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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 26th Mar 2019, 23:35
  #2581 (permalink)  
 
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Originally Posted by VicMel View Post
The AoA sensor was replaced possibly just as a hopeful guess. The assumption then seems to have been jumped on that as the MCAS uses AoA, the errant behaviour of MCAS must have been due to an AoA fault.
Nobody knew MCAS even existed. It & the need to use trim cutout to correct "STS running Backward" was not ever written up.

Last edited by BobM2; 26th Mar 2019 at 23:39. Reason: spelling
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Old 26th Mar 2019, 23:45
  #2582 (permalink)  
 
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nice to go into the simulator well prepped on what's happening reminds me of the sims they conducted to see if Sully could have made it back to the airport..startle factor missing, 40 seconds long gone..
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Old 26th Mar 2019, 23:57
  #2583 (permalink)  
tfx
 
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I was thinking Boeing and the FAA had been a bit slack here, but I am starting to change my mind. Clean stall, the back stick is supposed to increase all the way to the break. It doesn't in this airplane apparently because of nacelle lift. So they put a mouse in the system to drive the stab L.E. up at Vs plus a few knots to start to fly the airplane nose down so we have to pull that little bit harder. Fine. All this at low speeds - stick forces light and any runaway a non-event. Also they put it the FTM.

Now we have a situation where a dozy alpha vane sends spurious information to the mouse when hand flying it clean at say 240 knots. The airplane tends nose down in response, the pilot holds attitude in the normal fashion and trims the load out with the pickle switches. Back where we started. Five seconds later it does it again. At some stage the flying pilot or the support pilot or both are going to notice the trim wheel is running while the pilot is not trimming and follow the drill. Oppose the runaway, stop the wheel, and / or operate the stab trim cut-outs. (Is that right? - it is many years since I have been in a 737)

I don't see how it got away from them. There has to be more to it. I gather in both cases the stab trim jack has been found full scale stabilizer nose up. Unfortunately post-crash mechanical evidence is rarely relevant because everything changes during the break-up.

Be that as it may, we have two brand new, on the evidence to date perfectly flyable airplanes planted face first into the planet in broad daylight.

Either there is something the matter with the way Boeing and the FAA are doing things, or there is something the matter out here in the rest of the world. Something serious. MCL for instance raises it's hand immediately. Simulators are great training tools but you can't get hurt in one and those basic piloting defensive thought processes don't grow. The FAA is right to call for 1500 hours pre requisite for getting into an airliner cockpit. The rest of the world must follow that lead. We are going to have to toughen up. It has been made too easy. It is an airplane, not a sago pudding. It is not just a computer game, although many are selling that line. High time, I think for the regulators and operators world-wide to have a hard look at the way they are going about things.

It is them going to get the midnight phone calls.
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Old 27th Mar 2019, 00:07
  #2584 (permalink)  
 
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Several people have asked MCAS clarification questions in response to some of my recent posts. Rather than respond to them individually I offer the following as hopeful a fairly comprehensive description of the MCAS system that has been in the 737MAX fleet to date. Note that this does not reflect any of the changes about to be released. Hopefully Boeing will provide clear detail of those soon.

As always, if you still have questions after reading and trying to absorb the following please ask.

1. MCAS was designed to command airplane nose down stabilizer in response to high AOA up to an authority limit of 2.5 degrees for Mach less than 0.4 with lower authority at higher Mach numbers. If the pilot does not make any pitch trim commands, once AOA goes low MCAS will run the stabilizer in the airplane nose up direction back to the location from which it started.

2. MCAS is activated when all of the following are true:
a. Flaps are up
b. Autopilot is not engaged
c. Sensed AOA is above the MCAS activation AOA threshold

3. Once activated, MCAS will not command more than one increment of airplane nose down stabilizer motion until it has been reset. MCAS will be reset by either:
a. Pilot pitch trim command followed by a period of 5 consecutive seconds with no pilot pitch trim command.
- The assumption is made that pilot activation of pitch trim will be closely followed by continued pilot use of pitch trim to return the airplane to a column neutral pitch trim condition. MCAS seeing no further pilot pitch trim for a period of 5 seconds is interpreted as indication that the pilot has achieved column neutral pitch trim.
b. Return (by MCAS) of the stabilizer to its starting position per (1) above.
- Having returned the stabilizer to its pre-MCAS event starting point it is assumed that the airplane is back to a column neutral pitch trim condition.

