Lion Air 737 MAX crashed

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jimdavis
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Re: Lion Air 737 MAX crashed

Unread post by jimdavis » Wed Nov 28, 2018 9:35 am

Just received this from a very good mate of mine who is a retired senior SAA Captain. Very interesting:

jim

I see the 737 Max initial Investigation says the Plane was not Airworthy. As I understand it the previous Crew had a problem with new Anti Stall Devise and turned it off. Obviously the system was not fixed, replaced, so the next Crew, presumably turned it On but with no Maintenance Action the plane would be deemed not airworthy. Presumably the Dispatch Deviation Manual (DDM) would dictate the Procedure, it could say it must work before further flight! Whatever, if there is any sort of issue with anything it must go in the Tech Log and be signed off. At SAA the Pilots would enter the details and the Ground Engineer, as appropriate, sign it off. In exceptional circumstances the Captain could Sign it Off. The Crew which crashed should have at least known there was an issue with the thing. It could have been Signed Off as Tested and found Servicable. This should alert the next Crew that at least there were issues and plant a seed, if this thing gives <<moderated - language>> where and how do I switch it Off. If some of our SAA Ground Crews were anything to by these guys can be quite casual, their arses are not strapped to the thing. I remember an A300 on which it was impossible to get the Cabin Temperature down, the Cockpit Temperature was unbearable, this had been repeatedly recorded in the Tech Log and signed off. I had come up from Durban and said before I go with it to Cape Town Maintenance must find the reason for this. Same old <<moderated - language>>, they tried to sign it off but I refused to fly it. The heavies attacked me and were quite threatening! In the end they looked at the ducting and there was a hole in a corner of one of the high pressure, high temperature, Air Cycle Machine supply ducts! This hot air was blowing onto the Centre Fuel Tank and burnt a Fire Protection Blanket around the Tank! The B2K models did not have a Centre Tank but the C4 did. With no fuel in it the Tank could have exploded in flight.
The hole happened on a bend, a small foreign object some how got carried in the air inside and smacked a hole in the pipe! They had a pipe but no Blanket, they said they would dispatch it like that. Again I said no way would I take it with out the proper Blanket. A condition of the DDM was if an item was not described it automatically kept an aircraft on the ground. To get past it required approval from Head of Technical, as I recall also the Director of Flight Operations, to give the OK and this then went to the CAA for their Authorization or otherwise.
My experience of many Ground Staff, all types, at SAA is there was a bit of a culture that an aircraft couldn’t crash! Even on the Junkers they were a bit like that, a lot of the Pilots would disagree with me, all I can say is most are not Technical people or a case of not being prepared to admit that some of the stuff the sacred Airline did was not so good, even Safety Issue!
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Re: Lion Air 737 MAX crashed

Unread post by heisan » Wed Nov 28, 2018 10:56 am

Airwayfreak wrote:
Wed Nov 28, 2018 8:23 am
heisan wrote:
Tue Nov 27, 2018 10:43 am

From the actual FAA and Boeing releases, they admitted that there was no mention of MCAS in the differences training material. Boeing's reasoning being that a failure would be indistinguishable from a 'normal' trim runaway, and the resolution procedure is the same too - so why complicate things by adding separate training for it...
I am not convinced that this is true because United Airlines received MCAS training when they took delivery of their MAX's. Very strange indeed.

https://www.forbes.com/sites/tedreed/20 ... 64e70cf0f0 :
The addition of MCAS to the 737MAX is not specifically referred to in the United manual, but the procedure for recovery from automatic unwarranted deployment of similar systems is clearly spelled out and long has been, Insler said.
United Airlines did not receive MCAS training. The United Airlines ALPA simply said that he did not believe additional training was required.
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Re: Lion Air 737 MAX crashed

Unread post by Mouser » Thu Nov 29, 2018 7:36 am

Whew, not sure whether this is interesting or scary; or both.

But it seems airspeed and angle of attack sensors were dodgy (apologies if this is all known already)

https://www.theguardian.com/world/2018/ ... gators-say
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Re: Lion Air 737 MAX crashed

Unread post by Airwayfreak » Thu Nov 29, 2018 8:49 am

Sanddweller wrote:
Wed Nov 28, 2018 9:28 am
I am Max rated, and I can tell you with 100% certainty that there was nothing in the Max Fcom mentioning the MACS and there was nothing in the differences course we did..
I think it is clear that not all companies were advised of MCAS, Boeing and the FAA have admitted this. I know however that pilots were briefed about MCAS at United Airlines by way of a slide presentation and general discussion, despite certain internet searches here on Avcom purporting differently. MCAS was, and still is, not considered a fundamental or significant system enhancement. However, in light of the apparent conflict that has occurred when AoA sensors are U/S, a different approach will be taken.

