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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 1st Jan 2015, 20:56
  #921 (permalink)  
 
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yes i was also surprised but since Tuesday the Indonesians have been saying a C130 spotted a A320 like shaped shadow on the sea bed....just curious why this hasn't appeared
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Old 1st Jan 2015, 20:56
  #922 (permalink)  
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Airbubba :
Hmmm, this .1 nm offset must not have made it to the real world.
No it was refused in the end by ICAO for 2 reasons : mathematically on crossings with offset you increase the collision risk model (risk area is bigger ) and on principle/legal grounds that you cannot voluntary impose a decrease in navigation accuracy.
So yes with augmented GNSS coming in you will cross in opposite directions with the centre bar in the windscreens on top of one another .

Brings us back to making absolutely sure our barometric Altitude accuracy is perfect, especially in RVSM above FL400....
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Old 1st Jan 2015, 21:02
  #923 (permalink)  
 
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ADS-B format retains both ways of reporting barometric as well as gps altitude
Yes but the ICAO standard chosen was Mode S/Baro, not the GPS Alt. No single a/c ADS equipped flying today uses and transmit GPS Alt.
ATCWatcher, Pls recheck the docs:
DF17 velocity squitter (subtype 19) does transmit the difference between baro altitude and GNSS height.
A simple addition then calculates the GNSS height.
All newer transponders do transmit this and I can see it if I want (though it do not know what to do with it)
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Old 1st Jan 2015, 21:47
  #924 (permalink)  
 
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Originally Posted by John Farley
...
If you see that as me banging a drum of hate I can only apologise for confusing you.
I'm the one that shall apologize Sir, thank you.
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Old 1st Jan 2015, 21:49
  #925 (permalink)  
 
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But even before that started the THS had trimmed full up
I would be interested in discovering why this 'feature' exists. Is there any flight mode which requires 'full up' trim ?

Apologies for questioning this - I fly simple aircraft where the pilot selects the trim effect he wants without a computer doing it for him.
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Old 1st Jan 2015, 21:56
  #926 (permalink)  
 
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Island Air Photo...
I am sure there is no SOP in any Airline for pilots to just blast thru CB's.

I have not detected in this thread a cavalier attitude toward thunderstorms;
rather quite the opposite.
While flying formation in an F4 Phantom, my lead flew into an embedded Tstorm near Iwakuni, Japan. Airspeed was 400kts indicated at about 10,000 ft.
Was in the CB for maybe 10-15 seconds. We exited about 90 degrees off original heading and inverted, with lead aircraft on some other goofy heading and far from us. Our G meter showed a reading of a shade over 6 g's and a minus 2 g's. Fortunately there was no hail encounter.

They can quite easily destroy airliners, a fact I am certain the Captain and First Officer of the Air Asia A320 were well aware of.
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Old 1st Jan 2015, 22:27
  #927 (permalink)  
 
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Get back on topic

Boy, is this thread off-topic! Is there another one which I have missed which is discussing QZ8501?

The Guardian is reporting an expert as suggesting the plane landed on the sea, but was overwhelmed by waves.
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Old 1st Jan 2015, 22:28
  #928 (permalink)  
 
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THS trim

@ Rudder

Go find hundreds of posts on the AF447 threads that discuss THS control laws.

The THS only goes as far as it needs to so as to provide full elevator deflection both directions. So it's HAL rolling the big trim wheel like we used to to relieve stick/yoke forces for the desired AoA or gee or pitch attitude..

Only reason the AF447 THS trimmed to the limit was the pilot held back stick for a long time, and HAL obliged. You and I would have rolled the wheel back manually in the old days. Maybe we would have realized it was full back, maybe not.

I can see some conditions requiring full trim of the stabilizer, but rarely. Things like a screwed up cee gee, or loss of flaps or.......
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Old 1st Jan 2015, 22:31
  #929 (permalink)  
 
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Originally Posted by island_airphoto
Question for heavy metal pilots from a light metal pilot:
Many posts seem to be something like "a thunderstorm should not be able to take down a modern jet".
I knew that would come up, which is why I previously posted the case where an SR-71 failed to out-climb a thunderstorm and was destroyed, plus the case in Japan of an A-4 caught in clear air turbulence that was nearly destroyed. A thunderstorm can best any production aircraft ever made. I think the airframe of Chuck Yeager's X-1 was stressed to 25 g, I guess it could survive most things but it's not a production aircraft.
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Old 1st Jan 2015, 23:02
  #930 (permalink)  
 
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The Guardian is reporting an expert as suggesting the plane landed on the sea, but was overwhelmed by waves.
It appears more likely that the plane was shedding occupants on the way down.
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Old 1st Jan 2015, 23:05
  #931 (permalink)  
 
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To help with getting a perspective on stall recovery in large passenger jets, assuming still air, wings level nose up stall, how much height is lost to effect a recovery, lets say from 35,000 ft or from 20,000ft.
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Old 1st Jan 2015, 23:07
  #932 (permalink)  
 
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SCMP this morning 0804020115:

Analysts have claimed the pilot of the crashed AirAsia flight may have made an emergency water landing, only for the plane to be overcome by high seas.

The A320-200 left Surabaya, Indonesia early on Sunday and disappeared from radar over the Java Sea during a storm, but it failed to send the transmissions normally emitted when a plane crashes or is submerged.