4. Pilot pitch trim input at any time during the MCAS sequence as described in (1) above will stop MCAS stabilizer motion and end the current MCAS event while immediately moving the stabilizer in the direction of the pilot command.
a. If pilot pitch trim input is issued while MCAS is running the stabilizer airplane nose down, that motion will stop and the stabilizer will immediately move in the direction of the pilot command.
b. If pilot pitch trim input is issued while MCAS is running the stabilizer airplane nose up, that motion will stop and the stabilizer will move in the direction of the pilot command.
c. If pilot pitch trim input is issued after MCAS has completed its airplane nose down motion but prior to MCAS acting to take that motion out (as a result of return to low AOA), the stabilizer will immediately move in the direction of the pilot command.
d. It is assumed that the pilot issuing a pitch trim command is indication that the pilot is taking over the pitch trim task and will return the airplane to a column neutral pitch trim condition.


As a result of 1 through 4 above, given an AOA sensor that is failed so as to give an erroneously high reading (similar to what data appears to indicate occurred during the Lion Air accident flight), the following MCAS related scenarios can occur:

A. MCAS will activate (if flying manually) as soon as the flaps are retracted to up. Note that the stick shaker will have activated as soon as the airplane lifted off the ground regardless of the takeoff flap setting.

B. If the pilot does not make any pitch trim inputs, MCAS will run the stabilizer airplane nose down for one MCAS increment (as much as 2.5 degrees over approximately 10 seconds if Mach is less than 0.4). Without pilot pitch trim input, MCAS will not command further stabilizer motion in either direction. There is plenty of pitch control authority via the elevator using the column to counter the pitch disturbance generated by one MCAS increment of stabilizer motion.

C. If during or after the MCAS stabilizer motion per (A) above the pilot gives a pitch trim command the stabilizer will immediately start moving in the direction of the pilot command.
a. If the pilot pitch trim commands drive that stabilizer back to a column neutral pitch trim condition then the airplane will be back where it started from. In this event, provided sensed AOA is still high, MCAS will activate again once it sees a period of 5 seconds with not pilot pitch trim input. This process will repeat itself with the stabilizer never getting further than one MCAS increment out of trim. It appears that this sequence was repeated 20 or more times by the Lion Air accident flight pilot before he handed control over to his first officer.
b. If the pilot pitch trim commands are activated, but do not drive the stabilizer back to a column neutral pitch trim condition it is possible that successive activation of MCAS triggered by high AOA signal and ineffective pilot pitch trim inputs will lead to the stabilizer moving progressively further in the airplane nose down direction. It appears that this is what took place on the Lion Air accident airplane once the first officer took over control.


As for the reference in media reports this week regarding the crew’s need to intervene within 40 seconds of errant MCAS response to an AOA signal failed high, the following sequence of events would have to occur to so compromise pitch control power in that amount of time:
(a) The flight crew would have to allow a full increment of MCAS airplane nose down stabilizer motion to go in over 10 seconds without interrupting that motion via pilot pitch trim input.
(b) The flight crew would then have to have made a very short pitch trim command that triggered MCAS to reset, but did not re-establish anywhere near a column neutral pitch trim condition.
(c) After a 5 second pause wherein MCAS inferred that no more pilot pitch trim indicated the airplane was back to column neutral pitch trim, the flight crew would have to allow a second full increment of MCAS airplane nose down stabilizer motion to be inserted over another period of 10 seconds. Once again the crew would have to allow this stabilizer motion to go in without interruption via pilot pitch trim command.
(d) Once again, there would have be a repeat of (b) with a short, ineffective pilot pitch trim command.
(e) The final 10 seconds of this proposed 40 second sequence would be allowing another errant MCAS airplane nose down stabilizer motion increment to go in without interruption by pilot pitch trim command.

