Glasair Header Tank Flop Tube Installation Tips

The following illustrations show how to install a flop tube into the header tank. Note that it is mounted on the side to facilitate inverted, straight up and straight down flight conditions. Note that it will work for knife edge maneuvers only on the side which the flop tube hangs down.

Flop tube through header tank wall


It is vitally important that you check for clearance with no possibility of the flop tube jamming into a comer or catching on any fuel gauge components. As you are checking the range of motion, keep in mind that 6 g’s can pull the flop tube down fairly hard.

The flop tube is available from Aircraft Spruce Company and is their P/N 05-20500. The tube is available in various lengths. The builder should order a tube that is 3/4 the width of the builder’s header tank.

Flop tube attach plate
Flop tube attach plate

Mounting instructions

Weld the AN867-6 welding flange over the center 1-1/4″ diameter hole of the attach plate.

Locate the inverted fuel pickup assembly on either side of the header tank at the “half” tank position. (Ours are located on the left side.)

Bond the attach plate to the tank with a resin/cabosil mill fiber mixture. Radius the mixture around the edges of the attach plate and install a three layer bi-directional laminate as shown in the illustration.

NOTE: Line the inside of the header tank at all points the flop tube contacts with a three layer laminate.

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