It is VERY dangerous to talk to Lucas at Tru Trak on the phone – everyone needs to know that! I was chatting with him a month or two back about a problem we were having with Louise’s ADI (rapidly corrected by TT), and mentioned that I had lost an LED segment on my Pictorial Pilot, and would have to get that in to him when I had the time. Long pause…..”Paul, you’re still flying with a Pictorial Pilot? And you have GRT HX displays?! You need an upgrade!” Dangerous words, dangerous words….because when I went and looked at the prices, taking into account Tru Trak’s policy of full credit for traded in equipment, the leap from the PP and Altrak to a Digiflight II VSGV was nowhere near as much as I expected. That actually brought his suggestion in to the realm of possibility, and after a month of searching the budget, I found that I couldn’t resist. So I pulled the trigger and decided to do the upgrade at the same time I was installing a Dual AHRS in my GRT EFIS and doing the Condition Inspection. I knew I’d need to add some wires to the back, and there is no better time than when everything is opened up for inspection.
The PP/Altrak Combo has given me great service, providing me with altitude hold, heading hold, and Nav Tracking capability. The fact that the autopilot gave me a redundant attitude source played well with my redundancy scheme for IFR flight. Originally, I settle on the Pictorial Pilot because it included a turn rate display that would allow me to fly partial panel should the EFIS quit – but it didn’t take long for me to realize that in that case, I’d just engage the autopilot to keep the wings level and make turns, so the display wasn’t that significant. Going with the VSGV, I’d be giving up that familiar face, but I’d be gaining GPSS capability so that the EFIS could drive the autopilot to make predicted course intercepts and fly fully coupled approaches. In addition, the ability to digitally select altitude rates is very attractive when managing a descent from altitude in a slippery RV. And altitude pre-select is an added bonus for single-pilot IFR in an RV that can climb or descend at 2,000 fpm. I didn’t truly NEED these capabilities, but they sure would be nice to have since the price was right.
The swap was pretty simple from the standpoint of what I needed from Tru Trak. Lucas only had to send me a new panel unit (the brains and controls of the autopilot) and a new pitch servo. My Altrak’s pitch servo didn’t have trim sensing, and the Digiflight requires it – otherwise, the two servos are identical and fit the same bracket. Unfortunately, this means I needed one additional wire to the back of the airplane, and that added some time to the installation – but since I was combining the job with the GRT upgrade which needed new wires to the back for the magnetometer, it wasn’t a big delta. After the installation, I just needed to send my old Pictorial Pilot, Altrak control box, and pitch servo back to Tru Trak to complete the trade – oh, and a credit card number, of course. (When I actually got in to the installation, I realized that I really didn’t have a servo cable running from the panel to the back end, since my Altrak brain box was back by the servo – only control and indicator lights ran forward. But Steinair sells a pre-twisted servo cable “by the foot”, and that made the job much quicker.)
Once the new pitch servo wires and servo were in place, the rest of the action was up at the instrument panel. I disassembled the old Pictorial Pilot and Altrak connectors, and labeled each conductor with it’s function. It helped that all the existing wires had D-sub sockets already installed, and that’s what they needed, so about half of the job was simply unpinning the old connector body. I built a table of conductors that showed where each wire (connector and pin) came from in the old setup, and where it was to go on the new digitrack connector. Masking tape flags on the wires with pin numbers and functions written on them kept the memorization to a minimum. When I had all of the necessary conductors found and labeled, it was a simple matter of re-pinning the new connector body, and I was on my way.
In the “New conductor” category, I had to find the ARINC lines from my existing GNS 430 and EFIS bundles, and extend them through a DPDT switch to the autopilot. There are six ARINC lines on the GNS 430 pin-outs, and I actually surprised myself to find that five years ago (when I wired the plane), I put pins and wires into the connector for these, and left them bundled behind the panel! This made it a simple job to splice in what I needed to complete the schematics. It really helped that GRT has a drawing which shows all of the interconnects for a GRT/Garmin/Digitrak installation – that almost takes all the fun out of it (but sure eliminates mistakes induced by misinterpretation of the drawings. To prevent disappointment during initial smoke testing, I have a discipline of checking where each wire come from and goes to at least three times while the bundles are still open. Mistakes still happen, but this eliminates most re-work later on.
Speaking of initial smoke testing, I was very satisfied (when power was applied) to find that no replacement smoke will be required – it all stayed in the wires and boxes, where it belonged. Replacement smoke is VERY expensive, and you never want to have to buy any! In this case, the system powered up and I stepped through the initial ground testing very quickly, with all boxes checked off. I had to snip the wires on my “pitch servo reversal loop” (pins 1 &2 of the Digitrack harness are connected with a loop – if the pitch servo drives backwards, you snip it, and open the circuit), but other than that, the checkout was without error.
Flight testing is in the near future (winter weather seems to have found Houston), and I’ll report on how that goes. It should be fun learning all the new capabilities. We’ll see how many surprises I get in good VFR conditions before launching into the clouds…
Paul
The PP/Altrak Combo has given me great service, providing me with altitude hold, heading hold, and Nav Tracking capability. The fact that the autopilot gave me a redundant attitude source played well with my redundancy scheme for IFR flight. Originally, I settle on the Pictorial Pilot because it included a turn rate display that would allow me to fly partial panel should the EFIS quit – but it didn’t take long for me to realize that in that case, I’d just engage the autopilot to keep the wings level and make turns, so the display wasn’t that significant. Going with the VSGV, I’d be giving up that familiar face, but I’d be gaining GPSS capability so that the EFIS could drive the autopilot to make predicted course intercepts and fly fully coupled approaches. In addition, the ability to digitally select altitude rates is very attractive when managing a descent from altitude in a slippery RV. And altitude pre-select is an added bonus for single-pilot IFR in an RV that can climb or descend at 2,000 fpm. I didn’t truly NEED these capabilities, but they sure would be nice to have since the price was right.
The swap was pretty simple from the standpoint of what I needed from Tru Trak. Lucas only had to send me a new panel unit (the brains and controls of the autopilot) and a new pitch servo. My Altrak’s pitch servo didn’t have trim sensing, and the Digiflight requires it – otherwise, the two servos are identical and fit the same bracket. Unfortunately, this means I needed one additional wire to the back of the airplane, and that added some time to the installation – but since I was combining the job with the GRT upgrade which needed new wires to the back for the magnetometer, it wasn’t a big delta. After the installation, I just needed to send my old Pictorial Pilot, Altrak control box, and pitch servo back to Tru Trak to complete the trade – oh, and a credit card number, of course. (When I actually got in to the installation, I realized that I really didn’t have a servo cable running from the panel to the back end, since my Altrak brain box was back by the servo – only control and indicator lights ran forward. But Steinair sells a pre-twisted servo cable “by the foot”, and that made the job much quicker.)
Once the new pitch servo wires and servo were in place, the rest of the action was up at the instrument panel. I disassembled the old Pictorial Pilot and Altrak connectors, and labeled each conductor with it’s function. It helped that all the existing wires had D-sub sockets already installed, and that’s what they needed, so about half of the job was simply unpinning the old connector body. I built a table of conductors that showed where each wire (connector and pin) came from in the old setup, and where it was to go on the new digitrack connector. Masking tape flags on the wires with pin numbers and functions written on them kept the memorization to a minimum. When I had all of the necessary conductors found and labeled, it was a simple matter of re-pinning the new connector body, and I was on my way.
In the “New conductor” category, I had to find the ARINC lines from my existing GNS 430 and EFIS bundles, and extend them through a DPDT switch to the autopilot. There are six ARINC lines on the GNS 430 pin-outs, and I actually surprised myself to find that five years ago (when I wired the plane), I put pins and wires into the connector for these, and left them bundled behind the panel! This made it a simple job to splice in what I needed to complete the schematics. It really helped that GRT has a drawing which shows all of the interconnects for a GRT/Garmin/Digitrak installation – that almost takes all the fun out of it (but sure eliminates mistakes induced by misinterpretation of the drawings. To prevent disappointment during initial smoke testing, I have a discipline of checking where each wire come from and goes to at least three times while the bundles are still open. Mistakes still happen, but this eliminates most re-work later on.
Speaking of initial smoke testing, I was very satisfied (when power was applied) to find that no replacement smoke will be required – it all stayed in the wires and boxes, where it belonged. Replacement smoke is VERY expensive, and you never want to have to buy any! In this case, the system powered up and I stepped through the initial ground testing very quickly, with all boxes checked off. I had to snip the wires on my “pitch servo reversal loop” (pins 1 &2 of the Digitrack harness are connected with a loop – if the pitch servo drives backwards, you snip it, and open the circuit), but other than that, the checkout was without error.
Flight testing is in the near future (winter weather seems to have found Houston), and I’ll report on how that goes. It should be fun learning all the new capabilities. We’ll see how many surprises I get in good VFR conditions before launching into the clouds…
Paul
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