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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 26th Mar 2019, 05:41
  #2541 (permalink)  
 
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Finally we may get some answers.

Data released.
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Old 26th Mar 2019, 06:37
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Originally Posted by Capt Kremin
Finally we may get some answers.

Data released.
It hasn't been released. It has been shared with the other participants to the investigation, as stipulated by ICAO Annex 13.

It also won't speed up the public release of the data, because only the Ethiopian agency leading the investigation can do that.


Bernd
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Old 26th Mar 2019, 07:53
  #2543 (permalink)  
 
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Originally Posted by Capt Kremin
The CEO of the airline that had the accident has a massive conflict of interest and shouldn't be allowed to have any part in the publication of a report apart from supplying information to the Investigators.
The same is true for any party that has hide in the game. That would be Boeing and the FAA, both face FBI criminal investigation so far.

I think Ethopian airlines did wan’t to make sure that nobody tampers with the evidence, so they took the FDR and CVR for read out to the BEA. You can be sure that Boeing, FAA and NTSB was notified early on the data since they have persons at the BEA for this investigation. So far we have heard nothing to the contrary that lots of similarities exist between the Lion air and Ethopian air accident. If it was a completely different cause Boeing would have spread long rumours, since they have the most hide in the game and loose money by the millions a day. Both were almost brand new airplanes so maintainance issues are not that likely.
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Old 26th Mar 2019, 08:23
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Um...EDLB, have you seen the posts on the maintenance records on the Lion Air flight? The media pile-on on Boeing may not work out the way people think.
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Old 26th Mar 2019, 08:46
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Originally Posted by George Glass
Um...EDLB, have you seen the posts on the maintenance records on the Lion Air flight? The media pile-on on Boeing may not work out the way people think.
Yes I have. The plane was not airworthy and they tried with cleaning connectors and changing one AoA vane. But the problem was still there and the last crew did not use the trim cutout switches. Which still leaves open, what was the cause.
With that up to now unknown failure the overwhelming MCAS trim authority came to light.

And a few month later the next MAX stuck in the ground with similar erratic altitude pattern.
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Old 26th Mar 2019, 09:53
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Originally Posted by yanrair
Yes indeed. I have seen such commentary. It is premature and totally unproven. What I have said, I think, is that a runaway STAB whether continuous or intermittent (stop/start but always nose down) is containable - from a purely piloting / mechanical / aerodynamic point of view. If it is noticed it can be stopped. STAB OFF switches.
That is a fact, and it happened the day before. And of course the recent Boeing simulator sessions with line pilots at Seattle showed that they all stopped it. But of course, they knew what to expect, didn't they. But they were 737-max airline pilots and not Boeing test pilots.
Y
Purley from an investigative point of view and not as a pilot. If the prev flight used the stab cut out switches who and when would they be returned to the normal setting? Would a record of this switch change be made?

If they had been reset by maintenace or the pilots of the final flight might this not have been a clie something else was going on?

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Old 26th Mar 2019, 12:40
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EDLB, #2572
You could consider alternative explanations. Consider that the problem was not directly apparent to maintenance, only the electronic tag that there had been a fault - see #2552.
The systems were were reset and tested, the aircraft was serviceable.
Even after an AoA probe change the aircraft systems still indicated fully serviceable.

Would the software view - ‘bits’, check sum error (?), A to D conversation (?), apply to the following:-

Why the AoA value failed high - both Lion flights, Ethiopian assumed based on outcome.

That the offset could be reset with aircraft power-down, or WoW alternate switching, or Maintenance system self-test (explanations for having the maintenance log recording a fault, but none clearly identifiable by engineers or flight crew before the next flight.)

Would such a ‘failure’ be a random, probabilistic occurrence - just chance, or require an external disturbance - elect spike (FDR AoA error seen during taxi - generator switching? Lion FDRs indeterminate, Ethiopian unknown.)
Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

Add to the above; why apparently did the fault only apply to the left side (wait for Ethiopian FDR) - also ref reset, WoW alternating, maint tests, in the questions above,
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Old 26th Mar 2019, 13:15
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The 40-second which could've made or broken the Lion Air PK-LQP...
..
In Test of Boeing Jet, Pilots Had 40 Seconds to Fix Error

March 25, 2019
During flight simulations recreating the problems with the doomed Lion Air plane, pilots discovered that they had less than 40 seconds to override an automated system on Boeing's new jets and avert disaster.

