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

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

Old 10th Jun 2019, 12:00
  #281 (permalink)  
 
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Originally Posted by bill fly View Post

Given the ever increasing down time, basic changes could and should be made:

1) Decommission MACS feature and replace by a change to the mechanical feel in the control run, to achieve higher stick load at higher AoA with no stabiliser input
2) Build in a standby trim motor and scrap the trim wheel (see MD-80 for example)
3) Start from scratch with the trim electric logic and simplify the cut-out, column cut-out and trim switch confusion
4) Test fly and certify trim runaway situations on Max and NG
5) Create a “difference” course and market it to future operators at an attractive price - free for present operators
6) Make public the above, certify the Max and recommend the trim mod to NG operators

Takes time - takes money? So do crashes and down time, as we see.
Would you care to flesh out why you believe the fix Boeing have proposed to the FAA is not going to be safe?
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Old 10th Jun 2019, 12:42
  #282 (permalink)  
 
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Originally Posted by oggers View Post
Would you care to flesh out why you believe the fix Boeing have proposed to the FAA is not going to be safe?
I don’t believe I said their fix wasn’t safe, although that has been well fleshed out in at least three threads here Oggers, which have all been closed due to repetition.
Anyhow the stab isn’t there to create artificial feel corrections - the feel unit is - and should a false input occur, there would be a one-time survivable trimmable input made and not a powerful aerodynamic force.
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Old 10th Jun 2019, 12:53
  #283 (permalink)  
 
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An interesting issue is how the time in inactive storage will affect the airframes. It's one thing to keep them parked in the desert, quite another in the humid environment of the Pacific Northwest.
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Old 10th Jun 2019, 12:59
  #284 (permalink)  
 
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At 31st December Inventory represented 53.3% of Boeing's assets on their balance sheet with Goodwill a further 7%

Nasdaq Report

I guess next year's audit may be a challenging one



Last edited by Maninthebar; 10th Jun 2019 at 13:00. Reason: Insert url
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Old 10th Jun 2019, 13:17
  #285 (permalink)  
 
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With FAA and all other worldwide organisations involved, one might as well start to melt the 737-MAX airframes down and start over, because this is gonna take YEARS before the administration circle is round, and nobody is eager to put the final signature on paper.
And I repeat my question : How many of the grounded airframes are actually properly stored and maintained?
Or we are gonna see many funny and not so funny moments when they "eventually" would/should/could go flying again.

Pretty sure we will see a next "unfortunate event" in the first month after "release for flight".
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Old 10th Jun 2019, 13:21
  #286 (permalink)  
 
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Originally Posted by bill fly View Post


I don’t believe I said their fix wasn’t safe, although that has been well fleshed out in at least three threads here Oggers, which have all been closed due to repetition.
Ok so will you clarify if you believe the Boeing fix will be safe or not? If safe, what is the point of your list:

1) Decommission MACS feature and replace by a change to the mechanical feel in the control run, to achieve higher stick load at higher AoA with no stabiliser input
2) Build in a standby trim motor and scrap the trim wheel (see MD-80 for example)
3) Start from scratch with the trim electric logic and simplify the cut-out, column cut-out and trim switch confusion
...that adds cost and the potential to introduce new and unforeseen malfunctions, by comparison with the fix Boeing have come up with. Nor do I think there is any chance Boeing could get all those things done in the time the MAX will be grounded, which is an assumption your point is based on.
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Old 10th Jun 2019, 14:08
  #287 (permalink)  
 
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And I repeat my question : How many of the grounded airframes are actually properly stored and maintained

Wow, one massive slight on all the professional and competent engineers out there and the MROs and CAMOs. Why would you assume they are all incompetent?
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Old 10th Jun 2019, 14:11
  #288 (permalink)  
 
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Originally Posted by Icarus2001 View Post

Wow, one massive slight on all the professional and competent engineers out there and the MROs and CAMOs. Why would you assume they are all incompetent?
It may not just not be a matter of competence. Aircraft tend not to age well during inactive storage, and the longer they sit the more the problems, particularly if they are stored in humid environments.
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Old 10th Jun 2019, 14:18
  #289 (permalink)  
 
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Originally Posted by oggers View Post
Ok so will you clarify if you believe the Boeing fix will be safe or not? If safe, what is the point of your list:



...that adds cost and the potential to introduce new and unforeseen malfunctions, by comparison with the fix Boeing have come up with. Nor do I think there is any chance Boeing could get all those things done in the time the MAX will be grounded, which is an assumption your point is based on.
If I may reply:

It is difficult to say whether Boeing's solution is safe, there are many dependences. It may as well be, especially in scenarios we can foresee. However, moving the stabiliser in order to produce the right feel is potentially very dangerous - you are creating huge aerodynamic forces and if _anything_ in the logic driving it fails for whatever reason, you can be in deep trouble. Even if indeed all the possible failure paths are correctly handled (a BIG if, can we be 100% sure that all possible scenarios have been properly evaluated in such a complex system?), this is a very fragile solution and any future changes can bite you badly.

