Research: wing mods

As I'm about to receive the wing kit, I started researching about all the non-standard/not-in-plans things I wanted to have there.

A short list is:

• Aveo Ziptip wingtips/lights (both wings)
• Archer NAV antenna (left wing)
• Delta Pop COM antenna (right wing)
• Garmin heated pitot tube (left wing)
• Garmin magnetometer (right wing)
• Garmin roll autopilot servo (right wing)
• Ray Allen aileron trim servo (right wing)
• Speed brakes (both wings)
• Wires and cables for all the above
• Locking fuel caps
• Static wicks on the ailerons (with the respective bonding straps)

I also discarded a few other components, like the Ice Meister - I'm simply going to get ice lights instead, for much cheaper. If I change my mind later, it's always possible to install that at the bottom of the fuselage, where OAT probes are commonly installed.

Wing tips

I had previously posted about the Aveo Ziptips. I still plan to use them, and thus have to run wires to those lights on both sides. These are some of the most important wires, because they're long and "high" current - thus the thickest and most prone to causing interference with other equipment. The interference is the reason why they don't use the wing skins as the ground return path, and instead need dedicated ground wires, the whole thing shielded.

I considered running a single pair of high-current wires and have relays close to the wing tip to operate each light, but from a reliability standpoint that would mean that losing that circuit would cause me to lose all the exterior lights - not good.

Wires to each wing:

• Position power (.5A)
• Strobe power (4.5A)
• Taxi power (1.5A)
• Landing power (4.5A)
• Return A (5A)
• Return B (6A)
• Wig-wag enable signal
• Wig-wag synchronization between wings
• Strobe synchronization between wings

NAV antenna

I'm using the Bob Archer wingtip antenna for VOR/LOC/GS reception (and hoping the interference from the lights won't be too bad). I already have the antenna and now need to figure out how it gets combined with the Aveo wingtips.

Cable to left wing only: RG-400 coax

COM antenna

As mentioned in a previous post, while one of my COM antennas is going on top of the tailcone, the other will go under the wing in order to keep the belly clear for a Motopod.

Cable to right wing only: RG-400 coax

Garmin Pitot Tube

I'm leaving avionics purchases for as late as possible, but so far I'm planning on using a G3X touch with the GAP26-20 heated pitot, so I'm using that as a reference. The heating is another high-current connection to the wing (in fact higher current than the lights), so I'll be mounting the pitot tube on the opposite side of the COM antenna to minimize interference - it does also use a dedicated ground return wire.

To attach the pitot tube, I got the Gretz PBK-12 mount - these should be trivial to install, and my only concern is finding the right location so that they don't get in the way of the speed brakes.

Wires to left wing:

• 1 power wire (12A)
• 1 ground return (12A)
• 1 discrete signal

Magnetometer

Again, using the Garmin units as a reference, as mentioned in a previous post, this will be mounted in the wingtip. This will require some testing to see if the servos (autopilot and trim) on the right wing cause any significant interference - they're far enough that it may not be an issue (others have mounted it in the tailcone close to those servos without issues), but it's less than the 3m that Garmin recommends.

Wires to right wing:

• 1 power wire (<0.2A)
• 1 ground return (<0.2A)
• 2 RS-485 signals
• 2 RS-485 ground returns

Garmin roll autopilot servo

Garmin makes the mounting kit for its GSA28 servos to go into the right wing near the aileron trim servo, so that's what I'm planning for.

Wires to right wing:

• 1 power wire (2.8A)
• 1 ground return (2.8A)
• 2 trim inputs (1A)
• CAN bus pair
• Autopilot disconnect signal
• 2 RS-232 signals (TX/RX)

Aileron trim servo

The aileron trim servos go in the right wing per Van's instructions. They're driven by the autopilot servo (for auto-trim), such that no dedicated wires are needed for its control, just signal wires for the servo position sensor.

Wires to right wing:

• Position signal power
• Position signal ground
• Position signal reading

Precise Flight speed brakes

Yes, I'm installing speed brakes. Why? I could give you technical reasons with questionable data about engine shock cooling on descents, but I'll just say that they're cool, I got them cheap and they make for great short-field landings :)

Precise Flight doesn't provide installation instructions for their brakes for the RV, but they did send me their Mooney instructions as a reference for both the physical and electrical installations.

The electrical wiring is pretty simple, with 8 wires that connect from each wing to the controller and include all the motor, clutch, sensors, etc.

The physical installation will be trickier - it requires cutting a hole on the top skin of the wing, mounting the backing plate they provide beneath it, possibly with a doubler, plus a bottom support bracket. I'll figure out the details once the wings are here.

Wires to each wing:

• 4 motor/clutch power wires (1.5A?)
• 4 signal wires

Left wing summary

The items going on the left wing are:

• Wingtip lights
• NAV antenna
• Heated pitot
• Speed brake
• Fuel senders
• Stall warning

which require these connections:

• Position power (.5A)
• Strobe power (4.5A)
• Taxi power (1.5A)
• Landing power (4.5A)
• Return A (5A)
• Return B (6A)
• 2 pitot tube wires (12A)
• 4 speed brake wires (1.5A?)
• 13 low-current/signal wires
• 1 RG-400 coax

Total: 12 high-current wires, 13 low-current wires, 1 coax

I could use a single connector at the wing root, but I'd rather separate signal and power connections. Assuming that I can do about 50% of the rated current (due to contact loading), I'll likely get TE CPC series 4 or series 6 for power like the 207486-1, 796466-1 or even 208479-1 (so I have 4 pins for higher-current lines like the pitot heat) and a series 2 for signal.

Right wing summary

Being symmetrical would be too easy, so the right wing has different equipment:

• Wingtip lights
• COM antenna
• Autopilot servo
• Trim servo
• Speed brake
• Magnetometer
• Fuel sender

which require a lot more wires:

• Position power (.5A)
• Strobe power (4.5A)
• Taxi power (1.5A)
• Landing power (4.5A)
• Return A (5A)
• Return B (6A)
• 4 speed brake wires (1.5A?)
• 2 autopilot wires (2.8A)
• 2 trim inputs (1A)
• 24 low-current/signal wires
• 1 RG-400 coax

Total: 14 high-current wires, 24 low-current wires, 1 coax

For this one, I can also use a TE CPC series 2 for signals and a series 1 for power (since there's nothing higher than 6A and that's rated for 13A).

This is all obviously subject to change as newer avionics come out, or as I need to move things around for the magnetometer to be happy.