Silk Air MI 185

[Crockett]

Hi All

Have any of you read the recent articles a few weeks ago in Singapore media about possibility that new evidence shows that pilot did not do it as previously thought to be the case by a lot of people. Even though Final Crash Report was inconclusive at the time..

In fact...Crash investigators are now prepared to reopen the investigation apparently if the new evidence re Black Boxes is true..

The truth will come out eventually... even 5 to 6 years on..

Opinions anyone..???

[Kaptin M]

This is a "rumour network" - so what's the new rumour being cited as the cause?

And why has it taken "5 to 6 years" to surface?

[Hudson]

It had better be almost infallible new information. There were too may coincidences involved with that crash. Someone pulled three circuit breakers before the aircraft went into a very steep dive with not even one squeak of a radio call (despite a perfectly normal position report transmission less than a minute earlier).

Plus no sign of speedbrakes operated in the dive. Plus evidence of high engine power at impact - plus evidence from the FDR that just before the FDR circuit breakers were pulled that the stab trim setting was in normal cruise - yet the stab trim was found in full down electrical limit by the investigators. As I said - an awful lot of coincidences took place on that flight.

At the court proceedings held in Singapore there was compelling evidence of strange behaviour by the captain on several earlier flights.

[autoflight]

Too late for the airline to recover its reputation with a few rumours!

[Crockett]

Latest reports are that the data for the last few minutes of the flight from the FDR was in fact there, unlike previous reports that said last six minutes was not there..and that no data available before the aircraft left 35,000 ft.

It is reported that New data now available shows the aircraft at 16,000 with the rudder deflection of 30 degrees or words to that effect..just a minute or so before aircraft hit the ground..

Guess we continue to wait and see what happens next..

[Taildragger]

Crockett...

My compliments. By Singapore Media, do you mean that paragon of objective and truthful, unfettered by Government pressure, The Straits Times.?? If so, I believe everything they say. BTW, do they still have the Page 2 column... "What it should have been".??

[7times7]

I was following the story. Nothing appeared in the Straits Times, not surprisingly.

It first appeared only in TODAY newspaper, a rival group paper and later repeated on another so called tabloid.

http://www.channelnewsasia.com/stori...ew/707/1/.html

[Crockett]

Where there is smoke there is fire... I think the saying goes...

You have to admit that it is an interesting turn of events.....and somewhat embarrassing for all concerned in the investigation, whether from the Indonesian side or those who supposedly gave the FDR data to the Indonesian Investigators.. Was the information withheld and by whom....That is the question...

The truth will come out eventually.....

[ATC Watcher]

I am not so sure, Crockett, that the thruth will eventually come out if it indeed involves , even partially, rudder deflection.

By the way has anyone seen the accident report of the Turkish 737-300, that crashed in Turkey a few years ago, there also rudder deflection was suspected.

[lomapaseo]

No surprises here.

This should be expected when the data migrates from the impartial investigators to the lawyers who have an agenda.

I guess those that are attracted to news releases like this will just have to await a trial outcome of who's right.

[DocManhattan]

I wrote a number of pieces for Flight about this crash a while back, and I'm extremely sceptical about the Nolan Group's position. I met Tom Ellis (the lawyer cited in the Channel News Asia article) in 1998 and it was clear then that these guys had a determined agenda, which is to dump the blame for this tragedy at Boeing's door at all costs -- 'cause that's where the money is. They're lawyers - that's what they do. In all the interviews I did with parties on all sides of the dispute, nobody ever suggested to me that there may be any data from either the FDR or CVR beyond the clear times specified in the accident report when the recorders stopped working -- presumably the moment at which the CBs were pulled. For this sort of data to turn up now seems extremely unlikely, to say the least. Furthermore - both Ellis and Oetarjo Diran, the chief accident investigator, seemed keen to suggest that crash was caused by an uncommanded rudder hardover like the ones that were (probably) responsible for 737 crashes at Pittsburgh and Colorado Springs. However, in both those cases the aircraft were flying low and slow, at a speed where I understand you can no longer effectively counter a full rudder deflection with ailerons. Because they were low, they also didn't have much recovery time. MI185 was in the cruise -- well above the threshold speed -- at 35,000 ft (if memory serves me well), so plenty of altitude to recover. The crew had a clear sky, so orientation shouldn't have been a problem, then there's the lack of distress call, the trim, the engine power settings, the captain's financial and disciplinary troubles... the list goes on. Unfortunately, this seems to be one of those cases where we'll never know for sure. But based on the available information, the most likely conclusion is that the crash was caused deliberately. Grim, but that's how it is...

