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Turkish airliner crashes at Schiphol

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Turkish airliner crashes at Schiphol

Old 6th Mar 2009, 19:26
  #1621 (permalink)  
 
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A proper evaluation of the system - as designed - would have revealed the opportunity for a malfunctioning radio altimeter to cause a reduction to idle thrust in flight..
Oh for goodness sake - when will you realise that the above scenario is a non-event and has probably occured thousands of times, due to a myriad of different causes, and has probably never caused an accident before, due to pilots monitoring their goddam thrust settings! We've all experienced A/P and A/T misbehaviour and drop-outs and its our job to manage them.

Anyhoo -Safta - thanks for that sim info- good information, although mindful of the recent A320 crash and a few other incidences I reakon the same holds true for any aircraft with a moving stabilsor trim (i.e any aircraft with a wide speed range). Once you allow things to get so out of hand that you have a stall warning with a bucketful of nose up trim then you are in a close to irrecoverable situation.
As stated by rainboe and others and ignored by all the armchair experts, the absolute key is to not allow the situation to arise to start with. (or not have moving stabalisor trims - which means either you have to cruise at 150kts or take off and land at mach 0.8)

Saftas information is great - but come on guys, 30-40 secs of uncorrected negative speed trend and 8 seconds of shaker? Do we really blame the aircraft if a situation goes unchecked for so long?
I really hope and suspect that there is a deeper cause to this crash, as I find it hard to belive that the 'human factor' can be that off the ball to ignore such a major developing issue for such a long time.
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Old 6th Mar 2009, 19:30
  #1622 (permalink)  
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With ground filling the window, I have no doubt that anyone would apply full power. The Boeing recommended upset recovery (which all EU crews should have completed, I believe), says you may need to reduce power in a nose high low speed situation AND bank if necessary to get the nose down. Read the 'TOM stall' thread, and the PGF AB crash thread to see what the pitch/power couple can do.

Only the FDR will tell us what happened in the attempted recovery. It is pointless guessing.

I suspect there will be a lot more upset training mandated!

Post 1509 anyone? Might just have saved the day.
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Old 6th Mar 2009, 19:30
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I submit the stick shaker is coming on too late
OK, so we mod the stall warning system to take altitude into consideration, so that at low alt. it fires earlier.

I know, we'll take the alt. information from one of the Rad Alts - but it's giving false readings because the plug's corroded or the VSWR is up the creek.

Ah, yes.......

Last edited by Fred Bound; 6th Mar 2009 at 19:32. Reason: Typo
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Old 6th Mar 2009, 19:31
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Onset of Stall

My last post seems to have been unregistered.

Surely there are more signs of "onset of stall" before the stick shaker comes in...Is this true of a 'dirty' stall? I am talking about airframe buffet and in particular whether the sims reflect this correctly...

On 737/300/40/500 Level D sims I worked on for FAA/CAA approval the pilots only ever went to "onset of buffet" before recovery. Do the simulators reflect this "onset of buffet" with gear and flaps configured for landing correctly?

(edited for typos)
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Old 6th Mar 2009, 19:33
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The circumstances here were predictable based on the design of the systems. A proper evaluation of the system - as designed - would have revealed the opportunity for a malfunctioning radio altimeter to cause a reduction to idle thrust in flight.
I would tend to agree. In that sense, broadly speaking, this is a very similar type of event to the Spanair MD-80 in Madrid last year where (IIRC) pulling a circuit breaker to isolate a non-critical faulty sensor, as a side effect caused the critical take-off configuration alarm system to become inoperational.

Proper systems design and testing seems to become more and more important, as complexity increases.
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Old 6th Mar 2009, 19:46
  #1626 (permalink)  
 
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Interesting reading from a lot of experienced people but it mustn't be forgotten that it was a preliminary report talking about the RA and AT etc. I think the Dutch investigators stook their necks out divulging that type of info so early.

There could be the odd little suprise or two drop out of the full accident report.
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Old 6th Mar 2009, 19:47
  #1627 (permalink)  
 
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The Boeing recommended upset recovery (which all EU crews should have completed, I believe), says you may need to reduce power in a nose high low speed situation AND bank if necessary to get the nose down.
BOAC, I bow to your superior knowledge but is this an "upset recovery"? Surely it's an "Approach to Stall Recovery" according to Boeing? I quote:-

"The following is immediately accomplished at the [I]first[I] indication of stall buffet or stick shaker

