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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 25th Jan 2015, 06:09
  #2481 (permalink)  
 
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We simply don't know why the pitch up occurred or why it turned left.
We know why he turned left (weather deviation)
06:12 Contacts Jakarta center 125.70 at FL320, requests weather deviation left of M635 airway and climb to FL380
Dunno if climb was for the same reason ..........
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Old 25th Jan 2015, 06:53
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Unlikely to be a 90 degree deviation and it occurred after the pitch up.
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Old 25th Jan 2015, 07:13
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And climb was most likely because he was below optimum for such a short flight.
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Old 25th Jan 2015, 07:42
  #2484 (permalink)  
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Turn and Climb Timing

Unlikely to be a 90 degree deviation and it occurred after the pitch up.
Having no idea of the exact Wx that he was facing, I have no idea what his deviation was likely to be. I have no idea why 90 degrees would be more or less likely. However, the radar plots which have been doing the rounds lately show a left turn initiated at 23:16.52 at FL320 and rapid 'climb' starting at 23:17.18 while still at FL 320.

And climb was most likely because he was below optimum for such a short flight.
it has been stated many times that his increase in FlL request was denied. It's highly unlikely that he would initiate a unauthorized climb to move up to optimum .
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Old 25th Jan 2015, 08:53
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I think it unlikely that it would have been totally an updraft. But if it was the autopilot would maintain altitude until the speed increase approached Vmo/Mmo, then the automatic overspeed protections would raise the nose to control speed. This overides sidestick input from the pilots and MAY trigger a cascade of events ending in a high alpha attitude.

There are other scenarios involving no sensor fault but an unhappy combination of wind change, temperature spike and high vertical speed approaching a higher target altitude which can result in a low energy/high pitch situation.

Writers without Airbus experience should appreciate that the flight control programming is biased towards load relief and structure protection, hence the attitude constraints and the urgency with which overspeeds are "corrected" by the software.

Additionaly, from my own simulator training I suspect (but have not found mention in any manuals) that when a protection gets triggered it stays active until the original condition has been corrected, so that an overspeed protection will overide the stall protection from activating, and vice versa.
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Old 25th Jan 2015, 09:18
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I think it unlikely that it would have been totally an updraft. But if it was the autopilot would maintain altitude until the speed increase approached Vmo/Mmo, then the automatic overspeed protections would raise the nose to control speed. This overides sidestick input from the pilots and MAY trigger a cascade of events ending in a high alpha attitude.

There are other scenarios involving no sensor fault but an unhappy combination of wind change, temperature spike and high vertical speed approaching a higher target altitude which can result in a low energy/high pitch situation.

Writers without Airbus experience should appreciate that the flight control programming is biased towards load relief and structure protection, hence the attitude constraints and the urgency with which overspeeds are "corrected" by the software.

Additionaly, from my own simulator training I suspect (but have not found mention in any manuals) that
As a writer with Airbus experience, i can say that you very accurately described what i criticise since many years!

Reading what i have enlightened makes a scary story.
In short, the two recent Airbus fatal accidents have shown that whatever the protections wanted to protect (load relief and structure protection) has resulted in the exact opposite!

We can now wait for another lengthy and overcomplicated analysis of what exactly happened at which exact moment, what computer action went wrong and what exactly the crew should have done out of memory to counteract the overwhelmed and misguided program, or .... we can wait for a speedy and effective correction of the programming and design.

My bet is on the earlier in a years time and nothing on the second.
Waiting for the next Bus excursion.
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Old 25th Jan 2015, 09:21
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"it has been stated many times that his increase in FlL request was denied. It's highly unlikely that he would initiate a unauthorized climb to move up to optimum ."

