Moderators: jsumali2, richierich, ua900, PanAm_DC10, hOMSaR

 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Oct 12, 2019 11:54 pm

morrisond wrote:
Even with MCAS you could stall the MAX if you really wanted too - just hold hold the trim button (which stops MCAS) and pull


This may be where a lot of the confusion regarding whether MCAS is a "stall prevention" system or not arises. Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane the pilot could still stall the airplane... WITHOUT HAVING TO INACTIVATE MCAS. Just pitch up to stall AoA and the aircraft stalls. All MCAS would be doing while this is going on is increasing control column forces in a linear manner to meet a regulation.

If anyone has Boeing, FAA, NTSB, EASA etc. documentation showing that this is not accurate then I definitely stand to be corrected and would be very interested in seeing it.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
chiad
Posts: 1324
Joined: Tue May 16, 2006 4:24 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Oct 12, 2019 11:57 pm

FlyBoeingAirbus wrote:
What are the risks that the ultimate solution for the MAX is not limited to a “software fix”, but will in fact require a “hardware fix”?


I've been thinking about that too, infact since the grounding started.
It sounds like a momoth task If every finished frame needs to actually go back to the factory to be upgraded along with every other frame in various stages of completion.
 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:23 am

aerolimani wrote:
hivue wrote:
morrisond wrote:
Even with MCAS you could stall the MAX if you really wanted too - just hold hold the trim button (which stops MCAS) and pull


This may be where a lot of the confusion regarding whether MCAS is a "stall prevention" system or not arises. Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane the pilot could still stall the airplane... WITHOUT HAVING TO INACTIVATE MCAS. Just pitch up to stall AoA and the aircraft stalls. All MCAS would be doing while this is going on is increasing control column forces in a linear manner to meet a regulation.

If anyone has Boeing, FAA, NTSB, EASA etc. documentation showing that this is not accurate then I definitely stand to be corrected and would be very interested in seeing it.

I'm pretty darned sure the crew in both crashes were pulling back as hard as they could on the yoke, and yet, the planes didn't rise to a stall. Instead, they torpedoed. With the authority MCAS 1 had, and the speed and frequency with which it acted, it doesn't sound like it would have let you stall the aircraft. MCAS 2, on the other hand…


You didn't read my post. I said "Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane..." I think we all can agree that in the cases of JT and ET -- given that MCAS activated unexpectedly (as well as secretly) due to other system failures -- stalling was the least of their concerns.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 5:59 am

hivue wrote:
aerolimani wrote:
hivue wrote:

This may be where a lot of the confusion regarding whether MCAS is a "stall prevention" system or not arises. Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane the pilot could still stall the airplane... WITHOUT HAVING TO INACTIVATE MCAS. Just pitch up to stall AoA and the aircraft stalls. All MCAS would be doing while this is going on is increasing control column forces in a linear manner to meet a regulation.

If anyone has Boeing, FAA, NTSB, EASA etc. documentation showing that this is not accurate then I definitely stand to be corrected and would be very interested in seeing it.

I'm pretty darned sure the crew in both crashes were pulling back as hard as they could on the yoke, and yet, the planes didn't rise to a stall. Instead, they torpedoed. With the authority MCAS 1 had, and the speed and frequency with which it acted, it doesn't sound like it would have let you stall the aircraft. MCAS 2, on the other hand…


You didn't read my post. I said "Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane..." I think we all can agree that in the cases of JT and ET -- given that MCAS activated unexpectedly (as well as secretly) due to other system failures -- stalling was the least of their concerns.

The MCAS system was designed to meet the criteria of a regulation entitled "Stall Characteristics." That regulation is there for non-FBW aircraft, so that it is not easy for a pilot to accidentally pull the plane into a stall. In other words, the regulation is to discourage stalling, and thus MCAS is to discourage stalling. This is not logistical gymnastics. The logical through-line is quite clear.

As to "activated properly," I think what you mean to say is "Should MCAS 1.0 have been programmed properly in the first place…"
 
FlyBoeingAirbus
Posts: 5
Joined: Sat Oct 12, 2019 12:43 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 6:58 am

VW kept on suggesting that a “software fix” would be enough to resolve the diesel exhaust scandal. In retrospect, VW management of course knew that the necessary adjustments also necessitated a “hardware fix”. But they probably came to the conclusion that it would be “cheaper” to pay the very high fines (Tens of Billions) rather than actually fix the problem. Question now is what will Boeing do? If indeed a “software fix” is enough, then this should be resolved within the next few weeks/months. But in case the answer is that both a “software and hardware fix” will be necessary, then it is imo unlikely (regardless of the costs) that the MAX can be “re-certified” before 2021 at the earliest. I feel sorry for the thousands of excellent engineers at Boeing who seem to be working under tremendous pressure to compromise their code of ethics for the benefit of senior managers whose prime concern seems to be shareholder value. Alas it would seem that the lessons learned by the VW scandal are being ignored by Boeing. The only difference being that as long as a car has a “software/hardware” issue, the passengers can easily park their car and step out safely. For the pilots and their passengers, it is a different story! All the more important that regulators all around the world keep up the pressure and all involved make sure that of the MAX were ever to fly again, it will be considered the safest of all planes.
 
spacecookie
Posts: 213
Joined: Sun Jun 07, 2015 3:57 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 8:03 am

FlyBoeingAirbus wrote:
VW kept on suggesting that a “software fix” would be enough to resolve the diesel exhaust scandal. In retrospect, VW management of course knew that the necessary adjustments also necessitated a “hardware fix”. But they probably came to the conclusion that it would be “cheaper” to pay the very high fines (Tens of Billions) rather than actually fix the problem. Question now is what will Boeing do? If indeed a “software fix” is enough, then this should be resolved within the next few weeks/months. But in case the answer is that both a “software and hardware fix” will be necessary, then it is imo unlikely (regardless of the costs) that the MAX can be “re-certified” before 2021 at the earliest. I feel sorry for the thousands of excellent engineers at Boeing who seem to be working under tremendous pressure to compromise their code of ethics for the benefit of senior managers whose prime concern seems to be shareholder value. Alas it would seem that the lessons learned by the VW scandal are being ignored by Boeing. The only difference being that as long as a car has a “software/hardware” issue, the passengers can easily park their car and step out safely. For the pilots and their passengers, it is a different story! All the more important that regulators all around the world keep up the pressure and all involved make sure that of the MAX were ever to fly again, it will be considered the safest of all planes.


