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-   -   Malaysian Airlines MH370 contact lost (https://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost.html)

Willoz269 12th Mar 2014 00:17

This is baffling, at first I thought "up to 7 days before they find it"...now I am not so sure.

If reports are true that theaircraft turned back, it begs more questions than answers:

-Why was it no longer transmitting any comms, either radio, transponder, acars, nothing? (I would hazard a guess at fire onboard)
- What was so serious that necessitated a turn back?
- Why did they descend (if indeed eyewitnesses did see the aircraft), did they lose all instruments? all electrics, all displays, which explains loss of comms, etc as well?
- I was around 2AM...dark night, did they lose sight of mainland, no instrumentation, descended to get visual?

If so, this aeroplane could be absolutely anywhere. :uhoh:

Old Boeing Driver 12th Mar 2014 00:21

Overthwing/flt001
 
The quote above in Post #1977 was what I was going by.

"the signal disappeared without any trace"

Was it because it got to end of their coverage?

I think this is the only "official" statement, but does not retract the westbound statement. (Maybe I read it wrong)

GarageYears 12th Mar 2014 00:23

Until someone can convincingly explain how depressurization can be linked to the loss of the transponders... yes, there are two transponders in the T7, left and right, selectable via the transponder panel, it seems difficult to see how depressurization would lead to the transponders failing.

The external antennas are in different locations (though I can't find my reference to where exactly). Turning off the transponder isn't just a toggle or push-button, the switch is a rotary and you'd have to move it two positions to get it into the standby condition.

mm43 12th Mar 2014 00:28

Another "expert" is now being quoted in the New Straits Times

According to him, the Under Water Beacon (ULB) can emit a signal for hundreds of miles but if the black box is covered with debris or falls into a trench at the bottom of the sea, then the strength and range of the signal would be lower.
For the record a Towed Pinger Locator (TPL) can only be expected to detect an operational ULB 37.5kHz signal when no more than 2 - 3km from its source. Ninety percent reliability is around 1,800 meters, and water temperature inversion layers can often create a variable outcome.

wishiwasupthere 12th Mar 2014 00:30

First up, I'm not an airline pilot but a mere lowly GA charter pilot. But in the aircraft I fly, before changing a code on a transponder you turn it to standby. Is this the same in airliners? Following the path of some sort of catastrophic depressurisation, is it possible that Hypoxia dealt the crew it's fatal blow as they were in the process of changing the transponder code, hence it appearing to be turned off?

Ranger One 12th Mar 2014 00:32


Originally Posted by Buster Hyman (Post 8367935)
Very well, my Brother in Law was on that flight. (Assuming you mean the one where the O2 broke loose & ran amok in the cabin before exiting the fuselage). I thought of this in relation to the crew oxy & electronics location question. Massive damage from a rogue cylinder there.

Negative, he's referring to an incident about ten years ago where a QF 744 was discovered to have a serious structural crack in the fuselage during a heavy check.

IIRC from the bumpf that circulated at the time, the crack was determined to have been caused by improper paint removal during an earlier repaint, using a metal scraper tool, which gouged the metal; the gouge then acted as a stress-raiser, precipitating the crack.

Someone correct me if I'm wildly wrong on the above?

Old Boeing Driver 12th Mar 2014 00:33

Garage Years
 
That's the issue I keep coming back to.

A few posts ago, someone asked if the transponder could be turned off in the haste of changing codes in an emergency.

The response was that the knobs have a very different feel.

I lean the same way. I think it was turned off manually.

Why was the transponder turned off?

JamesCam 12th Mar 2014 00:36

GarageYears :


'Turning off the transponder isn't just a toggle or push-button, the switch is a rotary and you'd have to move it two positions to get it into the standby condition.'
True, but you are supposed to go to standby before changing the code, so possibly he forgot to switch it back on or passed out before he'd done so.

That said, I don't believe the above scenario to be the cause of the failure, it doesn't appear to be just the transponder that went quiet..

Edit: Sorry wishiwasupthere: missed your comment saying the same thing...

Ex FSO GRIFFO 12th Mar 2014 00:37

Question...
What is the RADAR facility / range at FJDG, anybody?
Track from 'disappearance point' to DG is approx 245T, and quite within the fuel range..?

