Fuel Capacity Question

Van's site lists the fuel capacity of the RV6A as 38 gallons. However, my fuel caps (which I believe to be standard Van's issue) list the capacity as 18 gallons. I'm no rocket scientist, but 18 + 18 does not equal 38. What gives?

Did you build your plane or buy it? I could be wrong, but I don't believe Vans sells fuel caps that are engraved with anything. My guess is that the previous owner (of the caps or the plane) had the caps engraved with the 18 gallon capacity.

Guy Prevost said:

Did you build your plane or buy it? I could be wrong, but I don't believe Vans sells fuel caps that are engraved with anything. My guess is that the previous owner (of the caps or the plane) had the caps engraved with the 18 gallon capacity.

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Check out my signature. I bought it flying. That would certainly explain things.

This could also be in reference to the "Usable" fuel in each tank.

One gallon (or more)of un-usable per tank is normal in most a/c.

Mike

Fuel capacity

Craig,
The "6" has a capacity of 19 gals. per tank. I have a plain old 6 and if I play with refueling, I can squeeze in 19.2 or 19.3.(pump meter ??) I always watch while their being filled if I can't do it myself and I always fill to the bottom gas cap neck. Shaking the wing slightly to get the air out. BUT, I base all my flying time on 18 gals per tank and always try to refuel at 5 gals (min.) per tank. I find that by doing this, the fuel lasts longer than my blatter.
Enjoy your RV, there just isn't anything better out there.
Rich

Thanks Rich,
Reason for asking is that I just had a JP fuel flow gauge installed, and wanted to know what to set the full level at. I'm pretty conservative, and have set the "low fuel warning" to come on at 10 gallons.

Suggestion for Craig

CraigH@KRPH said:

Thanks Rich,
Reason for asking is that I just had a JP fuel flow gauge installed, and wanted to know what to set the full level at. I'm pretty conservative, and have set the "low fuel warning" to come on at 10 gallons.

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Craig,
Congrats on buying a great airplane.
It would be a very good idea for you to determine what the usable fuel is in each tank of "your" airplane.
Run a tank till it quits (directly over a familiar airport with a good amount of altitude). This gives you the chance to see how long it takes to get a restart after switching to the other tank. Land and fill the empty tank, this will tell you what the usable in that tank on "your" airplane is. Repeat on the other tank to verify that one also.
Every RV is built by a different person and some of them do not have the same specs as all the rest (fuel pick up positions relative to tank bottoms, etc.)

BTW this is something that every builder should do during there flight test period, though very few do.

Determine Usable Fuel Qty....

I have a neighbor that talks of deliberately shutting down the engine of a single engine airplane in flight. I could look again, maybe at an update, but don't believe that procedure is called for in the FAA AC on experimental airplane flight testing. Enough said.

One probably safer way to determine usable fuel, in flight if you must, is by using the boost pump. When it cavitates, it makes a lot of racket, but there is still time to switch to the other tank, while keeping the engine lit. Then land, fill the empty tank, and you've just determined usable fuel plus whatever might be in lines, carb bowl. Fuel temp matters, but 59F+- should be close enough.

Alternatively, you could more safely do this on the ground by getting the airplane in a given pitch attitude, remove the fuel line where it attaches to the eng driven fuel pump, and run the tank out/dry using the boost pump into a fuel container. Refill tank and get the usable fuel qty, verify gauges etc...

Back to in flight engine restarts. Should get turns you need to fire mags/plugs from windmilling, but not a good time to have a weak battery, starting system, or degraded fuel system, eg boost pump, etc..

Link McGarity
RV6/N42GF/FD38
Wellington, FL

I have run both tanks out of fuel in flight. I didn't do this on purpose, but was just trying to get the fuel low so it would be easy to drain. Each time I did have a full tank on the other side.
When the fuel is gone the engine starts coughing and sputtering. I just switched tanks and turned on the aux fuel pump. After about 3 seconds the engine starts puring again.
I was at 5000 feet and over a number of airports when I did this testing.

It suprised me, but the quickness of restoring normal engine operation only allowed my heart to skip a couple of beats.

Kent

To learn about engine out flight operations I ran my tanks (one at a time on separate flights dry. I also did tests just putting the fuel selector to off. I found in my RV4 that it was very hard to get he prop stopped (had to fly almost to stall, with throttle closed). I found the restart to be trivial. I've used the starter on a stopped prop and switched to a full tank on a windmilling prop. Since my background is gliding, it is sort of nice flying with the prop stopped but I'd need a heck of a thermal to see lift!

Changes in glide performance are interesting with a CS prop. Stopped, fine, coarse are all different.

Check this link for details on running tanks dry:
http://www.avweb.com/news/columns/182044-1.html

Non-event

My experience is the same as Kent's. I ran the tank dry as part of the test period to determine the time the engine would run on a tank, usable fuel, and to recalabrate the GRT capacitive probes (first calibration is at empty of usable fuel point). Restart was a non-event. I was at 12500 and within easy gliding distance of three paved airports.