US administration blames foreign pilots for 737 Max crashes
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Just guessing here :
I believe that the changes to the wiring diagrams that resulted in having the column cutout switches (the ones hidden in the control columns) work effectively for autopilot and STS but be ineffective for the MCAS signals pushed towards having a single electric channel feeding the STAB motor with a single cutout switch.
And removing one of the two switches was not desirable for keeping the FCTMs of the Max and the NG as close as possible.
Solution : 2 switches wired in serie. One is labeled "main" and the other "backup".
I believe that the changes to the wiring diagrams that resulted in having the column cutout switches (the ones hidden in the control columns) work effectively for autopilot and STS but be ineffective for the MCAS signals pushed towards having a single electric channel feeding the STAB motor with a single cutout switch.
And removing one of the two switches was not desirable for keeping the FCTMs of the Max and the NG as close as possible.
Solution : 2 switches wired in serie. One is labeled "main" and the other "backup".
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https://www.wsj.com/articles/boeing-...et-11558439651
Boeing Official Played Down Scenario That May Have Doomed Ethiopian Jet
Talking to pilots, executive suggested sensor troubles could be nuisance rather than serious hazard
By Alison Sider and Andy Pasztor
Updated May 21, 2019 11:59 a.m. ET
Four weeks after faulty sensor data led a 737 MAX jet to crash in Indonesia last year, a high-ranking Boeing Co. BA 1.69% executive raised and dismissed the possibility of a bird collision triggering a similar sequence of events that could cause a second accident.
U.S. aviation authorities increasingly believe that a version of that scenario, described by Boeing executive Mike Sinnett at a November meeting with American Airlines pilots, may have led to the Ethiopian Airlines crash nearly four months later, according to officials familiar with the details. The crash happened after a sensor sent faulty data—possibly due to a bird strike—causing an automated flight-control system known as MCAS to misfire and repeatedly push the nose of the plane down.
At the meeting, Mr. Sinnett, vice president of product strategy, expressed confidence that well-trained pilots following established procedures could safely respond to a potential repeat of such equipment trouble, according to a recording of the meeting, which was reviewed by The Wall Street Journal. He also said he felt “absolutely” confident that heightened pilot awareness of potential dangers further reduced the chances of another accident.
Now, Ethiopian Airlines is pushing back against criticism of its pilots by complaining the plane maker didn’t do enough to warn them. The carrier suggests that Boeing’s failure to provide functioning cockpit alerts about problems with sensors made it more difficult for the Ethiopian crew to recognize the hazards they confronted before the second MAX accident in March.
The plane’s computers received erroneous data from a sensor known as an “angle of attack” or AOA vane about the pitch of the aircraft’s nose, activating a system that strongly pushed down the nose and ended in a fatal, high-speed dive.
“Although the pilots followed the procedures” spelled out by Boeing and U.S. safety regulators to counteract the automated commands, “none of the expected warnings appeared in the cockpit, which deprived the pilots of necessary and timely information,” Ethiopian Airlines said Friday.
Cockpit alerts such as a speed indicator and a stall warning called the “stick shaker”—which vibrates the pilot’s controls—did activate during the flight, according to a preliminary report issued by the Ethiopian government. But an indicator warning that the AOA sensors were out of sync didn’t go off, and excerpts from the cockpit voice recorder released as part of the preliminary report also indicate that despite those clues, it took the crew about five minutes to realize the AOA sensor problem.
U.S. aviation authorities regard a collision with one or more birds as the most likely reason for trouble with the sensor, according to industry and government officials familiar with the details of the crash investigation.
In his discussion with the American pilots months earlier, Mr. Sinnett raised the possibility of a bird hitting or damaging a sensor on a MAX jet shortly after takeoff. But he then appeared to play down the resulting risks, suggesting that pilots could quickly resolve such a situation and that the result of relying on what are called AOA alerts could be nothing more than the nuisance of flying back to the departure airport.
