Gazelle Transponder

[skipzoid]

Dear All.

Please dont flame me if this is the wrong area;

A friend of mine operates a Miltary Gazelle Helicopter SA341 and has been told that the transponder is intermittant by ATC. The first time this failed he was charged nearing £380 to change one of the selectors on the control box for a part that costs less than a fiver from RS components - Had the RS part number printed on the selector which we found when a second selctor failed, it was an easy (and cheap) part replacement (also the soldering done during the previous repair was shoddy) , third time the transponder failed he was charged nearing the same to have the upper/lower antenna relay pulled out(behind the P2 seat, next to the switch in the rear), sprayed with switch clean and reinserted, he was later told that the relay is a common failure and most just operate in the lower position anyway to avoid the problem. The transponder has failed again, whilst it sounds as though its unreliable this is over a period of four so not too bad really for nearing a thirty year old piece of equipment.

The question; is it possible to test these on the ground without specialised equipment? any suggestions of what/where to check before it goes back in for another potentially expensive repair for a simple job?

[Phalconphixer]

Don't know about what changes have occurred in the last few years on Gazelles but the last time I worked on one I'm pretty sure the transponder was a Plessey PTR446A linked to a PV447 or PV1447 controller.

If on the other hand the IFF/SSR transponder is a Cossor 1500 /1520 with a mechanical controller all is not lost...

Either way there should be someone at Shoreham with access to a Cossor CRM544 Test Set. Maybe talk to some of the Avionics outfits or helicopter maintenance people there...
Just a thought....

pp

[Greeny9]

If it is an ex Army gazelle it will be the PTR446.
It does need specialist test equipment to check the system out.

[Phalconphixer]

You could also try talking to the Avionics people at FR Aviation at Bournemouth...nice, knowledgable people...worked there for 15 years!
pp

[wigglyamp]

Any current avionic company will have an ATC600A, IFR4000 or TIC 220 test set. You could try Southcoast Avionic at Shoreham who have two of the above and can certainly test thye installation.

[Old n Airborne]

I worked for Cossor/Raytheon and have worked on all types of kit incl IFF for Heli's.

The problem you may find is that your friend wants to keep everything original, sadly the kit is only designed for 25 years of working life, but are often supported after this time when 2nd users like far east military users take them on - in truth if it is not required like IFF in a warzone - they leave it switched off or fit a modern avionics suite!

If you want to know how owners want to 'keep original' someone asked me to build the original IFF for a Spitfire! I had all the information to do it including the original prints, schematics etc but when i quoted him £270k to build a new one from scratch, he decided he wanted to keep the original box so i suggested to him to have all the internals all modern adapted from an of the shelf transponder. It worked and was far cheaper.

My advice, if the kit is that un-reliable - buy a modern transponder off the shelf, gut out the old case and get a good electronics house to wire it in for you, i know that sounds easy but there is alot of work required.

You should be able to find a suitable interface with the right wiring schedules for the aircraft, if anything gutting it out would save a few lbs in weight.

and no im not volunteering to do it! =)