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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 15th Mar 2019, 18:30
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Originally Posted by BobM2
Being an airline captain has always required a logical approach to problem solving & a good knowledge of the equipment flown. If on take-off rotation you get an immediate stick shaker, on ONE SIDE ONLY, with the aircraft climbing & accelerating normally, it should be obvious that you have a sensor failure. You're not going anywhere except back to maintenance. There is no reason to clean up the airplane or climb above pattern altitude. Just fly the circuit, make a normal landing & return to the gate. MCAS never gets activated.

Aircraft manufacturers & federal regulators have spent decades trying to make the airplanes "idiot proof". It can't be done. Any revision Boeing does to their software will be a futile attempt to make the airplane "double idiot proof", but maybe it will placate the public.
Right. But how do you diagnose a stick shaker on one side only, if you’re the PF and it’s on your side? Not to mention that the control columns are physically connected. OK, given enough time you could, with good CRM but much like a hard GPWS, having a mindset of ‘oh, it’s a likely false warning’ is not a fantastic survival trait.

There are many reasons you could get stick shaker activation near the ground, one of the more prominent ones being that you are close to stalling, be it from lack of high-lift devices, windshear, unreliable airspeed or whatever. I remember the BA 747-400 that rotated at JNB and got a stick shake because some LEDs had retracted without pilot input - the pitch/power was right but the config changed from that selected.

If the aeroplane is flying and climbing, then getting it to a safe height and trying to diagnose the problem(s) and work out what to do is normally the preferred course of action. There are always exceptions (which might be MCAS) but the mindset of rushing round a short circuit, especially if you were constrained by weather and/or terrain, without having examined any other options is relying a bit on luck over judgement...
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Old 15th Mar 2019, 18:40
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Originally Posted by DaveReidUK
Yes, that's what I meant. In the old days, we would call that a compiler directive. The same would apply to the bit of code (also a $$$ option) that adds the AoA indicator to the PFD.
Don't think it's a compiler directive - if it was then each set of options would have to have a separate compilation. I suspect the license turns various bits & pieces on or off, according to the $$$ (or $$$$$$$$$) paid.
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Old 15th Mar 2019, 18:43
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Originally Posted by joig
If the trim is at max down and the pilot uses the Stab trim cut out switches does that mean that the aircraft is permanently trimmed down ? If this is the case can the pilots have any hope of recovery?
Manual trim wheel still provides crew means of moving the stabilizer to offload column force.
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Old 15th Mar 2019, 18:46
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Originally Posted by Sailvi767


They remove all power from the trim motors and completely disable the system.
MCAS includes logic and wiring to bypass pull column cutout switch when active.
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Old 15th Mar 2019, 18:47
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why not....

Dear gents

I followed this thread for a few days. the cause of the accident of the ET seems to point in the direction of a MCAS system activated due to a faulty AoA sensor and the crew nor being aware of the real problem.
In the first place, as mentioned allready in other posts, such a crucial system operating on a sole sensor (if this is correct) without any indication of "MCAS active" is an absolute nogo.
My proposition: install a "MCAS active" indicator/annunciator light right in front of the pilots (glareshield) and if this warning gets active together with a "AoA" disagree message on the ECAM, every pilot, even probably a 200 flighthour copi in ET, knows what to do right away.....
By heart item..... Stabilizer Motor Cut off Switches to OFF. ...... and then sort out the problem.
I am aware of the thing.....yet another warning.... I flew Airbus 330 and 340 for abt 7 years and know abt the random and erronuous multiple failures (luckily only in the Sim) on the AB ECAM, which can drive you nuts.
But as I remeber in the old days, on the MD-80 we had this big "STALL" warning flashing light right in front of us, impossible not to notice this one when activated.

And @ FC eng84.... thanks for all yr explanations, great stuff
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Old 15th Mar 2019, 18:49
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FCeng84, #1538,
Does that still apply if near or at jack stall; any difference between electric actuation and manual in this regard ?
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Old 15th Mar 2019, 18:57
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Originally Posted by Smythe
Article that looked at pilot filings on the MCAS issue...looks like it was common at early DEP, but handled by turning off Autopilot?

