Boeing 737 Max8 Aircraft Crashes and Investigations [Part 2] 44

[Alistair_Heaton]

This thread is a continuation of:

thread815-445840


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Another 737 max has crashed during departure in Ethiopia.

To note the data in the picture is intally ground 0 then when airborne is GPS altitude above MSL. The airport is extremely high.

The debris is extremely compact and the fuel burned, they reckon it was 400knts plus when it hit the ground.

Here is the radar24 data pulled from there local site.

It's already being discussed if was another AoA issue with the MCAS system for stall protection.

I will let you make your own conclusions.

 

[waross]

Hi SparWeb. I didn't mean to imply that there would be no more grandfathering, just that it may become more restrictive.
If TC and EASA move towards more restrictive grandfathering there will be a lot of pressure on the US industry and the FAA to follow.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[thebard3]

20 years of fine cameras and one bad model ended their camera business.

Yet somehow, GM survive the Vega.

Brad Waybright

It's all okay as long as it's okay.

 

[Lou Scannon]

waross, I wasn't taking issue with your post. But I think you missed my point. Any aircraft design can be crashed. Some will do it on their own, while others put up more of a fight. Ergo, the design plays a role in all crashes. In other words, a really good design needs a lot of serious contributing factors before it will crash.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[saikee119]

One can foresee Boeing’s future could hinge on how the technical argument develops. After the two fatal incidents the MCAS system in the 737 Max8 is now implicated as it can “create” or “generate” an accident. MCAS can automatically initiate an Aircraft Nose Down (AND) after the flap has been retracted and the Angle of Attack (AoA) sensor gives out an erroneous reading. If the pilot counteracts the AND with an Aircraft Nose Up (ANU) by manually trimming the stability the aircraft’s tail the MCAS could repeat itself to fight the pilot’s intervention. This in-fighting between human and an automatic system was recorded in detail in the Indonesian plane's blackbox for over two dozen times. The end result was MCAS could in each automatic trim swivel the horizontally tail further to increase its aerodynamic resistance until it become too difficult for the pilot to trim it back. MCAS won in both occasions and downed the planes.

Boeing could be criticized for not coming clean with what the MCAS could do to the plane and only issued the relevant information after the first accident . The doomed Indonesian plane in the previous fight had a similar tug of war between the pilot and the MCAS system but was stopped by a jump-seat pilot’s advice to switch off the MCAS by the cut off switch of the Stability Trim. The maintenance competency and the safety culture of the Indonesian carrier were criticized but the downed 737 Max8 plane was only 2.5 months old and has not had its minor and major check maintenance yet.

Unless other shortcomings come to light Boeing can claim 737 Max8 is safe as long as the pilot flips the cut out switch terminating the unwanted intervention of MCAS triggered by a defective AoA sensor. This argument will probably difficult to rebuff if Boeing does not patch the MCAS system. If Boeing finds it necessary to change the MCAS materially then it would be an admission of gilt for a bad if not unsafe design, would it not?

In any case would it be fair to a pilot to be ready in full combat mode to fight the MCAS system a few minutes after the plane leaves the ground when the flap is retracting to its home position, say in six minutes like the Ethiopian accident? No doubt the two Ethiopian pilots would be criticize not remembering by heart to flip the cut off switch mentioned in the FAA directives released after the Indonesian accident but would the flight carriers still buy the 737 Max8 after knowing its nasty MCAS system that claims to be a safe feature but in fact dangerous if not switched off in an event of a frequently occurred sensor error. No doubt if the senor is defective it got nothing to do with Boeing’s design or installation and most probably just a supply chain issue.

 

[itsmoked]

Nicely summed up saikee.

Repetitively played tug-of-war between the pilots and the MCAS with the MCAS cheating by having more authority available than the pilots.

Like a game of Monopoly with the banker having sticky fingers.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Alistair_Heaton]

If the solution is do nothing to the MCAS....

I know what the pilots solution will be....

Turn the electrical trim off for takeoff. And only turn back on with 10k worth of fresh air under your arse.

 

[itsmoked]

Yeah.

Sadly, I suspect this MCAS issue would never ever take another plane down. The problem is essentially solved now. (Though sketchy AoA sensors need to be eliminated.)

I'm sure right now the thinking of every last MAX pilot - everyone of them - is 'any hint of vertical irregularities' TURN OFF MCAS.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

I recently came across the story of QF72 (2008).