To summarize, getting in trouble over the course of just 40 seconds requires the crew to not trim when then should and make two very short, ineffective trim inputs following each of the first two MCAS stabilizer motion increments. This represents a worst case scenario.

Last edited by FCeng84; 27th Mar 2019 at 00:18. Reason: formatting
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Old 27th Mar 2019, 00:11
  #2585 (permalink)  
 
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I want to but can't read that, never heard of paragraphs ? or spacing sentences so it becomes legible ?
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Old 27th Mar 2019, 00:20
  #2586 (permalink)  
 
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Salute!
BobM2

The STS running backwards was from a photo or copy of an entry by the previous Lion crew. It was early in the Lion crash threads. And the lack of entering the shaker on the normal log or squawk book is obvious. And nothing about turning off power to the trim motor? Hmmmm....

What at would YOU do if you knew the previous flight had the shaker going on and manual trim was required because they had turned of trim motor power?

Gums asks...




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Old 27th Mar 2019, 00:26
  #2587 (permalink)  
 
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Originally Posted by tfx View Post
I was thinking Boeing and the FAA had been a bit slack here, but I am starting to change my mind. Clean stall, the back stick is supposed to increase all the way to the break. It doesn't in this airplane apparently because of nacelle lift. So they put a mouse in the system to drive the stab L.E. up at Vs plus a few knots to start to fly the airplane nose down so we have to pull that little bit harder. Fine. All this at low speeds - stick forces light and any runaway a non-event. Also they put it the FTM.

Now we have a situation where a dozy alpha vane sends spurious information to the mouse when hand flying it clean at say 240 knots. The airplane tends nose down in response, the pilot holds attitude in the normal fashion and trims the load out with the pickle switches. Back where we started. Five seconds later it does it again. At some stage the flying pilot or the support pilot or both are going to notice the trim wheel is running while the pilot is not trimming and follow the drill. Oppose the runaway, stop the wheel, and / or operate the stab trim cut-outs. (Is that right? - it is many years since I have been in a 737)

I don't see how it got away from them. There has to be more to it. I gather in both cases the stab trim jack has been found full scale stabilizer nose up. Unfortunately post-crash mechanical evidence is rarely relevant because everything changes during the break-up.

Be that as it may, we have two brand new, on the evidence to date perfectly flyable airplanes planted face first into the planet in broad daylight.

Either there is something the matter with the way Boeing and the FAA are doing things, or there is something the matter out here in the rest of the world. Something serious. MCL for instance raises it's hand immediately. Simulators are great training tools but you can't get hurt in one and those basic piloting defensive thought processes don't grow. The FAA is right to call for 1500 hours pre requisite for getting into an airliner cockpit. The rest of the world must follow that lead. We are going to have to toughen up. It has been made too easy. It is an airplane, not a sago pudding. It is not just a computer game, although many are selling that line. High time, I think for the regulators and operators world-wide to have a hard look at the way they are going about things.

It is them going to get the midnight phone calls.
I rather agree with you TFX, a previous LionAir crew recognised the root-cause of their problem and selected STAB TRIM CUTOFF switches to CUTOFF so the problem is far from dififcult to identify. Indeed they later took several other NNC measures that seem, on the face of it, to be rational and sensible. Thus they identified the threat, if not the cause which in this case is largely irrelevent. But what scares the crap out of me they soon selected the electric trim back on! That isn't the way of a professional crew. They soon selected it back off again, thank God, when the trim runaway re-occurred but then inexplicably continued the flight in manual control(no a/p) and manual trim with the stick shaker running continuously! These are fundamental aberrations of simply unbelieveable proportion in an ATPL and something no normal Professional pilot would consider doing for a moment. Lion Air's crew attitude and operating standards must surely take a massive hit from these shocking errors. It isn't good enough to hide behind the company's shameful, disgraceful shoulder-sloping repetition of the wet excuse that "nowhere in these checks did they say to land at the nearest suitable airport." As if an ATPL needs to be told that! That is a disgraceful way for a company with sloppy procedures to try to shift blame onto an implied fault in Boeing's manuals and demonstrates a company culture of either blissful unawareness or wilful disregard of normal Professional procedures, airm*****ip (Oh bugger! I nearly swore again!) I mean cheesy excuses for blind unthinking magenta-line following and no apparent command presence at all.

