October 9, 2004 HOME

This afternoon, I pulled out the Structural (autopilot) roll and pitch servos and looked them over for the first time.  Eeek!  While the workmanship generally look good, I found this (pic below) point where the control wires are stressed against sharp bare metal.  The grommet was split.  There was no way to relieve the tension since the wires are stretched pretty tight from the plug housing to the stepper motor.  Fortunately, the problem was only with the pitch servo and today I am planning on installing the roll servo in the right wing.  It does bother me that it would be shipped in this condition because, this is an obvious future failure point in a critical flight system.

As you can see, the roll servo looks fine.  The wires are both properly protected by the grommet and not stretched as tight as well.  I can live with this. (no pun intended!)

First, I made up a cable to the DB-9 connector.  It includes black and red 20g wires.  My color code indicates that black is always ground and red is always 12v hot.  I don't actually understand why there is a constant 12v to the servo, but that is what the schematic calls for.

Here begins the installation of the roll servo in the right wing.  Remember, the wing is upside down on the bench here.  So, if you really want the right perspective, stand on your head and look at the pictures :-)     This long bracket replaces the Van's symmetrical bracket that normally holds the bottom leg of the aileron bellcrank in alignment.  The new bracket bolts to the main spar through the same holes as the original bracket.  Below that you can see an additional support bracket that is added to hold the servo from the top.



Here it is!  All installed.  OK, I did skip several steps in between, but it is all straight forward.  Just follow the drawing that comes with the TruTrak.  The only drilling you need to do is one hole 2" from the bellcrank pivot point to attach the actuator push/pull tube.




Here is a shot taken from the rear (still upside down) for a different perspective.


Rapping up the day, I ran RG-400 cable through the left wing for wingtip VOR antenna.  The cheapest RG-400 I could find came from Sky Craft Parts in Florida.  It was $.85 a foot for anything over 100'.  A bargain compared to many other sources.  I ordered 150', even though I only estimated I'd use about 60'.  By the way, this stuff is really heavy, you want to use as little as you reasonably can.




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