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

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

Old 24th Dec 2019, 12:23
  #221 (permalink)  
 
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Originally Posted by MechEngr View Post
An airplane in flight is essentially a teeter-totter balanced on the Center of Pressure (CP) for the entire airplane and is considered to be the point where the lift acts. One element of this is that lift from positive AoA produces a nose-down pitch torque. To counter that, the horizontal stabilizer produces a nose up pitch torque by pushing down on the aft end of the fuselage. When these are balanced everyone is happy, or at least the AoA isn't changing. Of note is that the stabilizer functions as a wing that produces lift opposite to the lift of the wing and has its own local AoA.

If one looks at all possible stable AoAs one would like to see a linear relation between the AoA of the wing and the stabilizer trim position required to balance it. But the Max seems to have another player on the teeter-totter and that is the nacelle of the engine which starts producing noticeable nose up pitch torque at high AoA. So the stab trim position is no longer quite as linear as it was. Since the elevator also affects the pitch torque, that's where the effect could be noticed by the pilot as they move the controls without adjusting the trim. The function of MCAS is to make it so the pilot doesn't experience this new player.

Because it's just to offset the new player and depends on AoA and airspeed (because the amount of lift the stabilizer produces depends on those things to generate nose-up torque) it really isn't moving much or fast; it just has to be fast enough to keep up with AoA changes to the aircraft and to speed changes, neither of which ought to be particularly high. It gets more pronounced at low speeds because not only does the requisite high AoA needed to provide lift at low speeds increase the effect from the engine nacelles, the lower speed also means the stabilizer has less dynamic pressure to work with. This is no different than, say, rudder authority at low speed; the rudder has to move a lot farther to get the same effect at low speed than high speed.

AFAIK that's the intended MCAS function. To meet a linearity requirement for pilot controls by rebalancing a larger input from the engine nacelles than was existent, but could be ignored, on earlier models. It's not fast enough for a negative stability situation, so that's not it.
Nicely explained, MechEngr, but that's the trim stability of a glider... Now add two large bonks with thrust/drag not vectored through cg and in line of flight, and you get another big factor influencing pitch moments. As we do not know in what flight regime(s) the unacceptable pitch up tendency occurs, the power (or idle drag) of the engines add to influencing factors you mentionned. What I cannot figure out - maybe some of you can - is the fact that the unwanted non-linearity does not occur with flaps/slats slightly extended.
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Old 24th Dec 2019, 14:34
  #222 (permalink)  
 
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I also think that MCAS was never triggered in normal airline use. Day to day flying only uses a small, benign part of the flight envelope.

However, there might be situations (e.g. escaping extreme wind shears), where the relevant part of the flight envelope is entered. Having an unpredictable handling of the aircraft in such a situation might be the trigger for the next catastrophic accident.

I think there is more to it than just unusual handling characteristics w/o MCAS.
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Old 24th Dec 2019, 14:38
  #223 (permalink)  
 
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You should not expect to find any records of MCAS activation; they are not hazardous, exceptional, nor of interest unless the aircraft approaches an already identified safety boundary.
The design was intended to be a background operation, not seen or felt by the crew other than by close observation of trim activity.
MCAS activation is no more unusual than STS operation.
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Old 24th Dec 2019, 14:51
  #224 (permalink)  
 
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MCAS can be shown to be very logical.

But regardless of the parameters that activate it, and the absence of any intuitive means to inhibit a false activation, it still seems strange to invoke the most powerful effector on the airplane as a means to adjust stick force. What happened to springs and variable linkages?

Also, let's not forget that MCAS became lethal when its authority was increased to deal with a second, lower-speed-range issue of non-linear force-to-alpha relationship. That's where someone needs to look at the "naked" characteristics - because MCAS 2.0 is more easily inhibited, increasing the chance that a MAX will enter that corner of the envelope unprotected.
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Old 24th Dec 2019, 15:07
  #225 (permalink)  
 
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Originally Posted by JPcont View Post
I don’t understand why the MAX is still grounded. The control problems should be relatively easy to solve (with additional actuators) when the understanding of the underlying problem is present.
It seems likely that a solution involving additional actuators would threaten certification under the existing type certificate.

My guess is that MACS was used to fix something else that stick force problem (in the control engineering referenced as open loop gain). My guess is that the system was there to prevent to enter to a envelope where the the real problems begins.
That makes sense to lots of people who have been paying close attention to this issue.

For the political reasons it was named and defined to system that makes the “feeling” like NG.
I think the reasons are probably related to regulatory and sales and marketing issues rather than "political" ones.