The pilots tested a crisis situation similar to what investigators suspect went wrong in the Lion Air crash in Indonesia last fall. In the tests, a single sensor failed, triggering software designed to help prevent a stall.

Once that happened, the pilots had just moments to disengage the system and avoid an unrecoverable nose dive of the Boeing 737 Max, according to two people involved in the testing in recent days. Although the investigations are continuing, the automated system, known as MCAS, is a focus of authorities trying to determine what went wrong in the Lion Air disaster in October and the Ethiopian Airlines crash of the same Boeing model this month.

The software, as originally designed and explained, left little room for error. Those involved in the testing hadn't fully understood just how powerful the system was until they flew the plane on a 737 Max simulator, according to the two people.

Compounding the flaws, pilots received limited training about the system before the first crash. During the final minutes, the captain of the Lion Air flight flipped through a technical manual trying to figure out what was happening.

In a tacit acknowledgment of the system's problems, Boeing is expected to propose a software update that would give pilots more control over the system and make it less likely to trigger erroneously, according to three people, who spoke on the condition of anonymity to describe the private meetings.

There are common procedures in place to counteract MCAS, as currently designed. If the system starts pushing the plane's nose down, pilots can reverse the movement via a switch at their thumb, a typical reaction in that situation. In doing so, they can potentially extend the 40-second window, giving them more time to avoid a crash.

To fully neutralize the system, pilots would need to flip two more switches. That would shut off the electricity to a motor that allows the system to push the plane toward the ground. Then the pilots would need to crank a wheel to correct whatever problems had emerged.

The pilots, in the simulations, followed such procedures to successfully shut off the system and land safely. But they did so with a far better understanding of how it worked and prior knowledge that it would be triggered -- benefits that the pilots of the fatal 737 Max crashes did not have.

If pilots don't act hastily enough, attempts to disable the system can be too late. In the Lion Air crash, pilots used the thumb switch more than two dozen times to try to override the system. The system kept engaging nonetheless, most likely because of bad readings from a sensor, until the plane crashed into the Java Sea, killing all 189 people on board.

John Cox, an aviation safety consultant and a former 737 pilot, said pilots are highly likely to use the thumb switch to extend the 40-second window to several minutes. But that may still not be enough time to diagnose and solve the problem, especially if the pilots, like the Lion Air crew, were not informed of the system.

"There is a limited window to solve this problem, and this crew didn't even know that this system existed," he said......

In the current design, the system engages for 10 seconds at a time, with five-second pauses in between. Under conditions similar to the Lion Air flight, three engagements over just 40 seconds, including pauses, would send the plane into an unrecoverable dive, the two people involved in the testing said.

That conclusion agreed with a separate analysis by the American Airlines pilots' union, which examined available data about the system, said Michael Michaelis, the union's top safety official.

One of the people involved in the training said MCAS was surprisingly powerful once tested in the simulator. Another person found the system controllable because it was expected. Before the Lion Air crash, Boeing and regulators agreed that pilots didn't need to be alerted to the new system, and training was minimal.

At least some of the simulator flights happened on Saturday in Renton, Wash., where the 737 Max is built. Pilots from five airlines - American, United, Southwest, Copa and Fly Dubai - took turns testing how the Max would have responded with the software running as it was originally written, and with the updated version, known as 12.1.....
==========
For the full article:
- https://www.nytimes.com/2019/03/25/b...ion-error.html

Last edited by patplan; 26th Mar 2019 at 13:27.
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Old 26th Mar 2019, 14:28
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Salute!

