No "BOTH" positions allowed on RV's

[vic syracuse]

Please, please, please don't do this. I was performing a prebuy on an RV-8 today and for the second time I found a fuel valve with a BOTH position. Huge NO-NO! A both position in a low wing aircraft will fool you into thinking it works correctly, especially when both tanks are either full or above the fuel pickup. But let one of the tanks get below a fuel pickup and even if you happen to have a full tank on the other side, it will suck air. Probably at the worst time, like when turning base to final. More accidents are caused by modifications to the fuel systems than any other modification. It was a even very nice Andair valve, too. 😓

[bkervaski]

Yikes! What did the owner/builder say?

[vic syracuse]

Originally Posted by bkervaski

Yikes! What did the owner/builder say?

Wasn't built by the current owner, who is now deceased. The airplane had been completely destroyed once, then rebuilt, and ground looped twice after that, so who knows who did this mod.

Vic

[rapid_ascent]

Wow. That sounds like just the kinda plane I'd be looking for if I was in the market.

[Sam Buchanan]

In spite of the overwhelming presence of the internet, and the push to have EAA Technical Counselor visits mid-build, I am still surprised/dismayed by how many "lone wolf" builders there are that aren't seeking technical help from anyone. The fuel valve error should have been caught....by someone....

In our area we always gently suggest a social visit by local builders when we find a new project under way. Multiple sets of eyeballs can prevent heartache further down the road.

[ty1295]

I can surely see this as an easy gotcha for someone. I didn't step in this pothole myself, but could see the simple overlook not thinking.

Vic (and others) please keep these things posted, as it helps everyone for sure.

[RV6_flyer]

When I was a DAR, I once would NOT issue the Airworthiness Paperwork to an RV-6A builder/owner/applicant till the builder changed the fuel selector to one that did NOT have BOTH. I explained how one tank could be full, the other sucking air with the switch in BOTH and the engine would quit running.

The builder / applicant changed the valve while I waited / watched.

[Bevan]

it is my understanding that a L R fuel valve with no "BOTH" position still has one of you place the selector half way between the L and R. I has to be this way so that when switching tanks, the 2nd tank kicks in before the former tank is cut off. If so, be sure to place the fuel selector all the way to one position or the other and be aware of consequences for failing to do so on a low wing aircraft.

My opinions only. YMMV

Bevan

[160kt]

The Aero Commander 112 and 114 single engine low wing airplanes have fuel selectors with a both position AND a POH that recommends using the both position. I think some here are a bit extreme. Any empty tank will allow "sucking air". Doesn't matter if your fuel selector has only a Left and Right position or also includes a Both position. When the tank is dry you simply change from the empty tank. If the pilot understands his fuel system as he is supposed to then there is no surprise. He will know what happened and what is to be done to correct. It's a standard checklist item to place fuel selector on fullest tank when taking off or landing. The certified design accounts for running a tank dry and switching to a tank with fuel. What's the big fear here?

[jrs14855]

When I was finishing my last build, a non RV, the closest tech counselor was 200 miles away. I did get one inspection early on but that guy did not have anything to offer despite being a Oshkosh Grand Champion builder. One EAA chapter eliminated the Tech position out of liability concerns. They are mostly a social group, only a couple of builders.
I know some outstanding tech counselors, all are a long ways away.