Further work on pitot mast spacer an pitot tube.

On further examination the aluminium pitot mast spacer made recently was too wide by about 1mm, at 19mm. This was filed down to 18mm, more closely matching the pitot tube itself. This results in a better fit in the hole, a more uniform cross-section (when tightened onto the spacer) for the pitot mast, enabling it to be smoothly withdrawn from the wing without interference with the skin.

The 3/16" tubing of the pitot tubing was found to easily bind in the snug 3/16" holes formed in the mast spacer, caused by any residual bends in the tube. I increased the hole size to 15/64". I then realised that the loose fit of the pitot tubing in the mast spacer could - in the presence of vibration - cause cumulative abrasion of the tubing. The 3/16" aluminum of the tubing is evidently softer than the 6060 of the mast spacer.

So I increased the hole size to 1/4" allowing heatshrink tubing to be placed on the tubing to combat the problem of abrasion, while allowing enough clearance for the tubing+heatshrink to be inserted without binding.

Of course if I replace this pitot with a heated type in the future, its tubing will need to be covered with a thermally resistant tubing, rather than this heatshrink.

I cut the 3/16" tubing to 9.5 inches and flared with a 37 degree tool, after sliding on the AN3 hardware. I expanded the outer edge of the flare to 8mm diameter, using oil and cutting fluid as a lubricant as advised. I will torque and seal later.

I intend to bend the tubing in such away as to allow removal of the entire pitot + mast assembly from the outside of the skin without further bending of the tubing. I will probably construct an additional aluminium support for the tubing structure around the connection points, attached to the front spar at one of the stiffener locations. The purpose of the support will be to remove any possible side loads caused by the plastic tubing, as well as to suppress vibration and other motion of the tubing in the vicinity of the mast spacer.

Note the pitot is a Dynon unheated type with AOA