Just curious.....

GarageYears 12th Mar 2014 00:38

OBD... and I'll add that I don't think they could be turned off "accidentally" even in a hypoxic state. The mode control knob is completely different from the code rotary.

Old Boeing Driver 12th Mar 2014 00:43

Trqnsponder
 
I have never flown an airliner, and I can't remember any corprate jet where you had to switch the transponder to standby before changing codes.

Some corporate jets actually have a control wheel button that changes the squawk to 7700 if pushed.

Not saying some don't require this, just none I've seen. Don't mean to sound rude.

pigboat 12th Mar 2014 00:47


I have never flown an airliner, and I can't remember any corprate jet where you had to switch the transponder to standby before changing codes.
The idea of switching to STBY between codes was to avoid inadvertently hitting a 7000 code during the code change.

Acute Instinct 12th Mar 2014 00:50

Scribe Marks......
 
http://www.dca.gov.my/Division/Airwo...es/AN%2091.pdf

Will the DCA re-issue a follow up of this Airworthiness Notice, if this aircrafts last repaint took place in the mid to late 2000's?
Will the DCA direct the operator/MRO to conduct immediate inspections of its fleet to discount this possibility?
Will the DCA investigate whether the MRO continued to have, or took disciplinary action against employees who were found to have unapproved implements in their possession in the years following the issue of this AN?

Old Boeing Driver 12th Mar 2014 00:52

Pigboat
 
Great Handle.

I have run across the concept you mention. I think the original post was questioning whether it was a requirement to go to standby before changing codes, or a procedural one like you mentioned.

Maybe someone here with knowledge of MH procedures could clarify this.

It may he helpful in determining why the transponder was turned off.

NSEU 12th Mar 2014 00:52


in my opinion from the little evidence available, it had a depressurisation problem rendering the flight crew and passengers unconscious, resulting in the aircraft flying solely on autopilot and completely unmonitored from the malacca straights on an approximate track taking it over the indian ocean towards the island of madagascar via diago garcia, where at some point it ran out fuel.
Very unlikely. If the cabin altitude went to even 10,000', there would be a loud aural alert in the cockpit plus an EICAS message telling the flight crew that there was a pressurisation problem. I'm sure the pilots are regularly checked for health and wouldn't find 10,000' much of a problem. If they did succumb to lack of oxygen without realising there was anything wrong with pressurisation, the autopilot would have taken them to their destination and beyond (at their current cruise altitude). Also, as previously stated, depressurisation shouldn't have affected their transponders.

gulfairs 12th Mar 2014 00:53

transponder
 
The reason one switches to standby before changing the code, is that if one cycles the code numbers it does flash other transponder codes.
Which is also a reason for having "Ident".
The transponder is a radar aid, it is not a training line to air traffic control.
If there is no transponder, or its off , ATC just read a target: no identity, no altitude no TAS/IAS.no supplementary information

clayne 12th Mar 2014 00:56


Originally Posted by Ian W (Post 8367132)
The aircraft also underwent an extended maintenance ~ 2 weeks ago at which corrosion/cracking around the SATCOM mount should/would have been checked for.

No doubt this plane was taken care of - MAS typically has things in order. On the other hand, what about the aspect that the plane was last "touched" as short as 2 weeks ago?

Creampuff 12th Mar 2014 01:05

Surely the 777 does not have those steam-driven transponders with rotary code select knobs. Surely it would be fitted with the newer push-button code entry controllers that donít change the transmitted code until the fourth number in the code is entered. :confused:

ad-astra 12th Mar 2014 01:08

With the older rotary Transponders the policy of turning the unit to STBY has merit but with modern keyboard Transponders the likleyhood of an incorrect code is slim and is easily rectified.
The problem with turning the Transponder unit to STBY is that TCAS protections are now lost which in my mind is not an ideal situation.
By all means turn it to STBY but just realise the repercussions whilst it is off and god forbid if it is not turned back on.

Creampuff 12th Mar 2014 01:18

Turning it off is only one explanation, out of numerous, for a transponder ceasing to operate.


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