My guess is that the problem were solved if the politics, the "salesman's lies” and the lawyer advices were were forgotten and the raw engineering job from clean table were started. Some kind of spoiler in the wing root or somewhere near the pylon might be needed. There should be courage to think out of the box and forget the short term costs.
I don't think there's much question about that: you're almost certainly correct. However, that approach would effectively kill the MAX and be disastrous for Boeing's standing in the narrowbody market. So it almost certainly won't happen unless forces outside the company make it happen.
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Old 24th Dec 2019, 15:13
  #226 (permalink)  
 
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Originally Posted by safetypee View Post
MCAS activation is no more unusual than STS operation.
Except that it moves the trim farther, and faster, and usually in the opposite direction.

Last edited by Takwis; 24th Dec 2019 at 15:23.
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Old 24th Dec 2019, 16:54
  #227 (permalink)  
 
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Originally Posted by safetypee
MCAS activation is no more unusual than STS operation.
Originally Posted by Takwis View Post
Except that it moves the trim farther, and faster, and usually in the opposite direction.
Although MCAS 1.0 was given a huge authority range in "normal" activation it would likely use much less, just enough to get AoA back where it wanted it.

Thus a normal activation might not be all that noticeable, especially given that STS is also tweaking trim although in opposite direction.

Question for 737 pilots:
Unless one was looking at the trim wheel would you even notice that a particular (short, not pathological) trim tweak was opposite the expected STS direction in a dynamic situation where MCAS would trigger?
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Old 24th Dec 2019, 17:29
  #228 (permalink)  
 
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Originally Posted by clearedtocross View Post
Nicely explained, MechEngr, but that's the trim stability of a glider... Now add two large bonks with thrust/drag not vectored through cg and in line of flight, and you get another big factor influencing pitch moments. As we do not know in what flight regime(s) the unacceptable pitch up tendency occurs, the power (or idle drag) of the engines add to influencing factors you mentionned. What I cannot figure out - maybe some of you can - is the fact that the unwanted non-linearity does not occur with flaps/slats slightly extended.
MCAS does not respond to any of those things, which all commercial jets have and for which pilots already have to compensate, and aren't fundamental to understanding MCAS. Landing gear, the rudder/vertical stabilizer, flow around the fuselage, wing downwash affect on the horizontal stabilizer, cargo/passenger loads, compressability effects, et al, are complicated interactions when a simple explanation was wanted.

I expect that with flaps/slats that the pitch-down increases so much that the non-linearity contribution from the engine nacelles is back to being too small a relative contributor to notice.
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Old 24th Dec 2019, 17:32
  #229 (permalink)  
 
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More on the "recently-acknowledged" messages:

Boeing Discloses More ‘Very Disturbing’ Messages on 737 Max(Bloomberg) -- A new batch of messages between Boeing Co. employees on the development of the 737 Max paints a “very disturbing picture” of concerns about the plane, according to an aide to a House committee.

The documents were turned over to the Federal Aviation Administration on Monday, the agency said in a statement. The disclosure came the same day that Boeing ousted its chief executive officer.

At least some of them were written by the same Boeing pilot whose 2016 messages were released in October and were the subject of sharp questioning by lawmakers, according to a person familiar with their contents who wasn’t authorized to discuss them.

The communications haven’t been released publicly. The staff of the Transportation and Infrastructure Committee are still reviewing the messages and didn’t provide specific details about what they contain.

“But similar to other records previously disclosed by Boeing, the records appear to point to a very disturbing picture of both concerns expressed by Boeing employees about the company’s commitment to safety and efforts by some employees to ensure Boeing’s production plans were not diverted by regulators or others,” a committee aide said in a statement.

The committee will continue to review these and other records provided by Boeing as part of the committee’s ongoing investigation,” the aide said.

Boeing didn’t immediately respond to an emailed request for comment.

This was the second time that the Chicago-based company has delayed turning over to the FAA sensitive messages related to the development of the 737 Max jetliner, which was grounded in March after a design flaw was linked to two fatal crashes, in Indonesia and Ethiopia. The earlier episode prompted a rebuke by the agency and helped lead to growing tensions between the regulator and the planemaker.

The FAA didn’t comment in its statement on the content of the emails, saying only that they were under review. The company’s decision to turn the emails over to the FAA was reported earlier by the Seattle Times.

The way Boeing handled the second set of records rankled the agency, according to a person familiar with the issue who wasn’t authorized to speak about it. Boeing told the FAA the messages existed in recent days, but didn’t initially provide them or disclose their contents, said the person.

Boeing Chief Executive Officer Dennis Muilenburg stepped down on Monday, at least partly as a result of deteriorating relations with the FAA, according to a statement from the company’s board.