“The vast majority of AOA problems come from bird strikes after the airplane departs,“ Mr. Sinnett said. “You don’t want to have to return to base after a bird strike on an AOA vane.”
Ethiopian crash investigators said in a preliminary report that they “found no evidence of foreign-object damage” on the sensor. The point was reiterated last week in the airline’s statement, which specifically said no evidence of a bird strike has been found.
When birds hit such sensors, it is often difficult to find evidence conclusively proving that is what occurred.
U.S. government and industry safety experts, however, have said information downloaded from “black box” flight-data recorders points strongly to a sensor that was sheared off or otherwise rendered inoperable shortly after takeoff.
A Boeing spokesman declined to comment.
The October crash of the Lion Air jet in Indonesia and the Ethiopian crash in March took a total of 346 lives. The global fleet of 737 MAX aircraft has been grounded since shortly after the second crash.
Whatever caused the faulty data on the Ethiopian jet, Boeing has been on the defensive about its onboard alerting system. Alerts to inform pilots whether such sensors are transmitting incorrect data haven't been working on much of the global MAX fleet due to a software error stretching back to production, though they did function on American’s planes.
Despite the criticism of Boeing by Ethiopian Airlines, acting FAA chief Daniel Elwell last week said that the pilots of the Ethiopian jet didn’t fully adhere to required procedures. He also told a House aviation panel that the agency concluded working alerts “wouldn’t have changed either accident.”
Some pilots and safety experts disagree with his conclusion.
Write to Alison Sider at [email protected] and Andy Pasztor at [email protected]
Talking to pilots, executive suggested sensor troubles could be nuisance rather than serious hazard
By Alison Sider and Andy Pasztor
Updated May 21, 2019 11:59 a.m. ET
Four weeks after faulty sensor data led a 737 MAX jet to crash in Indonesia last year, a high-ranking Boeing Co. BA 1.69% executive raised and dismissed the possibility of a bird collision triggering a similar sequence of events that could cause a second accident.
U.S. aviation authorities increasingly believe that a version of that scenario, described by Boeing executive Mike Sinnett at a November meeting with American Airlines pilots, may have led to the Ethiopian Airlines crash nearly four months later, according to officials familiar with the details. The crash happened after a sensor sent faulty data—possibly due to a bird strike—causing an automated flight-control system known as MCAS to misfire and repeatedly push the nose of the plane down.
At the meeting, Mr. Sinnett, vice president of product strategy, expressed confidence that well-trained pilots following established procedures could safely respond to a potential repeat of such equipment trouble, according to a recording of the meeting, which was reviewed by The Wall Street Journal. He also said he felt “absolutely” confident that heightened pilot awareness of potential dangers further reduced the chances of another accident.
Now, Ethiopian Airlines is pushing back against criticism of its pilots by complaining the plane maker didn’t do enough to warn them. The carrier suggests that Boeing’s failure to provide functioning cockpit alerts about problems with sensors made it more difficult for the Ethiopian crew to recognize the hazards they confronted before the second MAX accident in March.
The plane’s computers received erroneous data from a sensor known as an “angle of attack” or AOA vane about the pitch of the aircraft’s nose, activating a system that strongly pushed down the nose and ended in a fatal, high-speed dive.
“Although the pilots followed the procedures” spelled out by Boeing and U.S. safety regulators to counteract the automated commands, “none of the expected warnings appeared in the cockpit, which deprived the pilots of necessary and timely information,” Ethiopian Airlines said Friday.
Cockpit alerts such as a speed indicator and a stall warning called the “stick shaker”—which vibrates the pilot’s controls—did activate during the flight, according to a preliminary report issued by the Ethiopian government. But an indicator warning that the AOA sensors were out of sync didn’t go off, and excerpts from the cockpit voice recorder released as part of the preliminary report also indicate that despite those clues, it took the crew about five minutes to realize the AOA sensor problem.
U.S. aviation authorities regard a collision with one or more birds as the most likely reason for trouble with the sensor, according to industry and government officials familiar with the details of the crash investigation.
