Steve ,I'm busting to know what a cutoff loop is,!
John Carrodus
John,
I remember Al Rabe describing a cut off loop where he does a tight loop at the end of the pattern to stop the flow of fuel to the engine. You can see him do it in his Snaggletooth flight video. Did he invent an internal tank configuration for that to happen?
I've never seen a diagram of how the tank is set up. Is it a function of how much fuel is left? I try it when I'm headed for an overrun with my uniflow tanks with no results except for the aforementioned overun. Nor do I see it happen during the three loops some flyers execute at the end of the pattern to unwind their lines prior to landing.
Ara
It takes nothing special inside the tank, a traditional T21 style tank will easily cut off as described. In fact, the problem with the T21 is that it does is far too easily, meaning you have to run excess fuel just to keep it from quitting the 4-leaf. The mechanism is simple, an inside loop when the tank is nearly empty moves the fuel forward and to the bottom of the tank, and uncovers the fuel pickup. It usually takes an *inside* loop, because the inside loop also yaws the nose out, making it even more prone to sloshing forward. If you are short on fuel, the same effect will happen in the first loop of the clover. If you get through the first loop without it quitting you can almost always count on it continuing to run through the rest of the maneuver, because outside turns yaw the nose in, and caused the fuel to stay closer to the back of the tank.
You do not need to do two loops unless you are in trouble, and doing a tight loop is not usually as good as a large one (because it takes less time and might be able to pick up again after its over).
My normal flight, I finish the pattern, fly around level until I hear the first hint of a bubble getting ingested, the fly a high overhead loop and it will go about 1/2 lap dead lean and then quit. The advantage to the high overhead loop is that it allows you to dive out of the loop in the direction you want to land on the right side of the circle.
If I just flying around level waiting for it to run out, it will go lean for about 20 feet and quit with nearly no warning, and at any relationship to the wind (since I have a lot of taper in the tank), it I might not have enough speed to get it around to the proper touchdown point.
Watch expert at some contest, those troglodytes such as myself who still fly IC almost always do something to cut it off at a desirable point in the circle.
Brett
p.s. I really liked Al Rabe, but, he certainly DID NOT invent it, it predated him by a lot, I have people tell me it was being done in the early 50s
Topic: Fuel Tanks (Read 1700 times)