Well you should use rather the Toyota example or the gm one there where people killed ... and they used the same principle you take in your example.
The 737 is grounded now for some time, what Worries me more is that the faa did not have a clue about what the hell they certified.
No one knows when the plane will be flying again and if it is 100% trustworthy.
On the top a lot of airline companies will use this to get great discounts. I think we can say that a clean sheet would have been cheaper for Boeing.
 
oschkosch
Posts: 589
Joined: Mon Oct 29, 2018 3:41 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 8:15 am

spacecookie wrote:
No one knows when the plane will be flying again and if it is 100% trustworthy.



Well according to what we have been told on a.net by many many posters, RTS in early 4th quarter is/was a piece of cake. But then again, you cannot have your cake and eat it too!
:stirthepot: :airplane: "This airplane is designed by clowns, who in turn are supervised by monkeys" :airplane: :stirthepot:
 
B777LRF
Posts: 2701
Joined: Sun Nov 02, 2008 4:23 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 8:45 am

Considering half of 'earlyQ4' is gone and Boeing have yet to submit anything* to the FAA, Dennis has a bit of explaining to do in the very near future-

* The often claimed myth on these pages Boeing submitted MCAS software in June/July is wrong. What they showed the FAA was a beta version, one which was based on fiddling with software only. It more than stands to reason that "solution" has been nixed, probably because several authorities baulked at accepting the notion this could be fixed via software only. The Max hardware will need a major revision, biggest stumbling block here are having the FCCs work in tandem (might require a 3rd FCC), having the equivalent level of redundancy achieved with 3 AoA sensors, possible introduction of EICAS and complete revision of check-lists and memory items.

My earlier prediction of Q4/2021 might yet prove to be overtly optimistic. At this point in time I'm starting to lean towards Boeing abandoning the entire program, as they come to the realisation it cannot be certified economically, and that any certification would mean loss of common type rating. The latter is the bedrock of the business case, and yanking that away will have profound implications.
Signature. You just read one.
 
rheinwaldner
Posts: 1863
Joined: Wed Jan 02, 2008 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 8:56 am

morrisond wrote:
aerolimani wrote:
It’s really hard to say a system is not designed to prevent or inhibit a stall, when the very regulation is was created to meet, is called “Stall Characteristics.” Perhaps all those media reports calling it a “stall prevention system” are not really so egregiously incorrect.


Even with MCAS you could stall the MAX if you really wanted too

Of course you could. Same with stick shaker. So are you saying, that the stick shaker does exist for another reason than to avoid stalls?

You can answer the question: approaching a stall, why is it important, that the control force stays constant? Correct, because otherwise pilots will end up in a stall.
Many things are difficult, all things are possible!
 
FlyBoeingAirbus
Posts: 5
Joined: Sat Oct 12, 2019 12:43 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 9:04 am

It used to be the case that when the FAA would give its “thumbs up”, legislators around the world would follow. But with some (or much) of the FAA’s credibility at stake following how the MAX was certified (and simply put the FAA was basically not taking MCAS into consideration), it is very questionable whether the MAX will be flying in any country anytime soon.

And here comes my question: How likely is it that the MAX, following a FAA “thumbs up”, would fly again ONLY in the USA pending further approval abroad (Europe, Asia, etc...)? (IMO very unlikely)
 
AirBoat
Posts: 60
Joined: Sun Jan 18, 2015 11:58 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 9:44 am

for mcas 1.0 working correctly, at high AOA the stick force would increase and the stabilizer would trim nose down. when AOA had reduced it was supposed to return to the previous trim setting.
One of the JATR comments was whether, when trimmed nose down, there was enough elevator authority to maintain level flight before the stabilizer got back to previous setting.(the mcas activation is reliant on AOA and not aircraft attitude, ie level or nose down)
 
Alfons
Posts: 310
Joined: Sun Feb 03, 2013 1:17 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 10:27 am

FlyBoeingAirbus wrote:
And here comes my question: How likely is it that the MAX, following a FAA “thumbs up”, would fly again ONLY in the USA pending further approval abroad (Europe, Asia, etc...)? (IMO very unlikely)


The question is, will the flying public step on an airplane, knowing that it's not certified as a safe plane by the rest of the world (95% of the planet).

USA has a very multi cultural population, with close and far families still living abroad. It hosts also a lot of multinational companies with HQ in the US or abroad, writing their own travel policies depending a risk assessment and insurance behaviour.

I believe that it's the end-user who will certify or not, the airplane as fit for making cash in the US, if FAA makes a solo attempt.
 
Delta777Jet
Posts: 1458
Joined: Tue Jun 13, 2000 6:19 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 12:40 pm

I am wondering why not more airlines cancelled their 737Max ! If I order 10 cars for my taxi business and the cars are known to be faulty and dangerous I would cancel them and order something else. I also would be worried that my passengers would refuse using a dangerous vehicle !
I still miss Trans World Airlines and the L-1011
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 12:42 pm

AirBoat wrote:
for mcas 1.0 working correctly, at high AOA the stick force would increase and the stabilizer would trim nose down. when AOA had reduced it was supposed to return to the previous trim setting.
One of the JATR comments was whether, when trimmed nose down, there was enough elevator authority to maintain level flight before the stabilizer got back to previous setting.(the mcas activation is reliant on AOA and not aircraft attitude, ie level or nose down)


MCAS does not incorporate a return to previous settings.
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 1:01 pm

mjoelnir wrote:
AirBoat wrote:
for mcas 1.0 working correctly, at high AOA the stick force would increase and the stabilizer would trim nose down. when AOA had reduced it was supposed to return to the previous trim setting.
One of the JATR comments was whether, when trimmed nose down, there was enough elevator authority to maintain level flight before the stabilizer got back to previous setting.(the mcas activation is reliant on AOA and not aircraft attitude, ie level or nose down)


MCAS does not incorporate a return to previous settings.

www.b737.org.uk/mcas.htm
'Technical Description of MCAS (Pre-Modifications)
MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance longitudinal stability characteristics with flaps UP and at elevated Angles of Attack (AoA). The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control Computer (FCC) using input data from sensors and other airplane systems.
The MCAS function becomes active when the AoA exceeds a threshold based on airspeed and altitude. MCAS will activate for up to 9.26 seconds before pausing for 5 seconds. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers (for the same AoA above the activation threshold).
After AoA falls below the hysteresis threshold (0.5 degrees below the activation angle), MCAS commands nose up stabilizer to return the aircraft to the trim state that existed before the MCAS activation.
The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.'


