AirAsia flight missing

[Evan]

Hi I'm no expert but I've been examining all the information so far and I'm surprised why no real "experts" have been discussing the possibility of some sort of mid-air breakup or explosion of the plane. We have seen nude bodies, bodies still strapped in their seats, and there's also reports of pieces of wreckage seen scattered on an island. This all seems very similar to China Airlines 611, which was a mid air structural failure. Just wondering why there's been very few discussion of such a possibility and why instead people keep focusing on the AF447 stall scenario.

Nobody is ruling it out. The concentration of the wreckage will tell us a lot. A midair typically scatters the wreckage over a large area. Floating wreckage of course scatters itself so we need to see where the submerged wreckage is. Thus far, they are reporting four large pieces lying next to each other. That seems more aligned with an AF447 scenario but if the rest of the wreckage is found further off then it becomes more of a mid-flight breakup scenario.

We can't speculate much more until we see some images of the wreckage. Apparently they already exist.

[georgel]

For example, the the MD-80 has two hydraulic systems. One of them is powered by the engine pump and a backup electric pump (only with AC, not from battery). The other one is powered by the other engine's pump and a one-way pressure transfer pump powered by the first system. There is no APU-driven hydro pump (although the APU can provide electric power for the electric pump) and there is no RAT. A you see, not a very redundant design.

The transfer pump is according to your specification a "two-way", e.g. transfers energy from the system with higher to the system with lower hydraulic pressure. Considering the fact that the flight controls of MD-80 do not require any hydraulic pressure to control the aircraft (e.g. the "traditional linkage" move(s) control tabs) the design has very sufficient redundancy. I like MD-80s though the airbuses are modern and I even I have to pass conversion soon ;(

[Gabriel]

The transfer pump is according to your specification a "two-way", e.g. transfers energy from the system with higher to the system with lower hydraulic pressure. Considering the fact that the flight controls of MD-80 do not require any hydraulic pressure to control the aircraft (e.g. the "traditional linkage" move(s) control tabs) the design has very sufficient redundancy. I like MD-80s though the airbuses are modern and I even I have to pass conversion soon ;(

Hmmm.... The pressure transfer pump in the A320 is two way, triggered automatically when the differential pressure between the two systems reaches a threshold (500 PSI IIRC) transferring power from the system with higher pressure to the one with lower.

But I thought that the one in the MD-80 is one way. There two hydro systems ann each of them have two power sources. System 1 (I'm inventing the number) is powered by the engine driven pump and an electric backup pump. The system 2 has also it's engine driven pump (from the other engine) and the transfer pump powered by system 1. System 1 can't be powered by system 2 in the same way (but has the electric pump that system 2 lacks).

Am I wrong? My... "knowledge" about the MD80 system comes from the best add-on ever for MSFS 98: The "MadDog".

And I love that plane too. My all times favourite.

[AVION1]

BEA is taking care of the investigations:
In the context of the searches aimed at locating the wreckage of the Airbus A 320-200, flight Air Asia 8501, BEA investigators are participating, with their Indonesian and Singaporean counterparts, in the underwater sea searches. During the morning of January 2nd, local time, a ship will be taking the investigators to the search area, with detection equipment including hydrophones, in order to try to locate the acoustic beacons from the two flight recorders (Cockpit Voice Recorder, CVR and Flight Data Recorder, FDR).

[Jpmkam]

Divers finally able to begin underwater search.

With the weather improving, divers prepared Sunday to examine wreckage of AirAsia Flight 8501 in hopes of retrieving the rest of the bodies and finding clues to what caused the plane to crash in stormy weather a week ago.

The breakthrough in the hunt for the Airbus A320 came after sonar equipment aboard search ships detected four massive objects on the ocean floor in the Java Sea, and Indonesian officials said they were confident they belong to the plane.

The biggest piece, measuring 18 meters (59 feet) long and 5.4 meters (18 feet) wide, appeared to be part of the jet’s body, said Henry Bambang Soelistyo, chief of the National Search and Rescue Agency.
Strong currents and big waves that had prevented divers from entering waters eased on Sunday. About 90 divers from Indonesia and Russia were being deployed to recover more bodies that officials believe are still strapped in their seats, said National Searh and Rescue deputy chief Tatang Zainudin.

[opa-opa]

Nobody is ruling it out. The concentration of the wreckage will tell us a lot. A midair typically scatters the wreckage over a large area. Floating wreckage of course scatters itself so we need to see where the submerged wreckage is. Thus far, they are reporting four large pieces lying next to each other. That seems more aligned with an AF447 scenario but if the rest of the wreckage is found further off then it becomes more of a mid-flight breakup scenario.

We can't speculate much more until we see some images of the wreckage. Apparently they already exist.