In his discussion with the American pilots months earlier, Mr. Sinnett raised the possibility of a bird hitting or damaging a sensor on a MAX jet shortly after takeoff. But he then appeared to play down the resulting risks, suggesting that pilots could quickly resolve such a situation and that the result of relying on what are called AOA alerts could be nothing more than the nuisance of flying back to the departure airport.
“The vast majority of AOA problems come from bird strikes after the airplane departs,“ Mr. Sinnett said. “You don’t want to have to return to base after a bird strike on an AOA vane.”
Ethiopian crash investigators said in a preliminary report that they “found no evidence of foreign-object damage” on the sensor. The point was reiterated last week in the airline’s statement, which specifically said no evidence of a bird strike has been found.
When birds hit such sensors, it is often difficult to find evidence conclusively proving that is what occurred.
U.S. government and industry safety experts, however, have said information downloaded from “black box” flight-data recorders points strongly to a sensor that was sheared off or otherwise rendered inoperable shortly after takeoff.
A Boeing spokesman declined to comment.
The October crash of the Lion Air jet in Indonesia and the Ethiopian crash in March took a total of 346 lives. The global fleet of 737 MAX aircraft has been grounded since shortly after the second crash.
Whatever caused the faulty data on the Ethiopian jet, Boeing has been on the defensive about its onboard alerting system. Alerts to inform pilots whether such sensors are transmitting incorrect data haven't been working on much of the global MAX fleet due to a software error stretching back to production, though they did function on American’s planes.
Despite the criticism of Boeing by Ethiopian Airlines, acting FAA chief Daniel Elwell last week said that the pilots of the Ethiopian jet didn’t fully adhere to required procedures. He also told a House aviation panel that the agency concluded working alerts “wouldn’t have changed either accident.”
Some pilots and safety experts disagree with his conclusion.
Write to Alison Sider at [email protected] and Andy Pasztor at [email protected]
An alternative reason for an erroneous AoA signal; overview including assessment of vane failures - see discussion and comments.
https://www.satcom.guru/2019/03/regu...n-systems.html
The incident report as referenced above, indicating a complex and difficult fault to identify as an internal vane failure.
Note the multiple AoA interactions resulting in several system alerts; similar to the 737. The experienced crew (same as first event) elected to abort the takeoff - see sensible AAIB assessment of the decision, because of the uncertainty of multiple alerts.
http://www.smartcockpit.com/docs/Boe...On_Takeoff.pdf
https://www.satcom.guru/2019/03/regu...n-systems.html
The incident report as referenced above, indicating a complex and difficult fault to identify as an internal vane failure.
Note the multiple AoA interactions resulting in several system alerts; similar to the 737. The experienced crew (same as first event) elected to abort the takeoff - see sensible AAIB assessment of the decision, because of the uncertainty of multiple alerts.
http://www.smartcockpit.com/docs/Boe...On_Takeoff.pdf
You cannot replicate the startle effect with a warned crew.
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Originally Posted by LowObservable;
10475835]
I have to say I'm getting a little tired of this kind of superficial blather from people who, according to their claims of experience, ought to know better. It's a bit ridiculously obvious that the third pilot didn't have to busy himself with the other things going on in the cockpit, and could place the trimwheels in the center of his vision and focus on them for long enough to see what they were doing. The other two pilots could not do so, just like the accident crews.
10475835]
I have to say I'm getting a little tired of this kind of superficial blather from people who, according to their claims of experience, ought to know better. It's a bit ridiculously obvious that the third pilot didn't have to busy himself with the other things going on in the cockpit, and could place the trimwheels in the center of his vision and focus on them for long enough to see what they were doing. The other two pilots could not do so, just like the accident crews.
It really isn't possible to say whether or not the first Lion Air crew would have eventually found their way to the trim cutoff switches without the jumpseater's help. What we can say is that until that point, the crew was maintaining aircraft control by opposing the MCAS input. It should be noted that the Captain was initially flying this aircraft, but at some point handed it over to the First Officer. Both pilots demonstrated the ability to maintain aircraft control in spite of MCAS.
