[Jim P]

Looks like I need to send in my Garmin 480 for a little work on the GPS receiver. The GPS passes the encoded altitude from AHRS to the transponder, so removing the GPS takes out the Mode C, but basic transponder capability is retained. Can FSDO/ MIDO issue a short term waiver to operate without Mode C under the local Mode C veil?

 

[SteinAir]

Hi Jim,

Not sure how you're avionics was wired up....but...there should be no reason that you couldn't just make yourself a little jumper wire (we're only talking ONE wire here) to run the RS-232 signal from the GRT right to the GTX Txpdr you have. Should just be a short wire, 2 pins and then run it from one pin on the "in" side of the 480 box to the "out" to the txpdr back on the connectors.

FYI...for others doing their own wiring, the way Jim did this isn't quite typical (not necessarily wrong, but not the norm). Typically encoding data would go to the txpdr first, then get passed to the GPS...not the other way around.

Anyway, if it were me I'd just make sure the data was going right from the GRT to the txpdr. No goofing around with the FAA, etc..

Just my 2 cents as usual.

Cheers,
Stein

 

[scottg]

Looks like I need to send in my Garmin 480 for a little work on the GPS receiver. The GPS passes the encoded altitude from AHRS to the transponder, so removing the GPS takes out the Mode C, but basic transponder capability is retained. Can FSDO/ MIDO issue a short term waiver to operate without Mode C under the local Mode C veil?

You do not need a transponder below a Class C. In, or above, then yes, but not below. Can I assume you will also stay below 10,000' and not be within 30 nm of a Class B? If so, then I think you're fine. Ref 14 CFR 91.215

With that said, I agree with Stein, connect it to the GRT and don't worry about airspace limitations. That and the safety benefits of having your altitude show up on TCAS equiped aircraft. You did say that you were operating around Class C airspace.

 

[Mel]

You DO need mode C within "mode C veil".

To answer your original question, the FSDO CAN issue a waiver.

 

[Rick_A]

I also have a 480 and GRT's. Stark wired my harness the same way that Jim's is wired - no Mode C unless the 480 is in the loop.

 

[Jim P]

Scott,

No, I'm not below Class C, it's SEA Class B with the 30-mile veil, so we need the Mode C.

Jim

 

[Low Pass]

I *believe* you can also call the ATC/TRACON for your Class B and ask permission (for a one time variance to go get it fixed). But my recollection is going back several years. Can't hurt to ask, and dealing with the air traffic authority has to be a lot easier than getting involved with the FSDO!

2 cents

 

[SteinAir]

I also have a 480 and GRT's. Stark wired my harness the same way that Jim's is wired - no Mode C unless the 480 is in the loop.

Like I said, it's not necessarily wrong, but certainly not the norm nor the way GRT wants it wired. After doing literally hundreds of these GRT's....we try to do it the way GRT wants it done:

http://www.grtavionics.com/File/Wiring Diagrams/WD-1002-03.pdf

It's the same for a 430, 530, etc.. There are many reasons not to run it through the 480 - too many to list in a simple post. Again, if it were me and I were without the 480, I would spend about 2 minuntes making a simple jumper wire. No craziness with the FAA, ATC or otherwise, and no flying around without a txpdr.

Just my 2 cents as usual.

Cheers,
Stein

 

[rv7charlie]

I fly a -4 with no transponder at all. I've operated into the New Orleans mode C veil (to St Charles, about 3 miles from the tower) a couple of times and I've gotten permission once to enter the Tampa veil to get into Lakeland for the January RV gathering. Both times I contacted Approach by phone ahead of time & it wasn't a problem. They just wanted me in radio contact as I approached the veil.

I've never asked for permission to actually enter the class B. I would bet that it just depends on the local management of the airspace. I've had the tower request a high speed pass before. (Not at a class B airport...)

Charlie