He had been cleared to climb from FL320 to FL340 and to await further clearance. He shot through FL340 in the zoom. A 90 degree turn is not a w/x 'deviation'; it would need a PAN call or at least to advise how many degrees. It's normal to state how many degrees L/R, or more usually, the number of miles off track required.
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Old 25th Jan 2015, 09:34
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Gretchenfrage, Australopithecus

As a writer with Airbus experience, I can say that you very accurately described what I criticise since many years!
Just a question from a VFR pilot: It would seem that a safer reaction to overspeed would be to apply speedbrakes/reduce thrust, instead of raising the aircraft's nose and potentially end up in a high-alpha situation. Or am I missing something?
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Old 25th Jan 2015, 09:41
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Fresh bid to raise fuselage fails

"The Indonesian admiral in charge of operations to recover AirAsia flight QZ8501 has told the BBC the fuselage may be too fragile to be lifted.
Rear Admiral Widodo's comments came after a renewed attempt to raise the wreckage from seabed failed when it kept breaking into pieces."
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Old 25th Jan 2015, 09:51
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"a safer reaction to overspeed would be to apply speedbrakes/reduce thrust, instead of raising the aircraft's nose"

In most airliners they are not speedbrakes, but spoilers. Fighters generally have speedbrakes. Spoilers reduce lift as well as increase drag. Hence in airliners they are generally only used on descent when reduction in lift is required and not in level cruise or climb as they reduce stall margins. In the rare event of an overspeed trend in level flight at altitude, you reduce thrust first and only then consider using spoilers. This was not an overspeed situation but a nose up pitch with reducing airspeed.
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Old 25th Jan 2015, 10:45
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RifRaf,


On all Boeings the handle to lift the spoilers is called the "Speed Brake lever".

Boeing are also very clear that when correcting overspeeds in cruise, thrust lever to idle positions should be avoided. Thus the preferred method is to apply speed brake first. This protects against slow engine acceleration time at altitude and the risk of overcontrolling speed and inducing a low speed event. That's straight out of the Boeing Flight Crew Training Manual for the B757,767,777,787.


I would try and avoid the sweeping statements.
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Old 25th Jan 2015, 11:27
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On Boeing jets, in cruise when one needs to reduce speed, the Speedbrake will be the first option.
Boeing does advice strongly against idling your thrust on cruise. The SPEEDBRAKE is there to accomplish the mission, but do it gently, like everything at altitude.

I seem to remember that AB recommends the same.


By the way...if in doubt: all automatics OFF, go to DIRECT LAW, fly the aircraft raw data like any other aircraft in the world .

First lesson I got during my TR on A320 now 14 years ago...is that still valid? Am I completely misled in this?
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Old 25th Jan 2015, 11:44
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Things obviously change.
Interesting, as I only flew 707s and 747s in the early days of autothrottles. Putting out spoilers in cruise then increased thrust if the A/T was still in. So you wound back or disconnected the A/T first. Your point about spool up times is valid, but if you anticipated the target speed you could easily spool up in time and flight idle rpm took spool up times into account. In a severe slowdown you still reduced thrust prior to spoilers but not necessarily to idle depending on the situation. Using spoilers against thrust was a no-no.

Undoubtably with better computation over time this has changed and the deployment of spoilers adjusts the thrust appropriately so that it's not working against the increased drag. You are correct with the Boeing terminology re "speedbrakes", but its mostly a simplified convention. Speedbrakes don't give you 'walkdown' as airline spoilers do? (did).

In most fighters you want to reduce speed quickly without reducing lift and turning performance, so you hang something out that's usually off the fuselage and not the wing. For airline purposes the distinction does not matter as Boeing has decided and "speedbrake" is the simpler generic term. However, it would be interesting to know how much the later Boeings' stall margins are affected by "speedbrake" deployment compared with the early models. No doubt the airbuses are similar to the later Boeings so I accept that speedbrakes are now the first option. I'd also be interested to know how much the lift dumping function relative to the drag increasing function of airliner "speedbrakes" has changed over time. No doubt it varies with the phase of flight whereas earlier it was one size fits all. Thanks for the correction.
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Old 25th Jan 2015, 11:46
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Originally Posted by RifRaf3
"a safer reaction to overspeed would be to apply speedbrakes/reduce thrust, instead of raising the aircraft's nose"

In most airliners they are not speedbrakes, but spoilers. Fighters generally have speedbrakes. Spoilers reduce lift as well as increase drag. Hence in airliners they are generally only used on descent when reduction in lift is required and not in level cruise or climb as they reduce stall margins. In the rare event of an overspeed trend in level flight at altitude, you reduce thrust first and only then consider using spoilers. This was not an overspeed situation but a nose up pitch with reducing airspeed.
The automatics could have thought it was overspeed.

Enter a warm air with a spike up in outside air temperature and the Airbus protections can give you a zoom climb. If that warm air is warm because it is an updraft of significant strength the zoom plus updraft speed could lead to an impressively rapid gain in altitude.