In the case of the second Lion Air flight & subsequent accident, initially the crew also maintained aircraft control by opposing the MCAS inputs. There is no official CVR transcript of the Lion Air accident flight, but there have been "leaks" that suggest that the Captain was initially flying and then turned over primary flying duties to the FO and then went "heads down" in the QRH to find an appropriate procedure. There is also a definite inflection point on the FDR data that shows a transition from the flying pilot successfully opposing MCAS to a situation where the opposing inputs are not large enough thus resulting in a greater and greater out of trim state. It is reasonable to speculate that this inflection point occurred when the Captain handed off control to the First Officer, and then didn't notice the FO losing the battle with the trim until it was too late.
In Ethiopian accident is that the Captain never really caught up with the trim even though he could have. Why that was the case is a bit of a mystery.
In summary, three out of five pilots who acted as the flying pilot demonstrated the capacity to maintain aircraft control with an erroneous MCAS input - the Captain and FO on the first Lion Air flight, and the Captain on the second Lion Air flight. Two pilots - the second Lion Air First Officer and the Ethiopian Captain did not.
The evidence strongly suggests that a majority of these non-Western trained pilots actually did have the required aviation skills to successfully oppose MCAS for a number of minutes of active flight and keep the plane aloft. Since they were able to do this for several minutes, there doesn’t seem to be a practical limit to how long they could have continued to do so. As a direct consequence, there is no compelling evidence that there was any “reaction time” required to solve the MCAS problem. Given significantly more time to work the problem, I think it is worth asking whether even a minimally proficient crew would have eventually worked out a solution to the errant MCAS inputs. Given enough time, it seems they would even have enough time to be phone patched right to Boeing.
Time was never a problem.
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It appears EASA has put their foot down pretty hard
Europe’s aviation safety agency has set out strict conditions before it will allow Boeing’s 737 Max aircraft back into the skies, in a sign of the depth of the rift emerging among global regulators after two deadly crashes.
EASA said it had three “pre-requisite conditions”, including demands that design changes by Boeing are approved by the European agency, before it would lift the grounding of the Max following the crashes in Ethiopia and Indonesia.
News of the conditions will heap further pressure on the US safety regulator, the Federal Aviation Administration (FAA), ahead of a meeting of global regulators in Texas on Thursday to review Boeing’s application to get the Max back in the air.
The conditions are: that any design changes by Boeing are EASA approved and mandated; that an additional independent design review being conducted by the agency is completed; and that Max flight crews “have been adequately trained”.
“We are working on having the 737 Max 8 return to service as soon as possible, but only once there is complete reassurance that it is safe,” a spokesman told the Financial Times.
Patrick Ky, EASA’s executive director, said in March the agency would make its own study of the Max’s safety and would not allow the plane to resume service until it was satisfied, irrespective of what the FAA decided.
https://www.irishtimes.com/business/...tors-1.3900462
EASA will also continue to analyse any new information that emerges about the two crashes in which 346 people died in Ethiopia in March and Indonesia in October.
The agency has communicated its conditions to both Boeing and the FAA, the spokesman added.
It is not unprecedented for EASA to conduct its own safety review, but it is unusual and underlines the splintering among regulators following the Max crashes.
Europe’s aviation safety agency has set out strict conditions before it will allow Boeing’s 737 Max aircraft back into the skies, in a sign of the depth of the rift emerging among global regulators after two deadly crashes.
EASA said it had three “pre-requisite conditions”, including demands that design changes by Boeing are approved by the European agency, before it would lift the grounding of the Max following the crashes in Ethiopia and Indonesia.
News of the conditions will heap further pressure on the US safety regulator, the Federal Aviation Administration (FAA), ahead of a meeting of global regulators in Texas on Thursday to review Boeing’s application to get the Max back in the air.
The conditions are: that any design changes by Boeing are EASA approved and mandated; that an additional independent design review being conducted by the agency is completed; and that Max flight crews “have been adequately trained”.
