, and monitoring of actuation to prevent a single fault form generating a runaway.
- Or the FAA (together with the aviation authorities in the rest of the world) somehow decide that it is safe based on operational statistics of the trim on the NG, grandfathering rights etc.

On the Falcon they were in a situation where the architecture supported DAL A, but the design process had failed to consider some failure modes, this made it an easier problem to solve than the MAX issue.
I can’t see how this can be solved by correcting some lines of code..
Windy, that is about the sum of the problem. As far as I can see, the MCAS highlighted an issue, which is the inherent weakness of the stabiliser trim system architecture. As an industry, the constraints of a manual trim backup that could end up in a condition where manual trim change would be compromised was lost in the cracks (age creases... etc) What may have been well known 50 years ago has been forgotten, and finally bit back. The conditions affording protection provided under § 25.255(a) Out-of-trim characteristics were exceeded in both of these cases (3 seconds at normal for envelope speed is much less than MCAS was able to achieve); and the crew were left to learn what has been forgotten and untrained for the last x number of years. § 25.672 Stability augmentation and automatic and power-operated systems appears to need a change to comply if MCAS's activity remains as it is.

The Max is able to be flown safely without doubt. It does need crew training to ensure that they comprehend at an implicit level what occurs and what must be done to deal with both an MCAS fault and an out of trim case that reaches the extent of exceeding the manual trim capability. None of this is hard to do at this point, however it was fundamentally, demonstrably impossible for a crew in exremis to sort this out without full comprehension and rational and complete guidance. Recall that all of the simple fixes that we have today, all of the platitudes and mnemonics etc all arose from crews that found new corners of the envelope of our corporate knowledge, and paid highly for that headline. It remains my view that it is unjust to beat up or deride the crew of either of these planes for being what the industry trains and accepts, and in the absence of any overt action to get to the point that they did on the design, the manufacturer is also a result of the system that has developed, warts 'n all. Personally, if anyone needs a driver to fly the envelope of the Max with the fault and the cure, I'm happy to drive the aircraft as PIC to make the point. The plane even with the system as it stands can be flown, but it needed the information as to what was occurring to develop, and that has only come about post hoc.

Training is absolutely overdue for the crews on this type on the MCAS and the out of trim case that MCAS has resulted in. Do that, and the plane should be flying today.

Any Ops program/NAA is welcome to PM if they want the basis of the training needed to give assurance of the outcome, or wish to fly the envelope of the max out with this issue. The simulator QTG validation does need to be assessed separately, however the plane can be flown safely. I still suspect that the 672 and 255 cases need an ELS statement to be concluded, and that comes from doing rational training. If that was done, it would not be the first time that a method such as an SFAR was applied to a design that had taught the operators some lessons along the way, as the rice rockets and the RHC's have done before.

X-mas for RTS is not a solution, it is a lack of confidence in their own competencies in sorting out the necessary ticks in the box. Am not a fan of the SLUF, almost all other Boeings have been better, but you can't argue the success of the design to date. Post this saga, the Max should be the most successful Boeing aircraft design to date, certainly it will be the best of the SLUF's. X-mas as a schedule is reminiscent of awaiting the chicken entrails to dry just so, or pending Feng Shui to be deemed right. Inform the pilots, and then train them correctly on the issues.
fdr is offline  
Old 13th Jun 2019, 08:15
  #373 (permalink)  
 
Join Date: Jul 2010
Location: Asia
Posts: 523
We're talking about things here which really should have been over and done with after the second generation of jet transports flew. There was a steep learning curve from the big propellor liners onto the B707 and the early accident rates reflected this. The early pioneers had to be good at their jobs, were highly trained and thoroughly tested. Now we have minimum experience pilots flying aircraft with the same basic DNA as the early transports, who are facing the same issues as 1960s pilots did without the proper training to deal with them.

Todays dumbed down training and reduced hours are more suited to modern types without inherent faults where most emergencies have an ECAM procedure to follow.
krismiler is online now  
Old 13th Jun 2019, 09:12
  #374 (permalink)  
 
Join Date: Oct 2017
Location: Tent
Posts: 333
Originally Posted by Lake1952 View Post
Paris, France - A Norwegian Boeing 737 MAX 8 had to land at the Paris-Vatry airport while it was en route from Malaga to Stockholm.The aircraft registered SE-RTB was conducting a repositioning flight from Malaga, Spain to its home base in Sweeden when German authorities refused permission for the use of German airspace.The aircraft took off from Malaga, Spain, on June 11 and began touring near German Airspace before it was forced to change its route by the German authorities.The Boeing 737MAXs have been grounded after the second fatal crash of the type in Ethiopia on March 10. The aircraft is not allowed to fly by international regulators since then except ferry flights.According to the company, Norwegian's Boeing 737 MAX 8 had been authorized by the European Aviation Safety Agency (EASA) to carry out a repositioning flight to join the airline's fleet in Stockholm.However, this authorization does not guarantee the use of airspace of other European countries. They have the right to refuse any access to their airspace.
Interesting move.