I understand the function still exists at V2.0, but there is an improvement to the logic. Quite what it is is not known.

'......….Furthermore the logic for MCAS to command a nose up stab trim to return to trim following pilot eletric trim intervention or exceeding the forward column cutout switch, will also now be improved.'

Ray
 
morrisond
Posts: 2729
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 1:02 pm

rheinwaldner wrote:
morrisond wrote:
aerolimani wrote:
It’s really hard to say a system is not designed to prevent or inhibit a stall, when the very regulation is was created to meet, is called “Stall Characteristics.” Perhaps all those media reports calling it a “stall prevention system” are not really so egregiously incorrect.


Even with MCAS you could stall the MAX if you really wanted too

Of course you could. Same with stick shaker. So are you saying, that the stick shaker does exist for another reason than to avoid stalls?

You can answer the question: approaching a stall, why is it important, that the control force stays constant? Correct, because otherwise pilots will end up in a stall.


Nice - taking a quote out of context. MCAS does not prevent stalls - it just helps you to know that you are approaching stalls. It's an added clue - along with the audio alarms that trigger before you get to even stick shaker.

It probably takes another good 20-30 seconds of effort after MCAS would trigger or the stick shaker would go off to actually stall the plane.

Transport category aircraft (or even Cessna's) aren't balanced on a knife edge where if you don't do everything perfectly and are inattentive for a split second you are in a stall. Even a stall isn't a death sentence - all aircraft are designed to be recoverable (although you really don't want to do one in a transport aircraft with people in the back) - and in fact the heavier more forward MAX engines would probably make it easier to recover as it pulls the nose down.

The stall characteristics are quite benign.

Here is a great video to watch. https://www.youtube.com/watch?v=zCJco59tqoQ

What pilot would miss all the clues in that video?

Tragically Boeing put about as much effort into MCAS where if it had been designed correctly would have improved safety. Almost 0.
 
Alfons
Posts: 310
Joined: Sun Feb 03, 2013 1:17 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 1:46 pm

Delta777Jet wrote:
I am wondering why not more airlines cancelled their 737Max ! If I order 10 cars for my taxi business and the cars are known to be faulty and dangerous I would cancel them and order something else. I also would be worried that my passengers would refuse using a dangerous vehicle !


You can not simply cancel after having signed purchase contracts, it's not a webhosting-30-day-money-back-guarantee product. The content of the contract, the federal laws of the country of juridiction set in the contract, your risk office, and your lawyer(s) will decide steps and pace, and orchestrate this phase. Furthermore, there are really just 2 manufactures worldwide, so you will try to do your steps wisely and future proof. There is always a "Restrisiko" (remaining risk) for a buyer.
 
asdf
Posts: 696
Joined: Tue Mar 18, 2014 12:03 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 1:47 pm

B777LRF wrote:
Having read the report, various summaries and not a few analysis the picture I'm getting looks as follows.

* The MCAS system is either a stall detection or stall preventions system, regardless of how Boeing labels it
* The 737 Max may exhibit aerodynamic qualities which makes it ineligible for certification under current rules, unless it's fitted with a stall prevention system
* The architecture of the 737 does not support the introduction of a stall prevention system
* Regardless of how fancy the MCAS software is, the 737 hardware does not provide a certifiable platform for such a solution
* The current system of check-lists and memory items is not up to the task
* Trimming of the horizontal stabiliser may have been certified under incorrect assumptions
* The way the aircraft presents failures and warning has not been reviewed as a whole, and may not be certifiable

Thus we're back at having the FCCs talk to each other, probably synthetic airspeed and AoA (in lieu of a 3rd AoA vane), a complete revision of cockpit procedures and check-list, possible EICAS integration as well as major revisions to the electrical trim and cut-out functions. All that to make the aircraft suitable for introduction of a MCAS system.

Small wonder Boeing kept this kludge under wraps, as the above changes would have made the entire Max proposition economically untenable. The ugly rear-mirror truth is, however, that Boeing may end up losing money on the Max program anyway AND having to spend untold billions developing a new narrow body family, all whilst enduring the most damaging effect on its brand ever, as well as that of it's national regulator.

It is, indeed, a deeply disturbing report.


very disturbing, but an excellent summary
and something many boeing technicans, managers und staff know till months if not years

so why do they still build those MAX models that have non to little chance of ever beeing used in flight operations?
the dream of the fix with a dirty software patch and a second AoA sensor is pretty much over guess

and they knew that this would happen as soon as the other regulators look into that case
did boeing believe that the FAA could enforce the other regulators to shut up and comply?

or do they really see a strategie in making to problem so big that it will push itself onto the agenda of the highest political level to safe the company ...?

i really have no clue which course they are on, now ...
maybe boeing dont no it neither
 
Agrajag
Posts: 128
Joined: Wed Mar 27, 2019 8:23 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 2:24 pm

Only the most blinkered Boeing apologist could read that report, understand it, then conclude 'nothing to see here, how about those poorly trained foreign pilots...'

I think this is a real Wizard of Oz style 'behind the curtain' moment. Nothing will ever be the same again in terms of trust in Boeing and the FAA.
The plural of anecdote is anecdotes, not data.
Slartibartfast had a point
 
User avatar
PW100
Posts: 4123
Joined: Mon Jan 28, 2002 9:17 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 2:42 pm

B777LRF wrote:
Considering half of 'earlyQ4' is gone and Boeing have yet to submit anything* to the FAA, Dennis has a bit of explaining to do in the very near future-

* The often claimed myth on these pages Boeing submitted MCAS software in June/July is wrong. What they showed the FAA was a beta version, one which was based on fiddling with software only. It more than stands to reason that "solution" has been nixed, probably because several authorities baulked at accepting the notion this could be fixed via software only. The Max hardware will need a major revision, biggest stumbling block here are having the FCCs work in tandem (might require a 3rd FCC), having the equivalent level of redundancy achieved with 3 AoA sensors, possible introduction of EICAS and complete revision of check-lists and memory items.