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.

This description is not currently in the 737 Flight Manual Part 2, nor the Boeing FCOM, though it will be added to them soon. This communication highlights that an entire system is not described in our Flight Manual. This system is now the subject of an AD.

I think it is unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models. The fact that this airplane requires such jury rigging to fly is a red flag. Now we know the systems employed are error prone--even if the pilots aren't sure what those systems are, what redundancies are in place, and failure modes.




https://www.theatlantic.com/notes/20...ted&yptr=yahoo
MCAS does not operate when in autopilot - it is intended solely for manual flying to ensure that the reduction in backpressure on the control column when in high AOA does not lead a pilot to inadvertently pull back into a stall. So the article you quote is not looking at the MCAS issue at all as the problem only occurred on engaging autopilot. It is probably looking at ASRS reports from crews that in some way mis-set the autopilot causing it to attempt to fly to where the crew had set it to fly. It is most definitely not MCAS.

Trawling ASRS requires a certain amount of knowledge of what you are looking at.
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Old 15th Mar 2019, 19:06
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Originally Posted by deltafox44
I'm referring to FR24 CSV data sheet downloaded from their blog : https://www.flightradar24.com/blog/f...es-flight-302/

"nothing happens to the altitude till 207 knots is reached" : yes, altitude when reaching 207 kts is 7300 ft, it has been continuously rising for 16 seconds since 7075 ft at 182 kts

I admire your perspicacity (or is it imagination ?) but initiating rotation 225 ft above runway level puzzles me
QNH around 1006 could make this happen if the reference is 1013 once airborne. What was the QNH in Addis when the accident happened?
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Old 15th Mar 2019, 19:18
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How many turns does it take to go from max down to say a neutral position? Given they they were never that high from the ground , How long would it take them to trim from max down to something that would save the flight? What am trying to say is OK we have a trim problem disable trim motor via cut out switches.. Turn the manual trim wheel . Would they have the time to do this if the are only approximately 1000ft above ground?
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Old 15th Mar 2019, 19:21
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Originally Posted by YRP
This is not for a fix from scratch. This is what they have been working on since the Lionair crash.
The question is whether it will satisfy the regulators (worldwide not just the FAA now) now that the second accident has happened.
The real question is not: Does it satisfy the regulators: FAA is effectively a Branch of Boeing. Whatever Boeing deems satisfying will be for them as well..
The real question is: Does it reliably prevent re-occurrence.
Another MCAS crash will definitely finish off the MAX and possibly the whole Boeing. I hope stupid short sighted Managers won't kill this legendary plane maker.
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Old 15th Mar 2019, 19:22
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Originally Posted by ManaAdaSystem
QNH around 1006 could make this happen if the reference is 1013 once airborne. What was the QNH in Addis when the accident happened?
See your logic ManaAdaSystem, but ADS-B was reporting "airborne" 1013 altitudes from much earlier in the take-off roll (first one at 93 kts GS with 80% of runway still ahead), and QNH was reportedly 1029. I'm not buying a sustained climb as early as deltafox44 either just yet. And claiming only 225ft achieved in 16 seconds from rotation - in a Cessna maybe? Doesn't ring true as any 737 number for me. I don't see anything close to continuous at that point other than the velocity. Everything else is just granular data and straight lines between points may not be helpful.

How did we get any intermediate 1013 baro report of 7075' anyway if runway elevation was 7625' and QNH 1029? Is there a big dip ?
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Old 15th Mar 2019, 19:30
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Originally Posted by joig
How many turns does it take to go from max down to say a neutral position? Given they they were never that high from the ground , How long would it take them to trim from max down to something that would save the flight? What am trying to say is OK we have a trim problem disable trim motor via cut out switches.. Turn the manual trim wheel . Would they have the time to do this if the are only approximately 1000ft above ground?
I think it's approximately 60 turns from full nose down to 3 units which is about neutral.

Doesn't take that long to manually trim from neutral to full nose down or vice versa.


