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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 11th Jan 2015, 17:50
  #1761 (permalink)  
 
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If the crew failed to find the weather on radar that likely took them down, the first warning would likely be the sound of ice pellets hitting he aircraft.

Most of my tactical jet XC work (ancient history) was without available weather radar. The only operational restrictions applied from on high was, "do not fly into Weather Warning areas." As a result, we had the opportunity to fly into and through some otherwise interesting weather. Other than some spectacular St Elmo's fire, it was not that exciting.

For the meteorologists here, did conditions in the ITCZ on the airway that day equate to WW level storm intensity?

I'm betting that the weather is more likely to have interfered with the aircraft's sensors and thus precipitated this accident.
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Old 11th Jan 2015, 18:10
  #1762 (permalink)  
 
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Flat spin background

Originally Posted by jcjeant
With all the photos of aircraft parts available so far .. my feeling is a flat ditching of those parts .. little forward speed ... (my two cents)
Can't wait the analysis result of "black boxes" .........
Yes, I'm reading the wreckage as a flat impact with wings (+- 15 degrees) of level and low forward speed. This corresponds to a flat spin.

One ominous aspect of flat spins is the eyeballs out g that results from the rotation. This would rapidly disable the crew, particularly if they did not have their shoulder harness locked.

How to get into a flat spin? Not hard once you get real slow. Compressor stall one engine while at high power and high AOA.
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Old 11th Jan 2015, 19:08
  #1763 (permalink)  
 
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Matching up debris

If this helps anyone ive matched up the tail to approximately where it fits to the rear section.


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Old 11th Jan 2015, 19:14
  #1764 (permalink)  
 
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flat spin

"MACHINBIRD" IMHO if you'd ever done a flat spin, you wouldn't write :"One ominous aspect of flat spins is the eyeballs out g that results from the rotation. This would rapidly disable the crew, particularly if they did not have their shoulder harness locked."

I 've been teaching aerobatics and spin recovery ( positive, inverted, and positive flat and inverted) spins (in CAT "A" aerobatic airplanes...) for over 20 years and both my eyeballs are securely in place, or so say my FAA and JAR-FCL medicals.
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Old 11th Jan 2015, 19:14
  #1765 (permalink)  
 
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Originally Posted by Machinbird View Post
Yes, I'm reading the wreckage as a flat impact with wings (+- 15 degrees) of level and low forward speed. This corresponds to a flat spin.

One ominous aspect of flat spins is the eyeballs out g that results from the rotation. This would rapidly disable the crew, particularly if they did not have their shoulder harness locked.

How to get into a flat spin? Not hard once you get real slow. Compressor stall one engine while at high power and high AOA.
You don't need a compressor stall - high AOA and a small input to the rudder can put you into a spin relatively quickly. It was the standard method to enter a spin way back. Do it a fraction before the stall and you can have max lift on one wing and the other stalled. I would think that one of the Normal Law protections would stop you getting there unless it was all tied up with an overspeed protection because of a sudden increase in OAT.

I wonder if we are getting to a point where test pilots are going to be required to test departures from the flight envelope to see how the aircraft behaves and how to get it back? Otherwise a LOC for whatever reason that puts the aircraft immediately out of the envelope requires the crew involved to become test pilot capable in seconds.
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Old 11th Jan 2015, 19:21
  #1766 (permalink)  
 
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Originally Posted by formationdriver View Post
"MACHINBIRD" IMHO if you'd ever done a flat spin, you wouldn't write :"One ominous aspect of flat spins is the eyeballs out g that results from the rotation. This would rapidly disable the crew, particularly if they did not have their shoulder harness locked."

I 've been teaching aerobatics and spin recovery ( positive, inverted, and positive flat and inverted) spins (in CAT "A" aerobatic airplanes...) for over 20 years and both my eyeballs are securely in place, or so say my FAA and JAR-FCL medicals.
Wouldn't the g experience in the cockpit depend very much on the center of rotation of the fuselage? In a Cat A aerobatic aircraft the cockpit is not a lot forward and indeed may be on the center of rotation - probably with the design intent to reduce g when the aircraft is rotating. Now in a larger non-aerobatic aircraft that is not a design decision.
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Old 11th Jan 2015, 19:28
  #1767 (permalink)  
 
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Spin?

There is no where near enough wreckage for me to start concluding what the impact angles or energy may have been. However, there is one piece of evidence that has come in and must be taken into account. With the destruction of the aft pressure bulkhead I don't think it is possible that the impact of the tail was low energy. One POSSibility may be that the tail came down as a separate piece and the open end of the tube hit first with the hydraulic effect opening the pressure bulkhead and the bottom of the fuselage.
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Old 11th Jan 2015, 20:09
  #1768 (permalink)  
 
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VS damage: sideways on impact, starboard side down

Edit: with linear witness mark from subsequent impact with port HS?
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Old 11th Jan 2015, 20:12
  #1769 (permalink)  
 
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I have been wondering about this strange tail section torn off and went and took a look at a pretty recent water event - this one with a very successful outcome for everyone onboard. Also an A320.