"The....Australian Transport Safety Bureau....finds incorrect data on measures such as airspeed and angle of attack (a critical parameter used to control an aircraft's pitch) was sent by one of the A330's three air-data computers – each of which has its own sensors on the fuselage – to other systems on the plane. One of the three flight control primary computers then reacted to the angle-of-attack data by commanding the plane to nosedive."

It's curious that the lessons are just not being learned. Some subtly-flawed logic remains in place as accepted design dogma, leading to unnecessary incidents.

Note also that this mentions triple redundancy. So the ultimate solution isn't that.

 

[Alistair_Heaton]

When I get home tonight I will find the accident report for that one. Then we can see what the engineering is and miss out the jorno crap.

Never done a type rating on a proper bus but I know they have 2-3 different flight laws. There are also a load of protection systems such as alpha floor.

The a330 does have 3 air data computers but only 2 AoA vanes according to my geeky plane spotting first officer.

 

[thebard3]

I just perused the report (it's long and I didn't read the whole thing yet). Section 2.6.1 'Role of software in safety-critical systems' gives a good summary of the accident and the associated risks that maybe contributed to the 737 MAX crashes too.

Brad Waybright

It's all okay as long as it's okay.

 

[Alistair_Heaton]

You got a link to so I don't have to go looking for it?

 

[RVAmeche]

I think this is it

QF72 Accident Report

 

[waross]

How about stepping back and looking at the overall picture.
I understand that the MCAS system was implemented to compensate for flight characteristics caused by the new engines.
Maybe the solution is to use higher landing gear and put the engines in a position that does not need MCAS.
MCAS may not be the only problem with the MAX8.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VEBill]

The A330 does have 3 air data computers but only 2 AoA vanes according to my geeky plane spotting first officer.

QF72 report (footnote 28, page 15): "There were three AOA sensors, three pitot probes and six static ports on the aircraft. There were only two TAT probes; one provided data direct to ADIRUs 1 and 3, the other provided data direct to ADIRU 2."

...the jorno crap...

That's a bit harsh. The linked article appears to quite reasonable.

Keep in mind that even an official investigation can sometimes be short-sighted (at first), requiring an interested party to push - in this example combined with luck in actually finding further physical evidence. e.g. UA 811

 

[saikee119]

MCAS may not be the only problem with the MAX8

May be but it is bad enough for some if

(1) The existence of MCAS was not communicated to the purchasers who bought the plane nor the pilots who flew the aircraft.
(2) MCAS was not part of the pilot’s operating manual for the plane.
(3) No MCAS training was ever planned for the pilots until the system started to kill everybody in the 737 Max plane.
(4) MCAS can take over the plane based on just one faulty senor’s erroneous signals to make the plane dose-dive. It can repeat itself if the pilot intervenes. It does not stop until the plane is destroyed. This is known to cause the first fatal accident. The second accident has remarkable similarities. The jackscrew found in the second crash site has been reported in the full nose-dive position. Ethiopian authority has indicated “to the best of their knowledge” the MCAS was in play for the brief duration of flight 302 from Addis Ababa
(5) The sudden take over by MCAS has been reported by American pilots too and aired in specially arranged channels.
(6) The logged/established MCAS malfunctions are (1) Indonesian plane flight immediately prior to the accident (stopped by a kill switch by a off duty pilot), (2) Indonesian doomed flight in Oct 2018 and (3) Ethiopian doomed flight in Mar 2019. Even the anonymous reports by the American pilots are totally ignored the fault frequency of MCAS is one should never be associated with commercial passenger flights.
(7) Unless the pilots remember and know how to activate the kill switch the MCAS system is so lethal that it could kick in so quickly during the take off to leave insufficient time for the pilot to return back to the airport. The first Indonesian and the second Ethiopian planes were crashed in 12 and 6 minutes respectively.

If the public were force the manufactuer's CEO to fly the 737 Max to show the safety of his plane I will bet my money that he would put his hand on the kill switch (Stab Trim cut off) before giving the pilot the green light to take off.

I am sure the intention of MCAS is good and the installation is essential to the operation of 737 Max but its implementation is now a laughing stock for the manufacturer. It would be revealing to see how much engineering has been compromised by the commercial interest in the coming investigations.

