Garmin Mode S GTX-330/328 difference

[Kiltie]

I'm getting mixed views on the capabilities of each of these transponders. Garmin market the GTX 328 as a "VFR" transponder, and the more expensive GTX 330 as "IFR" capable.

However, one dealer at Aero Expo said that the 328 was sufficient for IFR flight below FL150 at less than 175kts indicated cruise airspeed.

I am aware of the TIS capabilities of the 330 but my primary focus is on IFR legality in the UK. Is the 328 indeed capable for ATC purposes and not just restricted to VFR use after all?

[IO540]

I think the answer is what equipment the ANO requires, what type approval it needs, and what type approval the 328 has relative to the 330.

I am pretty sure the 327 (https://buy.garmin.com/shop/shop.do?pID=124#)(no 328 on the garmin.co.uk website) is fine for UK-style IFR i.e. outside the airways system. There, you can legally navigate using a rubber duck floating in a bucket of water.

Garmin say: TSO C74 Class A1, certified to 50,000 feet.

Airways equipment levels is a different thing.

Apart from the traffic (which we will never get in the UK) I can't see what is different that is relevant, but will leave it to somebody who knows the regs and has some references.

[Kiltie]

Thanks. The 327 is non-Mode S. The 328 and 330 are Mode S. If what you say is true then the 328 is not much use to me then as I use the airways system in the UK.

Does anyone have any quick pointers toward the relevant ANO requirements?

[mm_flynn]

If you search for the various Mode S AICs they will give the requirements. However, the key one is if you are going to fly IFR, then something that is certified VFR only (i.e. the 328) isn't going to cut it.

In the UK Class G it doesn't really matter due to the 'In the Mind' nature of being IFR or VFR.

Given it sounds like you have an IR - Book your upgrade, get your exemption to keep flying until the upgrade is fitted, live with the fact that you are £3k lighter in the pocket (maybe think NATS has given you London LARS in return if it helps make the £3k hole feel smaller ;) - very helpful in Scotland!)

[gubbo]

the GTX 328 can be used for IFR certificated aircraft as long as they fly slower than 175kts and lower than 15,000 ft.

[bookworm]

One thing to bear in mind if you're looking a longish way into the future:

"The new GTX-328 will not offer TIS, EHS or ADS-B functionality."

Europe will eventually go to ADS-B over 1090ES, and GTX-330 owners should be able to make that work with only config changes.

Maybe gubbo can tell us if there's likely to be an upgrade path for the GTX-328 or whether its a fundamentally different product?