Dbarbee
Pre-takeoff checklist
- Joined
- Jan 20, 2015
- Messages
- 119
- Location
- Sapulpa, OK (KRVS)
- Display Name
Display name:
Daniel Barbee
The avionics shop wrapped up the installation of the TruTrak Vizion autopilot in my C177B Cardinal last weekend and I braved the cold to go try it out on New Years Day.
Installation:
The install took about 2 weeks but that included the shop taking a few days off around Christmas, a couple of unexpected events that took them away from it, connecting my 430 gps output to my EDM830, and some rearranging of my circuit breakers. Overall the progress was steady and uneventful. The installer commented that the illustrations in the manual for the roll servo were a little hard to match up to what they could see through the inspection covers but they eventually concluded that it could only go one way. The roll servo pushrod was missing from the kit but TruTrack sent one promptly and it didn't slow the progress. The shop originally estimated "around $2,000" for the install but I haven't gotten the final bill yet. I expect it to be a little higher but not too much. With the cost of the TruTrak ($5,000), STC ($140 including $40 EAA membership), and installation (~$2,000) the total cost should be under $7,500.
Test Flight:
Track Select Mode (TRK): Roll control was very firm and responsive and rolled out right on the selected track and held it very well.
GPS Steering Mode (GPSS): Followed a flight plan and a GPS approach from the 430w flawlessly, including 90 degree turns, and kept the CDI dead center. Turn anticipation, procedure turns, hold entries, and holds all worked perfectly.
Vertical Speed Mode (SVS): Vertical speed control was about what I expected for an autopilot without auto electric pitch trim. There seemed to be a delay between the time I put in a new VS command and the time that the AP responded and the pitch control seemed mushy. Occasionally when asking for a climb or descent, the trim indicator would initially ask for pitch trim in the opposite direction. It also didn't seem to be able to nail the VS on the VSI as well as the lateral modes did. When the AP asks for a trim adjustment it's difficult to tell if it needs a little or a lot. I expect this to get better as I learn to use the AP and learn how it responds.
Altitude Hold Mode (ALT HOLD): Worked reasonably well with minimal deviations, even in light turbulence. The up/down pitch trim indicators came on a lot in the light turbulence, which I expected since the Cardinal can take quite a bit of pitch pressure to hold the nose up/down during down/up drafts.
Vertical Approach Mode (GPSV): The vertical approach mode didn't work. I set up for an LPV approach on the 430w with the AP in GPSS Mode and ALT HOLD. I never saw GS ARM or GS CPLD on the display and the AP stayed in ALT HOLD mode as the airplane passed through the glideslope. I tried it a second time with the same results. (I didn’t try it in zero vertical speed mode but suspect the results would be the same) After reviewing the setup procedure I verified the 430w ARINC 429 configuration and everything looked right. Hopefully this will turn out to be just a configuration setting somewhere in the 430w or the Vizion.
Any suggestions on things I can check?
Missed Approach Mode: supposed to command a climb at 500 fpm on the current track when activated during an LPV approach. I was not able to test this mode since the AP would not enter approach mode.
Control Wheel Steering Mode (CWS): I tested the control wheel steering from TRK mode by holding the CWS button on the yoke and changing the heading and releasing the button. The AP locked onto the new track as expected. (I don’t anticipate using the feature very much)
Emergency Level Mode (AP LVL): I put the airplane into a nose high bank and pushed the AP LVL button. The roll servo firmly engaged and gently leveled the wings. The pitch servo engaged but the AP was much slower to bring the nose down than it was to level the wings. I repeated this with a nose low bank with the same results. Even though the pitch seemed a little sluggish, it did stabilize the airplane in straight and level flight.
Automatic Envelope Protection Mode (AEP): Over-bank protection kicked in around 40 degrees of bank and firmly nudged the yoke back below 40 degrees. I tried the Minimum Speed Protection by slowing to stall speed. I couldn't get a full stall break so the AP must have been trying to lower the nose but it didn't have the same positive feel that the bank protection did. I didn't want to fly the airplane close to VNE so I didn't try the Maximum Speed Protection.
Gyro Bank Mode (BANK): I haven’t tested the gyro bank mode yet which is basically roll mode if the AP loses GPS input.
Summary:
Overall I'm very happy with the TruTrak's lateral control (TRK & GPSS) which is primarily what I wanted. Without automatic electric pitch trim I think the VS and Altitude Hold are working about as well as they can, especially considering the high pitch force needed in the Cardinal sometimes during turbulence. Don't get me wrong, the vertical modes did OK and will probably perform better once I get more familiar with using them, they just didn't feel as firm and positive as the lateral modes.
By the end of the 2 hour flight I was getting the hang of the buttonology and after a few more flights I'm sure I'll have it down. One issue I discovered was the location of the control unit in the old ADF indicator hole right above the flap handle. Several times I inadvertently put in 10 degrees of flaps while trying to adjust the autopilot. I'll probably swap places with the intercom during my next upgrade.