One has to wonder whether LionAir should have been let off the EU banned list so soon...

Boeing may have made errors in their systems design but the more I read the more I see how appallingly badly LionAir crews (and maintenance?) mishandled the accident flight and those that preceeded it whilst having all the means at hand to prevent the disaster.

The Ethiopan report, should it be open and transparent, will go a long way to corroborate or refute these remarks but I'm not holding my breath on either count.

Last edited by meleagertoo; 27th Mar 2019 at 12:12.
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Old 27th Mar 2019, 00:33
  #2588 (permalink)  
 
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Originally Posted by FCeng84 View Post
Note that this does not reflect any of the changes about to be released. Hopefully Boeing will provide clear detail of those soon.
I bet they WILL!
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Old 27th Mar 2019, 00:37
  #2589 (permalink)  
 
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Originally Posted by meleagertoo View Post
I rather agree with you TFX, a previous LionAir crew recognised the root-cause of their problem and selected STAB TRIM CUTOFF switches to CUTOFF so the problem is far from dififcult to identify. Indeed they later took several other NNC measures that seem, on the face of it, to be rational and sensible. Thus they identified the threat, if not the cause which in this case is largely irrelevent. But what scares the crap out of me they soon selected the electric trim back on! That isn't the way of a professional crew. They soon selected it back off again, thank God, when the trim runaway re-occurred but then inexplicably continued the flight in manual control(no a/p) and manual trim with the stick shaker running continuously! These are fundamental aberrations of simply unbelieveable proportion and something no normal Professional pilot would consider doing for a moment. Lion Air's crew attitude and operating standards must surely take a massive hit from these appalling errors. It isn't good enough to hide behind thecompany's shameful, disgraceful shoulder-sloping repetition of the wet excuse that "nowhere in these checks did they say to land at the nearest suitable airport." That is an utterlt disgraceful way for a company with sloppy procedures to try to shift blame onto Boeing's manuals and thus demonstrates a company culture of blissful unawareness of normal Professional procedures, airm*****ip (Oh bugger! I nearly swore again!) I mean cheesy excuses for blind unthinking magenta-line following and no apparent command presence at all.

One has to wonder whether LionAir should have been let off the EU banned list so soon...

Boeing may have made errors in their systems design but the more I read the more I see how appallingly badly LionAir crews mishandled the accident flight and those that preceeded it whilst having all the means at hand to prevent the disaster.
Your point is not lost. But I am drawn to the testimony given by an American (nationality, not airline) Max crew who, on their first flight, found that they did not understand the meaning of certain unique indications provided by the Max but flew anyway whilst they tried to find out what they meant from their company. That doesn't seem like solid airman-ship either to me.
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Old 27th Mar 2019, 01:47
  #2590 (permalink)  
 
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Originally Posted by gums View Post
Salute!
BobM2

The STS running backwards was from a photo or copy of an entry by the previous Lion crew. It was early in the Lion crash threads. And the lack of entering the shaker on the normal log or squawk book is obvious. And nothing about turning off power to the trim motor? Hmmmm....

What at would YOU do if you knew the previous flight had the shaker going on and manual trim was required because they had turned of trim motor power?

Gums asks...

