What It Looks Like

Stinger missiles they are not. Those sleek wingtip appendages on some airplanes are less threatening but more practical auxiliary fuel tanks. Most high-performance airplanes go fast partly because of their larger-displacement engines. Creating more power takes more fuel. But since more fuel requires more tank capacity and adds weight, most manufacturers compromise in terms of fuel capacity. The result is limited range and endurance - not a happy compromise for pilots who like to fly far as well as fast.

The solution: Install auxiliary fuel tanks, such as the 15-gallon-capacity wing-tip tanks pictured here on a single- engine Piper Comanche. Typically, tip tanks hold from 15 to 20 gallons of fuel each, adding at least two hours of endurance. An added benefit of many tip tank modifications is that they result in an increase in the allowable maximum gross weight of the airplane so that the weight of the extra fuel doesn't detract from payload.

Tip tanks can be relatively simple or fairly complex to use in flight. They are restricted to use in level cruise flight and are not for takeoff, landing, or maneuvering. If the fuel in a tip tank is pulled from the tank by the engine-driven fuel pump, as is the case with the Comanche, you simply switch the fuel selector from a main tank to a tip tank and monitor fuel consumption using the fuel quantity gauge and the clock. (If you know the fuel consumption habits of the airplane, you can accurately estimate fuel used based on how long the tank has been providing fuel to the engine.)

If the tank has its own electric pump to send fuel to the engine-driven pump, more fuel may be extracted from the tip tank than the engine needs. In that case, the excess fuel may or may not be returned to the main wing tanks. Managing fuel with this type of design is more complex because the tip tanks drain quickly, and one or both of the main tanks has fuel added to it. Fuel management is an exercise in strict clock watching and notetaking to keep track of which tank has been used for how long, and therefore how much fuel remains. If it's the kind of design that requires you to pump fuel from the tips to another tank, you can overfill the tank, and excess fuel is vented overboard to prevent excessive pressure in the tank.

As you move into high-performance airplanes, you may well find yourself using one that is equipped with tip tanks. Make it a point to read the flight manual supplement explaining their operation, then go out and enjoy those long trips.