PM Advance thrust levers to maximum thrust
Smoothly adjusting pitch attitude to avoid ground contact or obstacles
Level the wings (do not change flaps or landing gear configuration)
Retract the speedbrakes
When ground contact is no longer a factor:
Adjust pitch attitude to accelerate while minimising altitude loss
Return to speed appropriate for the configuration

The Upset Recovery in the Boeing QRH also states inter alia:-

"These techniques assume that the aircraft is not stalled. A stalled condition can exist at any attitude and may be recognised by continuous stick shaker activation accompanied by one or more of the following:-

Buffeting which could be heavy at times
Lack of pitch authority and/or roll control
Inability to arrest descent rate

If the airplane is stalled, recovery from the stall must be accomplished first by applying and maintaining nose down elevator until stall recovery is complete and stick shaker activation ceases."
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Old 6th Mar 2009, 19:55
  #1628 (permalink)  
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Badly written post, FFB - I was referring to the ensuing fun in the sim. It was the 'elevator' the sim guys did not have due to the trim, just like the PGF 320 - and probably the BA038 had they had significant engine power to recover from the near stall and the TOM 'incident' - hmm!
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Old 6th Mar 2009, 19:57
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Badly written post, FFB - I was referring to the ensuing fun in the sim.
Ok all is forgiven!
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Old 6th Mar 2009, 19:59
  #1630 (permalink)  
 
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The circumstances here were predictable based on the design of the systems. A proper evaluation of the system - as designed - would have revealed the opportunity for a malfunctioning radio altimeter to cause a reduction to idle thrust in flight.
So what do you suggest?
Millions of $ redesigning and retrofitting a new radalt system to the entire 737NG fleet?
Or reminding pilots that when they are not getting the thrust they need from the autothrottle, they may switch it off and apply thrust manually?
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Old 6th Mar 2009, 20:00
  #1631 (permalink)  
 
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We allowed the 8 seconds based on the probability that the crew would have been surprised by the stick shaker and may not have reacted immediately.
8 seconds of stick shaker!!!!

No wonder you couldn't recover. What was your minimum speed during the manoeuvre?

Sounds like you wanted to prove something and did. But it's not very relevent as I don't recall an 8 second gap being mentioned in the press release. And of course you weren't using an NG.

Did you try recovering from the shaker without delay?
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Old 6th Mar 2009, 20:02
  #1632 (permalink)  
 
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It is upto the pilot to understand the consequences of pulling circuit breakers. This is stated in any aircraft's POH
Please, read up on that accident. The pilots actually did not make that mistake. They made a much more basic and fatal one. Just as in this 737 case
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Old 6th Mar 2009, 20:03
  #1633 (permalink)  
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Originally Posted by fs
Or reminding pilots
- the really worrying thing is we appear to be having to 'remind' pilots more and more.

Don't forget to throttle back when you land

Do monitor your speed on finals

Do have some idea of min stall speed before you try it

etc etc.

Something is not right.
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Old 6th Mar 2009, 20:05
  #1634 (permalink)  
 
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I confess to being rather bored by all this poring over and implied criticism of the aircraft systems. It seems that one Radio Altimeter failed - so what?

Commercial pilots are all required to hold an Instrument Rating. This means being able to fly the aircraft solely by reference to instruments. To do this, one develops the ability to scan across the instrumentation - attitude, speed, altitude, heading, back to attitude, etc. Especially on any approach - be it manual or automatic - a professional pilot should maintain that scan. This where the first indication of something unusual will be apparent. If it is manual flying, a manual correction is made. If it is autopilot flight, the automatics may need adjusting or, if there is a serious discrepancy, even disconnecting. Either way, a necessary correction to the flight path must be effected. This is what professional piloting is all about.

The idea that the pilot is simply a bystander to the electronic wizardry and only gets involved when the automatics provide a warning is absolute nonsense. There may be need for software criticism in order to improve its performance but do not let us overlook the fact that the pilot is in charge of the aircraft, whatever the automatics are doing - or trying to do.

Piloting comes first - automatics may help the pilot but are subsidiary to his/her primary function. Pilots are responsible for flying the aircraft. They may indeed use the automatics but then it is essential that they should watch the automatics to ensure they deliver the required aircraft flight path and performance. Failing to do this is nothing less than professional negligence.


JD
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Old 6th Mar 2009, 20:14
  #1635 (permalink)  
 
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1677 Jumbo

Jumbo

Maybe it was professional negligence, but assuming nothing else comes out in the report regarding the throttles being closed, do you not agree that in this particular accident, the plane would not have crashed and lives lost had the duff radalt not caused the throttles to be backed off?