“We are working on having the 737 Max 8 return to service as soon as possible, but only once there is complete reassurance that it is safe,” a spokesman told the Financial Times.
Patrick Ky, EASA’s executive director, said in March the agency would make its own study of the Max’s safety and would not allow the plane to resume service until it was satisfied, irrespective of what the FAA decided.
https://www.irishtimes.com/business/...tors-1.3900462
EASA will also continue to analyse any new information that emerges about the two crashes in which 346 people died in Ethiopia in March and Indonesia in October.
The agency has communicated its conditions to both Boeing and the FAA, the spokesman added.
It is not unprecedented for EASA to conduct its own safety review, but it is unusual and underlines the splintering among regulators following the Max crashes.
SLF here, system engineer background...
I am still wondering why there are two cutout switches, renaming them from previous versions, removing the possibility of cutoff of automatics...
From a system design, i would question any engineer that feels the need to have two cutout (a primary and a back up) when the whole systems is based on a single input and a single actuator. The CB is already a back up of a failing cutout switch. The understanding of the reasons why such idiotic cut out system was designed is the basis to fully understand how the whole system was though... or NOT
I am still wondering why there are two cutout switches, renaming them from previous versions, removing the possibility of cutoff of automatics...
From a system design, i would question any engineer that feels the need to have two cutout (a primary and a back up) when the whole systems is based on a single input and a single actuator. The CB is already a back up of a failing cutout switch. The understanding of the reasons why such idiotic cut out system was designed is the basis to fully understand how the whole system was though... or NOT
1. because they tried to make the cockpit appear as similar to the previous versions as possible and
2. two switches in series are a big factor less likely to fail closed than one
Two birds with one stone...
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Ooops, there goes a few more months!
Looking forward to what comes out of tomorrows meeting.
Particularly from EASA, Canada MOT, Russia , Australia and China.
Oh and not to forget Indonesia and Ethiopian CAA.
Not able to post the next few days , so any links appreciated.
Regards
CptB
Looking forward to what comes out of tomorrows meeting.
Particularly from EASA, Canada MOT, Russia , Australia and China.
Oh and not to forget Indonesia and Ethiopian CAA.
Not able to post the next few days , so any links appreciated.
Regards
CptB
Lawsuit - Thugge v Boeing
Does not appear to have been posted on pprune.
Estate of one of the passengers on the Ethiopian aircraft and others v Boeing.
http://cdn.cnn.com/cnn/2019/images/0...e-v-boeing.pdf
84 pages. The full complaint. Civil Action No. 2:19-cv-01443-DCN
Highly critical of Boeing, as you would expect in a legal claim of this nature within an adversarial legal system. Relates the management of the rudder hardover events of decades ago and the management of the current MCAS issues for example. Makes for attention-getting reading.
I have not extracted any of it to post here since it seems that the document cannot be copied/pasted.
Estate of one of the passengers on the Ethiopian aircraft and others v Boeing.
http://cdn.cnn.com/cnn/2019/images/0...e-v-boeing.pdf
84 pages. The full complaint. Civil Action No. 2:19-cv-01443-DCN
Highly critical of Boeing, as you would expect in a legal claim of this nature within an adversarial legal system. Relates the management of the rudder hardover events of decades ago and the management of the current MCAS issues for example. Makes for attention-getting reading.
I have not extracted any of it to post here since it seems that the document cannot be copied/pasted.
Salute!
Yep, they are going after Boeing and could have a little jab at FAA, but mainly Boeing. We may finally get to hear from the "third pilot" when testimony is heard. Get the popcorn ready.
Always respected Mary, but I will be surprised if she is seen a lot on TV as the lawsuit is in progress. However, with present news and legal stuff going on in the U.S., we might still see her. Just seems she is jumping on too soon.
Gums sends...
Yep, they are going after Boeing and could have a little jab at FAA, but mainly Boeing. We may finally get to hear from the "third pilot" when testimony is heard. Get the popcorn ready.
