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KI256 problems, replacement options, etc

Interestingly, Garmin claims the GI275 supports the KFC-200:
GI275 autopilot capability
This is revision C, dated Aug 2020.

And there is an KI256 adapter plate for the GI275, which also seems to confirm that this could be a replacement:
KI256 adapter plate for GI275

Looking at all the additional boxes that are optional with the GI275 depending upon desired functionality, there is likely to be more to it than first meets the eye.

Last Edited by chflyer at 01 Sep 18:46
LSZK, Switzerland

The autopilot version of the GI275 (most expensive of the 3 options) directly emulates the KI256 with no need for any interfaced converters.

Avionics geek.
Somewhere remote in Devon, UK.

wigglyamp wrote:

The autopilot version of the GI275 (most expensive of the 3 options) directly emulates the KI256 with no need for any interfaced converters.

So once it gets EASA approval it is a direct KI256 replacement and those of us with KFC150 can say goodbye to vacuum?

EIMH, Ireland

KI256 adapter plate for the GI275

That is just a metalwork adaptor.

The autopilot version of the GI275 (most expensive of the 3 options) directly emulates the KI256

Awesome! When did this come out and does it exist? It must have a substantial battery backup.

I wonder if they tested it with the KFC225 which uses a nonstandard LVDT excitation frequency and which works with the KI256 but not with certain products which emulate the KI256 closely enough to pass on the official King KI256 factory test fixture

Administrator
Shoreham EGKA, United Kingdom

It does exist and people in the US are having them installed by the dozens. Some with King autopilots with the GFC500 as a natural upgrade path when a servo breaks.

tmo
EPKP - Kraków, Poland

Having been watching some old Sandel videos I think the issue with building an electronic KI256 replacement – as mentioned e.g. above – is that while the FAA has certified a purely mechanical solution to a primary attitude instrument (KI256, or any other vacuum or electric AI) and no doubt this is because they have been in widespread use for perhaps 100 years they are unwilling to accept any AHRS solution unless it has a background erection mechanism (as discussed e.g. around here) and that requires either airdata or GPS to be introduced.

The KI256 can be confused it by flying round and round for a long time but once certified nobody will un-certify it

So you would be looking at a fairly complex device. Aspen (EFDxxx+EA100) or Garmin (GAD43) solved this but their boxes already contain all the required extras.

That would give you certified primary attitude. Then you have the next challenge: certified primary attitude reference for an autopilot. Again, the KI256 gets in “under the wire” because of ancient history. I suspect it is harder because some flight testing is required, with each autopilot which is to be on the STC, and around the loading and speed envelope (because the dynamic response of the AI affects the pitch/roll control loops in the autopilot).

Administrator
Shoreham EGKA, United Kingdom

The Garmin GI275 is a fully certified replacement for the KI256 and STC’d on multiple aircraft so it can be done successfully without lots of external interface boxes. But as suggested, it does require a GPS input and has internal air data computation.

Avionics geek.
Somewhere remote in Devon, UK.

I suggested to Sandel almost 10 years ago that they develop exactly such a product. They had the technology in-house, more or less. They could have sold many thousands, at say 5k-10k $ each (a new KI256 lists/listed at some 10k). The then owner of the company – a really nice guy btw – said it is almost impossible to certify.

How much would a GI275 cost, for a TB20 with a KFC225? Does the GPS have to be a WAAS one and what’s the cheapest way to get that? Could the GPS in a GTX335 be used?

Administrator
Shoreham EGKA, United Kingdom

Do it right with 2x GI275 and a proper navigator and you will have significantly enhanced functionality, clean up most legacy round gauges and lose the vacuum system.

Alternatively, a G3X + G5, which also opens the upgrade path to the G500.

Last Edited by T28 at 26 Oct 08:49
T28
Switzerland

which needs a GPS to fly an ILS!

No thanks – even if you paid for it

It is also nonexistent. So now I have to spend my time linking to other threads explaining this, in case somebody reads this and thinks they can put a GFC500 into a TB20.

A number of people have already installed a G5 with a King autopilot and discovered only afterwards… one-liners are cheap and easy.

The Garmin GI275 is a fully certified replacement for the KI256 and STC’d on multiple aircraft so it can be done successfully without lots of external interface boxes. But as suggested, it does require a GPS input and has internal air data computation.

How much would a GI275 cost, for a TB20 with a KFC225? Does the GPS have to be a WAAS one and what’s the cheapest way to get that? Could the GPS in a GTX335 be used?

Administrator
Shoreham EGKA, United Kingdom
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