Saturday, November 05, 2005

Altitude Hold

In this photo you can see just barely see the pitch servo below the large black battery. to the left of the battery, you can see the control unit. Our altitude hold system is the Treo Avionics The installation is fairly simple, first you locate the four components. The first is the Pitch servo. I located it directly behind the instrument panel and a short control arm will attach it to the elevator control horn.

Second, the two panel mounted components were installed in holes that we had cut out in the panel previously. We cut the holes originally based on dimensions from the trio web site. A small LCD and a rotary knob provide the interface to the altitude hold.

Then the 'brain' was installed. A small box that stands vertically, and must be oriented top-up and face the db connector forward. It was also mounted directly behind the instrument panel on the small shelf that we installed originally to hold the GRT AHRS boxes. (They didn't fit there). Now the shelf has the EFIS backup battery, the pitch servo, the altitude hold control box, the low voltage indicator/backup battery management module and the control relay for the backup battery. It is getting a bit crowded and I still have to find a place for the control rod for the manual gear extension.

After all of the boxes were mounted, I started in on the wiring. Locating the 4 conductor tefzel insulted shielded wire recommended by Trio isn't easy. I ended up calling Trio and bought 20' from them. If I had known it was so hard to find, I would have bought it at the same time as the altitude hold system.

I didn't like the solder on DB connectors that were provided. The rest of the aircraft is using high quality machined ($0.30/each) crimp pins provided by B&C ( I got some empty DB shells ready and started crimping pins and cutting wires. Each panel mount box gets a DB-9 and the controller uses a DB-25. The servo has a plastic molex style connector.

After it was all wired up, I ran a temporary power and ground wire to it to test before I strapped the whole bundle down into the aircraft. The LCD displayed 'System Test' endlessly. A re-inspection of the wires found that I had crossed two signal pins. After fixing that error, I powered it up and all worked fine. Configuration of the system will have to wait until I get the canard re-mounted and hook up the control arm.

I still need to fasten the bundle down, hook up the power wire to the panel mounted switch, run the permanent ground wire, run power to the switch, and hook up the control stick mounted disconnect button. Something to do on Monday...

No comments: