Indonesian aircraft missing off Jakarta
Salute!
Thank you, Coucourse.
That sums it up.
And we were told there were no cosmic computer crapola connected to the trim and the feel and the.....
Then we find that a slew of sensor inputs that included AoA were melded together and massaged and then a signal went to the feel system, and when A/P engaged, to the stab trim system.
Hh well, I move to the Tech Log due to Mod deletions of my posts concerning AoA, stability, static stability, etc.
Gums....
Thank you, Coucourse.
That sums it up.
And we were told there were no cosmic computer crapola connected to the trim and the feel and the.....
Then we find that a slew of sensor inputs that included AoA were melded together and massaged and then a signal went to the feel system, and when A/P engaged, to the stab trim system.
Hh well, I move to the Tech Log due to Mod deletions of my posts concerning AoA, stability, static stability, etc.
Gums....
[snip]
FAA:
This AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer.
FAA:
This AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer.
Holy Moley
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It is inconceivable this system was not challenged during test with loss of/compromised AoA, to elicit this very behaviour.
Inconceivable, but clearly they did not know. Because if they knew, and the system was approved, somebody got some splainin’ to do.
FAA:
This AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. We are issuing this AD to address this potential resulting nose-down trim, which could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain....
Erm, other than that, what’s for supper...?
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SEATTLE TIMES RE FAA AND BOEING
https://www.seattletimes.com/busines...ncy-directive/
https://www.seattletimes.com/busines...ncy-directive/
FAA follows Boeing’s 737 safety alert with an emergency directive
Originally published November 7, 2018 at 2:47 pm Updated November 7, 2018 at 3:36 pm
GOES ON ..
The FAA said its directive addresses the potential impacts of false information coming from a sensor on the plane's exterior.
By
Following Boeing’s safety alert Tuesday evening in response to the Lion Air 737 MAX crash in Indonesia, the FAA on Wednesday issued an Emergency Airworthiness Directive, effective immediately, mandating that airlines must update pilot procedures according to the instructions in the alert.The FAA said its directive addresses the potential effects of false information coming from a sensor on the plane’s exterior that reports the plane’s “angle of attack” (AOA), which is the angle between the wing and the flow of air the jet is moving through.This key data point is fed into the flight computer along with the temperature and air speed. These three metrics affect one another and are used by various systems that control the airplane’s flight.Dominic GatesSeattle Times aerospace reporter
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Nevertheless, there is a tendency in engineering (I'd say particularly in software, but that may just be because that's what I've done most of) to "improve" by adding complexity and to use every piece of input data just because you can, which is great until some inputs are garbage, which then cascades to all outputs... Normally ADIRU is considered as two halves, more or less independent (think you can switch off the air data half on the 'buses and the inertial half stays on - and groundspeed comes from inertial), but there are connections between the two, and at the end of the day it's a box with a bunch of inputs including AOA and a bunch of outputs including groundspeed, so someone may have found a way to introduce a dependency.
I went looking for details out of interest, I didn't find anything but then one link lead to another and I stumbled across an FAA notice about loss of GPS signal leading to loss of yaw damper and stall warning system fail (among other issues). Just let that sink in for a minute, stall warning dependent on having GPS signal!
Maybe it's just me, but that notice made me a believer - if someone can design and build and get certified an aircraft where stall warning is dependent on having a GPS signal, then I have no problem believing someone managed to get the groundspeed display to depend on AOA.
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Max only?
SEATTLE TIMES RE FAA AND BOEING
https://www.seattletimes.com/busines...ncy-directive/
https://www.seattletimes.com/busines...ncy-directive/
FAA follows Boeing’s 737 safety alert with an emergency directive
Originally published November 7, 2018 at 2:47 pm Updated November 7, 2018 at 3:36 pm
GOES ON ..
GOES ON ..
It used to be “pencil whipping” on the shop floor, which amounted to fraud, and caused a flight attendant to be lost in Hawaii.
Remember. Now it just occurs in plain sight, no attempt to hide, or even explain. Airframer say jump, FAA say: “How High?”
Trust, But verify. Unless it’s too expensive? Not the first time a system was untested while carrying passengers.
Boeing did the same thing with Yuasa batteries. The fleet was grounded, but not by Boeing
Remember. Now it just occurs in plain sight, no attempt to hide, or even explain. Airframer say jump, FAA say: “How High?”
Trust, But verify. Unless it’s too expensive? Not the first time a system was untested while carrying passengers.
Boeing did the same thing with Yuasa batteries. The fleet was grounded, but not by Boeing
Last edited by Concours77; 7th Nov 2018 at 23:47.
Runaway stabilizer is a memory drill,at least on the NG.It is considered time critical and therefore should be done from memory.It appears in this case there may have been a failure to recognize the REAL problem given the information that the crew hopefully would have been aware of from the previous tech. log entries regarding an airspeed unreliable problem.They may have been completely side tracked in their thought processes once airborne.
Runaway stabilizer is a memory drill,at least on the NG.It is considered time critical and therefore should be done from memory.It appears in this case there may have been a failure to recognize the REAL problem given the information that the crew hopefully would have been aware of from the previous tech. log entries regarding an airspeed unreliable problem.They may have been completely side tracked in their thought processes once airborne.
This was not a UAS. The flight deck is not the place for engineering the systems, that is done in design. Hopefully.
NOT Unreliable air speed. Unreliable kit, Boeing admits this in the AD letter. Please read it.
I know, modify the walk around. “Get a ladder, check AOA vane is “free and correct...”
Simples.
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Runaway stabilizer is a memory drill,at least on the NG.It is considered time critical and therefore should be done from memory.It appears in this case there may have been a failure to recognize the REAL problem given the information that the crew hopefully would have been aware of from the previous tech. log entries regarding an airspeed unreliable problem.They may have been completely side tracked in their thought processes once airborne.