I don't think they've said anything about the relative position of the wreckage, I think people are just assuming they were found together.

Also the news about scattered pieces found on a beach has been reported by Yahoo news as well:

"Other chunks of debris measured up to 12 meters (39 feet) long. Suspected plane parts also were seen scattered on beaches during an aerial survey"

[georgel]

But I thought that the one in the MD-80 is one way. There two hydro systems ann each of them have two power sources. System 1 (I'm inventing the number) is powered by the engine driven pump and an electric backup pump. The system 2 has also it's engine driven pump (from the other engine) and the transfer pump powered by system 1. System 1 can't be powered by system 2 in the same way (but has the electric pump that system 2 lacks).

Am I wrong? My... "knowledge" about the MD80 system comes from the best add-on ever for MSFS 98: The "MadDog".

You are wrong. The transfer pump is bi-directional. I am still current on that type and I love it, too, though after a decade I am "forced" to follow the mainstream and move to the flying computer (airbus)...

[Gabriel]

You are wrong. The transfer pump is bi-directional. I am still current on that type and I love it, too, though after a decade I am "forced" to follow the mainstream and move to the flying computer (airbus)...

I realize that we are , but I can't resist.

So, this is the hydraulics switches that the MadDog add-on for MS98 had (this photo seems to be the real stuff, but it was the same in the add-on)



The engine pumps have three positions: Hi, low and off. Off is self explanatory. Low is the "normal" position for most of the flight. "Hi" is used for take-off and approach, when the demand of hydraulics is increased (flaps, slats, landing gear...).

We also have the auxiliary electric pump with three positions: off, on and override. on and override are the same except that override bypasses the overload protection (if there is some hydro problem and the electric hydro pump is taking more power than it should, normally the protection would cut it, but in override we keep using the electric pump until its destruction).

And we have the transfer pump with just on and off.

For take-off and landing, the transfer pump is set to on and the auxiliary pump to override, so they are both already working should one of the engine pumps (or one of the engines itself) fail. My understanding was that the auxiliary pump pressurized system 2 powered by the electric system (AC), and the transfer pump pressurized system 1 powered by system 2.

But now you say (and I see) that the transfer pump works both ways (unfortunately, I don't have FS98 anymore, if not I would go and check if this behavior was correctly simulated, because I suspect it was not, I think that eng poum 2 off and aux pump off = syst 2 inop regardless the trans pump, in the add-on I mean).

However, it has to be manually activated, unlike the one on the A320 that is activated by pressure difference between the two systems.

Correct now?

[georgel]

[quote=Gabriel;
Correct now?[/quote]

Yes. Hydraulics systems are called left & right. The right system with inoperative engine driven and auxiliary pumps can be pressurized by the transfer pump provided left hydraulic system is pressurized and more importantly there is enough hydraulic liquid in the right system after so many faults on the right system side. An yes, the transfer pump should be on but it is normally on during takoff & landing for this power transfer to occur automatically...

[Evan]

No end in sight...

[EconomyClass]

Probably too late for this question, but they are running Why Planes Crash on Weather Channel, including the Delta plane slammed into the ground by wind shear in Dallas. Since there was a thunderstorm here, could wind shear have caught it and slammed it into the ocean?

[TeeVee]

No end in sight...

it's almost always like that there

[Highkeas]

Probably too late for this question, but they are running Why Planes Crash on Weather Channel, including the Delta plane slammed into the ground by wind shear in Dallas. Since there was a thunderstorm here, could wind shear have caught it and slammed it into the ocean?

A friend of mine was one of the experts on this program.

Also I believe wind shear only occurs near the ground. But turbulence and high wind can occur at any altitude.

[opa-opa]

Adam Air crash in 2007

For some comparison, Adam Air 574 which broke up in mid air and crashed in roughly the same area in Jan 1 2007, it took about 20 days to find the black boxes, and this was in waters 2000m deep.

While here we have a plane that supposedly flew into the water in one piece, in about 50m of water, it's day 11 and we don't even know where the main wreckage is.

Not saying there's some conspiracy going on, but the recovery process does seem a bit unusually slow.

[Evan]

A friend of mine was one of the experts on this program.

Also I believe wind shear only occurs near the ground. But turbulence and high wind can occur at any altitude.

Windshear can occur at any altitude. In aviation is is defined as a 30 kt or greater change in airspeed or a 5kt change in vertical speed (a definition expected to be improved by Gabriel). They could have encountered an updraft, suddenly increasing AoA and possibly lifting them to an unsafe altitude, possibly followed by a downdraft. The kind of windshear that 'slams' airplanes into the ground is a low altitude phenomena. With significant height, a pilot should be able to recover before the ground rises to meet him. If he is in a full stall or missing some control surfaces, that is a different story.