wheel well (aircraft structural component). A part of an aircraft structure that houses the landing gear when it is retracted. Wheel wells may be part of the wing, engine nacelle, or fuselage.
“When able” (air traffic control). A phrase used in conjunction with ATC instructions that gives the pilot latitude to delay compliance until a condition or event has been reconciled. Unlike “pilot discretion,” when an instruction is prefaced with “when able,” the pilot is expected to seek the first opportunity to comply. Once a maneuver has been initiated, the pilot is expected to continue until the specifications of the instructions have been met. “When able,” should not be used when expeditious compliance is required.
whetstone. An abrasive stone used to wear away, or sharpen, the edges of cutting tools.
whiffletree. A pivoted beam used in an aircraft control system to allow more than one force to act on a common point. For example, two pulling forces may be applied to the ends of a whiffletree, and the device being pulled is connected to the point between the pulling forces.

whip antenna (radio antenna). A flexible, vertical antenna often used with high-frequency (HF) and very-high-frequency (VHF) radio equipment. The length of a whip antenna is one-quarter the wavelength of the frequency to which the antenna is resonant. A whip antenna is nondirectional; it transmits or receives its signals equally well in all directions.
Whittle, Sir Frank. The British Royal Air Force Flying Officer who in 1929 filed a patent application for a turbojet engine. Whittle’s engine first flew in a Gloster E.28 on May 15, 1941. The first jet flight in America was made on October 2, 1942, in a Bell XP-59A that was powered by two Whittle-type General Electric I-A engines.
wicking (soldering problem). A problem that occurs when solder flows up around the individual wires in a stranded electrical conductor until it reaches the insulation. When stranded wire is soldered, there should be a short piece of the bare wire between the end of the solder and the beginning of the insulation. This bare section allows the wire to flex smoothly so it will not break when it is vibrated.