Sorry, the pictures are small but I have links to highres pics at the end of the post.

Notice the similarity in the tail section. This is fron the transport of the recovered plane so no stabilizers...




The actual plane on the museum. Stabilizers are put back to place. Surprisingly similar damage as seen on AirAsia.



Some links to highres photos:

http://journeysbyjill.files.wordpres...2/img_0168.jpg

http://smithsonianscience.org/wordpr...light-1549.jpg

http://tinyurl.com/m978xrt

EDIT; Seems like the last picture won't show properly sometimes. I have saved it on my computer if someone is really really interested...

EDIT 2: Followed advice and used tinyurl.

Last edited by MrSnuggles; 11th Jan 2015 at 21:10. Reason: strange link - added tinyurl
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Old 11th Jan 2015, 20:27
  #1770 (permalink)  
 
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I can no longer find the NTSB report for 1549. Angle of the plane on impact would be interesting for those of us unfamiliar with it, if anyone can recall. Believe speed was approx. 153kt.
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Old 11th Jan 2015, 20:42
  #1771 (permalink)  
 
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Modern airborne radar is better than the "crap" we had 30 years ago? Surely you jest.

I could see the control tower on an airport from 5 miles out with the old radars, I could see individual airplanes parked on the ramp. I could see the weather clearly and make my own decisions as to the amount of water carried by parts of the cloud and thus make my own decision as to the parts to avoid. I flew years and years in the tropics and experienced hundreds of severe encounters at some of the worst levels (around 13,000 to 15,000 feet).

I give you the new radars are easy to use and they do the deciphering for you, but often they are wrong and always exaggerate. They are useless for fine work, cannot do even a small part of what was done by the older radars. They are cheaper to buy and to maintain, and are much lighter, so I see the reason for them, but don't kid yourself that they are better for the purpose they were built.
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Old 11th Jan 2015, 21:02
  #1772 (permalink)  
 
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susier

Here is, I believe, the full report:

http://www.ntsb.gov/investigations/A...ts/AAR1003.pdf

I just found another angle showing how/why an aircraft can be ripped apart from below...


Last edited by MrSnuggles; 11th Jan 2015 at 21:11. Reason: adding image
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Old 11th Jan 2015, 21:04
  #1773 (permalink)  
 
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flat spin

Good point, IAN G, about center of rotation. But, as you know, its real tough to get into a flat spin... which requires deliberately held full back stick (as AF# 447) AND out-spin aileron, i.e. a crew trying to stop the spin with ailerons (toward the high wing) instead of rudder. Anyone who has ANY unusual attitude/spin training KNOWS this is wrong. Dead wrong. From the French BEA report, AF # 447 wasn't in a spin, but a long (4 minute...) falling leaf configuration... in and out of stall, with wings alternately rising and falling as the nose remained close to, or above, critical AOA.
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Old 11th Jan 2015, 21:17
  #1774 (permalink)  
 
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Modern airborne radar is better than the "crap" we had 30 years ago? Surely you jest.

I could see the control tower on an airport from 5 miles out with the old radars, I could see individual airplanes parked on the ramp. I could see the weather clearly and make my own decisions as to the amount of water carried by parts of the cloud and thus make my own decision as to the parts to avoid. I flew years and years in the tropics and experienced hundreds of severe encounters at some of the worst levels (around 13,000 to 15,000 feet).

I give you the new radars are easy to use and they do the deciphering for you, but often they are wrong and always exaggerate. They are useless for fine work, cannot do even a small part of what was done by the older radars. They are cheaper to buy and to maintain, and are much lighter, so I see the reason for them, but don't kid yourself that they are better for the purpose they were built.
boofhead, thanks for that - have often wondered about these "modern" radars too
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Old 11th Jan 2015, 21:35
  #1775 (permalink)  
 
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RE Numerous posts

Safety vs cost and who decides: Black boxes have nothing to do with safety other than supplying new knowledge to prevent a similar future event. Ingenuity as per IanW, not bales of money, should be aimed at crash location improvements. But focusing money, attention, and ingenuity on wreckage location is attention not aimed directly at accident cause. Crash location improvements directed by hindsight have to wait for identical circumstances to recur, but even then black boxes cannot fully inform about the nature or extent of pilot confusion.

While holding the interest of many (including me), exactly how 8501 impacted the ocean is in many ways irrelevant to 'safety' because final impact most resulted from loss of control long before. Impact speed and attitude were not chosen by the 8501 pilots (unless Mr Snuggles is on to something). Falling leaf, spin, flat spin, or other descent profiles are mostly irrelevant because pilots don't train for them and pax jets aren't designed to complete or withstand recovery from them.

Accidents are ~0.001% (or pick a tiny %) of all flights. Some accidents such as airframe failure resulting from completely unforeseen forces or airframe inadequacies are unavoidable, but they get included in the 0.001%. 'Normal' rarely applies. What does usually apply is a confluence of events/circumstances peaking, like ocean rogue waves, in a very short amount of time, from a few seconds to hardly more than a minute. The last opportunity to avoid an accident is the time between the next to last and last decisions in a short chain. Accidents seemingly surrounded by normality, and accidents of an exceedingly rare confluence of factors, both share pilot confusion and inattention as high ranking primal causes.

