OK I will investigate replacing my DG in the Worrier with a GI275. The objectives are:
HSI capability with a link to a GNC255 VOR/ILS and a KLN94.
Also getting VOR/LOC tracking with an installed S-tec 20. (already works on the KI209) Not planning on investigating roll steering for the KLN94 so not sure how a track change will work on a fly by waypoint with GPS as the NAV source.
Standby attitude indicator, eventually might investigate replacing the AI with a GI275 and pull the vacuum system.
Not planning on engine monitoring
Not clear why the GI275 requires a database and how much the subscription costs? Not sure how good the standby battery is? Not sure what the cost will be and what add ons and what the installation cost will be.
Why the GI275? It seems it requires less surgery on the panel than the G5.
Will post on progress, but input on some of my naïve questions appreciated
Not clear why the GI275 requires a database and how much the subscription costs?
It has an embedded VFR GPS that you can use for navigation.
Not sure how good the standby battery is?
One hour.
RobertL18C wrote:
Not clear why the GI275 requires a database and how much the subscription costs?
Cost: See https://fly.garmin.com/fly-garmin/support/pricing and choose “GI 275” in “Model”. (The OnePak and PilotPak are for “all avionics in the plane of G500, GTN and later generations, but not GNS; scroll down for individual prices”.)
I think most “EHSI” boxes have a map of some sort e.g. the Sandel SN3500 has.
The real Q is whether that map expires and renders the product non-functional. That would, of course, be outrageous 
RobertL18C wrote:
Not clear why the GI275 requires a database and how much the subscription costs? Not sure how good the standby battery is? Not sure what the cost will be and what add ons and what the installation cost will be.Why the GI275? It seems it requires less surgery on the panel than the G5.
We elected for the G5 in HSI-mode over the GI275 (going in right now, alongside a GTN650Xi replacing our GNS430) to replace our DG for the following reasons:
1. It doesn’t need a database (which on the GI275 supports, as I understand it, functionality we’re not really after)
2. The shop said supply of the GI275 was unpredictable
3. Our proposed G5/GTN650Xi was something the shop said they’d done plenty of and were very confident of avoiding complications (not necessarily so with the GI275)
4. We have no autopilot and thus no autopilot-related requirements
The GI275 does of course slot in like a regular instrument and look neater. However we’re cool with how the G5 will look.
Probably the biggest risk here is that given your KLN94 and autopilot requirements, whichever shop does it will probably be working it out as they go along!
From one US site:
A dual GI275 installation in a TB20, in the US somewhere
Peter wrote:
A dual GI275 installation in a TB20, in the US somewhere
And GFC500 which is more important
Only one thing more to be replaced to get really nice panel – King radio.
Emir
The King KX155/165 radios brought a level of reliability previously unheard of to GA, as 8.33 is not required in the USA I guess the owner took the view that if it’s not broke don’t fix it.
You’re right – I had 165 in my TB20 and while GNS530 had two failures in 4 years, KX worked flawlessly.
