Crash: Lion B38M near Jakarta on Oct 29th 2018, .....

The Aviation Herald ^ | Last Update: Saturday, Nov 24th 2018 22:46Z | Simon Hradecky

[the_daug]

On Nov 22nd 2018 the KNKT gave a presentation to Indonesia's Parliament about the findings so far. The KNKT told the parliament that the FDR contained 1790 parameters spanning 19 flights. The last two flights, the flight from Denpasar to Jakarta as well as the accident flight, were showing the same issue, the right hand speed (first officer's IAS) signficantly higher than the left hand speed (captain's speed). The captain's AoA indicated about 20 degrees higher than the first officer's AoA. As result the left stick shaker activated immediately after takeoff and operated, with a brief period where it stopped during a descent shortly after takeoff, continuosly throughout the flight. When the aircraft levelled off at 5000 feet automatic nose down trim inputs occurred which were countered by manual trim up inputs by the crew. The nose down trim inputs were created by the Maneouvering Characteristics Augmentation System (MCAS), a tool which will lower the nose of the aircraft to prevent a stall. Until the end of the flight the automatic nose down trim inputs were countered by manual nose up trim inputs by the crew. During the end of the recording the automatic nose down trim inputs increased, the pilots still trimmed nose up however shorter. Overall the stabilizer trim position moves increasingly towards nose down until it was no longer possible to counter the pitch down moment via the yoke. Throughout the flight there had been no problems with the engines. On the previous flight from Denpasar to Jakarta the same problem existed, the automatic trim inputs however did not occur. The crew must have done something preventing the MCAS system producing the nose down trim inputs. Following the presentation the KNKT released first information in Indonesian including some FDR graphics.

[SkyDancer]

Lots of speculation but we won’t know until the boxes are found and information retrieved.

[zipper]

This was not what is known as “runaway trim”. The MCAS worked exactly as it was supposed to, with tragic results, because of systems interactions (AOA vane on Captain’s side causing stick shaker and creating the condition causing the MCAS to intervene). MCAS is unique to the 737 Max — it isn’t on the 737 NG, classic, etc., and none of the world’s 737 Max crews have ever known about the existence of MCAS, until now.

If they had left the flaps down this would not have happened (no MCAS with flaps extended) as seen during the seconds following the initial stick shaker. But that’s a systems insight unknown to them since Boeing never told the operators about the existence of MCAS or its systems characteristics.

Additionally, the crew was likely confused by the intermittent nature of the (MCAS-induced) nose down trim — every time either pilot used nose-up yoke trim to counteract the nose-down trim, the MCAS cut out for about 5 seconds, then resumed nose-down for up to 10 seconds (or until interrupted by nose-up yoke trim again). This happened over a dozen times as the Captain flew the airplane, suppressing the symptoms of MCAS intervention, making the down-trimming actions insidious, probably until he handed over the controls to the first officer (who unfortunately didn’t interrupt the MCAS with opposite trim in a timely manner, resulting in further nose-down trim to the point of no return).

If the crew had activated the stab trim cutout switch it would have precluded MCAS activation — but until the flaps came up all they had was a stick shaker induced by the defective AOA vane, not MCAS activation, so their mindset was not focused on the trim at the time. Apparently the previous crew never experienced MCAS trim activation (perhaps the flaps were left extended).

This was an experienced crew with 6,000/5,000 hours for the Captain/First Officer, respectively. Perhaps if they had been better trained they would have tried using the Stab Trim Cutout switch, but like the crew of Air France 447, tragically the best remedy just wasn’t apparent to them given the sequence of events and the confusion.

Boeing is indeed culpable to a large degree, as we will see. They never told crews (or the airlines) about MCAS. There was no training at any airline associated with MCAS. They didn’t think it was important enough (and it’s worth noting: airlines want to keep training as short as possible since training costs money, requires instructor/simulator time, and means down time for crews vs. flying revenue trips). There will be consequences for Boeing.

[SkyDancer]

Good report. It’ll be interesting what the NTSB comes out with after the boxes are found. The NTSB works in cooperation with other nation’s flight accident investigators.