There once was a time where a prudent Boeing would have grounded the fleet, rectified the problem.
That Boeing is long gone.
Infected by the requirements of a capital market and 'commercial returns' the smart money men have focus on the BA NYSE price and personal financial incentive. it is worth considering that Boeing were perhaps well aware of the issue.
Remember. Now it just occurs in plain sight, no attempt to hide, or even explain. Airframer say jump, FAA say: “How High?”
Trust, But verify. Unless it’s too expensive? Not the first time a system was untested while carrying passengers.
Trust, But verify. Unless it’s too expensive? Not the first time a system was untested while carrying passengers.
Regulatory capture plain and simple.
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To get back to the accident at hand, what would have happened to this LA Max if this problem had occurred immediately after take off or like the Rostov accident, on a go around? I suspect they wouldn't have had time to execute a recovery let alone establish they were experiencing air data issues from an AoA sensor. It would look awfully similar to RoD. If I was an airline with orders for MAX right now, I'd be a little apprehensive.
This appear to be a knowledge issue as well as a training issue.
I fail to see a causal factor being design or certification related.
The corrective action addresses the shortcoming
It does little good to wave the blame flag.
I fail to see a causal factor being design or certification related.
The corrective action addresses the shortcoming
It does little good to wave the blame flag.
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so what is different about MAX v NG?
That is correct. If for some reason the electric trim system runs away, it can be cut off. Once cut off one can use the manual trim wheels to manually trim the aircraft. The aircraft remains perfectly controllable. Further, even with a trim that has runaway to the mechanical limit of the system, the aircraft remains perfectly controllable. It's just that control column forces might be high and you might want the other pilot to assist you in overcoming the adverse column forces to lessen fatigue.
There have been several instances where the stabilizer ended up at the stops and the elevator lacked authority to maintain attitude. At least one A320 crashed because the crew kept pushing to capture the glideslope from above and ran the trim all the way out. As far as I know the B737 manual states that during stall recovery with high engine power full nose down elevator might not be enough and reminds the crew to use aircraft nose down trim.
Caution: Speculation
Have the AoA sensors been positioned differently in the MAX where they are more vulnerable to damage from an air bridge or other ground equipment?
Has the supplier been changed, perhaps to a more easily damaged version?
I suspect that Lion Air has been operating other 737s without this problem; so why now on the MAX
With the possible exception of Rostov on the Don, the STS/AoA system has been operating safely for a near half century.
I am reminded of a Greek military airman on night watch who used pitot tubes for chinups. Fortunately the damage was discovered on the ground
Has the supplier been changed, perhaps to a more easily damaged version?
I suspect that Lion Air has been operating other 737s without this problem; so why now on the MAX
With the possible exception of Rostov on the Don, the STS/AoA system has been operating safely for a near half century.
I am reminded of a Greek military airman on night watch who used pitot tubes for chinups. Fortunately the damage was discovered on the ground
So seat of your pants can kill you just as easily as a lot of fancy computers. Genuinely, I think - in 2018 - you're probably safer in an Airbus during indicating problems because the Airbus guys have had unreliable airspeed, UPRT and OEB48 drummed into them ad nauseam, that... - now, i'll end up eating my own words here - ...that they should be on top of their game knowledge wise to deal with this sort of issue. Perhaps this training on the Boeing is yet to catch up?
I speak as an Airbus captain who experiences something to do with UPRT/UAS in every six months, that the company would have pretty good ground to stand on should i cock one of these events up on the line. I can't see how they could drive the training home any better than they currently do.
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Can someone explain to me why anyone in their right mind would design a system whereby information from one sensor (in this case, the AoA sensor) corrupts the information coming from other independent systems (airspeed, altitude, and indeed even seemingly groundspeed)?
The equivalent in a car would be to allow the external temperature sensor to mess with the speedometer reading and the fuel gauge reading. Oh, and also allowing it to floor the throttle!!!
If airspeed and altitude readings remain unaffected, the pilot is surely going to have a much better view of what the plane is doing and what has gone wrong.
The equivalent in a car would be to allow the external temperature sensor to mess with the speedometer reading and the fuel gauge reading. Oh, and also allowing it to floor the throttle!!!
If airspeed and altitude readings remain unaffected, the pilot is surely going to have a much better view of what the plane is doing and what has gone wrong.
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Despite the outcry from some posters above in the light of the Boeing bulletin and FAA directive, the fact remains that existing procedures should have brought this aircraft safely back to ground.
The bulletin and the AD both say this.
It appears that maintenance and training are the major contributors to this tragic accident.
Maintenance: a maintenance culture that allows an aircraft to fly 4 successive sectors with a known issue affecting air data is completely unacceptable, and it certainly wouldn’t happen in any airline with a proper attitude towards maintenance and safety.
Training: given the above was allowed to occur, a well trained crew should still have been able to handle it. In the absence of well trained crew, an accident was simply a matter of time.
There is no such thing as pilot-error in an airline, only a poor training system which allows poorly trained pilots to operate.
The bulletin and the AD both say this.
It appears that maintenance and training are the major contributors to this tragic accident.
Maintenance: a maintenance culture that allows an aircraft to fly 4 successive sectors with a known issue affecting air data is completely unacceptable, and it certainly wouldn’t happen in any airline with a proper attitude towards maintenance and safety.
Training: given the above was allowed to occur, a well trained crew should still have been able to handle it. In the absence of well trained crew, an accident was simply a matter of time.
There is no such thing as pilot-error in an airline, only a poor training system which allows poorly trained pilots to operate.