And all that stuff, if they get it right, still leaves a platform with insufficient natural stability margin without MCAS. At least, that is what the JATR report is hinting/suggesting. It basically says that MCAS is a stall protection system, or at minimum a stall identification system.
If so, then system requirements with respect to reliability and reduindancy (of this stall protection system) are probably way beyond software changes only.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
Kikko19
Posts: 681
Joined: Sat Apr 22, 2017 4:45 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 3:00 pm

Alfons wrote:
Delta777Jet wrote:
I am wondering why not more airlines cancelled their 737Max ! If I order 10 cars for my taxi business and the cars are known to be faulty and dangerous I would cancel them and order something else. I also would be worried that my passengers would refuse using a dangerous vehicle !


You can not simply cancel after having signed purchase contracts, it's not a webhosting-30-day-money-back-guarantee product. The content of the contract, the federal laws of the country of juridiction set in the contract, your risk office, and your lawyer(s) will decide steps and pace, and orchestrate this phase. Furthermore, there are really just 2 manufactures worldwide, so you will try to do your steps wisely and future proof. There is always a "Restrisiko" (remaining risk) for a buyer.

So if I purchase a car that has defects which eventually killed several people I cannot ask for a rescission of the contract and get a refund? an army of lawyers would love to see that contract and I guess you missed the millions of cars recalled far smaller defects.
 
User avatar
PW100
Posts: 4123
Joined: Mon Jan 28, 2002 9:17 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 3:02 pm

morrisond wrote:
MCAS does not prevent stalls - it just helps you to know that you are approaching stalls. It's an added clue - along with the audio alarms that trigger before you get to even stick shaker.

It probably takes another good 20-30 seconds of effort after MCAS would trigger or the stick shaker would go off to actually stall the plane.

Transport category aircraft (or even Cessna's) aren't balanced on a knife edge where if you don't do everything perfectly and are inattentive for a split second you are in a stall. Even a stall isn't a death sentence - all aircraft are designed to be recoverable (although you really don't want to do one in a transport aircraft with people in the back) - and in fact the heavier more forward MAX engines would probably make it easier to recover as it pulls the nose down.

The stall characteristics are quite benign.



The JATR has serious doubt with that position . . . :

JATR Final Report wrote:
Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment during the flight program WAS DUE TO UNACCEPTABLE STALL CHARACTERISTICS WITH STS ONLY. The possibility of a pitch-up tendency during approach to stall was identified for the flaps-up configuration prior to the implementation of MCAS.

Finding F3.5-C: The JATR team considers that the STS/MCAS and EFS functions could be considered as stall identification systems or stall protection systems, depending on the natural (unaugmented) stall characteristics of the aircraft.

Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation



So it is important to define the natural unaugmented stall characteristics during a flight test program. JATR states that this had not been performed satsifactory for the MAX, and even suggested that FAA did not notice during the certification flight test campaign that the (approach to) stall flight tests had in fact been augmented, when they should have been unaugmented:

JATR Final Report wrote:
Finding F3.4-A: The acceptability of the natural stalling characteristics of the aircraft should form the basis for the design and certification of augmentation functions such as EFS and STS (including MCAS) that are used in support of meeting 14 CFR part 25, subpart B requirements.

Finding F3.5-A: The nose-down pitch identified during Boeing flight tests for stall appears to the JATR team to be the product of system augmentation with flaps and gear up, and is likely due to stabilizer motion from the MCAS function.

Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation



We know from the Ky-files that EASA had requested for such test flights as early as 22 May. And we have no word yet that they had been performed under FAA and/or EASA supervision.

Wonder why Boeing needs so much time to set up a supervised (approach to) stall test flight . . .
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
Agrajag
Posts: 128
Joined: Wed Mar 27, 2019 8:23 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 3:23 pm

Even their own sim didnt replicate MCAS properly.
The plural of anecdote is anecdotes, not data.
Slartibartfast had a point
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 3:41 pm

PW100 wrote:
morrisond wrote:
MCAS does not prevent stalls - it just helps you to know that you are approaching stalls. It's an added clue - along with the audio alarms that trigger before you get to even stick shaker.

It probably takes another good 20-30 seconds of effort after MCAS would trigger or the stick shaker would go off to actually stall the plane.

Transport category aircraft (or even Cessna's) aren't balanced on a knife edge where if you don't do everything perfectly and are inattentive for a split second you are in a stall. Even a stall isn't a death sentence - all aircraft are designed to be recoverable (although you really don't want to do one in a transport aircraft with people in the back) - and in fact the heavier more forward MAX engines would probably make it easier to recover as it pulls the nose down.

The stall characteristics are quite benign.



The JATR has serious doubt with that position . . . :

JATR Final Report wrote:
Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment during the flight program WAS DUE TO UNACCEPTABLE STALL CHARACTERISTICS WITH STS ONLY. The possibility of a pitch-up tendency during approach to stall was identified for the flaps-up configuration prior to the implementation of MCAS.

Finding F3.5-C: The JATR team considers that the STS/MCAS and EFS functions could be considered as stall identification systems or stall protection systems, depending on the natural (unaugmented) stall characteristics of the aircraft.

Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation



So it is important to define the natural unaugmented stall characteristics during a flight test program. JATR states that this had not been performed satsifactory for the MAX, and even suggested that FAA did not notice during the certification flight test campaign that the (approach to) stall flight tests had in fact been augmented, when they should have been unaugmented:

JATR Final Report wrote:
Finding F3.4-A: The acceptability of the natural stalling characteristics of the aircraft should form the basis for the design and certification of augmentation functions such as EFS and STS (including MCAS) that are used in support of meeting 14 CFR part 25, subpart B requirements.

Finding F3.5-A: The nose-down pitch identified during Boeing flight tests for stall appears to the JATR team to be the product of system augmentation with flaps and gear up, and is likely due to stabilizer motion from the MCAS function.

Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation



We know from the Ky-files that EASA had requested for such test flights as early as 22 May. And we have no word yet that they had been performed under FAA and/or EASA supervision.

Wonder why Boeing needs so much time to set up a supervised (approach to) stall test flight . . .

Certification test flights will be performed with the submitted for certification configuration standard aircraft when it is so submitted.