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Re: Lion Air 737 MAX crashed

Unread post by Deanw » Thu Nov 29, 2018 10:40 am

Source: The Boeing Company (NYSE: BA)
Date: Nov 28, 2018
Boeing Statement on Lion Air Flight 610 Preliminary Report

The Boeing Company is deeply saddened by the loss of Lion Air Flight 610. We extend our heartfelt condolences and sympathies to the families and loved ones of those onboard.

Safety is a core value for everyone at Boeing and the safety of our airplanes, our customers’ passengers and their crews is always our top priority. As our customers and their passengers continue to fly the 737 MAX to hundreds of destinations around the world every day, they have our assurance that the 737 MAX is as safe as any airplane that has ever flown the skies.

Boeing appreciates Indonesia’s National Transportation Safety Committee (NTSC) for its ongoing efforts to investigate the causes of the accident. Boeing is taking every measure to fully understand all aspects of this accident, working closely with the U.S. National Transportation Safety Board as technical advisors to support the NTSC as the investigation continues.
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Earlier today, the NTSC released its preliminary accident investigation report. The report provides detailed accounts of Flight 610 and of the immediately preceding flight of the same aircraft.

The report explains that the maintenance logs for the accident aircraft recorded problems related to airspeed and altitude on each of the four flights that occurred over the three days prior to Flight 610. The logs indicate that various maintenance procedures were performed, but issues related to airspeed and altitude continued on each successive flight. The logs indicate that, among other procedures, on Oct. 27, two days prior to the incident flight, one of the airplane’s Angle of Attack (AOA) sensors was replaced.

On Oct. 28, before the flight immediately prior to Flight 610, the pilot in command and the maintenance engineer discussed the maintenance that had been performed on the aircraft. The engineer informed the pilot that the AOA sensor had been replaced and tested. The report does not include records as to the installation or calibration of the new sensor, nor does the report indicate whether the sensor was new or refurbished. Although the report states that the pilot was satisfied by the information relayed by the engineer that the AOA sensor had been replaced and tested, on the subsequent flight the pilots again experienced problems with erroneous airspeed data, and also experienced automatic nose down trim.

The report states that the flight crew of the Oct. 28 flight turned off the stabilizer trim switches within minutes of experiencing the automatic nose down trim, and continued with manual trim through the end of the flight. The report further notes that the pilot performed three non-normal checklist procedures, including the runaway stabilizer non-normal checklist, which is a memory item prescribed by the 737 MAX Flight Crew Operations Manual, and reaffirmed in Boeing Flight Crew Operations Manual Bulletin TBC-19 and FAA Emergency Airworthiness Directive (AD) Number 2018-23-51, as the appropriate procedure to address unintended horizontal stabilizer movement, regardless of source.

The report indicates that the remainder of the Oct. 28 flight was uneventful and that the flight continued to its destination. The report also states that, after landing, the pilot reported some of the experienced issues both on the aircraft maintenance log and to engineering. The report states that the pilot ran the runaway stabilizer non-normal check list, but it does not state that he communicated that fact in the maintenance documentation following that flight.

The following day, Oct. 29, shortly after taking off, the pilots experienced issues with altitude and airspeed data that the pilots had previously experienced on the earlier flights, due to erroneous AOA data. Data from the flight data recorder summarized in the report also makes clear that, as on the previous flight, the airplane experienced automatic nose down trim. In response, the flight crew repeatedly commanded nose up trim. This sequence repeated for the remainder of the flight, during which the flight crew was able to maintain control of the airplane for approximately ten minutes. Unlike as is stated with respect to the prior flight, the report does not state whether the pilots performed the runaway stabilizer procedure or cut out the stabilizer trim switches.

In accordance with international protocol, all inquiries about the ongoing accident investigation must be directed to the NTSC.
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Re: Lion Air 737 MAX crashed

Unread post by jimdavis » Thu Nov 29, 2018 4:26 pm

I would like to hear from airline pilots. What is the procedure after the crew have notified maintenance that there is a problem with the flight controls?

Is the aircraft then officially considered unairworthy? And if so who has to sign it off as airworthy after it has been repaired?

