Pitot Tube

Since IFR is definitely in the plans, a heated pitot tube was in order.  I conveniently  received one of the Warren Gretz mounts for Christmas, and it was now time to install it.  The kit comes in either chrome plated or unpainted, but I felt the chrome option would look better and be much easier to deal with.  They are about $100, and you can get it from GretzAero or ACS.  Picture below shows the kit as received.  The nutplates don't come attached, but I was anxious and installed them before the pic.

 

The instructions are just marginal.  I spent a little time websurfing to determine where the optimal rib location would be.  I decided on one bay outboard the outer inspection panel.  It should remain clear of any airflow disturbances, and I should be able to access the back of it through the inspection panel if need be.  I was also a little disappointed in the fit and finish.  Neither of the backing plate or washer plate fit over the tube as delivered.  I had to file the openings a little bit with a half round file to get them to fit. 

First step in fitting the mount is to fabricate a small piece of angle to mount to the rib.  I used a left over piece of stiffener angle, and it seems to work well.  You will want to make sure the angle is long enough to accept the four support holes in the backing plate.  I cut mine a little short, so I had to adjust the holes to fit.  Once the angle is made, you clamp everything in place to the spar.  You will want to locate and drill the holes on the main spar first.  Prior to drilling any holes, be sure to use a scrap piece of .032 to lay on top of the area to ensure it does not bulge or protrude.

Once the plate is located, cleco the skin in place over the plate.  You can then back drill through the plate and bottom skin from the top side.  Prior to removing the skin, I had to trace the outline of the tube opening.

With the skin removed, you can cut out the opening.  It was quite a process to cut the hole:

  1. Unibit two holes to remove a majority of the area

  2. Use a dremel with a cut-off wheel to remove the rough chunks

  3. Use the sanding drum in the dremel to enlarge the opening very close to the right size

  4. Use a half-round and a round file to finish the hole

Once the hole was finished, I clecoed everything back together for a trial fit.  All looks good!