Autopilot use prior to FAF?

[alaskan9974]

I asked in Avionics, but maybe better suited to this section;

I know the Trutrak in certified installations has a 700’ agl limit and coupled approach limitation, can it be used legally prior the final approach fix using heading and altitude bugs, specifically during IPC or Checkride? The manual with limitations is bare, it just has the AGL limit, and no certification for coupled approach which I understand would be past the FAF from what I read.

 

[Clip4]

The manual states the autopilot has not been evaluated by the FAA to meet the certification requirement for coupled approach procedures, including coupled approaches.

 

[Walboy]

I think it would be a sensible use of the autopilot. I can't see a problem with using it during an IPC or checkride. However, you can expect it to mysteriously fail so don't become overly reliant on it.

@Clip4 answered a question you didn't ask. The OP acknowledged the autopilot's limitations in the original post.

 

[MauleSkinner]

An argument could be made that outside the FAF is considered a “terminal” procedure rather than an “approach” procedure.

 

[alaskan9974]

An argument could be made that outside the FAF is considered a “terminal” procedure rather than an “approach” procedure.

That’s how I see it, but when ATC says cleared for the approach, wouldn’t any published sections be considered to be on an approach.

 

[Clip4]

An argument could be made that outside the FAF is considered a “terminal” procedure rather than an “approach” procedure.

To me “coupled approach procedures, including coupled approaches” means everything inside the IAF.

 

[Martin Pauly]

An argument could be made that outside the FAF is considered a “terminal” procedure rather than an “approach” procedure.

That interpretation makes sense from a technical perspective. Autopilot limitations for engagement altitude exist to protect the aircraft if a malfunction suddenly causes an erroneous flight control input (e.g. full aileron deflection, or runaway trim). That is largely a function of how much altitude is available for recovery. Whether the autopilot is flying an enroute leg or the intermediate approach segment is not really relevant - in fact, the autopilot likely doesn't know the difference between the two; it's only after the FAF that the autopilot does something different.

Has anyone asked the manufacturer to confirm one way or another?

- Martin

 

[Hang 4]

Has anyone asked the manufacturer to confirm one way or another?

- Martin

Think that falls under the category of don't ask a question you don't want the answer to. As I understand it, TruTrak took a different approach (no pun intended) from Garmin when certifying the AP. Garmin tested in each specific airframe and certified it for all modes, so you can fly down to mins on an approach in an airplane certified on the GFC500 STC. TruTrak took a more generic approach and did not certify by type with testing.

Instead they put in fairly restrictive requirements for when the AP can be used. From a strict regulatory perspective, you can't use it on an approach (however that might be defined), from a practical standpoint, it works fine and has done that across thousands of experimental aircraft with no issues.

What your DPE might allow and not allow is yet a different question. He's likely the one to ask.

No advice to the OP here, just what I've gleaned from the numerous threads on TruTrak.

 

[MauleSkinner]

in fact, the autopilot likely doesn't know the difference between the two; it's only after the FAF that the autopilot does something different.

And many/most autopilots don’t do anything different…altitude losses specified in an AFM/POH Supplement are based on certification that says how long the test pilot has to wait after the malfunction before he can take control of the airplane.

 

[Walboy]

Doesn't the definition of "coupled approach" mean that a nav system is providing steering inputs to the autopilot like GPSS steering for example. My interpretaton of the limitations is that using heading and altitude hold is not coupled, regardless of what segment of an approach one is on.

That's what the OP is asking about; using heading mode. Bracketing the course using the heading bug is all he is asking about.

 

[alaskan9974]

Doesn't the definition of "coupled approach" mean that a nav system is providing steering inputs to the autopilot like GPSS steering for example. My interpretaton of the limitations is that using heading and altitude hold is not coupled, regardless of what segment of an approach one is on.

That's what the OP is asking about; using heading mode. Bracketing the course using the heading bug is all he is asking about.

Essentially this, with the G5 driving it, makes it really easy to input what I was already bugging once inbound.