[Louise Hose]

Either the last year of the Land of Enchantment RV Fly-In at Las Cruces or the first year at Santa Teresa (I forget which one), departure morning was marked by the somewhat humorous sight of folks gathering around about a half-dozen tail-draggers, lifting their tails as high in the air as possible, and draining water out of the planes' snouts. Heavy, blowing rains the night before had entered the cowling and somehow prevented injected engines from starting the next morning. I haven't flown an injected engne and, with Junior's injected engine now on-site, I'd like to better understand what happened that night/day, whether Junior's engine might be prone to a similar incident, and, if so, what we can do to prevent it happening (i.e., will cowling plugs stop it?). Look foreward to being educated!

 

[Ron Lee]

Convert to an A model

 

[Mike S]

Just a WAG here, but injected engines dont have a fuel drain (sniffle valve IIRC) in the FAB.

Thus, water can pool in the FAB if the wind drives the rain into the air intake.

Merry Christmas

 

[Martin Sutter]

Hi Louise,

Depending on the configuration of the air intake duct, a small hole drilled on the bottom of the duct just before it joins the throttle body will allow any water that enters the duct to drain out before it enters the engine. That works well with Van's "snorkel" as supplied for the RV7 and 8 with F.I. engines with the forward facing horizontal throttle body. This duct has an annular bulge just before it connects to the throttle body and provides a trough to catch the water if a hole is drilled in the bottom of it. However I doubt that Van's supplies a duct for the RV3 so you will most likely have to make your own and it would be simple to mold a small depression in it and copy Van's design.

The other option is the installation of a sniffle valve in the bottom of the air plenum. This check valve allows accumulated fuel or water to drain though a tube that exits the cowling in the exhaust pipe outlet area.

Merry Christmas to you and Paul and hopefully better weather in California,

Martin Sutter
building and flying RV's since 1988
EAA Technical Councelor

 

[Walt]

Assuming you have vertical injection, a strategically placed hole in the bottom of the airbox will do the trick. This is also recommended to avoid pooling fuel in the bottom of the box (in case you forget you have FI and leave the mixture in with the FP running).

 

[Tandem46]

Louise,

I have the drilled hole mentioned above by Martin/Walt, but also, I have the standard cowl inlet plugs Vans sells. Our -7 has sat out in driving rain more than once in the last few years and we've never had any issues as long as the plugs were in.

 

[AlexPeterson]

If the problems at LOE were all with injected planes, it would seem to be a coincidence. I was there that year, and had no problem. All induction systems which could potentially pool water or fuel need to have a hole drilled in the appropriate place (as do the fuselages!). I have two holes in the bottom of the FAB, one just inside the filter and one at the aft end, outside the filter. The holes need to be large enough that the surface tension of the water doesn't prevent draining, maybe something like 3/16" or so. I glued a fitting to the outside of the FAB, over the hole which is on the inside of the filter. This is where excess priming fuel goes. I attached a hose to this fitting to direct the goo out the back of the cowl. If your injection system does not have a purge valve, it will barf fuel through the injectors after you shut it down (as fuel boils and percolates). This fuel ends up pooling in the FAB if there is no drain hole inside the filter.

 

[Louise Hose]

Rv-3B-A?

Convert to an A model

An "A" model RV-3B? Now wouldn't that be special!

Thanks, guys, for the information.

 

[Ron Lee]

Alex makes a good point about the hole size. I tested that a year or so ago when deciding what size hole I needed in the fuselage aft of the cabin to drain water. The water accumulation happened in Florida and was unexpected. I don't recall the hole size (which is a function of the water pressure of course) but may have been in the vicinity of 3/16". If I remember, I will measure it later.

 

[plehrke]

The holes need to be large enough that the surface tension of the water doesn't prevent draining, maybe something like 3/16" or so. I glued a fitting to the outside of the FAB, over the hole which is on the inside of the filter. This is where excess priming fuel goes. I attached a hose to this fitting to direct the goo out the back of the cowl. If your injection system does not have a purge valve, it will barf fuel through the injectors after you shut it down (as fuel boils and percolates). This fuel ends up pooling in the FAB if there is no drain hole inside the filter.

I have two holes as well. Used 1/8" holes. The diameter of the hole is also a function of the thickness of the material.
One other place nobody has a hole is in thebottom of the rudder. One year at OSH there was a lot of rain and I noticed the botom of the rudder was full of water. Since I had no drill, I went to the fly mart and bought some cheap hose to suck out the water. Drilled the hole when I got home.

 

[Geico266]

IMHO the easiest place for water entry into the fuel system in an RV is the cap tank caps. I usually put tape over the caps if rain is coming.

 

[N941WR]

...
One other place nobody has a hole is in thebottom of the rudder...

I must be nobody, both of my rudder bottoms have had an 1/8" drain hole in them. (Same with the FAB.)

My fuselage also has a drain hole right below the bolt for the tail spring. Only this is large enough to get a socket on the tail spring bolt.