Secondhand autopilot, and STC permission

with the possible exception of the TruTrak aka AeroCruise 100.

Which can’t fly an ILS

I don’t think in this day and age anyone would want to pay money to do a fresh install of any King autopilot system

It may be an easy option for some cases. If say you had a TB20 which had one of the very old King systems (not sure which APs the TB20 had in its history) and you just want to fit something which is a bit later. Currently the options are not very good.

However, it seems that the way this “STC permission” is interpreted by some in the business, you would need the permission even if you replaced all parts of an existing system, by installing a complete “new” system. I find that weird, since why not just replace part by part?

Peter wrote:

Which can’t fly an ILS

Agreed, that is not King’s fault. Not getting the AP certified for more airframes, on the other hand, clearly is.

As a side note, I understand, but am not sure, the TruTrak is pretty much capable of flying anything and the limitation is in paperwork. As in “not allowed” vs. “can not”.

I’d give some serious thought if lobbying a company that actually delivers a working product (Garmin, Dynon) isn’t a better way than moving to a “newer” King AP.

I totally agree on the “replace with like” approach – especially with a reasonable IA like the one you work with.

AIUI Trio ot Trutrak don’t support analog nav, so can’t track VOR/LOC/GS. Thread.

Whether this is a problem for you will depend but IMHO for Europe it is pretty useless, for any kind of “serious” IFR.

Right, it won’t fly a proper ILS (analog), I stand corrected; it will do anything that comes from GPS, including, I believe, vertical navigation. How disqualifying this is in reality will have to be an individual decision.

This may be relevant.

Wait a second. So if I would buy a used autopilot from an identical aircraft where all parts and paperwork was included, including the original STC, I cannot reuse it? I’d have to ask the manufacturer for permission to do so? This is serious? Was thinking about an S-Tec device.

I don’t think so.
Was the AP offered by the DAH as a factory option?
Or by STC?

UdoR wrote:

I cannot reuse it? I’d have to ask the manufacturer for permission to do so? This is serious? Was thinking about an S-Tec device.

You can’t install any STC without the explicit permission of the STC holder. Each aircraft make, model, and serial number may have a unique install kit that consists of brackets and parts to mount components and servos. Also the installation instructions are based on the specific aircraft the autopilot is being installed in. Voltages vary between aircraft and other equipment already installed can be a factor, for example tip tanks. Stec will sell you an STC kit for your aircraft and inspect and repair components. They don’t do this for free, but they are reasonable. However, it is not always economical to transfer an autopilot from one aircraft to another, especially with warranty considerations. Edit: other components such as the DG/HSI may require that modifications be made to the electronics. The instructions for this and their applicability are part of the kit.

You can’t install any STC without the explicit permission of the STC holder.

The questions which remain are:

• What if the STC holder is no longer around, or is not responding? With books and such there is the copyright expiry time (very very long)

• What if the installation is only partial (e.g. only replacing autopilot servos)? This is a very similar thing to the widely established exhaust “repair” industry where you avoid having to get an STC or a PMA, by getting the customer to supply one tiny part of his old exhaust and you build him a completely new one (probably not even bothering to include that bracket )

• What if the STC is a “bogus” one i.e. everything in it was previously covered by stuff in IMs, covered by a previously approved mod, etc? It is easy to get an STC for something which is wholly prior art, and a lot of STCs are like that. The FAA or EASA are not going to check for prior art, in the way the Patent Office does and you can still get a patent for something with prior art all over it, if sufficiently specialised. Controversial, because the STC holder was probably well aware, but was still hoping to make some money out of it. For any given proposed installation, there are likely to be a whole pile of old field approvals, IM circuit fragments, stuff in AC43-13 (structural stuff is a ripe area for STCs which an installer can get the client to pay for, but actually the procedure was in AC43-13 all along), in EASA-land you have the option of grandfathering a mod from any other EASA country and many of those require a considerable effort to find…

If the STC holder is no longer around, you won’t be able to obtain the permission required by 91.403(d) and will be unable to use the STC as the basis for installation. If the holder is still around, but unwilling to provide written permission to use for an STC they allowed you to use, they are in violation of 21.120 which requires them to provide written permission and you can report the issue to the FAA and likely take civil action to force them to comply or pay damages.

From FAA definitions: Maintenance means inspection, overhaul, repair, preservation, and the replacement of parts, but excludes preventive maintenance. Replacing a part requires that the part be approved for installation on type certificated aircraft by an authorized person and that meets the part’s airworthiness criteria. Replacing a part such as a servo on an aircraft assumes the original STC was already installed. As long as the mechanic can certify the part is airworthy by an appropriate means such as testing or a form 8130-3, they should be able to use the part. The aircraft already has the STC permission. The mechanic would have to confirm the suitability of the part and so on. Some manufacturers don’t provide maintenance manual data to determine if the part is airworthy, in which case the part would need to be returned to the manufacturer for overhaul or airworthiness determination.

Your third point suggests a misunderstanding of the use of an STC. It is FAA approved data developed by the STC holder and provides the basis for installation of an item on a certified aircraft. It is a modification to a TC. For example installing a different engine in an aircraft other than the one on the TC may be installed using an STC as the legal basis for the modification. Multiple STC from separate companies may each provide an independent basis to install the engine. If you have the written permission of one of the STC holders to use their data to install the engine, you may modify the aircraft using their STC. Or, you could get a field approval to install the same engine and not use either of the STC’s. IOW, the installation of the engine requires FAA approved data which may be provided by STC or other means. It is not proprietary to install the engine, it is proprietary to install the engine on the basis of a given STC holder’s data. Using an STC to obtain the FAA approved data and basis for the installation is often cheaper and quicker than developing your own FAA approved data using a DER and field approval process. Look at this FAA General Counsel Opinion that relates to the subject: