Turkish airliner crashes at Schiphol
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For all those 'Airbus haters' out there......Having throttles that move clearly does not increase your situational awareness of thrust activity to a foolproof level.
For those followers of the Helios accident it seems yet another 737 system has let down a crew that were working very hard.
I did not want to say it before but I get the impression every time I visit AMS that every other word from the controller is 'expedite'. Perhaps there should be less of that. There must now surely be inescapable evidence to suggest that CDA approaches are safer and that dumping everybody down to 2000' to start their approach will bite back someday.
For those followers of the Helios accident it seems yet another 737 system has let down a crew that were working very hard.
I did not want to say it before but I get the impression every time I visit AMS that every other word from the controller is 'expedite'. Perhaps there should be less of that. There must now surely be inescapable evidence to suggest that CDA approaches are safer and that dumping everybody down to 2000' to start their approach will bite back someday.
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Initial report of the board : RA1 failure leads to THR idle
On TV now : at 1950' RA 1 fails and reports -8 feet. ATHR goes idle and leads to loss of speed and stick shaker. More follows.
CS
CS
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retarding A/Ts
Rhythm method -
how does the NG autosystem work.. are you sure they would have to be actually making an automatic approach for the thrust levers to go into 'retard mode' at 28' ??
If they were making a manual approach with the flight directors in an Approach mode - would the thrust levers not close regardless if the A/T was engaged ? - you then have the question of whether the Rad Alt was possibly giving an incorrect reading..
how does the NG autosystem work.. are you sure they would have to be actually making an automatic approach for the thrust levers to go into 'retard mode' at 28' ??
If they were making a manual approach with the flight directors in an Approach mode - would the thrust levers not close regardless if the A/T was engaged ? - you then have the question of whether the Rad Alt was possibly giving an incorrect reading..
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Verbatim from press conference:
Advice issued to Boeing, will leave that to the pilots here.
- Capt in LH seat, (fully qualified) FO in RH seat doing a training flight, observer FO on jumpseat
- Normal approach, no changes, to 18R
- Descent on AP, normal procedure for TK
- At 1950 ft LH RadAlt indicated -8 ft and passed this info to the A/T
- From CVR: crew get aural landing-gear warning but not consider this a problem
- A/T pulled throttles closed
- Aircraft started to behave as if it were a few meters above the runway and about to land
- The crew did not at first react to this state of affairs
- stick shaker and other warnings went off at 450 ft
- From FDR: full power was then applied
- Because of the full power on the engines and the sudden contact with the ground, both engines broke off and continued another 250 meters forward
- FDR stores 25 hours, in this case 8 flights, same problem had occured twice previously before previous landings.
Advice issued to Boeing, will leave that to the pilots here.
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Almost correct
* Capt LH seat, (fully qualified) FO in RH seat, observer FO on jumpseat
* Normal approach, no changes, to 18R
* Descent on AP, normal procedure for TK
* At 1950 ft LH RadAlt indicated -8 ft and passed this info on the A/T
* From CVR: crew get aural landing-gear warning but not consider this a problem
* A/T pulled throttles closed (At 1950 ft. because A/P thinks aircraft is landing)
* stick shaker at 450 ft (Because no reaction by pilots on closing of throttles by A/P)
* From FDR: full power was then applied
* FDR stores 25 hours, in this case 8 flights, same problem had occured twice previously before previous landings.
* Normal approach, no changes, to 18R
* Descent on AP, normal procedure for TK
* At 1950 ft LH RadAlt indicated -8 ft and passed this info on the A/T
* From CVR: crew get aural landing-gear warning but not consider this a problem
* A/T pulled throttles closed (At 1950 ft. because A/P thinks aircraft is landing)
* stick shaker at 450 ft (Because no reaction by pilots on closing of throttles by A/P)
* From FDR: full power was then applied
* FDR stores 25 hours, in this case 8 flights, same problem had occured twice previously before previous landings.
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If the A/T is in retard mode, was this *because* it was taking the failed left radalt as its height input?
