18 August 2013

Wings: Pitot-static. AOA pitot mount.

The PBK-12 Gretz Aero bracket I'm using for Dynon heated AOA pitot requires you to fabricate a piece of angle to hold the mounting plate to the rib.  Below is an image from the instructions showing that angle.


To make this, we cannibalized a discarded rib I had from a previous mistake.  We pounded the pushed out rim around the lightening hole and cut part of the upper flange off.  Then we sized it to the left 9th rib on the inboard side.  Here are images showing the cut rib fit back together on the left and with the fabricated bracket (from the flange) on the right.


The mount requires a joggle to slip under the flange yet still be flush to the rib so the wing skin mates to the mount.  Below is an image from the instructions illustrating this.


The part comes pre-joggled, but it isn't quite deep enough to get under the flange properly.  Initially we tried to deepen the joggle with a hand seamer with unsuccessful results.  Turns out EAA has a great video instructing how to make your own joggle.  And, in a fantastic coincidence, the fuel sender hole covers from the RV-9A capacitive kit I bought (to steal parts from) is the same thickness of my main spar flange!  So I made a joggle jig with that part.  The large holes on the left are to ensure the dimples in the pitot mount don't get squashed.

 
 

Once joggled, it was lined up on the rib and match drilled.  You'll notice that the mounting plate doesn't butt up to the rib.  This was done intentionally because I wanted the mount to use 4 holes in the main spar flange.  If this wasn't done, it would only use three.

 

And finally, match drilled into the bottom skin.  The mount hole was also traced out for later cutting of the bottom skin.


Read the entries in my AOA series:

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