Wonder how Boeing and FAA take that stand!
Bend alot is offline  
Old 13th Jun 2019, 09:41
  #375 (permalink)  
 
Join Date: Feb 2010
Location: attitude is nominal
Posts: 577
Germany had their MAX flight ban limited to some fixed date first. That must have been the time when Norwegian planned (and filed?) their flight.
But then Germany renewed it before Norwegian could complete their ferry flight. They ended up not being let into german airspace by DFS.

Last edited by Less Hair; 13th Jun 2019 at 10:35.
Less Hair is offline  
Old 13th Jun 2019, 11:22
  #376 (permalink)  
 
Join Date: Mar 2006
Location: England
Posts: 835
HighWind, # 371,
A clear and balanced summary; I agree, although the future might not be the simple either-or alternatives.

The Max might have the simplest route. If trim does not meet the certification requirements and was a contribution in two accidents, keep the Max grounded until both MCAS and the trim system are improved.

The NG could be a simple logical argument, fails to meet requirements, ground the aircraft until improved. However, an ‘emotional’ but logically inaccurate argument based on ‘no accidents so far’, could allow the aircraft to remain in service, although the risk of failure is the same.

This choice has potential for splitting the regulatory authorities, purist vs practical, but could be managed with compromise. Everyone might wish to avoid using the piloting contribution in recognition and inhibition as a permanent solution.
If the NG is easier to recover than the MAX (effect of aero differences), then it could be argued that alleviation with pilot recognition and action to mitigate risk could keep the aircraft flying until the trim system is modified. There may be similar contributions from restricting wt, cg, and of course lots of training.
If the NG is more difficult, then the industry faces a pivotal point in certification and risk management, where short term compromise could be based on definitions of safety, ‘what we are doing’ vs ‘what we have’, and of course timing of modification.

The critical factor depends on who makes the decision and how is this presented; not Boeing, ideally FAA in conjunction with (all) other authorities; but then few things are ever ideal.


fdr, #373,
But ‘The Max is able to be flown safely without doubt.’
There is always doubt, particularly when considering human performance. This is the judgement which the authorities have to make, and with a background of two recent accidents to bias thoughts
PEI_3721 is offline  
Old 13th Jun 2019, 11:46
  #377 (permalink)  
Pegase Driver
 
Join Date: May 1997
Location: Europe
Age: 69
Posts: 2,609
Originally Posted by Lake1952 View Post
Paris, France - A Norwegian Boeing 737 MAX 8 had to land at the Paris-Vatry airport while it was en route from Malaga to Stockholm.The aircraft registered SE-RTB was conducting a repositioning flight from Malaga, Spain to its home base in Sweeden when German authorities refused permission for the use of German airspace.The aircraft took off from Malaga, Spain, on June 11 and began touring near German Airspace before it was forced to change its route by the German authorities.The Boeing 737MAXs have been grounded after the second fatal crash of the type in Ethiopia on March 10. The aircraft is not allowed to fly by international regulators since then except ferry flights.According to the company, Norwegian's Boeing 737 MAX 8 had been authorized by the European Aviation Safety Agency (EASA) to carry out a repositioning flight to join the airline's fleet in Stockholm.However, this authorization does not guarantee the use of airspace of other European countries. They have the right to refuse any access to their airspace.
The Germans, especially those sitting in an office , are always very good at applying the rules blindly. In any doubt , always say no, is how they have been trained . . That said there are many ways to reach Stockholm from Malaga , including one using he high seas, i.e avoiding any sate legal jurisdiction.(other than Spain and Sweden of course) .
ATC Watcher is online now  
Old 13th Jun 2019, 12:05
  #378 (permalink)  
 