[highcirrus]

DocManhattan

“However, in both those cases the aircraft were flying low and slow, at a speed where I understand you can no longer effectively counter a full rudder deflection with ailerons.”

Hmm. Not too sure whether that would really have been an issue in this case, with a rudder hard-over at M.74 and FL350. In that event, the overriding consideration must surely have been one of catastrophic damage to the tailplane – including possible separation – leading to inevitable, rapid and spectacular loss of the aircraft.

In those circumstances, “plenty of altitude to recover ….. clear sky, so orientation shouldn’t have been a problem” would seem to be irrelevant.

[DocManhattan]

...fair point, highcirrus, but the descent profile isn't consistent with a fin separation. It was a steep, high-power, high-speed swandive... And the wreckage showed no sign of that kind of damage (I'm almost 100% sure). So that's another argument against the rudder hardover theory...

[highcirrus]

DocManhattan

Actually I implied that the whole tail might have separated rather than just the fin. In that case a number of things are likely to have taken place during and subsequent to this event. An extremely violent flick would have instantly occurred during the rudder hard-over, followed by a very high energy autorotation, severe yaw-roll coupling and then a steep nose drop into a high angle dive. In the event the whole tail separated, elevator control would have gone forever, making this dive terminal. Interestingly, the circuitry of the DFDR, sited in the tail, would, in all probability, have sustained electrical shock load in this catastrophic event and tripped the flight deck circuit breakers. The flight crew, meanwhile, suddenly pointing straight down, following a shocking, sick-making, un-practiced, noisy and highly disorientating (despite clear skies) un-commanded manoeuvre would have, I can categorically assure you, instantly recognised their imminent demise – from which point, all bets are off as to whether any rational (though likely to be futile) action was carried out in the short time remaining.

On the point of the wreckage – and I will stand corrected here – I do seem to remember that the tail components were found some distance from the main body of the aeroplane at the crash site.

You also mention “captain's financial and disciplinary troubles” as being a contributory cause of the disaster. It may interest you to know that the alleged cause of the former trouble (gambling) is endemic down here (Singapore) and that many more than one pilot in the history of SIA/Silk Air has managed to operate quite safely and successfully, despite such desperate woes. However, if the airlines concerned are so mindful of such stress (they’re not, as it doesn’t show on a balance sheet) they might like to consider that a plethora of their pilots are currently operating under similar debt overhang duress, having burned their fingers, gambling in the property market of three years ago. Their positions are now made even more acute, as the pilot body is apparently responsible for losses incurred by the two airlines, during the SARS crisis and now have to make amends by sustaining a government imposed 40-50% pay cut (see Far East threads of this web site).

Finally, as you are a journalist, you might like to ask Boeing for their idea of the likely course of events, subsequent to a rudder hard-over in the circumstances specified (M.74/FL350). Having spoken with them, maybe you could then ask the FAA why they’ve quietly insisted on a complete re-design of the B737 rudder control system and why they have made phased installation into the world fleet mandatory.