A solution for fixing the feel that actually does not change the aerodynamics is inherently much safer - if there is a wrongly handled failure somewhere, you might get a wrong feel, but not a plunging plane.
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Old 10th Jun 2019, 14:38
  #290 (permalink)  
 
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It may not just not be a matter of competence. Aircraft tend not to age well during inactive storage, and the longer they sit the more the problems, particularly if they are stored in humid environments.
No, that is a different issue. We know aircraft do not store well. That is why there are maintenance procedures to help mitigate that risk.

Vilters is is quite clearly stating that most are not correctly stored or maintained, a slight on the engineers.
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Old 10th Jun 2019, 14:44
  #291 (permalink)  
 
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Originally Posted by oggers View Post
Ok so will you clarify if you believe the Boeing fix will be safe or not? If safe, what is the point of your list:



...that adds cost and the potential to introduce new and unforeseen malfunctions, by comparison with the fix Boeing have come up with. Nor do I think there is any chance Boeing could get all those things done in the time the MAX will be grounded, which is an assumption your point is based on.
I‘ll go further than that - firstly I don’t know what the „fix“ you want me to qualify is yet - it is the whole principle of using the stab which is potentially dangerous. If the „fix“ keeps that principle I don’t like it.

As to costs and time, I know that - mentioned it myself in the first post and as I said, sometimes you have to bite the bullet.

^_^

edit to acknowledge DonEsteban who says it well...
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Old 10th Jun 2019, 15:58
  #292 (permalink)  
 
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Originally Posted by bill fly View Post


I‘ll go further than that - firstly I don’t know what the „fix“ you want me to qualify is yet - it is the whole principle of using the stab which is potentially dangerous. If the „fix“ keeps that principle I don’t like it.

As to costs and time, I know that - mentioned it myself in the first post and as I said, sometimes you have to bite the bullet.

^_^

edit to acknowledge DonEsteban who says it well...
The STS stability system already moves the Stab without any pilot input as speed changes, hence the wizzing of trim wheels, the MCAS is control law software not hardware.

If Boeing are forced to bite the bullet and stop MAX production, they would have to buy back all the sold production including engines, what can you do with what will shortly be 500-600 aircraft, step in uncle SAM who will convert them for military use and thus out of reach of civil regulators.

It should be remembered that what the MCAS is designed to address is a very high AoA in a steep turn, something that is very very unlikely to occur, however it must comply with the regs on certification and thus we end up with MCAS

I get the sense that a whiff of politics creeping in, the pro Airbus lobby ( fair game) anti US ( Trump) sentiment, again fair game with using trade policy to change foreign policy

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Old 10th Jun 2019, 16:00
  #293 (permalink)  
 
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Boeing appears to be blundering around trying to retrofit a fly by wire system onto an ancient design, and are facing enormous pressures to do it cheaply and quickly. The MAX program has a history of apparently compromising safety in favor of cost and time. What could go wrong?

The problems that MCAS was intended to solve have not been well documented, Boeing has been a little close with the details of the problems with the flight envelope that required such a dramatic departure from their "the pilot flies the plane" philosophy of the 737. "We use software to make the flight characteristics conform to spec" may be a valid approach to aircraft design but you had better be damn sure that the software and the sensors that it relies upon are bulletproof, and certainly the sensors are not there with the current state of the art. Using just two sensors will never be acceptable; three sensors with a voting protocol is the current state of the art but three sensors of the same type can suffer from correlated errors (such as the icing that initiated the events that brought down AF447.) So not retrofitting a third sensor is the first safety compromise with the proposed fix.

The proposed fix involves disabling MCAS and limiting its authority. All well and good, perhaps, but now we have a plane where the elevator feel can change based upon a random event. In at least some cases, MCAS will be disabled without informing the pilot. This is arguably worse in some ways than the original behavior; even the "golden hands" pilots are going to be thrown off if suddenly the flight characteristics of the good old 737 that you are flying become something quite different. Imagine that your car suddenly changes the amount of authority that the brake pedal has; you attempt to slow down and the brakes lock up. OK, you figure that out and hit the brakes very lightly the next time, and then the car doesn't slow down. Now make this happen on an icy road at night...

The dilemma for Boeing is that if MCAS was ever necessary then it needs to be always active, and the fix is to deactivate it. The beancounters try to work their way around it by arguing that the cases where MCAS is necessary are rare, but Murphy's law ensures that whatever cases you needed MCAS for will occur at some time during the millions of miles that the MAX will fly in a year, and that with enough years that case will happen when MCAS is disabled.

One could train pilots on how to deal with the 737 MAX without MCAS but that violates the fundamental assumption that the plane is flyable with low-experienced pilots (the market for the 737) and that no new simulator time is required for the subtype. (It would also require that the simulator correctly models the 737 MAX which apparently it does not.)