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Old 15th Mar 2019, 19:35
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Originally Posted by .Scott
But Boeing is saying perhaps only 10 days...
https://www.cnbc.com/2019/03/15/boei...n-10-days.html

I'm a Software Engineer. Paint me incredulous.
the fix has been in development for 5 months and was due now anyway, they aren't starting from scratch.
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Old 15th Mar 2019, 19:37
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Originally Posted by joig
If the trim is at max down and the pilot uses the Stab trim cut out switches does that mean that the aircraft is permanently trimmed down ? If this is the case can the pilots have any hope of recovery?
you can manually turn the trim wheel to trim the aircraft once the stab trim cutout switches have been used.
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Old 15th Mar 2019, 19:38
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Originally Posted by Luc Lion
CORRECTION: Do you mean that what Boeing calls a "Elevator Feel Computer" is actually a mechanical computer ???

This is correct for the Elevator Feel Shift (EFS) module which simply increase by a factor 4 the system A pressure fed into the Elevator Feel & Centering Unit.
It is also true for the Elevator Feel & Centering Unit which transforms differential pressure into feel forces.
But the pressure normally fed into the Elevator Feel & Centering Unit is controlled by a computer unit, the Elevator Feel Computer, which uses airspeed and stab position inputs for computing how much hydraulic pressure it should transfer downstream.
I reckon that the AoA is NOT documented as an input data received by the Elevator Feel Computer ; AoA is only available to the EFS (in this area).

But an upgrade of the Elevator Feel Computer by adding AoA input and modifying its algorithms should not be more considerable than fixing the MCAS logic with dual AoA input.
The advantage of acting through the Elevator Feel System is obvious : no effect on the pilot pitch authority if the AoA probe goes mad in normal flight.
I cant answer for the specifics of the EFS computer other than that I am of the understanding that it is purely mechanical.

For sure there exists pure mechanical computers. Early fire control computers on various military ships during and after the WWII was purely mechanical. I have seen ducumentary about them and those computers was marvels of accurate mechanical engineering.

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Old 15th Mar 2019, 19:41
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Originally Posted by safetypee
FCeng84, #1538,
Does that still apply if near or at jack stall; any difference between electric actuation and manual in this regard ?
I take it that your question relates to moving the stabilizer when the elevators are at large deflection thus generating high loads on the stabilizer jack screw. I did some looking to see if I could find any mention of how much force / torque is needed to turn the manual trim wheel but could not find any reference. All of the descriptions I have read speak to using this means of positioning the stabilizer when electric trim has been disabled, but do not mention how much force / torque is required.
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Old 15th Mar 2019, 19:53
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Originally Posted by Chesty Morgan
I think it's approximately 60 turns from full nose down to 3 units which is about neutral.

Doesn't take that long to manually trim from neutral to full nose down or vice versa.
Have you tried this in the air? A friend of mine had a trim failure in the air. He found manual trim so hard he though he had a jammed stabilizer and ended up with a FL15 landing at nearest suitable airport.

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Old 15th Mar 2019, 19:57
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fly nice :
How does one get to co-pilot a MAX with 200 hours? MPL? I will choose my airline accordingly.
MPLs are used in the whole Lufthansa group, DLH, City line ,Eurowings Austrian etc.. since the outset . i.e years ago.. Not the problem .
Anyway if F/O on that ET flight was a contributing factor , the CVR will tell us that., but frankly I doubt it.
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Old 15th Mar 2019, 19:58
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Originally Posted by Photonic
I know the point was made earlier in the thread somewhere, but it's worth repeating that this has some similarity to the EC225's demise in the offshore oil industry.
Which like the 737 Max was a mid-1960s design stretched and tweaked and re-engined and only able to pass modern certification due to extensive grandfathering. Not a noble chapter in EASA history.
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Old 15th Mar 2019, 20:23
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Originally Posted by ManaAdaSystem


Have you tried this in the air? A friend of mine had a trim failure in the air. He found manual trim so hard he though he had a jammed stabilizer and ended up with a FL15 landing at nearest suitable airport.

I have used the Boeing manual trim system twice in the air. It’s a non event. You land at the flap setting specified in the QRH. Generally it is less than full to avoid large trim changes in the event of a go around.
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