[ProtectOurFreedom]

"...none of the world’s 737 Max crews have ever known about the existence of MCAS, until now...[Boeing] never told crews (or the airlines) about MCAS. There was no training at any airline associated with MCAS."

Can that possibly be true? That doesn't sound remotely possible. How can a major new system affecting control be secretly installed and no airlines told about it or trained on it?

I'm ignorant on these things, but that just defies common sense.

[editor-surveyor]

.
Its not a “Major new system.”

Its an old system renamed.

Systron-Donner getting richer by the day.

All commercial airliners have been remotely controllable for a long time.

[zipper]

None of the commercial airline industry pilots — of course the test pilots employed by Boeing knew.

---

“We’re p*ss*d that Boeing didn’t tell the companies and the pilots didn’t get notice obviously, as well,” president of Southwest Airlines’ pilot union Capt. Jon Weaks said to the Wall Street Journal. “But what we need now is… to make sure there is nothing else Boeing has not told the companies or the pilots.”

https://thepointsguy.com/news/boeing-denies-withholding-737-max-info-from-airlines-after-lion-air-crash/

[zipper]

I think the digital flight data recorder was recovered on the 11th of November, some data has been published (see below). Last I read the cockpit voice recorder has not been recovered.

http://i.piccy.info/i9/f2d217f2acc4fd83123f933bec8f3634/1542986401/132644/1270057/lionair_b38m_pk_lqp_jakarta_181029_knkt_data_Page_07.jpg

[SkyDancer]

Waiting on the CVR to see what they were saying. Hopefully it wasn’t something like Aloha snack bar or something.

[ProtectOurFreedom]

Wow, that is an astonishing article. Of note:

"Boeing said...that the stall-prevention system is not mentioned to pilots in the aircraft flight manual because it didn’t think pilots would fly the plane in such a way that the automatic system would ever take over..."

Pilots for American Airlines and Southwest were told MCAS was installed “to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall.” Southwest also told its MAX pilots that in theory, they would never see the system kick in. "Since it operates in situations where the aircraft is under relatively high g load and near stall, a pilot should never see the operation of MCAS."

I started up power plants for a living and never once did we even THINK about telling the operators we were training that "you don't need to know about this system because we don't think you will ever operate the plant in a way that this system will ever take over."

[zipper]

Waiting on the CVR to see what they were saying. Hopefully it wasn’t something like Aloha snack bar or something.

When I heard about it that's the first thing that crossed my mind too -- recalling Egypt Air 990.

https://www.theatlantic.com/magazine/archive/2001/11/the-crash-of-egyptair-990/302332/

[zipper]

Here is the DFDR data from the investigation (PDF file), unfortunately the narrative is not in English, but the data graphs are labeled in English.

http://avherald.com/files/lionair_b38m_pk-lqp_jakarta_181029_knkt_data.pdf

[zipper]

Yes, agreed. The fact that Boeing released an emergency airworthiness directive that advises crews of potential problems with MCAS is testimony to how important this previously unknown (to pilots) safety enhancement is, and a tacit admission that it played a role in the Lionair crash.

After Air France 449 crashed in 2009 the aircraft manufacturers sought new ways to prevent losses of control of aircraft in flight. So did the operators, through simulator training of stall recovery recognition and techniques.

The 737 Max is the latest iteration of the workhorse 737 fleet (certified in 2017, first deliveries in 2017). It’s the first generation of the 737 to have MCAS.

In this case the enhancement actually contributed to a loss of control, to at least some degree because the crew was not aware of the stall prevention system characteristics.

There was a really good article in Popular Mechanics about Air France 447, well written but without too much technical jargon:

https://www.popularmechanics.com/flight/a3115/what-really-happened-aboard-air-france-447-6611877/

[zipper]

The video on this page is a little over a minute long — a good summary.

https://www.nbcnews.com/news/world/lion-air-crash-scenario-wasn-t-covered-boeing-737-max-n935521

[saywhatagain]

"Would have been darn hard to fly manually with the two AOA disagreeing by 20 degrees and a significant difference in airspeed left vs right. "

No not easy, but very much doable. The "standby attitude indicator" is mechanically driven.

