13.4 Pitot/Static Remediation

This entry is part 59 of 67 in the series 13 - Electrical / Instruments

Prior to having the airworthiness inspection done, I was planning on getting the pitot/static/transponder check done. Friend and fellow builder Bob (who’s V-twin had a first flight 2 days after mine!) suggested checking the system for leaks prior to the check.

When I checked, it leaked like a sieve.  Couldn’t hold the altitude and airspeed for less than a second.  I pulled the panel (no small feat) and tightened all the fittings and still leaked. I isolated parts of the system and still had leaks. Spent a whole day trying to fix this and had to cancel the test, reassemble everything for the inspection, and come up with a plan B (actually, Plan A since the current system is a Plan B).

This brings us to our lesson for the day.  When learning to fly, you’re told that when a loss of power occurs, that you select a suitable landing spot (within gliding range) and stick with it!  Too often, as people descend, they see another spot that looks much better.  But when they try to make that spot, they run out of altitude. Now obviously, there are exceptions. But the idea of “Make a plan and stick to it” has merit.

This also applies to building. With the pitot/static plumbing, I researched all the different choices for tubing and fittings. What I decided on was “quick connect” system sold by SteinAir. I came across these when I was looking for a alternate static valve that had a toggle switch control.  The parts weren’t the cheapest (at least I thought), but it looked like a good choice.

Then someone told me that you can get “the exact” same type of fittings from Home Depot.  Early on, I made the decision not to use non-aviation parts unless I was absolutely certain that it either didn’t impact safety or that I could determine that the part was as good or better than the traditional aviation grade part. I could not make that determination with the Home Depot grade parts so that idea was dismissed.

Then I heard “Why are you going to use those fancy, expensive parts? Cessna, Piper, Beech have been using plain old NyloSeal parts for years and they work just fine.”  Well, I didn’t have a good answer for that. So I ordered a bunch of NyloSeal fittings and tubing from Aircraft Spruce. I mean, if it’s been working for everyone else, right?

Before ordering, I drew up a diagram:

Pitot-Static Diagram

Once all the parts were in, I hooked everything up and secured the fittings and tubing where necessary.

Here’s a picture after I installed the tubing and put the panel in place.  The arrows are pointing a various tubes and fittings.

2015-07-06 IMG_20140528_084725635

Not the prettiest installation, but it’s behind the panel and with all those fittings, there’s only so much you can do.

Once I discovered that the system was leaking and I couldn’t get it to not leak, I decided to go back to my original plan.

So I made up a new diagram. In the process, I decided to eliminate the “test points” in the system. I had asked the shop that’s been doing the pitot/static checks on the Cessna about what they like to see in a pitot/static system and he told me “test points so I don’t have to tap into a line.”  But it occurred to me that a single test point adds three connections to the system.  After I redesigned the system, for the new hardware, between eliminating the test points and having a 5-port manifolds, I reduced the number of connections from 44 to 28.

Old Pitot-StaticNew Pitot-Static

I also used the “banjo” elbows for attaching to the static ports on the sides of the fuselage. These fittings are very low profile which means that the interior trim will fit closer to the fuselage. Here’s a picture of a standard elbow (left) and the “banjo” elbow (right).  Oh yeah, another huge benefit is that both elbows are full 360 degree swivel.  Which means you don’t have to worry about “clocking” the fittings to get them pointed in the right direction.

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The end result is a much neater installation that had no leaks. I also used red tubing for the pitot side and clear tubing for the static side to make it easier to identify the two different lines.

2015-07-06 IMG_20150706_081241770_HDR 2015-07-06 IMG_20150706_081249678_HDR

This is what I removed.

2015-07-07 IMG_20150707_120757151

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