Air Asia Indonesia Lost Contact from Surabaya to Singapore

[phiggsbroadband]

Just wondering how many more AoA probes have been pressure washed since that 888 accident...

[MrSnuggles]

Did anyone check out the highres picture I linked to here: http://www.pprune.org/rumours-news/5...ml#post8814964 ?

To the right in that picture, looks like it took a hit by a small round thing? OR am I just imagining things? Anyways, it could have happened when the part hit the water!

Just thought about this when I read the post by VR-HFX here http://www.pprune.org/rumours-news/5...ml#post8817418 .

[Superpilot]

... and nothing the crew could do to save themselves.

I agree they didn't have a lot of time to react but this statement is not strictly true. As an aircrafter tester, the captain should've been aware of how to react in case the aircraft was not responding correctly. He was, after all, well used to pushing the A320 to it's limits (under Normal Law).

[mcloaked]

Replying to the post saying "An updraft will not in itself reduce airspeed. Updrafts add energy, not reduce it. The first reaction by the autopilot (or PF) would be to try to maintain altitude by putting forward pressure on the stick. This will in effect increase the speed because of the updraft wind vector":

There is something simple that can be calculated for the angle of attack instantaneous change due to hitting a sudden upcurrent such as in an active Cb. If the current airspeed is say 500kt and the aircraft is flying horizontally, then if a 50kt updraft is suddenly encountered then there will be an instantaneous change of AoA by an angle equal to arctan(50/500) which is about 5.7 degrees. It the aircraft was flying within a couple of degrees of the stalling angle of attack and encounters a transient strong upcurrent then there is a good chance of reaching the stalling AoA very rapidly. What the aircraft control response to that is will depend on how the fly-by-wire system has been coded to react, or how the pilot will respond if he/she recognises what has happened is not clear despite the various postulated scenarios already discussed. Equally there will be a reverse change to the AoA on exit from the same updraft so the net result will depend on how long the aircraft flies within updraft conditions and the velocity of the air within it. Is that not basic physics?

[BG47]

The Straits Times reports:

JAKARTA - Indonesia has suspended 61 flights from five airlines who have been found to have no valid permits to fly from the country, its transport minister Ignasius Jonan said on Friday.

The decision to review flight permits comes in the wake of the tragedy involving AirAsia flight QZ8501 which crashed into the sea while on its way from Surabaya to Singapore.

AirAsia was later found in violation of running the flight on a Sunday without valid permit from Indonesia.

Mr Jonan also said that the ministry has suspended 11 officials for negligence and have audited 5 airports in the country since the ill-fated crash.

[Toruk Macto]

How hard would it to be to have a basic AOA indicator installed in every commercial jet ? Then a basic training package to be included in every endorsement that trains to react in a situation when all hell brakes lose ? Consider it a last resort recall ? They seem to be taking care of passengers with new lounges , upgraded on board entertainment and meals , but in the end passengers may go without if they knew money went to a instrument that could make a difference ? Just a thought .

[Ian W]

Originally Posted by Propduffer

Although we don't know exactly what it was based on - because we were never told what radar had reported this, but in the first few days all the media was reporting that they had been told that the GS for QZ8501 was very low.

Now that we have the ADS-B information we can be sure this low groundspeed couldn't have come from secondary radar so it had to have come from a military primary radar. Or it might have been bogus information, but it has never been retracted afik.


Edit: After a bit of research I've come to the conclusion that the entire basis for the low speed assumptions for QZ8501 have been based on that radar plot which was released on day one of this event and had the numbers 363 which was taken to be the altitude and the number 353 which was taken to be the speed (IAS at FL 36.0).

That's not very solid evidence, that "radar plot" may have been composed for a news release quickly - it may have been mostly eye candy.

In modern systems the controller sees a 'track plot' that is made up from multiple surveillance inputs. Way back in the thread it was reported that secondary radar responses were lost first followed by ADS-B responses later. So the system was receiving both.

