GSU 25 install

The GSU 25 was installed on the F-768-R outboard subpanel. Just like the GEA 24, the spot I picked for it wasn't going to work because of clearance issues. In this case, the subanel has a slight angle to it at the bottom few inches. It may have worked, but I decided to move it upwards into the 'flat' part so I would have a nice even planed surface to work with.

The GSU 25 is an accelerometer and pneumatic to electrical converter that takes the airplanes acceleration and pitot/static pressures and converts those into electrical signals. Those signals are passed with other signals, like the GMU 22 magnetometer for the compass heading, into the digital display that is then processed and displayed on a screen.

Anyway, it's important that the GSU 25 is mounted securely and "level" with the plane's axes so that you get good information on your screen. My fear was that if I left it in the original position, because of the slight angle on the bottom half of the sensor unit I could get erroneous readings... not good for a pilot.

So I used Google sketchup to model the GSU 25. I should have been doing this a long time ago because it is a good layout tool. Basically I made a template with sketchup, using the Garmin installation manual's dimensions for the GSU. Then I overlaid where the mounting holes are, and printed it 1:1 on paper so I would have a nice dimensioned piece.

Once it was positioned on the right edge, I made sure that it was square.

Finally, I taped down my paper template and used a centerpunch to punch the centerpoints of each mouting hole to the F-768-L subpanel. 

Because this is an accelerometer, it was important to make sure the mounting area was stiff enough, so I wouldn't resonate the GSU sensor and get bad readings. Some J-hat channel riveted to the back seemed to stiffen the area up nicely.

Once the parts were prepped I tried my luck with a new Harbor Freight HVLP sprayer. My first go round at it was not great, but OK for primer I guess. I'm a little heavy handed and have a tendency to spray too much. My hangar neighbor Doug is a real life airplane builder and he gave me some tips on gun setup and use. Basically, do light coats, start with the edges, and don't hold the trigger at full blast the entire time :)

No photos of that, but got the subpanel primed all one color now. 

Need to order some 10-32 nutplates to mount the GSU, but I'm getting pretty close to finishing this out.