| January 31, 2007: We're installing the Advanced Flight Systems (AFS) Angle
of Attack system in the outboard leading edge of the left wing. People who own them swear by them, & I've
seen it in action… they rock! It provides information
about the wing's angle of attack. This is basically the
difference in the angle between the wing's chord and the relative
wind. The reason this is important is because this angle
determines if the wing flies or stalls. Keep the angle of attack
below the wings critical angle, and the wing flies. Let the angle
of attack go above the critical angle, and it stalls. Pretty
simple concept! You can get the kit in its entirety, or you can
opt for the 'A' and 'B' kits separately. Since we're considering
the AFS EFIS system (which displays the angle of attack info) for our
cockpit, we may not need the 'B' kit, so that's why we're going this
route.
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So
here are the components that come in the 'A' kit. Basically an
owners manual, directions, a bag with the pressure port components that
get mounted in the wing, a bag with the components needed to tie into
the pitot/static system of the airplane, a flap position microswitch,
and tubing to tie the various components back to the processing unit
(that comes later...)
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So
lets get started! First step is to mark the locations of the
ports. The locations are available on Advanced Flight Systems'
website. There are two ports, one on the top skin, and one on the
bottom. The locations for each are slightly different.
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Once
the locations were marked, I held the ports in place and, with a drill
bit inserted through the mounting holes, gave a quick pull on the drill
trigger to mark the mounting hole locations. After that, I
finished the holes off, and then temporarily mounted the ports to check
it all out. Well... the way these ports work is by measuring the
pressures on the upper and lower surfaces and feeding that info to the
processing unit. The way the ports measure pressure is through
tiny holes drilled in the skin surface. This means the upper skin
has a hole in it that is suseptible to water entry. To make this
a non-issue the port has a drain that should be activated prior to
every flight. In order to not get water in the tube that goes to
the processing unit, the tube attaches to a barb on the side of the
port instead of the bottom. The instructions mention to route the
tube from the port upwards for a few inches as a further measure to
avoid water contamination in the system. So, since the location
of the port on the wing's top skin puts it at an angle, I decided to
mount it so the tube barb mount pointed towards the rear. At this
location on the wing, facing the rear would put the barb at the highest
possible point... I followed directions good ;-) What I did not
do, obviously... was think! As you can see in the pic, this put
the tube barb mount pointing straight at the stiffener on the upper
skin. I could probably get the tube on there, but with a kink...
that'll never work! I could simply turn it around I guess, but
that would put the tube barb at the lowest possible point, and I don't
want to do that. Bummer...
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So, I decided to bite the bullet and drill two more holes
turning the port 90 degrees. The original two holes I'll leave
as-is. During final assembly of the port it will cover the two
holes and since it is also sealed with proseal, the holes will be
sealed as well. Whatever is left of the holes cosmetically on the
exterior will just be handled when it comes time to paint.
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Here's a shot with both ports temporarily installed.
Remember, the wing is on its nose… the upper port (with its
drain) on the left, the lower on the right.
We performed all of the above steps during Section 17, and more specifically, during its pre-assembly prior to tearing it down for deburring and priming. |
February 27, 2007: While dimpling the leading edge skins I drilled the AoA
port holes. These are some rediculously small holes,
and the drill bit, yeah that tiny thing in my hand, is provided in the
AoA kit. This small hole is enough for the system to get an
accurate pressure reading, but small enough to keep bugs out! It
wouldn't surprise me if this hole gets filled in when I prime the skins, but I'll
just run the drill back through it to make sure it's clear.
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March 17, 2007: After the installing the landing lights in the leading edges (before they're attached to the wing spar) I scuffed
the paint around the Angle of Attack ports in preparation for
mounting. I smeared a bit of E6000 on the mating surface to make
an air tight seal and then attached the ports with the supplied
screws. As you can see, there is plenty of room separating the
ports from the landing light assembly (this is a commonly asked
question, including myself when I was considering the two systems)
On a side note... I still haven't
decided how I want to handle the access issue to the upper port drain.
The simplest solution is to drill a hole in the bottom wing skin
so the supplied rod may be inserted to reach the drain. I'll
probably go this route, but I'm not willing to commit just yet.
Another common method is to relocate the drain so that it is
flush with the lower wing skin. This would require some
fabricating, and I'm not sure if I want to go this route. I'm
also entertaining the idea of having an access panel in the fiberglass
wingtip that I can use to reach in. I won't know if that'll work
until I get the wing together though.
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