The speed displayed can be:
* Generated by the ATC system from the distance between successive track positions and the time. Most systems smooth this by taking the distance between for example the latest report and the one 5 reports ago. This is normal with SSR
* Replicated from the ground speed field of the ADS-B report
* Multi-Sensor Comparison with the speed from one source used but validated/corrected by the other source(s)

What will not happen is that the speed will be invented.

The problem with a snapshot is that you do not know the history of the ground speed displayed. Even if the previous update was 450 followed by 353 then that may not be a significant slow down, it may be an effect of going outside the bounds of the smoothing Kalman filter. What is needed is the raw SSR and ADS-B data received (and required to be retained for 28 days by ICAO). What you may be seeing is a replay of the time the incident involved using standard replay tools that are used for local investigations and training it may even be a replay of the data sent to the controller's display rather than reprocessing the input data.

I would not impugn the ATC by claiming they were producing made up 'eye candy'.

[phiggsbroadband]

Sea State and Pings at Tail Crash site.....


BBC News - AirAsia QZ8501: 'Pings' detected in plane search

[Triskel]

Mr Snuggles - thank you for posting link to hi-res pics. From the apparent concave folding of the skin, the pressure hull was probably intact on entering the water (otherwise the water pressure would equalise inside and out). The hull probably broke on contact with the sea floor or perhaps on the way down (if the water was stratified, on encountering layers of different density)?

[PT6Driver]

Triskel
[QUOTE]Mr Snuggles - thank you for posting link to hi-res pics. From the apparent concave folding of the skin, the pressure hull was probably intact on entering the water (otherwise the water pressure would equalise inside and out). The hull probably broke on contact with the sea floor or perhaps on the way down (if the water was stratified, on encountering layers of different density)?/QUOTE]

As we saw in the AF incident and other cases where an intact plane contacts the sea at high vertical speed, the water is about as friendly as concrete. This causes conciderable damage.
I would have thought the main damage would be done on impact with the sea surface and secondary damage as the wreckage was moved by the currents. I doubt there is sufficient depth for density layers to be a factor.
Even the Hudson ditching caused considerable damage with for example a support from the cargo hold being punched up into the cabin injuring a flight attendant.
I would however concur with you opinion that the aircraft wss relatively intact at impact.

[etudiant]

Relatively intact at impact is not the impression that these images transmit.
The tail structure is torn off and the various hull pieces are widely separated, in water shallower than the airplane was long. To me that suggests the airplane may have come apart even before it hit the water.

[susier]

How likely is it for the FDR to have detached from the airframe if the a/c reached the surface intact?

[Lonewolf_50]

Originally Posted by Toruk Macto

How hard would it to be to have a basic AOA indicator installed in every commercial jet ? Then a basic training package to be included in every endorsement that trains to react in a situation when all hell brakes lose ?

We discussed this at some length during the marathon AF 447 threads. Some professional pilots do not see it as the answer ... the link is to a discussion in PPRuNe Tech Log.

You clearly identified what has to go with an AoA gage in the cockpit: training. When and where it is an aid, and normally an additional scan item, is the key enabler to another instrument being of use in the odd occasions where it would be useful.

The paper linked in that post tells why IFALPA isn't so supportive of it as a solution.
Further that point, and as noted some posts ago: would it have been of use in this incident if the flight deck crew went into a fairly rapid task overload? FDR analysis will clarify, but a small wager is made at this point that the answer is no, not in this case.

[MrSnuggles]

Triskel:

Mr Snuggles - thank you for posting link to hi-res pics. From the apparent concave folding of the skin, the pressure hull was probably intact on entering the water (otherwise the water pressure would equalise inside and out). The hull probably broke on contact with the sea floor or perhaps on the way down (if the water was stratified, on encountering layers of different density)?

Did you look at the right on the highres, just above the hyphen? (It needs to be the picture with the A upside down.) To me it looks like something round hit the airplane - or I need to adjust my medication... *joke* Maybe, just maybe they hit hail of some kind...? Absolutely not explanation in and of itself but might give a hint, possibly?