For some reason, incompetance, distraction, whatever, the crew didn't notice the loss of airspeed. sadly the cheese holes lined up: they wouldn't have done (in this case) had the radalt performed correctly.

Improving safety is surely about reducing the holes in the cheese?

James
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Old 6th Mar 2009, 20:14
  #1636 (permalink)  
 
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Jumbo Driver and Rainboe - I agree. The Wright brothers didn't have a Radio Altimeter. either.

If the wings were undamaged and contained some fuel, and the engines working and still controllable to some degree, that was all the crew needed to land on an airfield that they could see. Anything else was a bonus.

There may be very valid reasons why the crew got themselves into the position that they did, time will tell, but trying to blame electronics and computer systems is like the Supermarket clerk being unable to work out my change because " the computer is down"

Must go, my mobile phone has apparently received a text, and I need to find a passing 5 year old to work it for me.
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Old 6th Mar 2009, 20:15
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757 Driver

Oh for goodness sake - when will you realise that the above scenario is a non-event and has probably occured thousands of times, due to a myriad of different causes, and has probably never caused an accident before, due to pilots monitoring their goddam thrust settings! We've all experienced A/P and A/T misbehaviour and drop-outs and its our job to manage them.
Well this time it did lead to an accident and I fear this sort of explanation in the light of public awareness of what triggered the accident would not go down well with certain groups, say your passengers for instance. Yes the crew would appear to have been incompetent, but having exposed a new hole in the cheese to the scrutiny of investigators and the traveling public alike, it will be incumbent on the powers that be to institute a technical fix in addition to any remedial training requirements both specific to TLH and any more general requirements they may come up with. That's just the way the world works.

In other words incidents like a malfunctioning RA#1 that trips the A/T into an un-commanded mode at an inopportune moment is a benign failure that doesn't concern anyone outside the industry, until such time as it is linked with an accident like this one. Then it's no longer benign.

Last edited by MU3001A; 6th Mar 2009 at 20:37.
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Old 6th Mar 2009, 20:17
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Here's a couple of things for people to consider regarding rad alts and autopliots.
Rad alts are primarly autopilot sensors not primary flight instruments. There is one rad alt per autopilot which is used in the landing phase.
To meet the design requirements for autoland with multiple autopilots, you must have the autopilots operating independantly. Autopilots will be powered from separate electrical busses, utilize separate hydraulic systems and receive information from separate sensors. Because of this requirement, it is not possible to use rad alt info from another side to replace a bad sensor.
Rad alts monitor the aircraft height above ground. Its operates between 0 and 2500feet. Height is determined by bouncing raido signals off the ground. The frequency is in the 4.3Ghz range. Above 2500 feet, it is not used. Each rad alt has 2 antennae. One transmit and one receive. On most of the modern Boeings, the rad alt R/T and both antennae are monitored for faults and will supply fail flags for a hard fault. Intermittent faults are much harder to detect and may not show as a failure.
I spent most of my 30 years in aircraft maintenance working on B747s. I never saw a rad alt stop one from flying. I don't know of any aircraft that doesn't have an MEL to cover the dispatch of an aircraft with an inop rad alt.
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Old 6th Mar 2009, 20:21
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So what do you suggest?
Millions of $ redesigning and retrofitting a new radalt system to the entire 737NG fleet?Or reminding pilots that when they are not getting the thrust they need from the autothrottle, they may switch it off and apply thrust manually?
No redesign of the RA. Yet.

So far, this occurrence is unique and most probably fulfils the "acceptable failure risk" criteria.

Air transport is still a very safe form of travel. This nowadays tends to be forgotten whenever someone dents an airplane.

If the number of occurrences becomes excessive, then consider a redesign, or at least a revision of the certification criteria - for example, as actually happened some years ago for birdstrike protection.

In my opinion, the issue that has occurred too many times recently is allowing the aircraft to lose safe flying speed for any reason. This accident and Buffalo are recent fatal examples. I still suggest the solution in post #1234 as a cost effective technical measure, if any such is implemented. It should in any case be slightly more cost effective than redesigning and retrofitting radalts, IMHO.

Last edited by snowfalcon2; 6th Mar 2009 at 20:31. Reason: clarity
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Old 6th Mar 2009, 20:32
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The 'they were stupid, I'm better' attitude is extremely childish and extremely dangerous.
Very well said stunt pilot as i alluded to some pages ago. I think i said let's not get sidetracked. And still we hear about the intricacies of Rad Alts etc...

Put recents incidents together and formulate a picture. See threads A320 Perpignan, Tom Stall, etc... Build your own picture. But please keep an open mind until the full report is out. There is far more to this than first meets the eye...
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