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Re: Lion Air 737 MAX crashed

Unread post by Hop Harrigan » Thu Nov 29, 2018 8:45 pm

It’s highly improbable that the AoA sensor and the airspeed sensor would co-incidentally go faulty at the same time...unless...they share a common component! Such as a common pc board/connector or wiring. And, if that is the case, that’s some pretty crappy design!
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Re: Lion Air 737 MAX crashed

Unread post by MadMacs » Fri Nov 30, 2018 2:21 am

jimdavis wrote:
Thu Nov 29, 2018 4:26 pm
I would like to hear from airline pilots. What is the procedure after the crew have notified maintenance that there is a problem with the flight controls?

Is the aircraft then officially considered unairworthy? And if so who has to sign it off as airworthy after it has been repaired?

jim
Jim, the pilots record the defect in the technical log and it up to us ground engineers to rectify the problem. If the aircraft is in transit at a line station, the aircraft can be dispatched according to the Dispatch Deviation Manual, otherwise if not in DDM then it has to be repaired according to the maintenance manual. The engineer then records the action taken as well as the DDM reference. Part numbers of components changed are also recorded and he then signs the tech log which makes the aircraft airworthy.

A problem we often had was the way the pilots recorded the defect i.e. non technical types would be very vague and often I would come to the conclusion that it was a cover up for a mistake they had made. For example on said A300, a pilot landed and nearly veered off the runway so he snagged that the aircraft pulls to the left on landing. As a supervisor, it was up to me to ensure that the defect was repaired and we checked everything but could find nothing wrong, so I signed it off detailing the inspection done. The problem never came up again.

At JNB, all defects have to be repaired as the aircraft is no longer in transit and sometimes, if the problem was not too serious, I would discuss the issue with the Captain and if he was prepared to take the aircraft i would defer the item for when the aircraft returns to the hangar, which is every evening.

Flight controls are another issue and if a primary control is worked on, it requires two people to sign the defect off, the person who did the work and the second person must have a license with a release to service rating. The captain may sign the second part if there is nobody available with maintenance release and when the aircraft gets to a station with a suitably rated person, he must carry out the inspection and usually it is a supervisor who has this rating. This is called a dual inspection and flight controls require a test flight.

I remember way back one night, the Aussie flight, a B707, turned back with an inop yaw damper. While we changed it, the passengers disembarked and went for coffee in the departure hall. The plane then went on a test flight and the pilots asked us to go with. So here we were, flying around Johannesburg with all the pax belongings still on the plane. Luckily we we very honest in those days and never touched a thing.
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Re: Lion Air 737 MAX crashed

Unread post by jimdavis » Fri Nov 30, 2018 8:03 am

Thanks so much MM. Very interesting. Yep even on baby aeroplanes they need two signature to sign off primary flight controls, and I think engine controls as well.

In this case the elevator trim has more authority than the elevator itself. I wonder if it should also be considered to be a primary flight control. Or is it?

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Re: Lion Air 737 MAX crashed

Unread post by Raffles » Fri Nov 30, 2018 10:25 am

Here is an overview of the pitch controls of the NG, yeah it's probably out of date :P
Note that both the stabilizer and the elevators move, unlike a small plane which has a fixed stabilizer.

