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

Icarus2001 12th Mar 2014 01:23


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
Quite right Creamie.

Also in some jets I fly with the rotary code selector knobs, as soon as the knob is turned to change the code the TCAS/Transponder goes to standby mode until all digits are selected and set for something like 3 seconds, not sure of exact timing.

As far as this thread goes...Never have so many understood so little but written so much about it!

LASJayhawk 12th Mar 2014 01:24

Jet we don't know that. Both transponder antennas are close together. It the section of skin they are both mounted on departed the aircraft.....

Just as likely a major loss of electrics....or for some reason multiple databuses went down at once.

IMHO: until we recover her, were gonna drive ourselves crazy guessing.

Asking again any 777 or 767 drivers remember what the load shedding scheme is?

Frenchwalker 12th Mar 2014 01:24

Just to point our on some of the information provided by the Malaysian military last night around its last know position, more so around the fact the the aircraft descended to around 3000ft would this simply be to maintain VFR , cloud base in kl usually sits between 3000ft and 10,000ft

this would indicate the the PIC certainly had control of the Aircraft

1a sound asleep 12th Mar 2014 01:32

The stream of news and rumors is ridiculous

Malaysia's air force chief denied a media report that the military last tracked a missing Malaysia Airlines jetliner over the Strait of Malacca, far from where it last made contact with civilian air traffic control when it disappeared four days ago.

"I wish to state that I did not make any such statements," air force chief Rodzali Daud said in a statement on Wednesday.
Malaysia air force denies tracking missing jet to Strait of Malacca

training wheels 12th Mar 2014 01:33

Reagarding the transponder and why it was not returning a secondary paint on radar could be as mentioned above. If a decompressurization did occur, and in the process of changing the code from assigned code to 7700, the PNF left it in Standby mode and not return it to TA/RA mode due to increase in workload or partial or deteriorating awareness due to hypoxia, it may explain why the transponder was 'off'. Quite plausable and we all know how overloaded we can become during simulator proficiency checks for similar scenarios.

er340790 12th Mar 2014 01:43


It's the only scenario which I can piece together which fits the evidence. The aircraft could be anywhere from the last primary radar return to 3000nm west of there. - and may not be found for a very long time.
Given the arguably chaotic S&R response thus far - with zero results - you'd think it might be worth at least one attempted ariel or surface sweep along that path... if not already too late.

ManaAdaSystem 12th Mar 2014 01:45

I have never switched the transponder to standby before changing code.

win_faa 12th Mar 2014 01:50

ACARS via SATCOM
 
On the B777, if the SATCOM antenna is damage as a result of fuselage mount cracking could this disable ACARS transmission as well!??

Stanley11 12th Mar 2014 01:51


I have never switched the transponder to standby before changing code.
@ManaAdaSystem, I agree. In my 20+ years of flying, I've never done that. In fact, every time I changed code, I'd hit the 'ident' button (or toggle switch) to give out a pulse.

jet_noseover 12th Mar 2014 01:52

Ok, let me ask you this...Any of you had ever turned off the transponder on the flight for any reason? If so why?

lilkim 12th Mar 2014 01:53

Latest:

@STForeignDesk: #Malaysia official replies "it's not the right time yet" to question from #MH370 families if govt is hiding military data
#MalaysiaAirlines

Lonewolf_50 12th Mar 2014 01:53

Compromised cockpit remains an open possibility. :mad:
So do a few other not so happy scenarios. :uhoh:

The transponder thing was true in my fledgling days, but I doubt that 777 has such archaic avionics.

It is amazing how quickly the mods are ditching posts. Wow.

jet noseover:
Yes. Was trouble shooting mine. Turned it off, recycled the CB, turned it back on to stby to warm it up. A few minutes later, with the code assigned, it seemed to work based on ATC getting a good squawk out of me. This was over 20 years ago.

Australopithecus 12th Mar 2014 01:53

Ditto re stndby on ATC TX. When I learned to fly that was the accepted procedure. Forty-three years ago. Time has marched on since then.

Pitot Probe 12th Mar 2014 01:56

No never.

Only xpdr change I can think of is a checklist action to go from TA/RA to TA Only following ENG failure/shutdown.

LASJayhawk 12th Mar 2014 01:59

Jet, I did work on a KA200 that had a duel transponder failure coming into KLAS.

The seal on the R/H cheek panel was no good and they flew through rain.

Both TDR-90s had water pour out of them when I pulled them.

Unless they have added some wiz-bang feature, it is also possible that A transponder failed. And if they were busy, or ATC didn't call them to point it out, I doubt they would know.
No reply does not mean they were turned off...

Australopithecus 12th Mar 2014 02:07

The common element for the transponders, VHR COMM #1, the GPS recvrs and the Satcoms is the antenna locations on the fwd fuselage.

That said, and with the understanding that there is a lap joint AD in effect, and with the alleged transmission of cabin disintegration received in Utapao yet one more theory emerges.

The Aloha 737-200 was very much shorter and only just held together apparently, so the scenario of a fuselage failure on a 777 being possible, and then allowing for another hour of flight would be astonishing. Although it would explain many data points.

B777FD 12th Mar 2014 02:08

If the transponder is turned off/on standby, do ATC (civil or military) still get a contact with no associated information? A primary return?

I'm a little confused by the impression I am getting from various posts that a large jet can go "invisible" by switching squawk to standby. Can SSR work where PSR cannot?

Stanley11 12th Mar 2014 02:10


Ok, let me ask you this...Any of you had ever turned off the transponder on the flight for any reason? If so why?
I regularly operate within Military airspace. We turn it off (Standby) when operating within the circuit. When operating low in the training areas (definitely out of radar and transponder coverage), we turn it on but sqwark a common code.

To add (not relevant for this case), when we operate in such locations, it's known as 'flight monitoring'. I.e. the control agency will not be able to see us but know that we are somewhere in that area. We will call in every half hour to report. If we fail to do so, they will call to check. SAR will be dispatched only when we are way over due. I think this is very common for GA as well.

LASJayhawk 12th Mar 2014 02:12

B777FD If you go to standby, the transponder will still hear the interrogations, but not send out any replies. So no, it would not show up on SSR.

mattfl 12th Mar 2014 02:13

This is starting to sound like a variation of Helios Flight 522:

Helios Airways Flight 522 - Wikipedia, the free encyclopedia

The left turn may have been an attempt by one of the remaining crew-members to return to land. Some news reports claim it was a low as 3'000 after turning west - other reports say is was sill up near 30k. If it did drop from the cruse this is further evidence that possibly one remaining member of the crew was making a valiant attempt to save the lives of aboard.


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