The audio panel in my TB20 is original, so it dates back to 1990. It doesn’t work properly with the marker beacon lights and tones, and the cabin speaker all inop. It’s also old technology and can’t do the kinds of clever things that the new boxes can do, such as better squelch, stereo separation of sound sources, isolation from passenger chatter, record and play back last transmissions, easy connection to independent devices etc etc. The obvious thing to do would be to swap out the KMA24 and replace it with a new box from Garmin perhaps or from P.S. Engineering.
The boxes themselves are not that expensive – £1,000 or so. However, I am a bit concerned about the licensing and engineering aspects. Does anyone here know if the newer boxes are certified for installation into a G reg TB20 (or universally certified?) and if so, how much re-wiring will be necessary? Is a substantial new avionics wiring loom required?
Would some who has done such a thing like to give an indication of cost for the whole job?
Thanks in advance
Howard
PS Engineering pays a lot of attention to backward compatibility, and their PMA7000B is pin-for-pin compatible with KMA24. Unfortunately, PMA8000BT isn’t (it’s compatible with GMA340), but it shouldn’t be difficult to rewire your installation. And it’s ETSO approved. If you wish, I can also connect you to an avionics engineer at EGTN (30 NM from EGTB) who can do it in no time.
Oh that’s very interesting Ultranomad. Thank you. I’ll have a look at the PMA7000B and please could you also send me a private message with your engineer’s details. I’m very keen on my current chap who is a real TB20 expert, but he’s more than an hour’s flight away (and a 3+ hours journey home by train).
Ah, my research tells me that the PMA7000B is only pin compatible with the KMA24 if one wants only KMA24 functionality. To use the PMA7000B’s intercom facilities one does need to engage in also wiring up the device as an intercom…which is obvious with hindsight and which means that the slide out / slide in easy swap scenario is out of the window.
Expect 8 to 12 hours to have the job done right. It will require a licensed engineer and a minor change approval, if no other approval is available.
I thought that most of the “1000 quid” intercoms on the market are actually made by PS and just badged. Hence some have the same pinouts as PS use…?
I have had a PMA7000-something since 2002 and it works great.
The only issues found were that it didn’t have enough inputs and stuff like the TCAS and autopilot annunciations (which the respective STCs mandate are *un*switched so cannot be turned off) had to be wired into a single unswitched input via 560 ohm resistors, to form a “mixer”. This works perfectly. The stupid “top end” UK shop (145 and 21 approved, of course) had originally wired these signals together directly so the more powerful source “won” (which happened to be the TAS605) and the other one (the KFC225) could not be heard at all, and they never tested it.
In the TB20, access to avionics is very easy IF you have the two inspection/access panels under the windscreen, on the outside. If you don’t have these, any job takes twice as long. But access to the centre stack is always tricky. The whole stack comes right out, but
Re running wires directly in, almost every installer does that IME and even Socata have done that in my case on the new aircraft (!) and when I sent them a photo of the bundle of wires running straight in, the comms became rather difficult afterwards…
Smaller jobs can be done without centre stack removal because some access can be obtained by pulling out the radios, the MFD, etc, and sticking your arm in that way.
The intercom might be easy or not, and there are a LOT of wires going into it:
Re running wires directly in, almost every installer does that IME and even Socata have done that in my case on the new aircraft (!) and when I sent them a photo of the bundle of wires running straight in, the comms became rather difficult afterwards…
What do you mean by “running wires directly in” ?
The centre stack has connectors on all wires that enter it. These enable the whole stack to be removed, put on a bench, and worked on easily.
Pre-GT, these connectors are done as terminal strips, which is not great but OK.
On the GT, they are milspec-style circular connectors.
But there is a general tendency for installers to bypass these and run wires directly in.
OK, nice feature.
ps: shows how much I know about French planes ! lol
These direct wires can be a real nightmare. On some TB aircraft it would just be impossible to remove it, or one should be willing to spend on money to get the direct wires sorted and using connectors (including correct wiring on screened wires). Altough more expensive, I would recommend to do this, as the ability to get the centre console out is especially on large modifications a huge benefit.
Same is true for Robin aircraft, which can quite easily take out the whole instrument panel (if everyone installed correctly and used connectors for modifications) which can be a real benefit.