[DocManhattan]

OK, let's think this through. Firstly, as I recall a part of the tail assembly did separate, but that was already well into the descent. It was ripped off by aerodynamic loads, with the aircraft already far outside its flight envelope. That's the bit that was found away from the crash site. I don't know exactly which part of the empennage it was, but everything I've been told suggests that it came off as a result of the dive, and wasn't a cause of the dive. I know that parts of the tail were recovered from the wreckage (enough to prove the aircraft was trimmed nose-down, certainly), so it can't be that the whole back end came off the thing. And if a portion that big had separated, wouldn't that have shown up on radar? So that hypothesis seems pretty unlikely.

Also, my point about the descent profile is that the radar plots showed the aircraft coming down steadily, with no manoeuvres or apparent attempts to recover. It came down like a bat out of hell, and I very much doubt that an aeroplane would fly that steadily with its entire empennage off... Right, as to the flight mechanics of what happens when your tail comes off, I guess you're right, you would pitch down, but you'd be totally unstable, no? You might even try to use engine power to bring the nose up, but surely your descent would be much more haphazard than what we saw here? And that still leaves the mystery of the full nose-down trim... So I'm not convinced.

Boeing is always very tight-lipped in public about crashes involving its aircraft, cause it doesn't want to pre-empt an investigation and get itself into trouble. There have certainly been problems with the 737 rudder, which led to a redesign (check out the Pittsburgh and Colorado Springs crashes I mentioned above). All I'm saying is that MI185 was a completely different case.

I've heard it's a tough life for some pilots in Singapore, but not everyone reacts to the same stresses in the same way. Some hold out, some crack...

[Crockett]

Highcirruss and DocManhattan

Thank you for your insight..and obvious understanding of the possible events that may have occurred.. Very interesting..

Doc...Of course The Lawyers have a determined agenda... Whilst Mr Ellis is not representing me, I would be worried if he did not have a determined agenda if he was representing me..

The 737 Rudder problem is well documented over the years and again I say, where there is smoke there is fire..Let Boeing prove otherwise when it goes to trial.. The re-design requirements is fact not fiction. !!

As for the fiction... Boeing...there argument or cause for the accident is Pilot Suicide... Whilst Capt Tsu may have had some problems..They were not as bad as has been made out and it is far too simple an explanation... Guess the boys at Boeing and the lawyers representing them will say it is a "Cultural Thing " !!!... They would be very mistaken to use this arguement in a court of law in the USA..

Trial starts in October this year by the way...

[Crockett]

Just wanted to comment on something Iomapasoe said in this thread.. re "Impartial Investigators" ...

Whilst this may be generally true and investigators are supposedly impartial, I can assure you that in the case of SilkAir MI 185, sufficent stuff has gone on and so many parties involved in the investigation from all over the world that not supprisingly, some of them could very easily be described as having a direct interest in the results of the investigation and what was included or not included in the Final Crash Report, as the case may be..

I realise no system is perfect and it is a tough job to put on any crash investigative team even if they have access to all possible resources, but in the case of SilkAir MI 185, resources (equipment, expertise and people) were leant from all over the world.. some of these were most definitely interested parties and certainly not going to be impartial..

[highcirrus]

DocManhattan

You could be entirely correct in your reiteration of and belief in, events as presented in the final crash report and I’m certainly not sure of what bits of the tail assembly were found remote from the main body of the aircraft. Perhaps someone with definitive knowledge could confirm?

However, I would like to know how you surmise that “a part of the tail assembly did separate, but that was already well into the descent. It was ripped off by aerodynamic loads, with the aircraft already far outside its flight envelope.”

As far as I am aware, there has previously been no DFDR data available which covered this phase of flight and which would support this proposition, hence, I think you will agree, it must remain, for the time being, in the realms of pure speculation. Of equally valid pure speculation is my hypothesis of the sequence of events, which I previously made – or if not exactly that sequence, then variations around it – bearing in mind that events subsequent to whatever caused the initial upset, were taking place, as you quite correctly state “far outside the flight envelope” and would therefore be difficult if not impossible to predicate.