The TruTrak Vizion was a good fit for my needs, expectations, budget, and mission. I'm confident the GPSV issue will be resolved eventually so I'm not too concerned about that. I'd highly recommend it to someone looking for a low budget AP with lots of features but you've got to do your homework and understand it's limitations.
Installation:
The install took about 2 weeks but that included the shop taking a few days off around Christmas, a couple of unexpected events that took them away from it, connecting my 430 gps output to my EDM830, and some rearranging of my circuit breakers. Overall the progress was steady and uneventful. The installer commented that the illustrations in the manual for the roll servo were a little hard to match up to what they could see through the inspection covers but they eventually concluded that it could only go one way. The roll servo pushrod was missing from the kit but TruTrack sent one promptly and it didn't slow the progress. The shop originally estimated "around $2,000" for the install but I haven't gotten the final bill yet. I expect it to be a little higher but not too much. With the cost of the TruTrak ($5,000), STC ($140 including $40 EAA membership), and installation (~$2,000) the total cost should be under $7,500.
Test Flight:
Track Select Mode (TRK): Roll control was very firm and responsive and rolled out right on the selected track and held it very well.
GPS Steering Mode (GPSS): Followed a flight plan and a GPS approach from the 430w flawlessly, including 90 degree turns, and kept the CDI dead center. Turn anticipation, procedure turns, hold entries, and holds all worked perfectly.
Vertical Speed Mode (SVS): Vertical speed control was about what I expected for an autopilot without auto electric pitch trim. There seemed to be a delay between the time I put in a new VS command and the time that the AP responded and the pitch control seemed mushy. Occasionally when asking for a climb or descent, the trim indicator would initially ask for pitch trim in the opposite direction. It also didn't seem to be able to nail the VS on the VSI as well as the lateral modes did. When the AP asks for a trim adjustment it's difficult to tell if it needs a little or a lot. I expect this to get better as I learn to use the AP and learn how it responds.
Altitude Hold Mode (ALT HOLD): Worked reasonably well with minimal deviations, even in light turbulence. The up/down pitch trim indicators came on a lot in the light turbulence, which I expected since the Cardinal can take quite a bit of pitch pressure to hold the nose up/down during down/up drafts.
Vertical Approach Mode (GPSV): The vertical approach mode didn't work. I set up for an LPV approach on the 430w with the AP in GPSS Mode and ALT HOLD. I never saw GS ARM or GS CPLD on the display and the AP stayed in ALT HOLD mode as the airplane passed through the glideslope. I tried it a second time with the same results. (I didn’t try it in zero vertical speed mode but suspect the results would be the same) After reviewing the setup procedure I verified the 430w ARINC 429 configuration and everything looked right. Hopefully this will turn out to be just a configuration setting somewhere in the 430w or the Vizion.
Any suggestions on things I can check?
Missed Approach Mode: supposed to command a climb at 500 fpm on the current track when activated during an LPV approach. I was not able to test this mode since the AP would not enter approach mode.
Control Wheel Steering Mode (CWS): I tested the control wheel steering from TRK mode by holding the CWS button on the yoke and changing the heading and releasing the button. The AP locked onto the new track as expected. (I don’t anticipate using the feature very much)
Emergency Level Mode (AP LVL): I put the airplane into a nose high bank and pushed the AP LVL button. The roll servo firmly engaged and gently leveled the wings. The pitch servo engaged but the AP was much slower to bring the nose down than it was to level the wings. I repeated this with a nose low bank with the same results. Even though the pitch seemed a little sluggish, it did stabilize the airplane in straight and level flight.
Automatic Envelope Protection Mode (AEP): Over-bank protection kicked in around 40 degrees of bank and firmly nudged the yoke back below 40 degrees. I tried the Minimum Speed Protection by slowing to stall speed. I couldn't get a full stall break so the AP must have been trying to lower the nose but it didn't have the same positive feel that the bank protection did. I didn't want to fly the airplane close to VNE so I didn't try the Maximum Speed Protection.
Gyro Bank Mode (BANK): I haven’t tested the gyro bank mode yet which is basically roll mode if the AP loses GPS input.
Summary:
Overall I'm very happy with the TruTrak's lateral control (TRK & GPSS) which is primarily what I wanted. Without automatic electric pitch trim I think the VS and Altitude Hold are working about as well as they can, especially considering the high pitch force needed in the Cardinal sometimes during turbulence. Don't get me wrong, the vertical modes did OK and will probably perform better once I get more familiar with using them, they just didn't feel as firm and positive as the lateral modes.
By the end of the 2 hour flight I was getting the hang of the buttonology and after a few more flights I'm sure I'll have it down. One issue I discovered was the location of the control unit in the old ADF indicator hole right above the flap handle. Several times I inadvertently put in 10 degrees of flaps while trying to adjust the autopilot. I'll probably swap places with the intercom during my next upgrade.
The TruTrak Vizion was a good fit for my needs, expectations, budget, and mission. I'm confident the GPSV issue will be resolved eventually so I'm not too concerned about that. I'd highly recommend it to someone looking for a low budget AP with lots of features but you've got to do your homework and understand it's limitations.
