Cannot replace a Mode C transponder
 

The old Mode C transponder in my Super Cub has died and I have been told that no new installations of Mode C transponders can be performed on VH-registered aircraft. This is a VFR aircraft that goes into controlled airspace once in a blue moon. Is this right? It seems outrageous to me.

Unfortunately yes....

https://www.legislation.gov.au/Details/F2015C00342

paragraph 9E.2.

options are rip it out and stay out of class C/E airspace and below 10,000 feet or upgrade to Mode $.....:(

In a world of increasing madness and mindless bureaucracy some individuals likely hold the last remnants of common sense.

Should you be one of those individuals you will be pleased to note that its frequency of use is entirely at the owners discretion.

KT76A's for example, are abundant in the second hand market, I believe Bunnings will sell you a small allen key that fits in the small hole in the facia of the unit.

It is said that by turning this allen key it will release the tension on the locking pawl and rotate it flush with the unit.

Apparently when this happens the unit can be slid out of it's tray.

This is where the brilliance of common sense shines brightest.....it follows that if you reverse this process the unit will go back in the tray.

Many may not be aware but in some way there was a manufacturing mistake that led to all KT76A's being the same size.

Just sayin'

PS. Common sense also says...don't buy a Bunnings allen key, buy a good one, however if you do buy a Bunnings one and it fails your own common sense will be richer for the experience.

Note. From this point until the passing of the night of the 9th of August in the third quarter I shall relinquish my title of Obidiah and here after be named Justin Saine

Mode C transponder
 

This is true if you want to operate in in Class A, B, C or E airspace; or above 10 000 feet above mean sea level in Class G airspace.

See here for a the brief version and the linked Reg for the full version:
Mode S transponders, ADS-B and VFR aircraft | Airservices

However note that under this CAO this only applies to aircraft "modified by having its transponder installation replaced on or after 6 February 2014", thus you can fit any new parts you want to an existing installation:

Also Para 9E.3 exempts an aircraft which does not have "sufficient engine-driven electrical power generation capacity to power a Mode S transponder" which may apply to a cub depending on configuration.

Thanks, everyone. I shall do my utmost not to play CASA's coercive game. I can't see when I would ever go into Class A, B, C or E airspace anyway and this is Australia so I can't see the point of flying a Cub above 10,000 feet either.

Bastards.

.

Welcome to the club brother :ok:

Nothing stopping you replacing your U/S KT76A for example with another KT76A.

It is only a complete new installation that must be Mode S.

Replacing a faulty transponder is not a modification, installing a new type of transponder is.

Call your local shop and see what they have secondhand.

QDMQDMQDM..... Check your private messages pls

Got a quote last week to replace my old Narco AT150 Mode C with a BendixKing KT-74 Mode S for $6,000 all up installed. I think the unit alone is about $3,400. Could probably knock a thousand bucks off this by shopping around.

Plenty of KT76A's on the market at the moment . Even if the shop replaces the board entire the units serial number remains the same ;). I am guessing yours has the cavity gone U/S which can be expensive.

Thank God for pprune is all I can say. I'll let you all know the outcome.

So I'm sending it off to be repaired in the US for $100 fixed rate.

Meanwhile, my maintenance provider has told me that the avionics shop they use refuses to install any transponder which isn't Mode S.

I asked CASA a week ago what constitutes a 'new installation', but no answer.

It is a Avionics LRU and has a self test function.


If AD/RAD/47 Amdt 4 is not due any engine or airframe LAME can change it and certify for it.

The ETT test (I bet they don't do at your shop anyway) is done on the bench during your repair. This test will only be due next time your RAD 47 is due and it will not be a "new unit" then.


Typical avionics shop by the sounds.

Maybe they should go and read the reg again....

Transponders
 

From: https://www.casa.gov.au/standard-pag...pment-mandates

"From 6 February 2014, any aircraft registered in Australia before 6 February 2014 that is modified by the installation of new or replacement ATC Transponder systems must have a Mode S Transponder capable of ADS-B 1090 MHz Extended Squitter transmission installed"

So unless the aircraft is Modified by the installation (IE: New transponder model fitted under STC or Part 21 EO) then there is no need to install mode S.

So unless you are operating at major international airports or under IFR there is no need.

But ... surprise surprise... the CASA document is ambiguous. That often happens when people try to paraphrase something.

Are you saying the Mode S requirement is triggered (assuming the airpace class/altitude criteria are met) if I either:

1. install a new transponder system in my aircraft, or

2. install a second hand transponder system to replace the system currently fitted to my aircraft,

but not if I replace unserviceable components of an existing transponder system in my aircraft with serviceable components?

Why does the avionics shop referred to above have a different understanding?

Lead

1) "NEW" is key word - Point to your transponder, is it new? I doubt if it is a KT76A, at best newly overhauled. But that is not NEW.

2a) System is Key word - I don't recall reading that in context of this subject (but could be wrong) A replacement KT76A with different S/N is not any more than a component change.

2B) a complete change of system with a different model transponder will require it to be Mode S compliant - Installation being key word.

Yes endless amounts of repairs can be made to current mode C transponders.

Why use the avionics shop for LRU with self test function?

in other words, if the only thing that has changed after maintenance is the serial number of the transponder there is no need to upgrade.

The words "or" and "replacement" are key words too:I'm merely observing that perhaps the confusion is caused by CASA's guidance document?

Been away from the tools for a while but I would suggest that the supposed problem here is one of definitions...
An Aircraft Installation is by definition all of the major components and the interconnecting wiring.
An Aircraft System comprises the major and contributing LRU's
The replacement of any single LRU does not constitute a change of either the system or the installation:
In fact, one could remove all of the components and the interconnecting wiring and provided that the overall configuration remains the same in terms of LRU part numbers, the installation / system remains unchanged.
In other words, by definition, you can remove, repair and / or replace the Transponder, its mounting tray, its antenna(e), the interconnect and the altitude component with like for like items and nothing changes...

Changing a transponder with a like for like replacement should have no more compliance implications than changing its antenna or re-soldering a disconnected wire on the mounting tray

After replacement I would recommend a check of the transponder installation using the appropriate test equipment to ensure compliance...

As for why your Avionics shop wont do it... it's probably all about the money, plus it's highly likely that locally they don't have the ability, the skillset, or the inclination to repair obsolete equipment.