Always respected Mary, but I will be surprised if she is seen a lot on TV as the lawsuit is in progress. However, with present news and legal stuff going on in the U.S., we might still see her. Just seems she is jumping on too soon.
Gums sends...
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jimjim1;
Thanks for posting the link to the Thugge v. Boeing lawsuit. As you said, it "makes for attention-getting reading. I'm all too familiar with the history of the B-737 rudder problems, and think that some of the points of the lawsuit are misleading at best; however, as you said, the U.S. legal system is, if nothing else, extremely adversarial in nature. I've looked at some information on the Montreal Convention which limits air carrier liability (in most cases), but doesn't specifically cover aircraft manufacturers. Is there an international treaty limiting the liability of aircraft manufacturers?
Cheers,
Grog
Thanks for posting the link to the Thugge v. Boeing lawsuit. As you said, it "makes for attention-getting reading. I'm all too familiar with the history of the B-737 rudder problems, and think that some of the points of the lawsuit are misleading at best; however, as you said, the U.S. legal system is, if nothing else, extremely adversarial in nature. I've looked at some information on the Montreal Convention which limits air carrier liability (in most cases), but doesn't specifically cover aircraft manufacturers. Is there an international treaty limiting the liability of aircraft manufacturers?
Cheers,
Grog
Psychophysiological entity
Back to the switches for a moment. The RH switch wiring shows a little more complexity than simply a series backup toggle. Bear in mind, a million posts back, someone said each switch was 'dual gang' - but even so, the toggle lever could just fail* Anyway two it is. If only . . . if ONLY, Boeing had said, Now, this is what MCAS is, and this is what it does, If you don't like it, the right hand switch will turn it off. Leave the left one on if the wheels have stopped spinning and you want to be able to use thumb trim. IF only.
As it is, the left one still cuts all power to the horizontal stabilizer motor/clutches - even if we'd dearly love our thumb trim switches to still work.
Remember, the column pull back (hidden) rear switch still allows MCAS. It's been rewired to the point one pundit described it as no longer being there on the MAX.
A CB in a crisis? Okay if it's pre-flagged in red and in reach. Don't want to be twisting our spines when all kinds of g forces are being applied to our bodies. And certainly don't need to be looking in books of instructions on how to fly a plane. FFS, resorting to check-lists before quick memory actions would be unconscionable. It is the most powerful flying surface and even I know how it works learning with one foot in the grave.
I have every understanding that the bizarre circumstances diminished the crew's abilities, sad, but many top guns on here have eventually admitted that they may well have not known what's going of for those first few minuets.
It's vital 'we' know how anything connected to that 47' 1" tail works . . . and what every relay does, and as I've said before, know the importance of system interactions - the hardest part of any course for me - and I'd come off an electronics workbench to fly.
*
As it is, the left one still cuts all power to the horizontal stabilizer motor/clutches - even if we'd dearly love our thumb trim switches to still work.
Remember, the column pull back (hidden) rear switch still allows MCAS. It's been rewired to the point one pundit described it as no longer being there on the MAX.
A CB in a crisis? Okay if it's pre-flagged in red and in reach. Don't want to be twisting our spines when all kinds of g forces are being applied to our bodies. And certainly don't need to be looking in books of instructions on how to fly a plane. FFS, resorting to check-lists before quick memory actions would be unconscionable. It is the most powerful flying surface and even I know how it works learning with one foot in the grave.
I have every understanding that the bizarre circumstances diminished the crew's abilities, sad, but many top guns on here have eventually admitted that they may well have not known what's going of for those first few minuets.
It's vital 'we' know how anything connected to that 47' 1" tail works . . . and what every relay does, and as I've said before, know the importance of system interactions - the hardest part of any course for me - and I'd come off an electronics workbench to fly.
*
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Back to the switches for a moment. The RH switch wiring shows a little more complexity than simply a series backup toggle. Bear in mind, a million posts back, someone said each switch was 'dual gang' - but even so, the toggle lever could just fail* Anyway two it is. If only . . . if ONLY, Boeing had said, Now, this is what MCAS is, and this is what it does, If you don't like it, the right hand switch will turn it off. Leave the left one on if the wheels have stopped spinning and you want to be able to use thumb trim. IF only.