 

[Alistair_Heaton]

For all you prejudiced idiots who think 'simple' pilot incompetence killed 346 innocent people in the Lion Air and Ethiopian crashes, here is another captain who agrees with me:

Boeing (and many posters) say "Hey, it's just a trim runaway. Do the drill and all is good." But this is not the simple trim runaway that the QRH contemplates. It starts with a stall warning stick shaker shortly after lift off. Close to the ground this will, and should consume both pilots' undivided attention. After a number of seconds they realise that the airplane hasn't stalled and they start figuring out that they may have an airspeed and/or AOA problem.

This is a second problem to deal with on top of the first. And they can't shut the &%$#@ stick shaker off once they realise that it may be spurious. The PM will be frantically scanning the panel to try and find some clue what is going on. And this whole time, among the din of the stick shaker, the crew's concern for the airplane's flight path, and the confusing instrument indications, MCAS has been intermittently dialing in nose down trim. Not steadily, in a calm cockpit at altitude like the QRH contemplates.

But intermittently in the background of chaos, noise, and confusion. At some point, well past when it would have been timely, the task saturated PF realizes that the trim is working against him/her and the stab cutout switches get turned off. (hopefully). But the shitshow isn't over. Because of everything else going on, this took too long and the airplane is way out of trim. The Lion Air crew reportedly had 60 KG of back pressure on the yoke. Close to the ground, and relying on the lifting component of the underslung engines to help keep the nose up, the crew do not dare reduce power. Now the crew needs to manually trim the airplane, but the airplane is way, way off its trim speed. The B737 QRH makes reference to the large forces that may be required to break free a servo clutch:

"3 If needed: Use force to cause the disconnect clutch to disengage. Approximately 1/2 turn of the stabilizer trim wheel may be needed. Note: A maximum two-pilot effort on the trim wheels will not cause a cable or system failure."
Worse, the "Manual Stabilizer Trim" section of the Boeing FCTM talks about the air loads on a grossly out of trim stab requiring a speed change to reduce the force required to manually trim:
"Excessive air loads on the stabilizer may require effort by both pilots to correct mis-trim. In extreme cases it may be necessary to aerodynamically relieve the air loads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually."
Sweet Jesus how did this thing get certified?

A guy (or petite gal) has a 60 KG+ force on the yoke trying to stop the airplane from impaling itself into the hard ground just a few thousand feet below, and now he/she has to brute force trim the airplane as well, requiring involved coordination with the PM. Still with all the stick shakers, aural warnings, goofy instrument readings, and whatever else is happening to distract the crew and making communication almost impossible. It is not hard to see how quickly it becomes overwhelming. In addition to a fix for the airplane, if they keep the MCAS system (instead of designing a whole new wing or tail for the airplane), they will have to train the pilots who fly it to deal with its failure.

Right now, there is not a single Max pilot in the world who has been trained for this failure because - there isn't a single simulator in the world that can replicate it. But when they do, all those pilots that claimed "it's just a trim runaway" are going to have a very eye opening simulator session."

 

[Alistair_Heaton]

the above is from a 10k hour skipper on NG 737 and he is a yank

 

[zeusfaber]

Is there also a piece that says it's reasonable to anticipate a trim runaway if you've been fiddling with the trim, but otherwise, not? Or is that not true any more (or has it never really been true?)

A.

 

[saikee119]

The more I read about 737 Max and MCAS the more I am convinced of FAA culpable of the two disasters.

Alistair Heaton's suggestion, of the manufacturer's training of the pilots should be directed to coping with the failure of the MCAS, sounds like hitting the nail on its head. Who give the rat ass about the MCAS. The public needs the pilots trained to survive the events when the damn thing fails to work.

 

[waross]

Have I got this right?
The placement and the power of the new engines could cause unacceptable flight characteristics under some flight conditions.
It is during high power operation during climbs such as is common during take-offs that the unwanted flight characteristics are liable to occur.
MCAS was implemented to counteract this unwanted effect of the new engines.
Most pilots will be turning the MCAS system off during take-offs in the interests of safety and self preservation.
So, during the time when MCAS is most needed, it will in the future be turned off?
Maybe it's time to rethink the engine application.

We hear a lot about the expense of pilot retraining.
With a claimed 8% saving in fuel consumption, how many flights would it take to save the cost of retraining?

Bill
--------------------
"Why not the best?"
Jimmy Carter