One improvement would be better real time wx information (Langleybaston and ATC Watcher) to avoid the series of brand new surprises involved in 'picking your way through'. But there are numerous previous posts about the current limitations of both equipment and the operators of that equipment. Horizontal separation of five or fifteen miles from preceding flights no guarantee of identical weather.

The best solution would be to focus attention on how to elongate the time available to pilots to react to conditions to enable good decisions, better real time wx being one aspect. Time elongation is otherwise currently and systemically limited by both a very narrow range between overspeed and stall, and by momentary (where 60 seconds is a long time) failure of necessary instrumentation or agreement of automation components. More pilot time for thinking would prevent some accidents, time not currently available as events prove. My point is that accident prevention can't ignore the coffin corner of time, so while time needs to be addressed, the impediments are systemic. IanW's last paragraph in 1784 also applies.

Great set of Flt 1549 pics in MrSnuggles posts! Actual Utoob videos of the event show the angle of fuselage to water, which was notably glass smooth. The same impact angle where the point of impact chanced to be 20-30' fwd of that of 1549, and with the impact being not glass smooth but a 15' swell/wave instead could have holed the fuselage bottom of 8501 and directed a torrent of water into the fuselage, overpressuring the upper fuselage, parting the lower half of pressure bulkhead, and carrying away the aft floor, horizontal stab mounts (which escaped in 1549), FDR and APU. A lot of "could have's" remain.
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Old 11th Jan 2015, 21:38
  #1776 (permalink)  
 
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Have to agree with boofhead about the old radars. The "C" band would punch through everything and give you a clear picture of what lay behind the storm immediately ahead. Definition was absolutely superb. It was a sad day when they were removed for "progress" (cheaper).
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Old 11th Jan 2015, 21:42
  #1777 (permalink)  
 
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Modern Radar

I'm new to the blog, but very experienced with "old" radar. Many would argue that the old green screen radar scopes were more accurate. I agree in part, but I do not recall ever seeing a control tower or aircraft on the ground. I will admit I did not like the new digital color radar when it first emerged many years ago. In all fairness I always wanted to compare the old with the new in numerous difficult situations. Having 37 years with the airlines added greatly to my decision making process when interpreting course corrections for weather.

If you don't have this skill, avoid the situation to begin with or declare an EMERGENCY and turn around.
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Old 11th Jan 2015, 21:50
  #1778 (permalink)  
 
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Many thanks Mr. S, for the Hudson report link


Looks as if the pitch was 9.5 degrees and speed was 125kts, so I was mistaken about that.


Airbus ditching parameters:


'The January 21, 1988, Airbus certification test report stated that the fuselage of an A320 would "undergo no destruction liable to create a water passage" if the airplane ditched with the following parameters:


  1. landing gear retracted,
  2. 11 pitch,
  3. -0.5 glideslope, and
  4. flaps in landing configuration for minimum speed.


According to Airbus, the ditching certification criteria also assumed that engine power was available, that the descent rate was 3.5 feet per second (fps), and that the airplane landed longitudinal to any water swells. These criteria are consistent with the test results published in the NACA reports.'



There are similarities in that FR66 and aft of that were most severely affected (that is the point just forward of the rear door) however the VS was not caused to detach in that incident.


This point is interesting:


'As discussed previously, because of the operational difficulty of ditching within the Airbus ditching parameters and the additional difficulties that water swells and/or high winds may cause, it is very likely that, in general, after ditching an A320 airplane without engine power, the "probable structural damage and leakage" will include significant aft fuselage breaching and subsequent water entry into the aft area of the airplane. Therefore, it should be assumed that, after a ditching, water entry will prevent the aft exits and slide/rafts from being available for use during an evacuation.'

Last edited by susier; 12th Jan 2015 at 07:44. Reason: Add copy from report
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Old 11th Jan 2015, 22:21
  #1779 (permalink)  
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Regarding convection and why this flight had problems whilst others didn't, I feel it could have something to do with the fact that it was at a lower level (FL320) than any other flight (FL340-380).

In equatorial oceanic cumulonimbus, updraft strength can be enhanced above FL200 due to heat of sublimation of ice. Therefore it is possible that somewhere above this height and up to near FL320 the updrafts were especially strong but also still containing some supercooled water droplets and hence icing (observations showed -29 C at FL320, but in updrafts it could have been several degrees warmer than that). Flights higher up (-35 C at FL340, -40 C at FL360) were more unlikely to encounter supercooled water, therefore they may have escaped.

So, for 8501, possible airframe/sensor icing, affecting performance as the plane climbed to higher levels, and possible some ice crystal engine shutdown then to finish the job?

I have done a detailed analysis here.
 
Old 11th Jan 2015, 22:42
  #1780 (permalink)  
 
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Ber Nooly,

The higher you are the less airspeed due mach limitations. Hence less control surface effectiveness.
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