Great article, pat.
The 40 secind scenario appears to be simply allowing the MCAS to act without the crew using the trim switches. Eventually, unless power is reduced, the aero forces on the elevator and the awesome column forces required will not permit a recovery. And who wants to pull power back just after gear up? ( although I did for my LEF episode as I was light and could easily fly at 200 knots - it was the old " doing O.K. now, so don't change anything" procedure that lets you live to be old and grey) I also feel most of the 737 folks here would have used the trim switches for a time before treating the problem as a FUBAR trim system and then turning off the power as the previous flight crew did.

The MCAS mod should be interesting and provide a feast of fodder here on pPrune, huh?

Gums sends...
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Old 26th Mar 2019, 14:45
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Seattle Times article

https://www.seattletimes.com/busines...cation-process
Boeing has 737 MAX software fix ready for airlines as DOT launches new scrutiny of entire FAA certification process
March 25, 2019 at 1:22 pm Updated March 25, 2019 at 4:46 pm


Dominic Gates By Dominic Gates
Seattle Times aerospace reporter

Flight tests are likely to begin this week on the proposed software fix for Boeing’s 737 MAX flight control system, and the company has invited airlines to order it pending formal approval from the Federal Aviation Administration (FAA).

Boeing said Monday it is finalizing the proposed update. Some airline pilots flew 737 simulators with the updated system software in Renton on Saturday.

Company spokesman Gordon Johndroe said the MAX software fix will be offered to airlines “free of charge” and will be released only after it is certified by the FAA.

Meanwhile, the U.S. Department of Transportation (DOT) announced Monday the establishment of an expert “special committee” to review the FAA procedures for the certification of new aircraft, including the Boeing 737 MAX.

Retired Air Force Gen. Darren McDew, former head of the U.S. Transportation Command, and Captain Lee Moak, former president of the Air Line Pilots Association, will serve as the interim co-chairs of the panel, pending the appointment of other members.

Flaws in a new flight control system, called MCAS (Maneuvering Characteristics Augmentation System), that Boeing introduced on the MAX are suspected as having played a major role in two crashes in less than five months.

Boeing has been working on the software fix since last November after it became clear that MCAS had been inadvertently triggered before the crash of Lion Air Flight 610 the previous month. Evidence pointing again at MCAS in the crash of Ethiopian Airlines Flight 302 this month resulted in the FAA’s March 13 order to ground the plane.

On Saturday, Boeing held an information session for airlines and safety regulators in Renton to share details about the proposed software fix. The jetmaker said it also has invited more than 200 airline pilots, technical leaders and regulators for the next session in Renton on Wednesday.

A person familiar with how Saturday’s session was conducted said it was “very hands-on.” Airline pilots were able to fly the MAX with the updated software patch in a simulator, and were asked for their feedback.

A pilot with a U.S. airline that operates 737 MAX jets, who was briefed on the session, said his contacts “are very pleased with what they’ve seen so far in the software change.”

As early as this week, Boeing is likely to start actual 737 MAX flight tests for the purpose of certifying the new software.

An FAA spokesman said that as of noon Monday, the FAA was still awaiting details of Boeing’s fix. However, he added that “Boeing has kept the FAA in the loop throughout the process and we expect to receive the software from Boeing early this week.”

MCAS is designed to push the nose of the airplane down in certain stall situations by swiveling the horizontal tail. It’s triggered by a signal from a sensor measuring the plane’s angle of attack, which is the angle between the wings and the air flow.

The software fix will revamp how the system operates: One key change is that MCAS will be activated using input from both of the jet’s angle of attack sensors, rather than just one.

The update will also ensure MCAS is not triggered multiple times, as it was in the Lion Air crash. And it is likely to limit the maximum nose-down movement that the system can produce.

In addition to the software fix, Boeing has decided to include on the MAX, at no charge, two angle of attack indicators that were previously optional and available only at extra cost.

A person familiar with Boeing’s plans to get the grounding of the MAX lifted said that a light that warns when the two angle of attack sensors disagree will become a standard feature on the MAX from now on. And for airlines that request it, Boeing will retrofit this warning light at no charge on previously delivered airplanes.

In addition, Boeing will no longer charge airlines that choose an option to place the angle of attack data on the primary flight display.

But it’s unclear if these changes and the MCAS software fix, even if certified, will be enough to lift the grounding of the Boeing jets. For instance, the airplane’s flight manuals and the pilot training protocols will also have to be updated.

