Air Filter Up-Front

ExtraKatana · #1 04-22-2016, 10:11 AM

As a prospective secondary buyer(non-builder), I am looking at an injected engine with horizontal induction and a cowl that does not have a snorkel. The air filter is in front of Cylinder #2 and I have concerns about flying in the rain. The model does have alternate air where air would be pulled from inside the cowl, however I am thinking the filter would still be soaked after going through the rain and funneled into the engine.
What studies, recommendations, common knowledge is in place that says the air filter (and subsequently the engine) will not be swamped with water?

With a previous model (I owned) that did have a snorkel, rain was eliminated completely from the air filter when the snorkel was closed off by means of activating the alternate air.

rvbuilder2002 · #2 04-22-2016, 10:47 AM

If you use the Van's Aircraft terminology/description and the common definition, what you are describing is a snorkel installation (snorkel defined as a device that sources air from above...)

15+ years of service history has shown flight through rain to not be a problem. Flight through heavy rain can abuse the filter a bit because of impact velocity (folds the filter pleats aft slightly) but it doesn't seem to cause any operational problem with the engine.

Carl Froehlich · #3 04-22-2016, 10:57 AM

Air coming in via a filter in front of #2 cylinder sure sounds line a standard Van's type snorkel set up - but perhaps I don't understand.

Many RVs are flying with vertical intake, air box connected to the bottom and air coming in via a forward facing engine air inlet on the bottom cowl. To your point, Van's snorkel is designed to fit a horizontal engine intake with a filter mounted in front of #2 cylinder, but even so many builders choose to install a forward facing intake instead of using the snorkel.

So - bottom line. If you have an alternate air intake that sucks on the internal cowl area and is after the air filter, you will have not problem.

For me rain is not my worry on the filter. Getting snow and ice accumulation however is a concern.

Carl
Two RVs and 1000 hours and never had to use alternate engine air - but I have it!

ExtraKatana · #4 04-22-2016, 11:10 AM

Thank you for the terminology clarification. It does appear that in my previous model I had a forward facing Inlet. I have a snorkel now.

Caveman · #5 04-22-2016, 11:58 AM

Data point: 8 yrs and 500 hours with the snorkel as used in the standard IO-360 M1b installation and nary a problem and I've flown in moderate rain.

That being said, there was a post several years ago, (not sure if it was on VAF or Matronics) in which some RV'ers flew to the Bahamas and there was a torrential down-pour while the airplanes were on the ground. Some of their intakes took on some water and the recommendation was to drill a small hole at the low point of the snorkel to let any such accumulation drain. I drilled a 1/16th hole in mind if I remember correctly.

ExtraKatana · #6 04-22-2016, 03:33 PM

Thanks everyone for the replies. Looks as though there should be no worries. I do also have the 1/"16 hole in the bottom of the "snorkel" to drain any accumulating water.

roadrunner20 · #7 04-22-2016, 05:03 PM

I've been flying almost 10 years with forward induction & have never had an issue in moderate rain. The bypass was a SB due to someone flying through snow & the filter became clogged. The bypass was born.

RV7A Flyer · #8 04-22-2016, 08:43 PM

Quote:

Originally Posted by ExtraKatana

Thanks everyone for the replies. Looks as though there should be no worries. I do also have the 1/"16 hole in the bottom of the "snorkel" to drain any accumulating water.

Never had an issue with water, but I'm curious...has anyone done any tests to see what the minimum diameter hole is to drain X amount of water from a snorkel? I'm thinking of surface tension, etc., causing the water to not actually drain from a hole < Y" in diameter...

Just thinking out loud...