From my reading of the preliminary report, omly the left side AoA was abnormal. But say both (left/right) are abnormal/inop flight crews revert to the standby attitude indicator. Fly it and live another day.

Its only hard if flight crews do not have a good "scan" (most do not, and it must be practiced).

Companies like Lion Air have training on using the standby attitude indicator in their training syllabus (its required for approval) but because of the "time" and subsequent cost to perform in the simulator, it gets skipped over, yet signed off by the instructor.

[saywhatagain]

Good video, and I fully agree with your previous statement, this abnormal is NOT a runaway trim. However . . . LoL

Pilots are trained for multiple types of runaway stab trim, high speed and low speed. Even without knowing about the MCAS, specially without knowing about the MCAS, the "indication" is that of a low speed runaway stab trim. Thats fundamental. (meaning nothing particular unusual, or standard practice).

All the whining and crying by American flight crews that Boeing did not tell them about the MCAS system (which is bad) is obscuring the fact that hey, your stab trim not doing what its suppose to do for whatever reason . . . shut off the Stab Cutout switches.

Reading that one report stating the first officer became PF (pilot flying) yet did not attempt to maually trim the airplane, says to me the flight crew stopped working together. Captain has to manage.

If my flight crew had brain-farted and forgot to check the stab trim cutout switches, OR more importantly the instrument transfer switches, I would expect the PNF Pilot not flying to assist in manually control the trim wheel.

Also another factor that is not being talked about, If I understand correctly, the Captain was a "Indian national," first officer Indonesian . . . meaning that for neither crew english is not their mother tongue. Yet to communicate to each other would require them to speak english. Just that fact alone puts them 3 steps behind in a abnormal situation such as this. If they ever recover the CVR and listen, am sure many will be shaking their heads with palm to the face.

[ProtectOurFreedom]

Good article eleven days ago in Leeham News: "Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots" by Bjorn Fehrm, November 14, 2018.

The background to Boeing’s 737 MAX automatic trim The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System. It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines.

The nacelles for the MAX are larger and placed higher and further forward of the wing, Figure 1.

Figure 1. Boeing 737NG (left) and MAX (right) nacelles compared. Source: Boeing 737 MAX brochure.

By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.

The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity (the line in Figure 2, around which the aircraft moves in pitch) will contribute to destabilize the aircraft in pitch.

Figure 2. The 737-800 (yellow) overlaid on the 737 MAX 8 (purple), with the line denoting the CG in pitch. Source: Leeham Co. and 737 ACAP.

The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft’s natural tendency to Dutch Roll = Wagging its tail).

Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described last week which assisted the pilot to exit the stall. But not in normal flight.

The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt.

The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings.

But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the manoeuvre has a high pitch ratio. The aircraft’s inertia can then provoke an over-swing into stall AOA.

To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.

It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.

It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.

How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.

They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.

[SkyDancer]

saved it for later. TNX!!

[zipper]

All the whining and crying by American flight crews that Boeing did not tell them about the MCAS system (which is bad) is obscuring the fact that hey, your stab trim not doing what its suppose to do for whatever reason . . . shut off the Stab Cutout switches.

"Runaway Trim" checklists are designed around an event of the trim running continuously in one direction or the other, with the yoke trim switch being mechanically jammed internally toward completing the circuit toward either direction. But this was not that scenario -- the trim was only moving intermittently because the MCAS can be interrupted by actuating the yoke trim in the opposite direction momentarily -- stopping the MCAS for a five second interval until it starts again for up to 10 seconds, unless it is again interrupted. That's what happened about 20 times as the crew struggled to analyze what was happening. That's why they went so long in near-level flight, until the MCAS finally actuated long enough to reach full down-trim (first officer had likely just taken control at that time during the last couple of cycles of the MCAS). And the runaway trim scenario taught in the simulator doesn't piggyback on top of a continuous stick-shaker indicating a stall -- that is a compound emergency not addressed in the simulator. The result is a lot of confusion in the cockpit (and maybe compounded, as you said, by cultural/language barriers). It's unfortunate that the crew didn't think of using the Stab Cutout switches, but given the intermittent nature of the MCAS-actuated trim, the fact that the manual trim could not override the MCAS (trim controlled by MCAS still moves opposite trim wheel manual movement), the compressed time factor, and the fact that one or both of them had to struggle to keep the nose up due to yoke forces, it isn't too much of a surprise that they didn't run a checklist that was perceived as secondary to the first problem they experienced with the stick shaker on climbout (and remember at first there was no MCAS activation during initial climbout since the flaps were still extended).