Pitch Control
The pitch control surfaces consist of hydraulically powered elevators and an
electrically powered stabilizer. The elevators are controlled by forward or aft
movement of the control column. The stabilizer is controlled by autopilot trim or
manual trim.
Elevators
The elevators provide pitch control around the airplane’s lateral axis. The
elevators are positioned by the pilots’ control columns. The A and B FLT
CONTROL switches control hydraulic shutoff valves for the elevators.
Cables connect the pilots’ control columns to elevator power control units (PCUs)
which are powered by hydraulic system A and B. The elevators are interconnected
by a torque tube. With loss of hydraulic system A and B the elevators can be
mechanically positioned by forward or aft movement of the pilots’ control
columns. Control forces are higher due to friction and aerodynamic loads.
Elevator Control Column Override Mechanism
In the event of a control column jam, an override mechanism allows the control
columns to be physically separated. Applying force against the jam will breakout
either the Captain’s or First Officer’s control column. Whichever column moves
freely after the breakout can provide adequate elevator control.
Although total available elevator travel is significantly reduced, there is sufficient
elevator travel available for landing flare. Column forces are higher and exceed
those experienced during manual reversion. If the jam exists during the landing
phase, higher forces are required to generate sufficient elevator control to flare for
landing. Stabilizer trim is available to counteract the sustained control column
force.
Elevator Feel System
The elevator feel computer provides simulated aerodynamic forces using airspeed
(from the elevator pitot system) and stabilizer position. Feel is transmitted to the
control columns by the elevator feel and centering unit. To operate the feel system
the elevator feel computer uses either hydraulic system A or B pressure,
whichever is higher. When either hydraulic system or elevator feel pitot system
fails, excessive differential hydraulic pressure is sensed in the elevator feel
computer and the FEEL DIFF PRESS light illuminates.
Mach Trim System
A Mach trim system provides speed stability at the higher Mach numbers. Mach
trim is automatically accomplished above Mach .615 by adjusting the elevators
with respect to the stabilizer as speed increases. The flight control computers use
Mach information from the ADIRU to compute a Mach trim actuator position.
The Mach trim actuator repositions the elevator feel and centering unit which
adjusts the control column neutral position.
Stabilizer
The horizontal stabilizer is positioned by a single electric trim motor controlled
through either the stab trim switches on the control wheel or autopilot trim. The
stabilizer may also be positioned by manually rotating the stabilizer trim wheel.
Stabilizer Trim
Stabilizer trim switches on each control wheel actuate the electric trim motor
through the main electric stabilizer trim circuit when the airplane is flown
manually. With the autopilot engaged, stabilizer trim is accomplished through the
autopilot stabilizer trim circuit. The main electric and autopilot stabilizer trim
have two speed modes: high speed with flaps extended and low speed with flaps
retracted. If the autopilot is engaged, actuating either pair of stabilizer trim
switches automatically disengages the autopilot. The stabilizer trim wheels rotate
whenever electric stabilizer trim is actuated.
The STAB TRIM MAIN ELECT cutout switch and the STAB TRIM
AUTOPILOT cutout switch, located on the control stand, are provided to allow
the autopilot or main electric trim inputs to be disconnected from the stabilizer
trim motor.
Control column actuated stabilizer trim cutout switches stop operation of the main
electric and autopilot trim when the control column movement opposes trim
direction. When the STAB TRIM override switch is positioned to OVERRIDE,
electric trim can be used regardless of control column position.
Manual stabilizer control is accomplished through cables which allow the pilot to
position the stabilizer by rotating the stabilizer trim wheels. The stabilizer is held
in position by two independent brake systems. Manual rotation of the trim wheels
can be used to override autopilot or main electric trim. The effort required to
manually rotate the stabilizer trim wheels may be higher under certain flight
conditions. Grasping the stabilizer trim wheel will stop stabilizer motion.
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Re: Lion Air 737 MAX crashed

Unread post by richard C » Fri Nov 30, 2018 1:20 pm

You would have thought:

Pilot looks at very busy fault log describing issues with airspeed, AoA and trim, and thinks to himself - best I keep an eye out for that.

In other words, he departs knowing that his steed had experienced several of these failures in the preceding days, so surely there was no way on earth that he was scratching his head wondering what was going on - he already knew.

The previous pilots executed the memory item checklist to combat the nose-down trim - were these pilots negligent in not preparing for such an occurrence ? Did they not check the maintenance log ? Did the engineer not give them a heads-up ? In light of the faults logged, did they not brief for such failures just in case ?
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Re: Lion Air 737 MAX crashed

Unread post by StressMerchant » Fri Nov 30, 2018 1:48 pm

"Previous pilots handled situation" does not equal "safe to dispatch".
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Re: Lion Air 737 MAX crashed

Unread post by Thermalator » Fri Nov 30, 2018 2:16 pm

although not stated, one assumes this situation could also be solved by switching all automation to the other side of the cockpit.

Question do SOP's allow the pilot to perform the take off with all automation set to the B/RHS side ? which 'may' have been a logical move after reading the maintenance logs ?
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Re: Lion Air 737 MAX crashed

Unread post by Sanddweller » Fri Nov 30, 2018 7:14 pm

You don’t take off with any automataion on, besides the autothrottles. You set the Flight Firector to master on whichever side is flying that leg.

So in this case the FO could have done the take off, but maybe the captain felt he wanted to be flying for whatever reason.
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Re: Lion Air 737 MAX crashed

Unread post by MadMacs » Fri Nov 30, 2018 7:57 pm

richard C wrote:
Fri Nov 30, 2018 1:20 pm
You would have thought:

Pilot looks at very busy fault log describing issues with airspeed, AoA and trim, and thinks to himself - best I keep an eye out for that.

In other words, he departs knowing that his steed had experienced several of these failures in the preceding days, so surely there was no way on earth that he was scratching his head wondering what was going on - he already knew.

The previous pilots executed the memory item checklist to combat the nose-down trim - were these pilots negligent in not preparing for such an occurrence ? Did they not check the maintenance log ? Did the engineer not give them a heads-up ? In light of the faults logged, did they not brief for such failures just in case ?
Correct me if I'm wrong but I don't think the previous pilots had the same problem.
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