AFS AOA Water Drain

[flickroll]

I'm installing the AFS AOA system in my -8. The directions say to drill a hole in the lower wing skin to allow you to use a wire 'push' rod to drain the upper fitting of any water that might have collected. Everything I have read on VAF about this device is that is just does not seem to collect water, so I'm considering not drilling the lower hole. For the few times I'll park it outside overnight (OSH, etc) I'd just put a piece of tape over the hole to keep it free of water. Comments?

Thanks

[roee]

I too have heard that water doesn't tend to infiltrate because the pressure port hole on top of the wing is so small (#60). However, the potential for water to get in there still exists, so the prudent approach is to have a means to drain it.

The way AFS has you do it seems pretty elegant to me. The hole needed on the underside of the wing in order to reach the drain valve is also pretty small (#40). Too small to cause any appreciable drag, and no one will ever see it on the bottom of your wing. Why are you averse to drilling it?

I drilled mine. Come on, peer pressure

[TrueAirSpeed]

with hesitation.

RV-7 slider
IO-390
EMag/PMag

[flickroll]

Originally Posted by roee

Why are you averse to drilling it?

The only reason is that if it's not needed why drill it. The number of times my airplane will be exposed to water is very minimal. I may try it without and if it's a problem drill it later.

Have you ever drained water out of yours?

[Caveman]

Originally Posted by flickroll

Have you ever drained water out of yours?

No... but it never rains in N.W. Oklahoma. Seriously, I have flown in light rain 3 or 4 times and never had to drain it. Your mileage may vary! I'd still drill the hole just for piece of mind. If it did collect water on a long cross country, I wouldn't want to be hunting up an electric drill with the correct bit. Just my questionable 2 cents.

[664781]

I drilled mine and drain it after I wash the plane. Just a good practice if you use the AOA for all approcches.

[roee]

Originally Posted by flickroll

Have you ever drained water out of yours?

No, but it's not flying yet.

Draining it will be a standard item on my preflight checklist. And if over the lifetime of the airplane I never find a drop of water in it, that's great. It's just the difference between hoping there's no water in it and knowing there's no water in it.

Either way though, I don't see it as a very big deal. On the one hand, even if your AoA port becomes blocked (due to water intrusion or anything else), it's not a critical flight instrument as long as you don't become overly reliant on it, i.e. as long as you cross-check AoA against airspeed. On the other hand, drilling a small hole in the bottom of your wing and draining the AoA port on preflight is also cheap insurance against water intrusion.

[kentb]

Originally Posted by flickroll

or the few times I'll park it outside overnight (OSH, etc) I'd just put a piece of tape over the hole to keep it free of water. Comments?

Thanks

Will you put a red flag on your piece of tape?

Kent

[jarvis]

Take a peek at FLYVANSdotCOM for a clever approach to this drain hole. Look under "QB Wings/AOA Ports.

[roee]

Originally Posted by jarvis

Take a peek at FLYVANSdotCOM for a clever approach to this drain hole. Look under "QB Wings/AOA Ports.

I'd like to respectfully offer a critique of this builder's mod.

The builder states that the main objective for his modification was to keep the drained water out of the wing. Consider that at best you may get a drop of water out of that drain once in a blue moon, and consider that greater quantities of water will get into the wing regularly through other gaps and openings. The wings, like all other structures on the airplane, are not designed to keep water out. They are designed to allow water to drain out when (not if) it does get in. In light of this, I'd consider that the extra effort/complexity/weight of this modification solves a non-problem.

The builder also states that his modification helps find the drain valve with the pin. That may be, but finding it is not difficult. The photos on this builder's site look like he drilled the drain pin hole at the same chord as the lower pressure port (although I could be wrong, it's hard to tell for sure from the photo). If that's the case, that would be a contributing factor to the difficulty he noted. The hole for the drain pin should be positioned chord-wise about 3/16" further aft than the lower pressure port to align it properly with the upper pressure port. This is because the top and bottom skins of the wing are not parallel to each other as they taper in toward the leading edge.