I am assembling a Hobbico Avistar 40 MKII AWARF (old one) with an OS 46FX engine. After installing the tank w/presure, fuel feed, and fill lines (3 lines from tank) and the OS 46FX engine I find that the tank is positioned well below the carb of the engine. I also find that there is very little room to run the tank lines to the engine as the engine back plate is seems very close to the tank outlet lines. I have built the plane following the instruction supplied with the plane.

I have researched this site for information where the tank should be positioned and found the following statement:

As stated previously, the tank outlet lines come out of the firewall right in line with the engine backplate. The tank neck fits into the whole in the fire wall which supports the tank along with a preshaped tank support former at the back of the tank compartment. The engine was mounted utilizing the previously drilled holes and installed blind nuts in the firewall and utilizing a supplied GreatPlanes Adjustable Motor Mount which also is used to mount the front steering wire landing gear.

My questions:

What am I to do?

Will the plane fly as designed with the tank below the engine carb?

With the OS 46FX engine installed is it normal for the space between the fire wall and the engine back plate to be close? Engine was mounted toward the end of the engine mount.

What trouble will I be getting into if I attempt to fly the plane with the tank in it's present position?

Any and all suggestions and recommendations will be greatly appreciated.

Thanks,

pull your tank back a little bit. Dint make the neck of the tank stick out thathole. Run the lines out the hole. I donth thinkthat the positioning of the lines and carb like the quote really matter. Just prime the engine and once its cranked it will suck the fuel from the tank. The plane should fly fine with the tank anywhere around that general area where it is in the manual. Check the cg with no fuel in the tank, and it shouldnt affect flight.

Tom, as long as the tank neck is sticking into the firewall in the center of the motor mount go have fun with it. The tank is in a good position for the 46 engine. Thousands of them flying, no problems. IMHO one of the best all around trainers ever produced. Lost one the other day in a mid air. I say lost, not really, just part of the right wing and all the rear right horizontal stab gone. Still flew pretty good tho. Didn't get any pics of it when it happened so I had to take it off and fly around a bit to get some. I will always keep something like this in the hanger just to go out and have a lazy day with..........

Ed M>

I had an Avistar that I flown more than 50 flights with a 40 FX and absolutely loved it. I recently sold it to a buddy as it's such a great trainer. The fuel tank issue sounds all fine, I only used two lines and ran the supply line up and back down to the nipple on the engine for ease of refueling. Using the third for servicing is probably even better. Install the tank with the neck through the hole and tank against the supports in the fuselage and everything will work fine. Have fun with it!