Delta 744 Lost Comms

[John Golin]

Interesting! Having read a lot on the 744 comms it surprises me there was no comm available at all!

http://www.avherald.com/h?article=44ece404&opt=1

Delta Airlines Boeing 747-400, registration N672US performing flight DL-275 from Detroit,MI (USA) to Tokyo Narita (Japan) with 296 passengers, was enroute at FL300 when radio contact with air traffic control was lost prompting the crew to squawk loss of communication (losscomm). After attempts to resolve the problem had failed about 60nm south of Thunder Bay,ON (Canada), still in US airspace, the crew decided to return to Detroit, where the aircraft landed safely on runway 04L, still squawking losscomm, about 110 minutes after the problem arose.

[Jeroen Hoppenbrouwers]

I have no clue what broke down here. Audio control panels? Possible, but then there could still be Direct and ACARS should still work. Complete pedestal out? Hard to believe. Tuning problems? Could be, but there are the MCDUs to take over. VHF all three down? Weird. HF still left. Satcom, more than likely (I don't think they have my gear, though -- will check!). And as somebody said, they will have tried it all, for sure.

Interesting, indeed.


Jeroen

[John Golin]

Maybe, as mentioned in the comments,  someone did spill a coffee

[John H Watson]

Not all aircraft have the VHF Direct function (half of our 744's don't).

There have been instances in the past where Radio Control Panel failures have taken out all comms, but there have been modifications to reduce the risk of this.

The Audio Management Unit is modularised (separate power supplies for each pilot).

Coffee spills are unlikely to take out 3 individual RCPs (or even one RCP, for that matter).

Murphy's Law?

[Jeroen D]

So I know what I have to do if I loose comms and what the procedure is to land my little Cessna on a towered field.

So how does that work in the big commercial aviation world. Did they circle, look for light signals from the tower? Doubt it somehow! So how do you do it?
Jeroen

[Mundyas]

Hi
Looking at some old approach charts from London Gatwick.

Missed Approach.
With a Comms Failure Following Missed Approach . Ahead to I-GG 10d (without DME May 357R) etc etc. (Old chart).

Not a proper pilot but once procedure was to squawk 7700 on transponder for 1 minute, then 7600 for 15 minutes and repeat. (But you know this already I think)

It is a good question would like to know the answer too for commercial aircraft.
Andrew

[stekeller]

Well, I imagine you would follow the standard procedures (in the U.S.) for lost communications while flying IFR, which would be to squawk 7600 and then follow your flight plan to land at the time predicted in your flight plan - which would be really difficult for a flight to Tokyo.

But, the caveat is that you must land as soon as possible if visual conditions prevail. Otherwise, you would have no choice but to follow your flight plan. So I assume they had some VMC weather along the way. Clearly, some would be found between the U.S. and Japan. I also wouldn't want to test Russian ATC with no radios.

- Stekeller
KORD

[AI744]

The lost comm procedures these days may as well be scrapped.

In reality if you end up with no comms in an airliner you will be intercepted.

Then you can communicate via hand signals with the fighter sat outside your cockpit window.

[John Golin]

Interesting Mr Watson! I assumed VHFL Direct was pretty much standard...

[John H Watson]

Interesting Mr Watson! I assumed VHFL Direct was pretty much standard...

Later models appear to have it as standard (on the overhead panel), and, of course, it can be retrofitted  (I recall British Airways had a guarded switch at the base of the pedestal with which to activate it).

Rgds
JHW

[AI744]

Miscellaneous Communication Switches

VHF-L Direct Communication Switch G-BYGA - G-BYGG, G-CIVF - G-CIVZ

1 VHF-L DIRECT Communication (COMM) Switch

NORMAL - all communication systems operate normally.

VHF-L DIRECT - If loss of communication occurs, allows Captain to communicate on VHF-L transceiver if operable. Connects Captain's boom/mic headset and control wheel push-to-talk switches directly to VHF-L transceiver. No volume control is available.

[Phil Bunch]

Wouldn't cell phones help to some extent?  

Of course, you have to figure out what number(s) to call!!!  I can just imagine calling Information and asking for the number for ATC in say KJFK!

[frumpy]

Wouldn't cell phones help to some extent?  

You would have to fly low to stay connected. Imagine a 747 low-level
flying with sqawk 7600 close to London... I guess the airforce
wouldnt like that *g*

[Garry Richards]

You would have to fly low to stay connected.

Maybe not. At higher altitudes you would have line of sight to cellphone towers over the horizon.

[frumpy]

This makes sense - however, I tried it out a few years ago.
Connection was lost at higher altitude.

Contrary to this, I heard a pilot complaining that he forgot
to switch off his cellphone and got several welcome-SMS
from the service providers of the countries he flew over.

I think I will have to try again

p.s. I found that the antennas are vectored towards
the area they want to cover...

[Will]

Planes fly several miles high, while cell phone reception distance is on the order of hundreds of feet.  So the place would need to stay very low indeed.

[Shiv Mathur]

Will, I remember shortly after 9/11 asking on the earlier forum about
whether all those cell-phone conversations from the hijacked aircraft
were possible.  

There was a gentleman (can't remember who) who had worked in this
field who said that it was definitely possible.  

If I remember right, he said any glitches in reception would be a result of
moving rapidly from transmission centre to centre ... i.e.,  an issue not
of altitiude but rather of lateral movement.

Shiv

[Shiv Mathur]

But then again ...

http://www.physics911.net/projectachilles

Wow!  So were those 9/11 calls a lie?

[Will]

Well, interesting... I could be wrong, of course... but I'm still skeptical that a cell phone could be used at cruising altitude.  I wonder what the highest cell phone usable altitude is?

[Shiv Mathur]

The link I gave earlier gives us a pretty good idea.