ATC transponder testing

[weave1376]

Due to a recent incident here while someone on the ground was testing an ATC Transponder, we've now been restricted to testing at night (and certain altitudes), which is fine if you have a night shift, not so good when you've got to come to work at 4 in the morning and then do a full day's work afterwards...:zzz:
I was wondering if anywhere else has any such restrictions or proceedures regarding this type of thing or are you allowed to do as you want as long as you tell ATC beforehand?
Please let me know and share any thoughts!

Thanks,
Weave

[aveng]

We used a special code to indicate a atc system under test 2100 if I remember correctly.

[mono]

The problem with a code is that while ATC may know you are testing. The a/c at FL100 with its TCAS active doesn't! You can generate T/A's and R/A's if testing below an active flightpath.

We used to do a quick check of mode A to ensure radiated efficiency then go straight into the box to check accuracy of the other coded information.

[Spitoon]

I'm but a simple controller but perhaps I can offer something of relevance.

There is a UK CAA document - CAP 562 Civil Aircraft Airworthiness Information and Procedures - which offers 'guidance' to engineering personnel when testing transponders. It says...

4 Testing Considerations
4.1 Recognising that airborne TCAS aircraft operate by interrogating operational transponders, it is apparent that they will elicit replies from transponder equipped aircraft on the ground if they are in range and the equipment switched on.
4.2 This, therefore, presents the possibility that a ground operated transponder may trigger a nuisance advisory on a TCAS equipped aircraft operating in the close vicinity.
If the ground target is providing altitude data the TCAS logic should declare the aircraft to be on the ground and ought not to generate an advisory.
4.3 If no altitude data is provided the TCAS will generate a TA if the threat criteria are met.
If the ground is providing altitude data other than surface altitude, as may happen with a defective altitude encoder, or if a test pressure is being applied to the altitude encoder, the TCAS may generate both a TA and a RA if the threat criteria are met.
4.4 Maintenance organisations and personnel who are involved in the ground testing of transponders and TCAS equipment are requested to establish procedures and take precautions to ensure that the risks of causing nuisance advisories are recognised and kept to a minimum.
4.5 It is considered that nuisance advisories may be caused to any TCAS equipped aircraft flying in the vicinity of transponders which are being tested, this may also include aircraft passing overhead at medium altitudes. The problem may be more noticeable where ground testing of transponders takes place at airfields located beneath Terminal Control Areas or in the vicinity of Control Areas and Zones where air traffic movements are likely to be numerous.
4.6 The following advice is provided to minimise the possibility of causing nuisance advisories to TCAS equipped aircraft when ground testing transponders and/or TCAS:
a) When not required ensure that transponders are selected to ‘OFF’ or ‘Standby’.
b) For transponders under test, when equipped for altitude reporting, set the control unit to ‘Mode A/C’ and select Altitude Reporting ‘ON’.
c) Where possible, carry out testing inside a hangar to take advantage of any
shielding properties it may provide.
d) Always use the antenna transmission absorption covers when these are provided with the test set.
e) When testing mode C operation which require the altitude to be increased, radiate directly into the ramp test set via the prescribed attenuator.
f) In between test parameters, select the transponder to the standby mode.
g) The simulation of TCAS operation by the radiation from an antenna located on, or remotely based from a workshop, is not permitted.
NOTES: 1) The FAA have advised their staff of operational problems resulting in nuisance advisories caused by ground based transponders installed on hangars for the purpose of testing TCAS installations. Maintenance organisations are reminded that all UK aeronautical radio stations are required to be licensed by the Department of Trade and Industry and the CAA.
2) Air Traffic Control Units may be advised when testing is to be carried out if it is considered that there is a possibility of nuisance advisories being caused by the activity due to its proximity to operational runways.

I hope that might be of some use.

Having seen how transponder testing can cause a real problem to aircraft flying nearby I find it interesting that in para 4.4 the CAA just requests those involved in the ground testing of transponders and TCAS equipment to establish procedures and take precautions to ensure that the risks of causing nuisance advisories are recognised and kept to a minimum. I remember the days when the CAA would place a requirement on maintenance organisations etc. to do something like this which can - potentially - cause a hazard to aircraft. But now I guess it's all down to EASA to set the rules for Europe and the CAA just asks nicely for something extra to be done! Still, I'm sure EASA is doing a good job.....

Do I sound a bit bitter? Well, just a bit.....I've seen how EASA works and it looks like soon they're going to do the same to ATC!

[weave1376]

Thanks Spitoon, it does help, although as it's a "request", there's nothing in black or white to help us define when or where (FL) we test.:ugh:
I seem to get the impression that until even though testing goes on at various altitudes it's been just a question of luck that we have not had anything very serious happened... unless someone knows otherwise?

[oligoe]

Hy,

We had some local writen procedures established between our company and the airport authorities. (since we had a few TCAS TA issues...)

It was like : -XPDR code 7123
-ATC had to be contacted
- If possible, do the test at night, or we had to request a slot
for daytime.
-We had to tell them what altitudes we will use and for how long
(In our case they had to contact Zurich radar if we went above
FL100)
- A/C in hangar and doors closed

Regards,

og