And the ongoing investigations into the two fatal jet crashes may bring other contributing factors to the surface.

The DOT special committee will conduct a broader investigation into how the FAA certifies new airplanes as safe. The way that currently works, in a process mandated by Congress, is that Boeing does most of the safety evaluations itself, then passes paperwork to the FAA for review.

A Seattle Times story this month revealed concern among FAA technical staff that they were not given enough time to do proper oversight of Boeing’s work on the safety analyses during certification of the MAX, and that too much of the analysis was delegated to Boeing employees.

Announcing the special committee Monday, Secretary of Transportation Elaine Chao said, “This review by leading outside experts will help determine if improvements can be made to the FAA aircraft certification process.”

Boeing said in response that the company will work with the special committee “to advance our shared goal of an aviation industry that is safe and trusted by the flying public.”
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Old 26th Mar 2019, 14:53
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Obviously there are plenty of malfunctions in any aircraft that require "some" pilot input before 40 seconds. EFATO, TRO, Unreliable airspeed, Autopilot disconnect, TCAS. GPWS, runaway stabiliser .... to name but a few. The premise of the article is flawed in my view.
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Old 26th Mar 2019, 15:15
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Boeing are being quite generous now...
In addition, Boeing will no longer charge airlines that choose an option to place the angle of attack data on the primary flight display.
If they did that from day one we might be in a better place today.

A lot of people died before Boeing decided their optional extra came at a human cost.
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Old 26th Mar 2019, 15:36
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Originally Posted by Mike Flynn

Boeing are being quite generous now...


If they did that from day one we might be in a better place today.

A lot of people died before Boeing decided their optional extra came at a human cost.
Or people died because the pilots crashing had no idea how to shut of a runaway stab trim system?
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Old 26th Mar 2019, 15:48
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Mike, #2580, et al,




Mark on this instrument the AoA value as reported for the Lion accident; change seats, mark your new instrument similarly.
Which way should you move the stick according to the display - whose display, who holds the stick.
Actually what is required is to hold the stick centrally, against an unexpected and unexplained increasing nose down trim force.
Would these ‘new’ optional displays help with this situation - after what training, for what scenarios. Or are they just another distraction, requiring comprehension by a ‘surprised mind’ already challenged by the need to control the aircraft.

Aero 12 - Angle of Attack

P.S. which other flight instrument parameter would be closely associated with AoA. Airspeed, particularly as this scale has an AoA derived low speed awareness cue.
So why would we expect an AoA dial to be positioned nearer the altitude display?

PPS. The EFIS location and dial format might be better used to display pitch trim
position.

An ill-conceived thought, with trim in mind, cf # 2585



Last edited by safetypee; 26th Mar 2019 at 17:39.
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Old 26th Mar 2019, 16:22
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safetypee

PPS. The EFIS location and dial format might be better used to display pitch trim position.
I asked a question earlier in the thread, but it got lost. Do pilots ever look at the stabiliser trim analog scale on the pedestal during flight (after takeoff)?

You are asking a related question. My followup questions: Is there a digital value of stabiliser trim available on the flight control computers? Is this value used, or is trim driven from arbitrary positions by incremental turns of the jackscrew? Are there any software limits on the jackscrew position?

I may have this story backwards, but have not seen it discussed in relation to MCAS (nor in the Tech Log forum).
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Old 26th Mar 2019, 16:50
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Originally Posted by GordonR_Cape
You are asking a related question. My followup questions: Is there a digital value of stabiliser trim available on the flight control computers?
According to AMM info there certainly was in the NG, specifically "stabilizer position" is shown as an input to the speed trim function. I don't see why it would have been removed, but I guess that is possible.

Whether and how it is used in the MCAS algorithm I don't know - I haven't seen any public info on it, and I don't have access to any non-public info.
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Old 26th Mar 2019, 16:53
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Originally Posted by GordonR_Cape
safetypee



I asked a question earlier in the thread, but it got lost. Do pilots ever look at the stabiliser trim analog scale on the pedestal during flight (after takeoff)?

