View Full Version : Transponder Failure Indications

16th Nov 2004, 20:39
I've had recently on a few occasions pilots reporting that their Transponder is showing a 'failure' indication, but from radar all is showing fine. The aircraft concerned are all B737-300/700's, is this a common fault or am I unlucky enough to have just had all the freak shows recently? Possibly unlinked but one then declared about 5 minutes later that TCAS had failed too! Just a bad day there hopefully!

16th Nov 2004, 21:13
Funny you should mention that but I was taking EZY 6495 down to Prague this morning and during the flight we had a warning that TCAS had failed. But on arriving into Prague it was all back up and running again??!!??

As to the transponder I have not experienced that yet......

16th Nov 2004, 21:56

Yes - TCAS failures, Transponder failures etc etc - seems to be happening on a pretty regular basis.

Central Europe DOES seem to be a "black area" although that will have nothing to do with it.

I actually heard EZY from Newcastle to Prague this morning (did you hear me Chris?) and ATC were as always very understanding!

Safe flying and safe watching.

Flight Detent
17th Nov 2004, 10:10
Hi all,

As I remember it, the 737NGs indicate the Xponder failure on the ND screen(s).

I also remember that there is a sys1/sys2 selector on P8.

Is that only for altitude reporting, or the Xponder itself?


The Greaser
17th Nov 2004, 10:32
Funny how topjet and easyFO are cropping up together in various threads talking absolute drivel.

17th Nov 2004, 14:06
The Greaser - I wouldn't call it drivel, I call it an answer.

Ironically EasyFO, I was not the controller for your flight and haven't heard 3rd hand of your problem, but the 3 I have been involved with flew with Orange titles too. I don't want a 'bashing' thread so kept that out. There has been one other occurrance recently that I've heard about with another company on a B737-700 too, so its not just a close-to-home issue.

As Flight Detent asks, how do you get your indications, and is it the full transponder that shows a failure (if you know that part)?
On the TCAS part, can this affect your RVSM status? I was confused when a Birdseed B737 declared this as to how RVSM status was affected.

PPRuNe Radar
17th Nov 2004, 17:50
TCAS is not required for RVSM operations .. at least not by the authorities.

(The Greaser seems to be an expert in conspiracy theories .. he thinks Topjet 973K is also everyone else in every thread Topjet posts on :ugh: - I'm sure we have some 'Tech Log' stuff in the software to calm his rants ;) )

17th Nov 2004, 19:48
Thanks to the ATC!
The Greaser appears to have bad things to say about everybody - chill out Mr Greaser!

The simple fact is, EASYFO and myself both fly out of the same Airport - a conspiricy?

Secondly, I'm not a "journalist looking for cheap front page news"

Thank you.

Notso Fantastic
18th Nov 2004, 10:29
5mile- after all that, I don't think your question was actually answered. I fly another from Boeing's stable, but the system is probably the same. There are no indications on the transponder itself, but most systems are covered by an EICAS -engine indicated control & alert system (or something like that). On a screen that has engine indications etc., various status and alert messages requiring attention may appear. They probably had come up in orange or white letters 'Transponder Fail' and 'TCAS Fail' (or maybe the took a minute to deduce that if the Transponder had gone, so had TCAS, so they'd better mench it to somebody). We carry a list of all the facilities needed for RVSM, so if it occurs to people to look they can deduce whether they qualify.

Not so funny when you are flying back from MIA with no RVSM. You are firmly excluded from RVSM airspace which means no higher than 28,000'. Rather than expand the area of protection around affected aeroplanes, they are excluded from flying in that airspace and possibly from getting to their destinations.

18th Nov 2004, 15:50
Depending on the a/c a transponder fail indication will be either on the control head (an amber fail lt) or on EICAS/ECAM or both!!

The fail indication means that some part of the transponder system has failed (datalink/antenna/Tx/Rx/whatever)

If the ground readout was still good then it is most likely that the upper antenna or cable system failed. This would not affect normal squawk operation but MAY affect TCAS ops as the upper antenna is needed to provide a FULL omnidirectional transmission/reception pattern for ALL calls and SELECTIVE calls

PPRuNe Radar
18th Nov 2004, 17:51
Not so funny when you are flying back from MIA with no RVSM. You are firmly excluded from RVSM airspace which means no higher than 28,000'. Rather than expand the area of protection around affected aeroplanes, they are excluded from flying in that airspace and possibly from getting to their destinations.

That would depend if your transponder was U/S or just your TCAS.

If your transponder was U/S, then you might be accepted for the flight provided this was co-ordinated and agreed by the ATC agencies whose airspace you would fly through. Note that this is not solely RVSM related, it is applicable to airspace within which the carraige of a transponder is mandated. You would of course lose RVSM capability as a result since it is a requirement.

Neither the European Region, nor the North Atlantic Region, require TCAS as mandatory for flight within their RVSM airspace. However, the European Region may catch you anyway by its separate requirement for TCAS in ALL ECAC airspace if your aircraft is above 15000Kgs and carries more than 30 passengers. (From 1 January 2005, the criteria is above 5700Kgs or more than 19 passengers). Having said that, there is a 10 day alleviation for U/S TCAS equipment, provided you still have a serviceable transponder with altitude reporting.

The RVSM MEL should read:

1. Two independent altitude measurement systems each equipped with:

cross coupled static/source system with ice protection if located in an area subject to ice accretion,

display of the computed pressure altitude to the flight crew,

digital encoding of the displayed altitude,

signals referenced to a pilot selected altitude for automatic altitude control and alerting,

and static source error correcting.

2. One SSR transponder with an altitude reporting system in use for altitude keeping.

3. An altitude alerting system.

4. An automatic altitude control system.

If your airline has TCAS on its MEL for RVSM operations, then they are plain wrong. Point them at JAA TGL No 6 which details the above as the Minimum Aircraft Systems Performance Specification (MASPS) required.

JAA TGL 6 (www.ecacnav.com/rvsm/documents/TGL6rev1.pdf )

In short - No Transponder, no RVSM - No TCAS, no restriction.

18th Nov 2004, 19:15
So what do you squawk for transponder failure?