As search teams battled poor weather in the hunt for the black boxes, experts said the lack of transmissions suggested the experienced former air force pilot, Captain Iriyanto, conducted an emergency water landing that did not destroy the plane.

"The emergency locator transmitter would work on impact, be that land, sea or the sides of a mountain, and my analysis is it didn't work because there was no major impact during landing," said Dudi Sudibyo, of aviation magazine
Angkasa.

"The pilot managed to land it on the sea's surface," he added.

The plane, carrying 162 people to Singapore, was at 10,000 metres when the pilot requested a course change to avoid storms.

Although permission was granted to turn left, the pilot was not immediately allowed to ascend owing to heavy air traffic, and the plane disappeared from radar soon afterwards. Indonesia's search team scoured the sea for more than 48 hours before the first debris was spotted off the island of Borneo after a tip-off from fishermen.

So far, the search team has found eight bodies, but air safety officials said it could take a week to find the crucial black-box recorders.

An emergency-exit door and an inflatable slide were among the first items recovered by the search team, suggesting the first passengers may have started the evacuation process once the plane landed on water.


Coupled with the leaked radar evidence of rapid climb followed by rapid descent and the non-wearing of life jackets by recovered victims, I find this possibility unlikely.
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Old 1st Jan 2015, 23:15
  #933 (permalink)  
 
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Regarding the steep climb of the aircraft prior to the accident, I can imagine a couple of causes and keep in mind these are not mutually exclusive.

1. What is the barometric pressure variance at a fixed altitude above sea level in this sort of storm? A drop in air pressure (perhaps by an updraft) might artificially increase the apparent climb. Has this been factored in?

2. Strong convection-induced issues?

3. Erroneous instruments?

4. Software bugs (thinking of the MH124 b777 uncommanded climb).

I strongly suspect the fdr will be needed to resolve these questions.
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Old 1st Jan 2015, 23:21
  #934 (permalink)  
 
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'Controlled' ditching

Seems totally implausible, I'm sure if this was a potential outcome, during the descent the CC would have been making sure life vests were donned and barring the one erroneous report, there has been no suggestion that those souls recovered had them on. Such sensationalist reporting gives the poor grieving families a misplaced hope that there may be survivors out there. May those lost in this terrible tragedy rest in peace.
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Old 1st Jan 2015, 23:23
  #935 (permalink)  
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joema:

I knew that would come up, which is why I previously posted the case where an SR-71 failed to out-climb a thunderstorm and was destroyed, plus the case in Japan of an A-4 caught in clear air turbulence that was nearly destroyed. A thunderstorm can best any production aircraft ever made. I think the airframe of Chuck Yeager's X-1 was stressed to 25 g, I guess it could survive most things but it's not a production aircraft.
I believe that SR-71 was lost because both engines flamed out inside the TRW, rather than structural failure. It makes me think of the DC-9 that crashed trying to land on a narrow, tree-lined Georgia road after both engines was destroyed inside a TRW. But, they came out the other side intact.

The engines at issue should be of considerable interest to the investigators.
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Old 1st Jan 2015, 23:24
  #936 (permalink)  
 
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He was sceptical, however, that the figure cited of up to 24,000 feet per minute descent was possible, saying that terminal velocity is nowhere near that speed."
Terminal velocity would have nothing to do with it though would it? If it's in downdraught !

Likewise, this misunderstanding is exactly why press & media are annoying the hell out of me (and some pruners)
... suggesting that because radar recorded climb rates were so high.. "..it had to be in a stalled condition.

Rubbish !
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Old 1st Jan 2015, 23:31
  #937 (permalink)  
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Depends on stall entry speed, and altitude, as a result of AF447, we have all been required to undergo high altitude stall training, in an aircraft that was advertised as un-stall-able, by engineers that tried to design pilot error out of the system.

This is so good, the design, folks who have never flown airplanes before, can get it under their fingers in just a few months. Simple. We need to do that, sales in Asia are booming.

Now, sadly, we are trying to design the engineers out of the airplane, piloting can't be taught, it must be experienced, an involved apprenticeship that brooks no shortcut of any kind, we are re-writing butchered checklists in the hopes of saving lives.

Nothing like being there, in the cockpit, in the Shiite, to get a real feel for your mortality. And the cloud nine the engineers live on, safe at home in their feather beds.
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Old 1st Jan 2015, 23:38
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At the time of the crash the seas were said to include 3m swells. Would the chances for ending up with an unbroken plane after ditching on 3m waves be fairly low?
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Old 1st Jan 2015, 23:45
  #939 (permalink)  
 
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Mr. Dudi Sudibyo

...is not to be taken seriously, IMO.
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Old 2nd Jan 2015, 00:02
  #940 (permalink)  
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"piloting can't be taught, it must be experienced"

Do you seriously think the designers didn't have experienced pilots on their teams? The computer logic will take into account all rules of physics regarding flight and can make calculations a thousand times faster than a human. HAL can also be programmed with anticipatory logic so that if one sensor is providing eroneous data he can figure out what is going on. Like humans, if he has been made totally blind, then he can no longer perform safely and so he hands back control...usually at the worst moment. The false logic of some commentators here is that because a computer can't cope in every situation, a human pilot would be safer in every situation. Realistically, I don't think pilots would want the autopilot tripping off everytime the aircraft entered a few bumps.

Edit - I understand the point that is being made by some i.e. that HAL is a bad loser and won't give back control until the last possible moment...at which point the aircraft is on the edge of its flight envelope...but there is an off switch.
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