So it is a mess. It would be better to figure out how to engineer away the differences between the 737 NG and the 737 MAX without relying on software and sensors, or at least get it close enough. Obviously that won't be easy or they would have chosen that approach in the first place.
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Old 10th Jun 2019, 16:14
  #294 (permalink)  
 
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Curious that todays article about AA revising schedule to Sep, it mentions that pilots will need 45 days of training?!?!
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Old 10th Jun 2019, 16:18
  #295 (permalink)  
 
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Originally Posted by Smythe
So did the FAA. The FAA pointed to how many issues there were with landing gear, the importance of a locked indicator, and the SPOF issue with no indication of wings locked. The FAA wording was terse on the issue to say the least.
.
Smythe, you might want to check the list of EICAS messages and indications before you spout such nonsense...
Sorry, but that was directly from the FAA response to Boeing on the wings, the wind loads and lack of indicators that the wings are locked.

note 'must add' means it wasnt there?

More than one means must be available to alert the flightcrew that the wingtips are not properly positioned and secured prior to takeoff. Each of these means must be unique in their wingtip-monitoring function. When meeting this condition, the applicant must add a function to the takeoff warning system, as required by § 25.703(a)(1) and (2), to warn of an unlocked or improperly positioned wingtip, including indication to the flightcrew when a wingtip is in the folded position during taxi.
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Old 10th Jun 2019, 16:49
  #296 (permalink)  
 
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Originally Posted by Smythe View Post
Curious that todays article about AA revising schedule to Sep, it mentions that pilots will need 45 days of training?!?!
I think what they meant is that it will take that long to get enough pilots trained to accommodate the aircraft they have in the fleet. I believe AA has only one MAX sim, so it will take a while to cycle all their 737 pilots through for whatever training is required.
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Old 10th Jun 2019, 17:37
  #297 (permalink)  
 
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Originally Posted by Water pilot View Post
Boeing appears to be blundering around trying to retrofit a fly by wire system onto an ancient design, and are facing enormous pressures to do it cheaply and quickly. The MAX program has a history of apparently compromising safety in favor of cost and time. What could go wrong?

The problems that MCAS was intended to solve have not been well documented, Boeing has been a little close with the details of the problems with the flight envelope that required such a dramatic departure from their "the pilot flies the plane" philosophy of the 737. "We use software to make the flight characteristics conform to spec" may be a valid approach to aircraft design but you had better be damn sure that the software and the sensors that it relies upon are bulletproof, and certainly the sensors are not there with the current state of the art. Using just two sensors will never be acceptable; three sensors with a voting protocol is the current state of the art but three sensors of the same type can suffer from correlated errors (such as the icing that initiated the events that brought down AF447.) So not retrofitting a third sensor is the first safety compromise with the proposed fix.

The proposed fix involves disabling MCAS and limiting its authority. All well and good, perhaps, but now we have a plane where the elevator feel can change based upon a random event. In at least some cases, MCAS will be disabled without informing the pilot. This is arguably worse in some ways than the original behavior; even the "golden hands" pilots are going to be thrown off if suddenly the flight characteristics of the good old 737 that you are flying become something quite different. Imagine that your car suddenly changes the amount of authority that the brake pedal has; you attempt to slow down and the brakes lock up. OK, you figure that out and hit the brakes very lightly the next time, and then the car doesn't slow down. Now make this happen on an icy road at night...

T
So it is a mess. It would be better to figure out how to engineer away the differences between the 737 NG and the 737 MAX without relying on software and sensors, or at least get it close enough. Obviously that won't be easy or they would have chosen that approach in the first place.

Surely more difficult than merely the control feel issue.
Other reporting indicates there was also an issue at low speeds, which is why the MCAS authority was quadrupled and its activation envelope expanded. So no MCAS means wonky low speed behavior, not an appealing prospect for low time pilots.
Boeing may be able to provide a set of software and sensor upgrades that provide reasonable assurance of reliable operation, but the regulators overseas will need convincing. Not easy after this debacle.
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Old 10th Jun 2019, 18:23
  #298 (permalink)  
 
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The re-engine of the B737 to create the MAX was the creation of the troubles facing Boeing today. Perhaps someone will start thinking about engines again and conclude that the cheapest solution is to hang the old engines back where they were, safe and sound, in the first place and let Airbus get on with whatever they were up to.
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Old 10th Jun 2019, 19:46
  #299 (permalink)  
 
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continue with the NG then.....

the MAX debacle has served to highlight the misdirection Boeing has taken in producing a reverse engineered facsimile of a 1960s clockwork aircraft. Since the 1980s we've had Boeing aircraft such as the B757/767 and the B747-400 equipped with EICAS displays to provide crews with sufficient information to deal with non normals. To continue to build an aircraft into the 21st century that fails to supply the pilots with the right information during flight is just plain dumb.
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Old 10th Jun 2019, 19:59
  #300 (permalink)  
 
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While the MAX was a knee-jerk reaction to the neo, the NG was a reaction to the 320 in the first place.
At that point Boeing was going for a clean sheet aircraft, then the 320 forced the NG ($2 Billion vs $15 Billion)

If the Cl to NG redesign would have included taller landing gear, we might not be discussing this. The NG was all good, except for engine clearance, that has haunted them, and now...it is a nightmare.

the $2 Billion they saved by not redesigning the landing gear/wingbox was gone in the first 2 weeks of the grounding...great decision.

Still no clean sheet ac.
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