It is what actions are taken by the crew and the subsequent changes in air temperatures, wind changes and downdrafts that will decide what happens to the aircraft. From previous posts on this and AFR447 thread it would appear setting pitch and power for cruise (if the automatics will let you) is the best strategy. And from memory of previous posts this includes stop the trim doing whatever it is doing and manually override it to set what is required, push forward on the stick more than half way to break out of an Alpha prot zoom etc etc., These all appear actions to prevent the aircraft automatics causing issues.

See this report

The A340 crew received a TCAS TA at 14:09 hrs (A340 clock time) alerting them to the proximity of
the A330. At 14:20:40 hrs the aircraft entered a region of successive and increasing variations in wind
and air temperature, which in turn caused fluctuations in pitch angle, normal g, altitude, calibrated
airspeed, engine N1% and Mach number. One minute later in a particularly vigorous fluctuation, the
aircraft’s Mach number briefly increased to 0.87. This speed excursion above the Mach 0.86 limit
triggered a Master Warning at 14:21:40 and automatically disengaged the autopilot.
One second later
the TCAS issued an RA with a “DESCEND, DESCEND, DESCEND”audio warning. In the two second
period after the initial speed excursion above Mach 0.86 the Mach number decayed to 0.855 and then
increased again to 0.882. It remained above 0.86 for two seconds before decreasing and remaining
below 0.86 for the remainder of the turbulence encounter.

Five seconds after the autopilot disengaged, the thrust levers were closed and then the autothrust was
disconnected
, probably by the handling pilot in an effort to prevent another overspeed condition. Ten
seconds after the autopilot disengaged, the corrected or phase-advanced angle of attack (a computed
parameter which is not recorded but can be calculated by Airbus Industrie from the DFDR data) reached
the ‘alpha prot’ value. This angle of attack excursion beyond alpha prot caused a change in the pitch
flight control law from normal law (NZ law) to angle of attack protection law (AoA law)
. If both
sidesticks are at neutral, the AoA protection law seeks to hold the angle of attack constant at alpha prot
until a sidestick pitch command is made. If the stick is pulled fully aft then the angle of attack increases
to alpha max. If the sidestick is not moved aft, AoA protection law remains active until a nose-down
command greater than half forward travel is made or until a nose down sidestick input has been applied
for more than one second. The first recorded sidestick input was made at 14:22:08 which was some 28
seconds after the commencement of the Master Warning.
For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL 360
but once AoA law was invoked at 14:21:50 hrs, the aircraft’s attitude began to pitch nose-up. The pitchup
trend continued for 17 seconds reaching a peak of 15
nose-up shortly before the first nose-down
sidestick command was applied. Throughout this phase the aircraft climbed rapidly (reaching a peak
rate of about 6,000 ft/min) due to the increase in lift created by the flight control system’s capture of
alpha prot. The aircraft reached its apogee at FL 384 at 14:22:28 hrs where the airspeed had decayed to
205 KIAS and 0.67 Mach even though full thrust had been applied.
Page 11 of:
http://www.aaib.gov.uk/cms_resources...%2006-2001.pdf

So what happens at FL380 and 205KIAS/Mach 0.67 15deg nose up, if full thrust is applied and there is compressor stall on the left hand engine? You now have full thrust on the right engine and drag from the left engine. IMC in a grey goldfish bowl with severe turbulence is not a time to be the first pilot to flight test the aircraft's 'spin tolerance' with the aircraft helpfully playing all the various cavalry charges and stall warnings sufficient that you cannot hear each other.

Last edited by Ian W; 25th Jan 2015 at 11:49. Reason: Add clarification on overspeed.
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Old 25th Jan 2015, 11:52
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I know on the Boeing 787 direct law can be pilot selected. I thought on the Airbus only the aircraft computers could select direct law not the pilot unless he starts disabling systems to try and force the computers into direct law. Has there been a recent change in Airbus philosophy?
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Old 25th Jan 2015, 12:07
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On lifting and evidence...

"The Indonesian admiral in charge of operations to recover AirAsia flight
QZ8501 has told the BBC the fuselage may be too fragile to be lifted.
Rear Admiral Widodo's comments came after a renewed attempt to raise the wreckage from seabed failed when it kept breaking into pieces."
The fragility should not be surpring in general, and is certainly no surprise when you look at even the fuzzy under water pictures.