You are asking a related question. My followup questions: Is there a digital value of stabiliser trim available on the flight control computers? Is this value used, or is trim driven from arbitrary positions by incremental turns of the jackscrew? Are there any software limits on the jackscrew position?

I may have this story backwards, but have not seen it discussed in relation to MCAS (nor in the Tech Log forum).
The only time that stabilizer positioning requires or even benefits from reference to the absolute position of the stabilizer is when on ground, preparing for takeoff. When in air, pilot commanded movement of the stabilizer is completely based on establishing pitch trim such that no column input is needed and the pilot is able to maintain the desired pitch attitude / with the column in its spring centered detent. The cue for the pilot to move the stabilizer when in flight is steady column force needed to balance airplane pitching moments to keep the pitch attitude where it is needed to achieve the desired steady state flight path response. Where the stabilizer ends up to achieve pitch trim is a function of CG, weight, thrust, speed, Mach number, flap position, speedbrake position, gear position, and anything else that might impose a steady pitching moment on the airplane.

There are limits on the stabilizer travel both in the software that is used to provide automatic stabilizer control and in the pilot trim input paths via electric wheel mounted trim switch and manual cranking of the mechanical trim wheel. These are designed to allow for the range of stabilizer positions that are needed to be able to achieve pitch trim throughout the flight envelope including the allowable range of loading and flap/speedbrake/gear configurations.
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Old 26th Mar 2019, 17:04
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Originally Posted by bsieker
It hasn't been released. It has been shared with the other participants to the investigation, as stipulated by ICAO Annex 13.

It also won't speed up the public release of the data, because only the Ethiopian agency leading the investigation can do that.


Bernd
Can we finally at least expect some leaks of the data?
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Old 26th Mar 2019, 17:08
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Flight tests are likely to begin this week on the proposed software fix for Boeing’s 737 MAX flight control system, and the company has invited airlines to order it pending formal approval from the Federal Aviation Administration (FAA)
.

In my opinion, this should not need to be ordered, it should be a mandatory update SENT by Boeing
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Old 26th Mar 2019, 17:10
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Originally Posted by gums
Salute!

Great article, pat.
The 40 secind scenario appears to be simply allowing the MCAS to act without the crew using the trim switches. Eventually, unless power is reduced, the aero forces on the elevator and the awesome column forces required will not permit a recovery. And who wants to pull power back just after gear up? ( although I did for my LEF episode as I was light and could easily fly at 200 knots - it was the old " doing O.K. now, so don't change anything" procedure that lets you live to be old and grey) I also feel most of the 737 folks here would have used the trim switches for a time before treating the problem as a FUBAR trim system and then turning off the power as the previous flight crew did.

The MCAS mod should be interesting and provide a feast of fodder here on pPrune, huh?

Gums sends...
One of the key elements to the baseline MCAS logic is that it will only put in a single increment of stabilizer motion as long as no pilot trim command is given. This goes in over no more than 10 seconds (less if operating at Mach number greater than 0.4 where MCAS single increment authority is less than 2.5 degrees). The amount of elevator needed to balance one MCAS increment of stabilizer motion will be approximately 5 degrees due to the 2:1 ratio of stabilizer to elevator pitch control power. That amount of elevator can readily be commanded via the column with plenty of additional pitch control authority available to perform any maneuvers needed to maintain desired flight path and speed (if, for instance, climbing with a fixed throttle while varying path to maintain speed). Even in the presence of errant AOA data causing MCAS to activate when actually at AOA well below the intended MCAS activation point, MCAS will not move the stabilizer more than one increment without the crew making a pitch trim input. The only path to compromised pitch control authority via the column is for the crew to make pitch trim inputs but not make sufficient pitch trim inputs to return the stabilizer to the proper trimmed position.

Where this notion of "40 seconds" comes from is a total mystery - particularly when coupled with the statement "... without the crew using the trim switches". The scenario that led to problems after 40 seconds must have included short, ineffective periods of crew pitch trim switch commands that did not establish column force free pitch trim but did enable MCAS to insert another increment of airplane nose down stabilizer.

FCeng84 provides clarity ...
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