Ray
 
ubeema
Posts: 410
Joined: Thu Aug 23, 2012 3:48 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:02 pm

Kikko19 wrote:
Alfons wrote:
Delta777Jet wrote:
I am wondering why not more airlines cancelled their 737Max ! If I order 10 cars for my taxi business and the cars are known to be faulty and dangerous I would cancel them and order something else. I also would be worried that my passengers would refuse using a dangerous vehicle !


You can not simply cancel after having signed purchase contracts, it's not a webhosting-30-day-money-back-guarantee product. The content of the contract, the federal laws of the country of juridiction set in the contract, your risk office, and your lawyer(s) will decide steps and pace, and orchestrate this phase. Furthermore, there are really just 2 manufactures worldwide, so you will try to do your steps wisely and future proof. There is always a "Restrisiko" (remaining risk) for a buyer.

So if I purchase a car that has defects which eventually killed several people I cannot ask for a rescission of the contract and get a refund? an army of lawyers would love to see that contract and I guess you missed the millions of cars recalled far smaller defects.

Kikko19 - 737 market is a duopoly. The point is even if you could cancel right away, you cannot just walk over to the next manufacturer and replace your acquisition frame by frame because there will be none available. You will have to get in line potentially no less than ~7 years (very generous) if one is looking to replace your MAX with similar equipment.
 
kayik
Posts: 116
Joined: Thu Mar 14, 2019 10:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:12 pm

Engine availability is the major bottleneck for aircraft production. If MAX project is abondoned, there will be lots of engines available. Other things you need are tooling and trained workforce. Doubling A320 production would not take much time IMO.
 
planecane
Posts: 1572
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:21 pm

kayik wrote:
Engine availability is the major bottleneck for aircraft production. If MAX project is abondoned, there will be lots of engines available. Other things you need are tooling and trained workforce. Doubling A320 production would not take much time IMO.

Really? Then why does it take Airbus or Boeing years to achieve a 10% or so increase in production rate under normal circumstances?
 
User avatar
PW100
Posts: 4123
Joined: Mon Jan 28, 2002 9:17 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:23 pm

XRAYretired wrote:
Certification test flights will be performed with the submitted for certification configuration standard aircraft when it is so submitted.

Ray


That could certainly be the case. But since the unaugmented stall characteristics may drive further (hardware) requirements, it would be good to satisfy this part of the recertification up front with the certification bodies. Especially since it doesn't need the revised software to do that.

That could then also be used as good PR, which Boeing can certainly use some of at the moment.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
User avatar
tistpaa727
Posts: 176
Joined: Sat May 05, 2007 5:23 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:34 pm

kayik wrote:
Engine availability is the major bottleneck for aircraft production. If MAX project is abondoned, there will be lots of engines available. Other things you need are tooling and trained workforce. Doubling A320 production would not take much time IMO.


The supply chain would argue your assertion. Aircraft parts have looooong lead times. The aerospace industry is make to order, not make to stock. You don't hold inventory (very expensive inventory at that) on the off chance Airbus or Boeing will ramp up production and most companies can't afford to tie that much working capital up.
Don't sweat the little things.
 
planecane
Posts: 1572
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:44 pm

PW100 wrote:
XRAYretired wrote:
Certification test flights will be performed with the submitted for certification configuration standard aircraft when it is so submitted.

Ray


That could certainly be the case. But since the unaugmented stall characteristics may drive further (hardware) requirements, it would be good to satisfy this part of the recertification up front with the certification bodies. Especially since it doesn't need the revised software to do that.

That could then also be used as good PR, which Boeing can certainly use some of at the moment.


Good PR doesn't do anything for them at this point. Either the worldwide regulators will approve the certification package and test flights once submitted or they won't. Boeing already knows how the MAX will perform without MCAS. I'm sure they have already informed the EASA of how it will perform. If the EASA has an issue with the expected performance, they would have already let Boeing know. The test flight is just to prove to the EASA that it really performs like Boeing says it does.
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:47 pm

PW100 wrote:
XRAYretired wrote:
Certification test flights will be performed with the submitted for certification configuration standard aircraft when it is so submitted.

Ray


That could certainly be the case. But since the unaugmented stall characteristics may drive further (hardware) requirements, it would be good to satisfy this part of the recertification up front with the certification bodies. Especially since it doesn't need the revised software to do that.

That could then also be used as good PR, which Boeing can certainly use some of at the moment.

It is the case. Are you suggesting that Boeing/FAA have conducted 700+ test flights and not covered the prime reason why MCAS existed in the first place? I can think of no reason why they would not cover the bases.

Ray
 
Kikko19
Posts: 681
Joined: Sat Apr 22, 2017 4:45 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:47 pm

ubeema wrote:
Kikko19 wrote:
Alfons wrote:

You can not simply cancel after having signed purchase contracts, it's not a webhosting-30-day-money-back-guarantee product. The content of the contract, the federal laws of the country of juridiction set in the contract, your risk office, and your lawyer(s) will decide steps and pace, and orchestrate this phase. Furthermore, there are really just 2 manufactures worldwide, so you will try to do your steps wisely and future proof. There is always a "Restrisiko" (remaining risk) for a buyer.

So if I purchase a car that has defects which eventually killed several people I cannot ask for a rescission of the contract and get a refund? an army of lawyers would love to see that contract and I guess you missed the millions of cars recalled far smaller defects.

Kikko19 - 737 market is a duopoly. The point is even if you could cancel right away, you cannot just walk over to the next manufacturer and replace your acquisition frame by frame because there will be none available. You will have to get in line potentially no less than ~7 years (very generous) if one is looking to replace your MAX with similar equipment.

I understand very well, I wish there would be more. but that doesn't justify to buy faulty planes.let's cross fingers that the 737 will be fixed for good, the c919 will fly and there will be a a225 soon (ok it's still airbus).the main thing is competition between airlines.
 
gregpodpl
Posts: 78
Joined: Fri Jan 04, 2013 3:49 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 4:56 pm

ubeema wrote:
Kikko19 - 737 market is a duopoly. The point is even if you could cancel right away, you cannot just walk over to the next manufacturer and replace your acquisition frame by frame because there will be none available. You will have to get in line potentially no less than ~7 years (very generous) if one is looking to replace your MAX with similar equipment.