In October, Boeing disclosed to the FAA instant messages and emails by a high-ranking company pilot who in 2016 expressed misgivings about the software implicated in two fatal crashes on the Max.

Boeing had known about those messages since early in the year and turned them over to the Justice Department in February. It didn’t give them to the FAA immediately because of the criminal investigation into how the plane was approved, Bloomberg News reported at the time.

The delay angered the FAA, which is charged with overseeing Boeing. One of the agency’s key tenets is that entities it oversees must disclose safety issues or possible breaches of regulations. In some circumstances, failing to tell the agency about such an issue may be considered a legal violation.

“The FAA finds the substance of the document concerning,” the agency said in a statement on Oct. 18. “The FAA is also disappointed that Boeing did not bring this document to our attention immediately upon its discovery.”

The November 2016 instant messages disclosed in October, which were reviewed by Bloomberg News, were between between Mark Forkner, then Boeing’s chief technical pilot for the 737, and another 737 technical pilot, Patrik Gustavsson.

Forkner expressed concern that the flight-control feature later implicated in the crashes was “running rampant” and said he might have unknowingly misled the FAA about it. In separate emails he sent to an unnamed FAA official, he said he was “jedi-mind tricking” regulators outside the U.S. into accepting Boeing’s suggested training for the Max.

A lawyer for Forkner, David Gerger, said issues raised in the messages were the result of balky simulator software and not a result of problems with the plane itself. Forkner believed the plane was safe and didn’t mislead the FAA, Gerger said.

Gerger didn’t respond to requests to comment on the latest messages and whether they involved his client.
Emphasis added.
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Old 24th Dec 2019, 17:49
  #230 (permalink)  
 
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Boeing plans to hand out "safety" cards to convince pax that Max is safe.

For instance, if a traveler doesn’t want to fly after buying a ticket, getting to the airport gate or even after boarding the plane, Boeing says that the airline could offer to rebook a flight, have flight attendants or pilots talk to the concerned passenger or hand out 3-by-5 inch information cards detailing why the Max is safe... In the most extreme cases, Boeing suggests using “techniques related to an inflight medical emergency to de-escalate.

At times, the material is startlingly self-critical. In a draft memo Boeing prepared for airlines to share with employees such as flight attendants, the company suggests that airlines say: “Boeing understands that it fell short and let us down, as well as the flying public, and it has committed to continuous improvement and learning....

In a section of the presentation focused on social media and marketing, the company said it planned to “amplify any positive stories reported,” and that it intended to buy ads to promote the plane’s return to service. It said a company website dedicated to updates on the Max was being designed with “improved usability” and “stickiness” to “encourage more time on site and repeat visits,” phrases commonly used in the communications business.

The presentation said Boeing’s “digital and media team” would be “monitoring social conversations around the clock. "
If you can you should look at the "Customer Journey and Scenario map" presented in the article. Aside from the explicit sexism (the concerned passenger is a "she" in all scenarios) it is rather fascinating. For instance, "if anxious passenger is posting, then airline social care team provides information on the safety of the MAX and informs the airlines network operations center of anxious passenger, which informs flight crew, as needed."
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Old 24th Dec 2019, 18:01
  #231 (permalink)  
 
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Originally Posted by Water pilot View Post
Boeing plans to hand out "safety" cards to convince pax that Max is safe.

If you can you should look at the "Customer Journey and Scenario map" presented in the article. Aside from the explicit sexism (the concerned passenger is a "she" in all scenarios) it is rather fascinating. For instance, "if anxious passenger is posting, then airline social care team provides information on the safety of the MAX and informs the airlines network operations center of anxious passenger, which informs flight crew, as needed."
Well, that's . . . seriously creepy. Thanks for the pointer.

It looks like Boeing's not going to be comforted by the initial response to coverage of this scheme. Here's the most-recommended comment on the Times story:

I'm pretty sure we all know this is baloney. Boeing slapped a software fix on a physics problem. Nope. No way am I getting on one of these. Boeing has demonstrated more concern for short term profits than for passengers. It gutted its own technical expertise. No 3x5 card is going to make up for that. What a joke.
All the other top comments are in the same vein.
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Old 24th Dec 2019, 18:59
  #232 (permalink)  
 