Pilots are right to be upset that Boeing kept this feature of the Max a secret, and Boeing will have to learn it's lesson the hard way. I doubt Boeing will get much sympathy from the public by blaming the crew or by blaming LionAir's training program.

OR more importantly the instrument transfer switches

Which instruments would have made a difference?

[ProtectOurFreedom]

Excellent description. Thanks for writing that.

Question...if they went through 20 on/off cycles of the the hor stab trim actuation by MCAS, why wouldn’t they have turned off the Stab Cutoff switches? They must have been exerting tremendous physical effort to pull back on the yoke as you say, but wouldn’t a serious pitch control problem like this have led them to cut off / disengage the hor stab drives?

[saywhatagain]

Agree with POF above, good description on your part zipper. Much appreciated.

Re: instrument transfer switch . . . you ask . . . Which instruments would have made a difference?

The report from Aviation Herald states . . .

"the right hand speed (first officer's IAS) significantly higher than the left hand speed (captain's speed). The captain's AoA indicated about 20 degrees higher than the first officer's AoA."

Considering each side of flight instruments are independent of each other, if the instrument transfer switch does not work, then we have a double AoA failure and or double computer failure (not likely) and so far I have not heard anyone is suggesting that nor apparently does the FDR indicate that was the issue. Of course with the AoA, by the book go immediately to the tie-breaker . . . the standby attitude indicator. Reading the report, says the left side, Captain wrong, so switch to first officer side.

Report only says first officer side airspeed "significantly higher" does not make it wrong. Captain airspeed could be wrong. Tie breaker for speed is "standby indicator" and/or set a known power setting and at least we are in the ball park.

You are correct in that a "low speed" runaway stab trim is continuous, but you have to admit it is slow and feels intermittent. However, I agree with ProtectOurFreedom regarding stab trim. . . . all the flight crew had to do is look down at the stab trim setting and see the Stab Trim position indicator is beyond the green band (normal).

Only lack of proper training would any crew just sit there and say say "oh wow" gee I just have to pull on the yoke harder. At least grab the dang trim handle and start cranking. (proper training, not instincts). If it rolls forward again, as it did, without knowing anything about MCAS, all I know is my stab trim is screwing me up. Pretty sure we don't need a book to tell us what to do.

I agree with you and we both understand the amount of confusion going on the flightdeck in those moments. The noise alone of the original auto-pilot aural warning, followed by the stick shaker and then of course the GPWS aural warning pull out pull out er I mean pull up pull up requires a level of mental discipline to remain focused.

I agree with you on "compound emergency" which I refer to as a single source failure effecting several systems resulting in a lot of confusion. Admittedly, I have seen experienced crews in real life fail to identify that a single source was causing multiple failures. In each event, the source of confusion could easily be traced back to inadequate training, including many cases, the failure to execute good CRM and manage the flight deck properly. With the noise, lack of proper communication, dealing with the "result" of an abnormal, not the cause (source), unable to prioritize and manage the flight deck properly, they literally flew the airplane into the ground.

Another issue (I have many more I issues that I could address LoL) One has to ask the question, were they surprised? Startle factor? And most folks would probably say yes. But that begs the question, why? Surely they saw the problem written in the aircraft log book twice. (Or did they?? If not why not??). Had they seen it written in the aircraft log book, surely they would have briefed themselves what actions they would take if the same event occurred again. Thats just basic threat error management.

The above and much more is why the finger is being pointed to Lion Air training program