Also your drivers and maintenance can't drive the A car - you have to spend more time and money on training and equipment.

Other though: I'm curious how long Airbus will stay quiet here if the grounding will get extended. If hardware changes will be required - and I think they should be - Max can be grounded till 2021. And at that point A can benefit - even with small production increase.
 
User avatar
Grizzly410
Posts: 420
Joined: Sun May 10, 2015 8:38 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 5:58 pm

kayik wrote:
Doubling A320 production would not take much time IMO.


Well, sorry but... LOL

Believe me or not, but "Airbus Single Aisle rate 85 in 2020" as an objective is something I heard circa 2015. It isn't ready to achieve yet, far from it.
FALs are one thing you can duplicate rather easily, but the whole supply chain is huge and very, VERY complex.

Even in an unbelievable situation making massive investment in the A320 line no risk, something like 737 line being closed right away, the A320 line would need 5 years MINIMUM to accelerate sufficiently to compensate... And it's far from sure Airbus decides to accelerate that much instead of cashing in more margin and keep the rate under control.
In order to be old and wise, one must first be young and dumb.
 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 6:08 pm

aerolimani wrote:
hivue wrote:
aerolimani wrote:
I'm pretty darned sure the crew in both crashes were pulling back as hard as they could on the yoke, and yet, the planes didn't rise to a stall. Instead, they torpedoed. With the authority MCAS 1 had, and the speed and frequency with which it acted, it doesn't sound like it would have let you stall the aircraft. MCAS 2, on the other hand…


You didn't read my post. I said "Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane..." I think we all can agree that in the cases of JT and ET -- given that MCAS activated unexpectedly (as well as secretly) due to other system failures -- stalling was the least of their concerns.

The MCAS system was designed to meet the criteria of a regulation entitled "Stall Characteristics." That regulation is there for non-FBW aircraft, so that it is not easy for a pilot to accidentally pull the plane into a stall. In other words, the regulation is to discourage stalling, and thus MCAS is to discourage stalling. This is not logistical gymnastics. The logical through-line is quite clear.

As to "activated properly," I think what you mean to say is "Should MCAS 1.0 have been programmed properly in the first place…"


Once again you did not read my post correctly. I did not say "activated properly" but rather "activated appropriately." When Boeing pilots were testing an appropriately activated MCAS 1.0 long before the JT and ET crashes, they could have stall-tested the airplane (and may very well have done so as an item on the test card) without having to deactivate MCAS. They could have done this because MCAS does not prevent stalls. I was simply responding to morrisond's post implying that MCAS had to have been deactivated before the airplane could be stalled.

I think this is a lot of the reason why this thread has been in a death spiral recently. People each have their own idée fixe regarding the crashes and they read others' posts through their personal convictions. This is why, e.g., posters who dare to point out that the JT and ET crews are likely to share some blame for the crashes get labeled as Boeing shills.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
B777LRF
Posts: 2701
Joined: Sun Nov 02, 2008 4:23 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 6:34 pm

hivue wrote:
...because MCAS does not prevent stalls..


Yeah, well, you see, right there is where the real brains of aviation seems to disagree with you. They're politely calling it either a stall prevention or - detection system, but to most observers the latter sounds a bit hollow. The former, however, resonates quite well with a system introducing massive amounts of downwards deflection on the most powerful control surface on the aircraft, resulting in a huge reduction of an AoA value it detected was getting close to stalling. Yes, the stick might have lightened too, but if it walks like duck, quacks like a duck and tastes like a duck, chances are we are indeed talking about a duck, and not just an 'avian species most commonly seen near watery areas or on someones dish'.

But if that's your take, have at it.
Signature. You just read one.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 7:17 pm

hivue wrote:
aerolimani wrote:
hivue wrote:

You didn't read my post. I said "Should MCAS 1.0 ever have activated appropriately in the circumstances it was designed for in the absence of any failures in the airplane..." I think we all can agree that in the cases of JT and ET -- given that MCAS activated unexpectedly (as well as secretly) due to other system failures -- stalling was the least of their concerns.

The MCAS system was designed to meet the criteria of a regulation entitled "Stall Characteristics." That regulation is there for non-FBW aircraft, so that it is not easy for a pilot to accidentally pull the plane into a stall. In other words, the regulation is to discourage stalling, and thus MCAS is to discourage stalling. This is not logistical gymnastics. The logical through-line is quite clear.

As to "activated properly," I think what you mean to say is "Should MCAS 1.0 have been programmed properly in the first place…"


Once again you did not read my post correctly. I did not say "activated properly" but rather "activated appropriately." When Boeing pilots were testing an appropriately activated MCAS 1.0 long before the JT and ET crashes, they could have stall-tested the airplane (and may very well have done so as an item on the test card) without having to deactivate MCAS. They could have done this because MCAS does not prevent stalls. I was simply responding to morrisond's post implying that MCAS had to have been deactivated before the airplane could be stalled.

I think this is a lot of the reason why this thread has been in a death spiral recently. People each have their own idée fixe regarding the crashes and they read others' posts through their personal convictions. This is why, e.g., posters who dare to point out that the JT and ET crews are likely to share some blame for the crashes get labeled as Boeing shills.

My apologies for misquoting you. However, I will say that morrisond may or may not be correct in their assessment. The JATR report suggests that the flight testing and certification process seems to have been quite flawed. So, who’s to say which version of MCAS was active when they flew the test flights? Was it before or after they increased its authority? We know how Boeing says MCAS was intended to operate, but it doesn’t seem to me that Boeing is to be trusted these days.

As to the Boeing shills comment… Supposedly, this is the grounding thread. Thus, pilot fault seems like something that should be a part of the accident threads and not this one. And yes, those threads are still open. Thus, pages and pages of pilot fault discussion comes across as rather a distraction from the root cause of the grounding, which one cannot deny is the design issues with the aircraft itself. If pilos need more training, you issue directives to that extent. So yeah, while the reports will (hopefully) enlighten us as the pilots’ roles in the crashes, when certain posters steer page after page of discussion in that direction, it does rather seem like they might have alterior motives, even if their motives are as “innocent” as zealous fandom.