As it is, the left one still cuts all power to the horizontal stabilizer motor/clutches - even if we'd dearly love our thumb trim switches to still work.
*
As it is, the left one still cuts all power to the horizontal stabilizer motor/clutches - even if we'd dearly love our thumb trim switches to still work.
*
I do not accept the justification that two in series provide a better fail mode in case one contact is stuck, fused, etc. If that would be a design concept all switches should have a back up, and thousands of earlier 737 are unsafe. IMHO either CB are the fail safe in case contacts are fused. One CB cuts 115 VAC and the other cuts 28 VDC.
It can also be noted that one contact from the LF switch provides a cut out signal to FCC, which seems that was not used by the SW, since the FDR traces show MCAS activation with switches in CUT OFF position.
Would be interesting to know the number of occurrences of fused contacts on those switches....
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It can also be noted that one contact from the LF switch provides a cut out signal to FCC, which seems that was not used by the SW, since the FDR traces show MCAS activation with switches in CUT OFF position.
Would be interesting to know the number of occurrences of fused contacts on those switches....
Would be interesting to know the number of occurrences of fused contacts on those switches....
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Ooops, there goes a few more months!
Looking forward to what comes out of tomorrows meeting.
Particularly from EASA, Canada MOT, Russia , Australia and China.
Oh and not to forget Indonesia and Ethiopian CAA.
Not able to post the next few days , so any links appreciated.
Regards
CptB
Looking forward to what comes out of tomorrows meeting.
Particularly from EASA, Canada MOT, Russia , Australia and China.
Oh and not to forget Indonesia and Ethiopian CAA.
Not able to post the next few days , so any links appreciated.
Regards
CptB
It hasn't been "MOT"since 1996.
DP Davies insisted on modifications to the B707 before it went onto the British register due to its marginal handling on 3 engines under certain conditions. I wonder if EASA will do something similar with the MCAS ? Expect the Chinese to be the most difficult of all given the ongoing trade dispute with the US.
DPD also required the fitting of a stick nudger on UK registered 747s. This was because, (I quote page 262) with the flaps up and a trim speed of 1.3Vs, after a small elevator force to start the speed reduction, the stick force falls to zero while the aeroplane quietly progresses all the way to the stall on its own. The fix was the nudger. This is a gentle stick force augmentor of about 16lbs in the nose down sense which operates when the stick shaker starts to operate and remains effective until the stick shake cancels. In a fairly rough and ready manner it restores the pre-stall longitudinal stability and satisfies the requirements at little cost and with no snags.
Since the very start of this whole debate on the 737MAX, I have always wondered why Boeing didn't try something similar rather than using the MCAS to drive the whole horizontal stabilser.
Since the very start of this whole debate on the 737MAX, I have always wondered why Boeing didn't try something similar rather than using the MCAS to drive the whole horizontal stabilser.
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The fix was the nudger. This is a gentle stick force augmentor of about 16lbs in the nose down sense which operates when the stick shaker starts to operate and remains effective until the stick shake cancels. In a fairly rough and ready manner it restores the pre-stall longitudinal stability and satisfies the requirements at little cost and with no snags.
Since the very start of this whole debate on the 737MAX, I have always wondered why Boeing didn't try something similar rather than using the MCAS to drive the whole horizontal stabilser.
Since the very start of this whole debate on the 737MAX, I have always wondered why Boeing didn't try something similar rather than using the MCAS to drive the whole horizontal stabilser.
Exactly what Boeing was wishing to avoid.
Is MCAS really about stick feel only? It's power got boosted over the planned force as if the nose must be brought down at any cost before stalling it.
What is the raw, non MCAS, stall behavior of the MAX 8? Anything nasty?
What is the raw, non MCAS, stall behavior of the MAX 8? Anything nasty?