What inputs does the A/T normally use? Presumably having two radalts that disagree means that the A/T should fail safe by maintaining speed rather than deciding to reduce thrust?
To me this feels like a system design that has not anticipated possible failure modes.
What inputs does the A/T normally use? Presumably having two radalts that disagree means that the A/T should fail safe by maintaining speed rather than deciding to reduce thrust?
To me this feels like a system design that has not anticipated possible failure modes.
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Key factor according to press release:
Aircraft was on the GS and Loc. No deviations from that side. Auto throttle went to retard since it 'thinks' it's at 7ft RA and it's about to touch down. At the same time autopilot kept aircraft on GS --> airspeed reduced --> pitch up and so on....No corrective crew action taken...Stall and the rest we know.
So according to the investigation. We have an Autopilot and Auto Throttle with different intentions?
Conclusion:
IF the RA was a key factor in this event we can also derive that in case the pilots would have flown a normal CAT 1/2 approach this event could have been prevented because this type approach functions independent from the RA's
Agree?
Aircraft was on the GS and Loc. No deviations from that side. Auto throttle went to retard since it 'thinks' it's at 7ft RA and it's about to touch down. At the same time autopilot kept aircraft on GS --> airspeed reduced --> pitch up and so on....No corrective crew action taken...Stall and the rest we know.
So according to the investigation. We have an Autopilot and Auto Throttle with different intentions?
Conclusion:
IF the RA was a key factor in this event we can also derive that in case the pilots would have flown a normal CAT 1/2 approach this event could have been prevented because this type approach functions independent from the RA's
Agree?
Last edited by Dimiair; 4th Mar 2009 at 12:51.
Stercus Accidit
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Biggest journal report pilot's error, but other reports are that the aircraft had a faulty altitude meter information. It indicated that the aircraft was close to the ground instead of 2000ft which caused the AP to close the throttle.
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Flightglobal's piece is ambiguous about the throttle command event, in that it doesn't state what commanded idle thrust, only that it happened. How does the NG's system logic manage disagreeing input? Does it just disconnect?
Stercus Accidit
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Instruments on the left side seem to be faulty, on the right side worked okay. The same problem happened 2 times on the 8 previous flights.
Do we know it was a dual channel autoland?
I previously aid that the Autothrottle will command idle thrust below 28ft RA during a dual channel autoland (with the LHS as PF in our SOPs), but has that ben established from the press conference?
easylife, (from Boeing Vol 2 737NG), quote..
Autothrottle Modes
• RETARD – displayed while autothrottle moves thrust levers to the aft
stop. RETARD mode is followed by ARM mode
With the Autothrottle system disengaged, the thrust levers will only move when physically moved by the flight crew.
I previously aid that the Autothrottle will command idle thrust below 28ft RA during a dual channel autoland (with the LHS as PF in our SOPs), but has that ben established from the press conference?
easylife, (from Boeing Vol 2 737NG), quote..
Autothrottle Modes
• RETARD – displayed while autothrottle moves thrust levers to the aft
stop. RETARD mode is followed by ARM mode
With the Autothrottle system disengaged, the thrust levers will only move when physically moved by the flight crew.
Last edited by rhythm method; 4th Mar 2009 at 12:46. Reason: spelling
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No we don't. I was making an assumption. I just went through the books and it clearly states that 2 RA are needed otherwise the A/P will disconnected 2 sec after capturing.
So single channel retard? We don't know because we have to disconnect at 50' when in single channel.
So single channel retard? We don't know because we have to disconnect at 50' when in single channel.
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PieterPan- Only one RA signals the throttles to close in Retard. I'm not sure which. However, failure modes of indicators are designed not to fail at critical readings. RA is a digital system with self confidence tests.
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Did it go into flare as well?
CS
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As usual not one "probable cause" but many holes in the cheese slices lining up nicely. Nothing like some OE to being given to a new F/O to put a hell of a lot of distraction/additional duties into the picture. Chap in the back seat had the best view...all so sad.