The first question should be "what would maintenance have done?". Hopefully more than just resetting breakers & cleaning cannon plugs. Of course the airplane had been flying revenue trips for 3 days in an unairworthy condition with capt "unreliable airspeed & altitude". Were they flying that way in RVSM airspace? Maintenance that was done had only made it much more unairworthy with continuous stick shaker & "sts running backwards", but "just press on". Do they not get paid if they cancel a trip or was it a hot date waiting in Jakarta? Indonesia has one of the worst safety records & from the operation of this "airline" I can see why. Do they carry maintenance discrepancies to the next D-check in 20,000 hrs? Of course, it's easy to blame Boeing for not selling them an airplane that can fly safely with mounting unairworthy discrepancies for an indefinite time. Three days is not nearly enough.
What would I have done? On my airline, I would have sat comfortably in the crew room while someone more qualified made a maintenance test flight, since these write-ups involved serious control issues.
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Old 27th Mar 2019, 02:06
  #2591 (permalink)  
 
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Aviation Week Network: Boeing’s 767 Tankers Also Use Augmented Pitch System KC-46

Aviation Week Network: Boeing’s 767 Tankers Also Use Augmented Pitch System KC-46, March 25, 2019

Boeing’s 767 Tankers Also Use Augmented Pitch System KC-46, March 25, 2019

Steve Trimble | Aerospace Daily & Defense Report

Boeing’s 767-based tankers use a version of the pitch augmentation system that grounded the 737 Max 8 fleet, the manufacturer and U.S. Air Force officials say.

The disclosure provides a new data point in the unfolding story of how Boeing installed the Maneuvering Characteristics Augmentation System (MCAS) on the narrowbody airliner fleet.

Both the KC-767 and KC-46 fleets delivered to air forces in Italy, Japan and the U.S. rely on the MCAS to adjust for pitch trim changes during refueling operations.

In the 1980s, Boeing’s engineers considered using a pitch augmentation system for the commercial version of the 767, but dropped the idea after finding that vortex generators provided adequate control.

By 2011, Boeing had already delivered KC-767s to Italy and Japan fitted with the first version of MCAS. The use of the system then spread as Boeing won the Air Force’s KC-46 contract in February and launched the 737 Max 8 in August.

But Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.

The single-aisle airliner uses one angle of attack vane — either the captain’s or first officer’s — to generate the data used by the flight computer to activate the MCAS.

By comparison, the KC-767 and KC-46 are designed to use two sensor inputs to feed angle of attack data, Boeing says.

Boeing spokesmen declined to elaborate on which sensor inputs are used to provide the data in the tanker design. The options include multiple angle of attack vanes and flush-mounted static ports.

How the MCAS functions has come under the microscope since the March 10 crash of a 737-8 on Ethiopian Flight 302. It was preceded by a Lion Air 737-8 crash in October after an abrupt dive. Preliminary findings released by Indonesian investigators linked the Lion Air crash to erroneous data provided by angle of attack sensors. An Ethiopian airline official said preliminary information about the Ethiopian crash revealed similar control problems.

The U.S. Air Force has launched a review of flight procedures for the KC-46, a spokeswoman says.

'The USAF does not fly the models of aircraft involved in the recent accidents, but we are taking this opportunity to exercise due diligence by reviewing our procedures and training as part of our normal and ongoing review process,' she says.

Last edited by airman1900; 27th Mar 2019 at 02:12. Reason: Fixed quote
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Old 27th Mar 2019, 02:31
  #2592 (permalink)  
 
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Originally Posted by BobM2 View Post
The first question should be "what would maintenance have done?". Hopefully more than just resetting breakers & cleaning cannon plugs. Of course the airplane had been flying revenue trips for 3 days in an unairworthy condition with capt "unreliable airspeed & altitude". Were they flying that way in RVSM airspace? Maintenance that was done had only made it much more unairworthy with continuous stick shaker & "sts running backwards", but "just press on". Do they not get paid if they cancel a trip or was it a hot date waiting in Jakarta? Indonesia has one of the worst safety records & from the operation of this "airline" I can see why. Do they carry maintenance discrepancies to the next D-check in 20,000 hrs? Of course, it's easy to blame Boeing for not selling them an airplane that can fly safely with mounting unairworthy discrepancies for an indefinite time. Three days is not nearly enough.
What would I have done? On my airline, I would have sat comfortably in the crew room while someone more qualified made a maintenance test flight, since these write-ups involved serious control issues.
In many regulatory regimes, airlines can and will cancel flights and compensation to the crew, probably half way through a working day!
A commercial decision impacts pilots. Who could have ever thought that pilots would feel obligated to continue, haggle for make-up flying and probably also stress on the financial impact said cancellations create?