Join Date: Jan 2008
Location: Reading, UK
Posts: 10,644
Originally Posted by ATC Watcher View Post
The Germans, especially those sitting in an office , are always very good at applying the rules blindly. In any doubt , always say no, is how they have been trained . . That said there are many ways to reach Stockholm from Malaga , including one using he high seas, i.e avoiding any sate legal jurisdiction.(other than Spain and Sweden of course) .
Probably need to take the wings off first.
DaveReidUK is online now  
Old 13th Jun 2019, 12:22
  #379 (permalink)  
Pegase Driver
 
Join Date: May 1997
Location: Europe
Age: 69
Posts: 2,609
Originally Posted by DaveReidUK View Post
Probably need to take the wings off first.
but No, ask the Israelis, or the Russian air force, they know how to fly (mostly) legally around any airspace.
ATC Watcher is online now  
Old 13th Jun 2019, 12:50
  #380 (permalink)  
 
Join Date: May 2019
Location: Somewhere over the rainbow...
Posts: 0
Originally Posted by PEI_3721 View Post


The NG could be a simple logical argument, fails to meet requirements, ground the aircraft until improved. However, an ‘emotional’ but logically inaccurate argument based on ‘no accidents so far’, could allow the aircraft to remain in service, although the risk of failure is the same.

This choice has potential for splitting the regulatory authorities, purist vs practical, but could be managed with compromise. Everyone might wish to avoid using the piloting contribution in recognition and inhibition as a permanent solution.
If the NG is easier to recover than the MAX (effect of aero differences), then it could be argued that alleviation with pilot recognition and action to mitigate risk could keep the aircraft flying until the trim system is modified. There may be similar contributions from restricting wt, cg, and of course lots of training.
If the NG is more difficult, then the industry faces a pivotal point in certification and risk management, where short term compromise could be based on definitions of safety, ‘what we are doing’ vs ‘what we have’, and of course timing of modification.

The critical factor depends on who makes the decision and how is this presented; not Boeing, ideally FAA in conjunction with (all) other authorities; but then few things are ever ideal.

Despite all the angst relating to the 737NG family, it should be acknowledged that it has amassed one of the best safety records of any commercial aircraft every built. To Boeing's credit, the stab trim system (pre-MCAS) had been so incredibly robust and reliable that many airlines became complacent and simply stopped training adequately for its possible failure modes.

This highlights an interesting problem relating to the overall level of safety of complex systems. I recently read an interesting book by Malcolm Gladwell titled "What the Dog Saw", a collection of articles that were previously published in The New Yorker magazine. In one section, Mr Gladwell discussed various forms of failures (business, intelligence, safety) that seemed incredibly obvious in retrospect. He rightfully asks how so many people could miss things that were so "obvious"?

One problem is that human beings are frequently subjected to massive amounts of data that are conflicting and ambiguous, and it is only after the fact that we are able to properly discern which of the data was pointing to the problem. From what we know so far of the MCAS debacle, it appears that numerous individuals made decisions that, in the context of their particular view of the problem, seemed reasonable at the time. It was only after the sum total of those decisions came together at a certain place and time that the systematic failure became obvious.

Another counterintuitive problem arises when steps taken to improve overall risk of a system fail to do so because of a change in behavior induced by those very improvements - a phenomenon known as risk homeostasis. Mr Gladwell gives an example of a study conducted in Germany when antilock brake systems (ABS) were being introduced. Half of a fleet of cabs had ABS installed, and the other half retained the old style brake system. The drivers were then monitored for three years. Contrary to expectations, the ABS-equipped drivers had worse accidents records than their counterparts without ABS. Why? The investigators determined that the drivers with ABS systems took greater risks. They drove faster in wet conditions, they made sharper turns, they were more likely to tailgate, etc. In effect, the drivers were "consuming" the risk reduction by increasing the riskiness of their driving behavior.

I would submit that there is a similar phenomenon occurring in aviation. As manufacturers fielded demonstrably safer aircraft, airlines compensated by producing less proficient pilots. Whether this phenomenon was fully appreciated at the design engineering level is not entirely clear. However, in regards to the MAX accidents, Boeing was apparently expecting the pilots to be more skilled than they actually were, and the airlines were expecting the aircraft to be more resilient than it was. Each side made assumptions regarding the level of risk inherent in their choices based on their perception of the level of risk maintained by the other.

I suspect that risk homeostasis will continue to be an issue in aviation. Manufacturers and airlines are profit-driven entities, and their will always be a temptation to be less vigilant toward their individual contribution to a safer system if they perceive (rightly or wrongly) other factors are increasing the level of safety.

Last edited by yoko1; 13th Jun 2019 at 15:43.
yoko1 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.