That said, it does seem to be the moderators’ approach to now funnel any and all discussion, even remotely connected to the grounding, into this thread. Recently, there was an attempt to open a thread discussing the role of congress in relation to the FAA and its certification process. Even that one got rolled into this thread. Personally, I think more side discussion would be beneficial to the forum, overall.
 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 9:20 pm

B777LRF wrote:
Yeah, well, you see, right there is where the real brains of aviation seems to disagree with you.


That's interesting if correct. Please provide authoritative documentation from those brains stating that the MAX can't be stalled if MCAS is activated in the circumstances it was designed for and I'm converted. For now, if it doesn't look like a stall prevention system and doesn't walk like a stall prevention system and doesn't quack like a stall prevention system it's not a stall prevention system.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 9:39 pm

hivue wrote:
B777LRF wrote:
Yeah, well, you see, right there is where the real brains of aviation seems to disagree with you.


That's interesting if correct. Please provide authoritative documentation from those brains stating that the MAX can't be stalled if MCAS is activated in the circumstances it was designed for and I'm converted. For now, if it doesn't look like a stall prevention system and doesn't walk like a stall prevention system and doesn't quack like a stall prevention system it's not a stall prevention system.

How do you feel about the JATR’s alternate suggestion that it could be called a stall identification system? If you think that definition suits, then I would ask you why one needs to be able to identify a stall.
 
User avatar
par13del
Posts: 10337
Joined: Sun Dec 18, 2005 9:14 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 9:56 pm

aerolimani wrote:
How do you feel about the JATR’s alternate suggestion that it could be called a stall identification system? If you think that definition suits, then I would ask you why one needs to be able to identify a stall.

If MCAS identifies that a stall is on the way or is in progress what does the JATR participants say MCAS should be programmed to do, something that it is not doing now?
 
asdf
Posts: 696
Joined: Tue Mar 18, 2014 12:03 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 10:01 pm

XRAYretired wrote:
.....Are you suggesting that Boeing/FAA have conducted 700+ test flights and not covered the prime reason why MCAS existed in the first place? ....


as far as i understood it was 700 simulator flights

the told us that flight count three months ago
if they really would have flown those flights this would have been more than 5 flights a day, every day, even weekends beginning on the day after the ET crash
 
User avatar
AirlineCritic
Posts: 1765
Joined: Sat Mar 14, 2009 1:07 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 10:04 pm

Well, MCAS prevented those two airframes from stalling, ever again.

On a more serious note, the debate about stall prevent system or not seems a bit too much drama about naming things. We do know what the system does, how much does it matter what it is called. FWIW, I used to think that if the creators didn't want to label it as a stall prevention or even stall discouragement system, then we should not call it that. But, when EASA and JATR start to call it differently, I realized that maybe calling it more directly as something involved in stall avoidance would make sense. But again, too much drama about names, I guess because "stall" sounds more serious than "control feel".

By the way, there are a lot of debates on this thread about various things, and I'm getting a bit tired when individual posters (including myself perhaps) claim something that bigger groups of professionals dedicated to investigation or regulation have said otherwise. We might be a bit more humble than claiming our own idea is right, if an expert panel has said otherwise.
 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sun Oct 13, 2019 10:51 pm

aerolimani wrote:
How do you feel about the JATR’s alternate suggestion that it could be called a stall identification system?


I feel confused. Boeing implemented MCAS to operate in total secrecy so there is no possibility it could have identified an impending stall to a flight crew. But I take your meaning. If MCAS 1.0 were set up to alert the crew when it activated as anticipated with no failures in the airplane then that could be considered a form of impending stall identification. But the crew could still go ahead and stall the airplane.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 12:09 am

hivue wrote:
aerolimani wrote:
How do you feel about the JATR’s alternate suggestion that it could be called a stall identification system?


I feel confused. Boeing implemented MCAS to operate in total secrecy so there is no possibility it could have identified an impending stall to a flight crew. But I take your meaning. If MCAS 1.0 were set up to alert the crew when it activated as anticipated with no failures in the airplane then that could be considered a form of impending stall identification. But the crew could still go ahead and stall the airplane.

Have you read the reg which MCAS was designed to help the plane meet? Unless I am mistaken, the reg is written (and enforced, even for Boeing and the MAX) to ensure that pressure on the yoke/stick never decreases as you approach stall, because a lessening of pressure could encourage a pilot to pull back further, thinking that they must not be approaching a stall because the pressure has eased. A system, regardless of by what means, which keeps this pressure consistent, must therefore be there to discourage stalling. Now, how about a system which supposedly creates that pressure, but also coincidentally produces an aerodynamic result of encouraging the noise to point back down again?

My caveat here is that I am merely an interested party, with no formal education in the business of aircraft design and operation. So… if anybody else has a more complete or more correct understanding of the intention behind 14 CFR 25.203 - Stall characteristics, I would really welcome it. To date, I can’t recall anyone here tackling this question.

Downloads available here: https://www.govinfo.gov/app/details/CFR ... -sec25-203
 
User avatar
SheikhDjibouti
Posts: 2228
Joined: Sat Sep 30, 2017 4:59 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 1:04 am

asdf wrote:
XRAYretired wrote:
.....Are you suggesting that Boeing/FAA have conducted 700+ test flights and not covered the prime reason why MCAS existed in the first place? ....
as far as i understood it was 700 simulator flights

the told us that flight count three months ago
if they really would have flown those flights this would have been more than 5 flights a day, every day, even weekends beginning on the day after the ET crash

Excuse me if I am stating the obvious, but that is the beauty of simulators; you do not need to worry about waiting for the plane to be fuelled, waiting for pushback, taxying out to a runway, waiting for ATC clearance, etc, etc.
And yes, you could take off at midnight (PST) with the sim set for full daylight. So test "flights" could take place 7-days a week, around the clock.

Basically set it up for the parameters you want to investigate, and perform your test.
Then press the reset button, and within 60 seconds there you are performing another "test flight", Simples!

I cannot say for certain that is what is meant by their "700 test flights". Until I hear that they performed 700 (simulated) take-offs, 700 (simulated) landings, and spent 700 (…) hours in the simulator, actively flying the MAX (and that's just a minimum), I suggest there could be some doubts as to exactly what these 700 test flights amount to. I am not suggesting that 700 take-offs (& landings) are strictly necessary in this instance, but currently all we have is a number without any proper qualification.