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Suggestions for the 3x5 card:
  • The Boeing 737 Max was a perfectly safe aircraft before the first crash, which was the pilot's fault.
  • The Boeing 737 Max was a perfectly safe aircraft before the first second crash, which was the pilot's fault.
  • The Boeing 737 Max was is a completely fixed and is now a perfectly safe aircraft before the first second and the next crash which was will be the pilot's fault.
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Old 24th Dec 2019, 19:01
  #233 (permalink)  
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Originally Posted by Water pilot View Post
Suggestions for the 3x5 card:
  • The Boeing 737 Max was a perfectly safe aircraft before the first crash, which was the pilot's fault.
  • The Boeing 737 Max was a perfectly safe aircraft before the first second crash, which was the pilot's fault.
  • The Boeing 737 Max was is a completely fixed and is now a perfectly safe aircraft before the first second and the next crash which was will be the pilot's fault.
You should be their PR guru....funny but true.Merry Christmas to you and all of the readers/posters on the forum.
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Old 24th Dec 2019, 19:10
  #234 (permalink)  
 
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Originally Posted by Water pilot View Post
Suggestions for the 3x5 card:
  • The Boeing 737 Max was a perfectly safe aircraft before the first crash, which was the pilot's fault.
  • The Boeing 737 Max was a perfectly safe aircraft before the first second crash, which was the pilot's fault.
  • The Boeing 737 Max was is a completely fixed and is now a perfectly safe aircraft before the first second and the next crash which was will be the pilot's fault.
Merry Christmas to you!
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Old 24th Dec 2019, 20:58
  #235 (permalink)  
 
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That is quite incredible. Now I really believe the MAX is doomed.

Merry Christmas to all!
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Old 24th Dec 2019, 23:39
  #236 (permalink)  
 
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Originally Posted by Water pilot View Post
Boeing plans to hand out "safety" cards to convince pax that Max is safe.



If you can you should look at the "Customer Journey and Scenario map" presented in the article. Aside from the explicit sexism (the concerned passenger is a "she" in all scenarios) it is rather fascinating. For instance, "if anxious passenger is posting, then airline social care team provides information on the safety of the MAX and informs the airlines network operations center of anxious passenger, which informs flight crew, as needed."

What will they do for the "anxious pilot?"
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Old 24th Dec 2019, 23:41
  #237 (permalink)  
 
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Originally Posted by Water pilot View Post
Suggestions for the 3x5 card:
  • The Boeing 737 Max was a perfectly safe aircraft before the first crash, which was the pilot's fault.
  • The Boeing 737 Max was a perfectly safe aircraft before the first second crash, which was the pilot's fault.
  • The Boeing 737 Max was is a completely fixed and is now a perfectly safe aircraft before the first second and the next crash which was will be the pilot's fault.
Wonder what they will put on the 3x5 cards for the FAA and EASA.
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Old 25th Dec 2019, 01:18
  #238 (permalink)  
 
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Extract AV week Dec 23 Page 12

From piece titled Boeing 737 Pilots Focus on Modified procedures


Critically, Boeing believed an uncommanded MCAS activation would be diagnosed quickly as runaway stabilizer and
be managed by following the appropriate checklist. When the Lion Air crew did not respond in this way, Boeing and
the FAA decided a reminder of the runaway stabilizer procedure would suffice while Boeing was taking a few months
to update the MCAS software.

But the March 10, 2019, crash of Ethiopian Airlines Flight 302 was linked quickly to the MCAS as well, leading to the grounding of the MAX -aircraft MAX fleet and a deeper examination of where Boeing and the FAA had gone wrong.

Among the many findings:

The complexity of the manual trim-wheel procedure, which applies to all 737s, was not well understood.

The new 737 training modules emphasize that pilots may need to use two hands to crank the wheel during a runaway trim scenario.
*** That means it takes BOTH PILOTS ***

It also says "unloading" the stabilizer—attempting to reduce airspeed and take the counterintuitive step of not pulling bark on the yoke even though the aircraft is trimmed nose down—may be necessary to move the trim wheel.

**** JEEEZZZZZZZ ****

Which also means you are in great position to Kiss your a** goodbye !!

Last edited by Grebe; 25th Dec 2019 at 01:20. Reason: formatting
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Old 25th Dec 2019, 02:05
  #239 (permalink)  
 
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The new 737 training modules emphasize that pilots may need to use two hands to crank the wheel during a runaway trim scenario.
*** That means it takes BOTH PILOTS ***
I am pretty sure both pilots will have TWO hands so my calculator says ONE pilot can wind the trim wheel.
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Old 25th Dec 2019, 02:16
  #240 (permalink)  
 
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Originally Posted by Grebe View Post
From piece titled Boeing 737 Pilots Focus on Modified procedures
I believe a similar issue existed/exists with the B727. But I think the only way to get there was a concocted situation in the simulator. But it is nice to know about. I never feared, wrenching or flying that bird.
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