GFC 500 in a Mooney ...

[NicoN]

A colleague said, that the GFC500 provides vertical guidance by using the servo not direct on the elevator but  using the elevator trim.

Therefore he has the idea that you need 2 Servos to have lateral guidance AND vertical guidance including elevator (auto)trim.

I thought you need 3

[ArtVandelay]

Hmmmm, making it complicated.

The trim servo will allow the elevator servo to work with less resistance.

3 servos, without the trim servo you would need to adjust the trim manually, but I don’t know anyone who just installed 2 servos.

[Pinecone]

If you have only two servos, the autopilot does not adjust the trim, you need to do that manually.

There IS a pitch servo the drives the elevator directly in all installs.

[kortopates]

Many C172’s have only the two servo install. It’s very annoying since anytime you either change airspeed/power or want to change altitude the AP starts annunciating TRIM UP or TRIM DOWN.
You become the third servo and you’ll be called on a lot more than you would likely expect. Okay for a trainer that spends most its time in the pattern but quite annoying for an owner flown xctry airplane.


Sent from my iPhone using Tapatalk

[NicoN]

Right, we also have electrical trim but not auto-trim.

So, the answer is: we need THREE servos

Next question:

We have 2 GI275 installed; do we ONLY need Servos (3) and a mode controller, or do we need another G5 or GI275?

[Stanton R]

If the GI 275 are installed as an ADI and HSI and are mod 1 then you will need the mode controller, servos and install kits.