[The Ancient Geek]

ANZ Perpignan

It was not an Air New Zealand captain or pilot in the seat for the Perpignan crash. He was a German pilot for the safety checks to return the plane to Air New Zealand. Very sad circumstance ... and nothing the crew could do to save themselves.

The crash was caused by pilot error - plain and simple.
The pilot was not a qualified test pilot.
Airbus specify that the AOA functional test MUST be carried out above 10000 ft AGL because if the test fails a lot of altitude will be lost in recovery.
He carried out the test at low level with predictable results.

[Machinbird]

Relatively intact at impact is not the impression that these images transmit.
The tail structure is torn off and the various hull pieces are widely separated, in water shallower than the airplane was long. To me that suggests the airplane may have come apart even before it hit the water.

Gents, best pull in your horns. This aircraft impacted with significantly less velocity than did AF447. Granted that it is a smaller aircraft and thus a bit harder to tear up into little bits, but the degree of deformation and disassembly was much higher in AF447.

This aircraft hit with very low forward velocity, from all appearances. Perhaps a spin or flat spin. Kinetic Energy goes as the square of the velocity. A spinning aircraft should have lower kinetic energy than a deeply stalled one at terminal velocity.

[AirScotia]

This aircraft hit with very low forward velocity, from all appearances. Perhaps a spin or flat spin. Kinetic Energy goes as the square of the velocity. A spinning aircraft should have lower kinetic energy than a deeply stalled one at terminal velocity.

My physics is rusty, but isn't velocity a product of speed plus direction? A spinning aircraft may not have forward speed, but it does have plenty of changing direction, therefore plenty of velocity. So it will hit the ocean with plenty of energy, I assume?

[Ian W]

Originally Posted by etudiant

Relatively intact at impact is not the impression that these images transmit.
The tail structure is torn off and the various hull pieces are widely separated, in water shallower than the airplane was long. To me that suggests the airplane may have come apart even before it hit the water.

I would think that any breakup could have occurred on impact. The fuselage if the concertina effect is correct would have been crushed from beneath and the hold and passenger cabin filled with water and possibly with engines/wings detached could have sunk fairly rapidly but all the parts would be carried and rolled along by the 4 to 5 knot currents until they embedded sufficiently in the seabed mud in a position that the current no longer moved them that could take from minutes to hours. So parts being miles apart would not be at all surprising. If the entire tail empennage complete with pressure bulkhead was one of the pieces after hitting the sea surface it may well have floated in severe winds for hours or even a day or so. This would drift the tail in a totally different direction to the rest of the aircraft and it could easily be several miles in a random direction before eventually sinking.

Tracking the pieces using winds and currents is possible but all sorts of assumptions have to be made on how long each would float what the sea state, currents and winds were at the time how long to get stuck in the mud etc. The calculation would probably depend more on the assumptions than any data.

[Lonewolf_50]

Originally Posted by Machinbird

Gents, best pull in your horns. This aircraft impacted with significantly less velocity than did AF447.

Do you arrive at that provisional conclusion based on the condition of the bits so far found, on the track info available, or both?

This aircraft hit with very low forward velocity, from all appearances.

If true, then should not most of the major parts of the wreckage be near to each other?
EDIT: deleted. Ian W explained how it might come about that way.

A spinning aircraft should have lower kinetic energy than a deeply stalled one at terminal velocity.

Note: I will guess that Airbus did not do spin tests on the A320 family. Maybe computer modeling is sufficient to make an informed estimate of what it will do in such a condition. Absent that info (which some people may have seen, but I have not) how an A320 spins is a bit of a guess.
@thecrozier:

I can't remember but was 447 in a spin most of the way down or just stalled with a fairly constant heading?

The latter, except with slowly changing heading.

FWIW too close a comparisons to AF 447 seems to me premature.

[AirScotia]

@thcrozier

I can't remember but was 447 in a spin most of the way down or just stalled with a fairly constant heading?

I recall that it made a slow, smooth turn. No spinning.