A mainline carrier in Australia has a very low minimum contract, paying the pilots for extra flying, that at whim is cancelled. Effectively remuneration can vary for roster to roster.
With personal debt levels very high, makes for a commercially compliant workforce.
Naturally the regulator in Australia sees zero conflict with such a strategy. The chairman likely a member of the invite only, Chairman's lounge.

Revolving doors between regulator and industry.
Regulatory capture.
Normalisation of deviance.

The 737 MAX a symptom of the place these roads lead.
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Old 27th Mar 2019, 02:47
  #2593 (permalink)  
 
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Boeing spokesmen declined to elaborate on which sensor inputs are used to provide the data in the tanker design
Did they tell the pilots?

This one statement shows what is wrong right now at Boeing. You can unintentionally kill more people with an airplane than almost any other technological device. Playing "need to know" games so that you can sell products into applications for which they may not be perfectly suited is unacceptable when so many lives are at stake. What possible harm comes from telling the journalist what they want to know? If the military system also relies on a single sensor, we should know that even if it is uncomfortable for Boeing. "We screwed up and we are going to fix it" is a perfectly acceptable engineering response to a problem, even if you get punished in the short term by the stock market.
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Old 27th Mar 2019, 03:16
  #2594 (permalink)  
 
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Water pilot

The article seems clear that the military B767 variants use two AOA inputs for MCAS, while the passenger B737 MAX only uses one.
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Old 27th Mar 2019, 03:17
  #2595 (permalink)  
 
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It appears Boeing 737 Max 8, B38M, will get a much longer rest in China...
..
China suspends airworthiness certificate for Boeing 737 Max jet

China suspended a so-called airworthiness certificate for Boeing Co's 737 Max jet, saying it needs to review a proposed modification before determining whether the plane is safe to fly after two recent crashes.

The move raises the possibility of the Max being kept out of China's skies should authorities there deem a fix for software linked to the disasters inadequate.

The decision was taken in light of uncertainty surrounding the model and an anti-stall system that's the focus of a probe into the loss of an Ethiopian Airlines plane on March 10, according to the Civil Aviation Administration of China.

It will be reviewed once Boeing has detailed the changes, the body said...
---------
.

China not taking Boeing 737 MAX 8 airworthiness certificate applications

China’s civil aviation regulator has stopped taking applications for Boeing’s 737 Max 8 airworthiness certification since March 21, an official at the regulator’s news department said on Tuesday.

China was the first to ground the newest version of Boeing’s workhorse 737 model earlier this month following a deadly Ethiopian Airlines crash, prompting a series of regulatory actions by other governments worldwide....

Earlier on Tuesday, financial magazine Caijing reported that the Civil Aviation Administration of China (CAAC) had suspended certification for Boeing 737 MAX 8 aircraft, citing an internal document issued on March 21....

It took Boeing 15 months to get the airworthiness certification for the aircraft from CAAC, which it obtained in October 2017, Caijing said, citing industry insiders.

Boeing did not immediately respond to a Reuters request for comment.
===========





Sources:
- https://www.straitstimes.com/asia/ea...ng-737-max-jet
- https://in.reuters.com/article/ethio...-idINKCN1R71CN

Last edited by patplan; 27th Mar 2019 at 03:24. Reason: format corrections
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Old 27th Mar 2019, 03:20
  #2596 (permalink)  
 