I have not seen any in-depth official statements on the lifting goal and strategy - what is exactly meant to be achieved. If a poster has some info on it, I would be interested. The goals are probably interesting for many posters, the lifting strategy probably for less.

What one would expect in a 'global attention' case like this is to get some international professional salvage guys in. I have seen foreign aerospace expert involved but not underwater salvage guys. Expertise is expertise, both up and below. Such an approach would not 'lose face'. It is common international practice. These specialists may have a row of proven options in mind.

A few days ago I was thinking ... most shipbuilding having moved to Asia... dont they have a floating/semisubmersible 2nd hand shipdock somewhere, float that to the location, submerse it as required, and get wreckage in without having to lift much, not having to take risks breaking the surface, and even more when lifting, and later more when tying on deck, with these risks repeated in the next land-based phases...? With this option you could collect the lot in situ with less risk. Later tow the dock to shore. De-ballast, and there you are. You even have a longer weather window with this....
For the smaller parts you might also take a few, certainly available, shipping containers (20 or 40x8x8 foot), reinforce them, make a few holes in them, cover the holes with a mesh, sink them on locations, and repeat what I just said for the shipdock. Bonus advantage is, container lifting gear is standard. And it might even help the divers in a number of ways.
The specialists I mentioned would immediately know if this was feasible.

In this case a way shallow water recovery almost seems more of a challenge than much deeper water. There you can get the 'big boys' in ... like the 'dockships' and 'servants' and the lifting barges and big lift semisubs.

Before lifting the tail, there was probably enough opportunity to photograph and video the lot. With the main and wing that is much less certain.

I certainly hope that we do not need evidence from the main and wing ... keeping in mind all the cases where investigators were in the end looking for specific components to be able to close the case.
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Old 25th Jan 2015, 12:20
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Originally Posted by RifRaf3
"it has been stated many times that his increase in FlL request was denied. It's highly unlikely that he would initiate a unauthorized climb to move up to optimum ."

He had been cleared to climb from FL320 to FL340 and to await further clearance. He shot through FL340 in the zoom. A 90 degree turn is not a w/x 'deviation'; it would need a PAN call or at least to advise how many degrees. It's normal to state how many degrees L/R, or more usually, the number of miles off track required.
He had been cleared to FL340 but there was never a response to that clearance. That tells me they never heard it. It also tells me they did not respond because they were already too busy dealing with the problem that caused the aircraft to climb unintentionally. I believe it had to be a mechanical/software issue, a weather related updraft, or a combination of both.

I can't see any other explanation as to why they never responded to the ATC clearance they were given.
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Old 25th Jan 2015, 12:22
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The salvage people are never backward in coming forward - and are to be found in Singapore - but there are restrictions on their ability to operate in Indonesia, which would need a high level clearance.
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Old 25th Jan 2015, 12:39
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The automatics could have thought it was overspeed.

Enter a warm air with a spike up in outside air temperature and the Airbus protections can give you a zoom climb. If that warm air is warm because it is an updraft of significant strength the zoom plus updraft speed could lead to an impressively rapid gain in altitude.
Yes, I wondered if that might be the case/possible?
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Old 25th Jan 2015, 12:41
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"He had been cleared to FL340 but there was never a response to that clearance. That tells me they never heard it. It also tells me they did not respond because they were already too busy dealing with the problem that caused the aircraft to climb unintentionally. I believe it had to be a mechanical/software issue, a weather related updraft, or a combination of both.

I can't see any other explanation as to why they never responded to the ATC clearance they were given.He had been cleared to FL340 but there was never a response to that clearance. That tells me they never heard it. It also tells me they did not respond because they were already too busy dealing with the problem that caused the aircraft to climb unintentionally. I believe it had to be a mechanical/software issue, a weather related updraft, or a combination of both.

I can't see any other explanation as to why they never responded to the ATC clearance they were given."

That's a good point and a distinct possibility.

I also agree with Ian W that the zoom climb was probably caused by the system responding to a perceived overspeed for whatever reasons that have been outlined and that the left turn may have been caused by a left eng fail/stall. Alternatively it may have been a left bank to lower the nose, but that assumes that they had gained manual control by then. However, there appears to have been no actual overspeed.
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