Rotorway Forums

Fuel level sender

• The photo below is what we found when we tilted a clients helicopter back during our pre-flight inspection. You can see the puddle of fuel on the ground that leaked out of the gasket where the fuel level sensor attaches to the fuel tank. The build instructions have the builder use 5 screws placed into the soft plastic tank and often they can loose their grip and not hold the sender in place.
  
• If the fuel level sender is not leaking then it was installed correctly and should not be a problem. If the sender does leak then I am offering a fix that I have used several times to insure a good seal and return us to flight within a relatively short period of time.
  

 
The fuel sender attache point can sometimes leak fuel when we do autos and quick stops due to the fuel sender screws not holding the sender securely to the top of the fuel tank. They could strip out and leak when we progress in the training to the point of performing flares during autos and quick stops.
If the fuel sender gasket begins to leak we will need nut plates and machine screws to solidly attach the sender unit to the tank. Shown below are aluminum riv-nuts installed, we used fuel resistant gasket seal and another cork gasket and then machine screws with fuel resistant sealant on the threads to attach the sender. 

Installing the nut plates on the inside of the fuel tank requires drilling holes for the rivets and catching all of the drilled debris to keep it out of the tank. The other caution is to not drop the nut plates into the tank when positioning them in place on the underside of the tank top. I have done this several times with success but it is a bit nerve wracking. Caution, if the fuel tank has fuel or fuel vapors remaining it is best to remove that fuel tank and do the work on the work bench where there is less likely of igniting any fuel residue left in the tank. 
The photo below shows where the fuel sender is attached to the fuel tank.

Here the riv-nuts are ready for installing into the tank, They mush out on the inside of the tank preventing them from rotating (sometimes) or pulling through and the threads allowing the sender attachment screws enough bite to allow you to pull the plastic lip snugly up against the sender base to make a complete seal. I have had better results with nut plates installed on the underside of the tank lip with rivets.
If this area is not leaking, it is not a problem.

Some cork gasket seal applied between the riv-nuts to take up the gap


 

Fuel resistant sealant was used to seal the new cork gasket to the tank. Be sure to put some fuel resistant sealant under the head of each screw so that fuel does not wick up to the top of the sender and leak.