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Levels of automation

Originally Posted by FCeng84 View Post


Please indulge my adding a few comments. Today’s commercial aviation has embraced use of automation to enable optimization for performance. This has led to configurations that do not have certifiable handling characteristics without at least a minimum level of computer augmentation. On these airplanes there is no way for pilots to select complete manual. The higher level automation provided for workload relief can be turned off but not the lowest level of automation required to provide acceptable handling qualities.
I am glad to see this topic being broached. The present incident has in common with other LOC incidents the feature that the crew is faced with an all of nothing situation. Continue to rely on automation which may exacerbate a bad situation, or choosing to go manual which may be a time consuming and unfamiliar transition in a situation where time is of the essence. This is akin (worse) that a car driver having to disable power steering and brakes because of a malfunctioning cruise control. Surely there should be a lower level of automation the pilot could revert to but still giving him/her power assistance with the control surfaces, and some degree of automatic recovery, while bypassing higher level problems. This lower level should involve only the most basic, reliable components. Does Airbus do this already?
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Old 27th Mar 2019, 03:49
  #2597 (permalink)  
 
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The AoA measurement vane with the calibration and usefulness, is not a science but an art. To rely on the AoA measurement, especially on a DEP climb (forget if there is a turn) to be able to determine if the ac is near stall is simply voodoo engineering.

Some enlightened reading would be on the calibration, latency, and overall algorithms created to try to make some use of the readings. The AOA readings must be coupled with airspeed, weight, flaps settings, and winds aloft.

Front landing gear doors open, sideslip, vertical winds, and of course, banked turns...all render the readings useless without an algorithm.

Last algorithm went from 0.5 degrees to 2.5 degrees to make it work....and we see how that went.

Add yet another algorithm that they 'think' might work. (but didnt they already do that?)

Last edited by Smythe; 27th Mar 2019 at 04:02.
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Old 27th Mar 2019, 05:16
  #2598 (permalink)  
 
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I think someone mentioned that if the runaway trim wasn't dealt with within 40 seconds then there was basically no way back. Is this correct? It may not explain why the crews let the problem get away from them, but it would explain why perfectly capable aircraft flew into the ground or water.

Edmund
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Old 27th Mar 2019, 05:31
  #2599 (permalink)  
 
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Here is a thought perhaps worth repeating. A while back, pilots had the idea they were the last link in the safety chain, and someone else’s accident was a gift you could not turn away from, especially if it was fairly recent and an airplane you were flying. You only had to ask yourself two questions. First, what can I do to keep that from happening to me, and second, what else can I do to keep that from happening to me? There is more to it no doubt, as we will see when the facts are all out.
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Old 27th Mar 2019, 06:40
  #2600 (permalink)  
 
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Originally Posted by Smythe View Post
The AoA measurement vane with the calibration and usefulness, is not a science but an art. To rely on the AoA measurement, especially on a DEP climb (forget if there is a turn) to be able to determine if the ac is near stall is simply voodoo engineering.

Some enlightened reading would be on the calibration, latency, and overall algorithms created to try to make some use of the readings. The AOA readings must be coupled with airspeed, weight, flaps settings, and winds aloft.

Front landing gear doors open, sideslip, vertical winds, and of course, banked turns...all render the readings useless without an algorithm.

Last algorithm went from 0.5 degrees to 2.5 degrees to make it work....and we see how that went.

Add yet another algorithm that they 'think' might work. (but didnt they already do that?)
I think that you are nearer the mark than most other posts. I am still seeing posts that A/P should be engaged to overcome trim runaway (contrary to Boeing revised OP). Currently, all there is to go on is the Lion Air FDR. However, there are material differences between the "previous flight" and the doomed flight data. It would appear that issues are far more complicated than it may first appear. At the heart of the issues are the algorithms that process the AoA and computed air speed. The doomed flight had stick shaker on take-off rotation unlike the previous flight (stick shaker started at an altitude about 400ft). The published data does not include all the parameters available.

It is not known how the MCAS system actually works. Obviously, somebody at Boeing knows precisely how it works, but they are not going to be posting on PPRuNe any time soon. The real info will be supplied by depositions. The contributions here, are educated guesses based on the limited information available. Even so, it seems that the Preliminary Report into Lion Air may have been too casual about the potential risks. Boeing may have been to casual about the risks. There are some obvious defects in the MCAS system, even from the scant information available. Those defects may be complicated or exacerbated by the changes to the aircraft's flight characteristics in the MAX design. In short, Boeing will have a lot of explaining to do to restore confidence.
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