Please also bear in mind that during this terminal excursion, the very marked compressibility effect present, at perhaps M1.0+ following the initial, accelerating steep dive hypothesised, would have been a dramatic oscillation of Centre of Pressure with resulting grave pitch instability. It is entirely possible to speculate that the crew may, in extremis, and before finally losing control of the aircraft, have trimmed forward, in the absence of elevator control, to arrest a very high “G” pitch-up that could at the instant, have destroyed the aeroplane – hence the stab trim found in the full down position.

In respect of descent profile: “radar plots showed the aircraft coming down steadily, with no manoeuvres or apparent attempts to recover.” Here it is probably best to re-examine the provenance of the evidence presented to the inquiry. Was the above summation arrived at on the basis of display tapes presented in evidence and derived from civil area radars or were similar tapes analysed that were derived from more accurately profiling, military height-finding radars? If the latter, then a true picture of the descent profile could be obtained.

Moving on; if I might say, when things do go unexpectedly and very badly wrong in any jet aircraft, as far as I’ve ever been able to observe, they do so extremely quickly and to the point where subsequent recovery to safe flight may be difficult – For which reason, I think we should all keep open minds on a subject which perhaps comes under this category and which a lot of people consider far from adequately explained.

It will therefore be interesting for all of us to read of the new DFDR evidence which Crockett helpfully indicates will shortly be available, along the lines of:

“Latest reports are that the data for the last few minutes of the flight from the FDR was in fact there, unlike previous reports that said last six minutes was not there..and that no data available before the aircraft left 35,000 ft.

It is reported that New data now available shows the aircraft at 16,000 with the rudder deflection of 30 degrees or words to that effect..just a minute or so before aircraft hit the ground..”

I’m sure you realise that rudder hard-overs in the B737 are not necessarily restricted to relatively slow flight and low altitude regimes (Pittsburgh and Colorado Springs crashes). They can happen anywhere in the flight envelope – a point that begs the question, why is it that “MI185 was a completely different case”?

[Hudson]

The accident aircraft was fitted with a rudder pressure reducer which shortly after take off cuts back the hydraulic pressure to the rudder PCU such that it reduces the rudder pedal authority by about a third, allowing crews more time to respond and recover from unnecessary large rudder deflections. If any rudder pedal is pushed to its limit when the RPR transitions to reduced, then pressure airloads on the rudder reduce max rudder deflection and rudder pedal position. (this is an extract from Cockpit Panel Notes by captain Bill Bulfer USA).

So if the rudder went uncommanded sudden hard-over at cruise altitude then the RPR would come into action and the recovery would be straight forward for any competent 737 pilot.

You might lose a couple of thousand feet but it is recoverable. We have done it in the simulator. It would be too much of yet another amazing coincidence that the RPR would mysteriously fail at that precise instant an uncommanded rudder deflection occurred.

Additionally, I would guess that despite full purposeful rudder input by a pilot who was intent on topping himself, there is no way that the rudder would get to 30 degrees because not only the RPR would prevent this but blow back during any dive would negate anywhere near that figure.

During the court case held in Singapore, the records of each pilot revealed that both had recently been certified competent on unusual attitude recoveries in the simulator. And the captain was an experienced aerobatic fighter pilot. Upside down on his back was ops normal for him in his previous job.

Of course, one way of ensuring that you want to dive the aircraft at the max speed in the minimum time is to whack on full available rudder while at the same time applying full aileron and stick your thumb on the stab trim switch until you run out of forward electrical trim. That takes 8 seconds from normal cruise trim setting to full forward setting. Plausible scenario?

The suggested use of high power to get the nose up in a dive was suggested by an expert witness at the court case. I doubt if any sane pilot would seriously whack on full power in a near vertical dive near Mach One in order to try and raise the nose. Especially when the evidence indicated that the speed brakes were retracted. But certainly the "new" FDR evidence makes for interesting speculation, if nothing else.

[DIRK DIGGLER]

Errrrrr........what's your point cirrus?