Thanks for the info, MD 
PS I have some friends who make a habit of pushing these aircraft repair and modification approval issues, sometimes for their own practical benefit and at least once so they could repair and sell a damaged plane they bought cheaply – the planes value was affected by the apparent difficulty in obtaining approval for a simple repair. The advantage for them (other than their stubborn persistence) is that its never their only plane, so they have time, and they have storage space. It would be interesting to see the situation if somebody like that installed a used autopilot legally on an N-registered plane under an approved and filed 337, and then requested autopilot manufacturer support… My guess is they’d get that support, after some ‘convincing’. It might take a year though!
Some people enjoy different sports than others 
But there is a point of view (which I have just read on a US forum, prob99 posted by an avionics installer) that every use of any STC requires a written permission from the STC holder. This guy even went as far as saying that a permission on the STC itself does not count. With stuff like that circulating in the USA mere mortals have no hope!
Correct, the same applies to the EASA changes. For a reason, as designing an STC or modification cost time (money) and certification fees. Having a lot of minor changes I think it is only fair that someone “owns” a change of modification, as I put my time in it.
Anyone is free to apply for their own approvals.
at least here in Europe it is the paperwork which will drive costs through the roof. I’d say today cost of paperwork is approximately the same again as the actual hands on electrical work.
I would go even further, and say that an average change cost more time doing paperwork, then the actual installation, and that the cost in most cases exceeds the labour for installation.
It doesn’t matter what opinions people have, only what the FAA approved STC says (in writing) and that the A&P IA will approve the installation based on the STC data. The 337 makes no reference to the manufacturer of the hardware, only the FAA approved STC.
Not precisely true. In order to legally install an STC or use the STC data for an installation, one must have explicit permission from the STC holder. Some STC holders provide blanket permission statements (example Garmin) while others do not. Some record it by serial number and N number as Stec does. It is illegal under US FAA regulation to use the STC without the STC owner’s permission.
Usually the first step is to obtain all the part numbers needed to install the autopilot in a given aircraft make and model and compare this with what the seller of the used equipment has for sale. Stec will sell the STC for a used autopilot and grant permission to its dealers to install it. This includes the installation diagrams and instructions along with the mounting hardware which is appropriate for the new installation, They will also test and certify/repair the equipment if requested.
Often this is not an economical proposition as the cost of the STC, plus the cost of any repairs, plus the cost of the used equipment will make the choice of a new system more attractive. If I recall, the STC package including the installation kit (brackets, etc.) is on the order of one or two thousand dollars or so. The real expense is testing and overhauling components. They were once a great company to deal with and as they underwent ownership changes by some big companies, they became unresponsive. Now that they are back in the hands of their own management by a LBO, they are restoring their customer support.
Well I do not believe a DR400 has an FAA type certificate so it probably can’t be operated on the N reg.,and therefore all the FAA STC talk does not help the OP.
However, the point embedded in the discussion is that every autopilot has to be configured for the exact airframe type, hence the ability of manufacturers to charge a lot for “re-configuration”. Is there anyone who could re-configure a fairly old autopilot such as the one the OP is considering at any price?
In order to legally install an STC or use the STC data for an installation, one must have explicit permission from the STC holder. Some STC holders provide blanket permission statements (example Garmin) while others do not. Some record it by serial number and N number as Stec does. It is illegal under US FAA regulation to use the STC without the STC owner’s permission.
I surely understand that. In the field, dealing with the A&P IA who in actuality approves the installation, I would maintain that the written STC limitations drive the process. That’s simply because what’s explicitly written in the STC is the only mechanism by which FAA records the existence of “permission”.
However, the point embedded in the discussion is that every autopilot has to be configured for the exact airframe type, hence the ability of manufacturers to charge a lot for “re-configuration”.
That could be approached by negotiation, i.e. telling the manufacturer you have signed-off paperwork which makes the installation legal. Then asking them to tell you in writing that they’ll provide no support for a legally airworthy aircraft. It’s a game that can be played (with mixed success, naturally) just as its a game the manufacturer is playing with the owner of the aircraft.
Much harder as I said originally if the STC is a one time approval, and lists the aircraft serial number.
PS This discussion really highlights why I have essentially no interest in avionics or IFR equipped aircraft, because you can never break free of the avionics manufacturer as you can an airframe manufacturer on N-registration, especially when the airframe manufacturer no longer exists.
And simple if called out in the documentation of the aircraft manufacturer. You might want to check that, as it could save a lot of money.
That’s a really good point! You don’t need an STC if it was covered by the original Type Certificate.
But things like the gain of the control loops will be different for a PA28 vs an Extra 300, hence the need for re-configuration and the opportunity for a large cost
The KFC autopilots deal with the loop gains by a 3.5" diskette containing a “certification file” which is loaded into an RS232 connected laptop and uploaded to the Configuration Module (a $1 93C46 EEPROM in a little box mounted somewhere near the autopilot).
This config file is aircraft model specific. They are hard to get hold of; only dealers authorised for that autopilot model can get it. I have tried to get the KFC225/TB20 one for about 10 years… I have a spare KC225 computer but no spare config module.
How STEC do it I don’t know. Maybe they tweak some pots in the AP computer box?
If the autopilot is part of the DR400 type certificate (TC), then you do not need an STC. All you need is the autopilot unit with EASA Form 1 (all avionics shops with the maintenance manual can produce that) and somebody to install it.