Does anybody outside of Boeing have any actual details regarding the test flight program? No, I thought not.

p.s. Do I get a bonus prize for incorporating "MAX" and "minimum" into the same sentence? :twisted:
Nothing to see here; move along please.
 
hivue
Posts: 2077
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 2:32 am

aerolimani wrote:
Have you read the reg which MCAS was designed to help the plane meet?


My understanding is that it is this one --

https://www.law.cornell.edu/cfr/text/14/25.173

It has been mentioned in earlier MAX threads. Yes, I have read it.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 2:45 am

hivue wrote:
aerolimani wrote:
Have you read the reg which MCAS was designed to help the plane meet?


My understanding is that it is this one --

https://www.law.cornell.edu/cfr/text/14/25.173

It has been mentioned in earlier MAX threads. Yes, I have read it.

I am quite sure that is not the correct reg, and not the one which prompted the creation of MCAS. Unless we all have been grossly misinformed, the correct reg is 14 CFR 25.203 - Stall characteristics. Please refer to the appropriate document downloadable here, from the US government’s official source for documentation: https://www.govinfo.gov/app/details/CFR ... -sec25-203

Again, if anyone better informed can chime in with an interpretation of the precise intention behind this reg, I would really appreciate it.
 
2175301
Posts: 1866
Joined: Wed May 16, 2007 11:19 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 3:32 am

I believe that there is some confusion about what is really going on, and why the timetable has been extended to this point.

My understanding is that Boeing successfully tested MCAS version 2 in June as was ready to proceed with Return to Service based on the software changes done and tested at that point.

However, EASA and other regulators had other concerns and thus ran some other scenarios on the 737 Max... which included the 5 specific bit flip (from radiation) which caused a failure in a test flight.

Now, I speculate that the statistical odds of that specific 5 bit flip happening in real life is far rarer than what is required to certify an aircraft (odd of failure is too small); but, it was a way to "force" Boeing to address the 1960 computer structure to bring it to more modern concepts; which also provided the various regulators to dig and ask more questions...

Then Boeing had to redo the computer architecture so that you have 2 independent computers comparing values for many things. Overall, that is a net improvment in many ways... but took time and involved other new risks in changing software.

A few weeks ago it was announced that Boeing had identified another issue to be fixed. It is my understanding that this relates to the change in the overall computer software as part of the architecture change, and not MCAS (my source for that works for Boeing, just not specifically on the 737Max issue).

My understanding is that since June what has mostly been discussed with regulators involves the testing required to validate all the control computer changes... which just happens to have within it the new MCAS software, and this is not specifically for testing MCAS - although it will include some MCAS testing. Because of the full range of things controlled by these computers there is a lot more range on issues than just MCAS that the various international regulators can question and raise concerns on.

I do believe that they are approaching the end of it... It has been reported that EASA has not been able to communicate what is needed to address some concerns they have... That indicates to me that all the real known issues are resolved and they are trying to figure out how to better modernize an old grandfathered design. Not that their is any real issues with it (otherwise they could be clear on what those issues were and their requirements). My experience is that you can never answer all questions and concerns in a complex system. There is always "I'm not comfortable about something... but, see no obvious fix that is possible or realistic."

Both the NTSB and JATR reports have some great observations about how things were done and recommendations for change. There are ZERO requirements by anyone to implement any of those recommendations as part of Return To Service; nor have I heard of any Regulatory agency saying anything like that. Since they all were involved with the development and draft review of the report... there is nothing in there that they likely did not know a month or two ago.

Have a great day,
 
morrisond
Posts: 2729
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 3:41 am

aerolimani wrote:
hivue wrote:
aerolimani wrote:
How do you feel about the JATR’s alternate suggestion that it could be called a stall identification system?


I feel confused. Boeing implemented MCAS to operate in total secrecy so there is no possibility it could have identified an impending stall to a flight crew. But I take your meaning. If MCAS 1.0 were set up to alert the crew when it activated as anticipated with no failures in the airplane then that could be considered a form of impending stall identification. But the crew could still go ahead and stall the airplane.

Have you read the reg which MCAS was designed to help the plane meet? Unless I am mistaken, the reg is written (and enforced, even for Boeing and the MAX) to ensure that pressure on the yoke/stick never decreases as you approach stall, because a lessening of pressure could encourage a pilot to pull back further, thinking that they must not be approaching a stall because the pressure has eased. A system, regardless of by what means, which keeps this pressure consistent, must therefore be there to discourage stalling. Now, how about a system which supposedly creates that pressure, but also coincidentally produces an aerodynamic result of encouraging the noise to point back down again?

My caveat here is that I am merely an interested party, with no formal education in the business of aircraft design and operation. So… if anybody else has a more complete or more correct understanding of the intention behind 14 CFR 25.203 - Stall characteristics, I would really welcome it. To date, I can’t recall anyone here tackling this question.

Downloads available here: https://www.govinfo.gov/app/details/CFR ... -sec25-203


That's a pretty good description - in an ideal world the controls getting heavier are a further clue that maybe you are pulling too hard and it would help to keep away from actual stall but it's really far away from where it looks like MCAS triggers if you watch the Aviation Week video I linked too above that dangerous stall actually happens.

Its a good reg but I doubt that it will ever prevent a stall that causes loss of life in situations where the pressure just lessens vs going negative.

Remember on the MAX this is only when it's really light and at aft COG - that is not going to happen that often. And when the plane is that light all the thrust from those big fans will make it even harder to stall unless you are at a really high AOA - most likely way above normal operations.
 
morrisond
Posts: 2729
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Mon Oct 14, 2019 3:48 am

aerolimani wrote:
hivue wrote:
aerolimani wrote:
Have you read the reg which MCAS was designed to help the plane meet?


My understanding is that it is this one --

https://www.law.cornell.edu/cfr/text/14/25.173

It has been mentioned in earlier MAX threads. Yes, I have read it.

I am quite sure that is not the correct reg, and not the one which prompted the creation of MCAS. Unless we all have been grossly misinformed, the correct reg is 14 CFR 25.203 - Stall characteristics. Please refer to the appropriate document downloadable here, from the US government’s official source for documentation: https://www.govinfo.gov/app/details/CFR ... -sec25-203

Again, if anyone better informed can chime in with an interpretation of the precise intention behind this reg, I would really appreciate it.


I believe it was the 25.173 that was the one that was being discussed before as well and that was the one the MAX didn't meet.

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos