Von Ohain, Dr. Hans Pabst.  The designer and developer of the first turbojet engine to power an airplane. His HeS3b engine was built in Germany by the Heinkel Company and it flew in a Heinkel He178 airplane on August 27, 1939. 

Vortex.  A whirling mass of air that sucks everything near it toward its center. 

Vortex dissipater.  A high-velocity stream of compressor bleed air blown from a nozzle into an area where vortices are likely to form. Vortex dissipaters destroy the vortices that would otherwise suck debris from the ground into engines mounted in pods that are low to the ground. 

Wake. The high-velocity stream of turbulent air behind an operating aircraft engine. 

Wankel engine. See rotating combustion (RC) engine. 

Waste gate. A controllable butterfly valve in the exhaust pipe of a reciprocating engine equipped with an exhaust-driven turbocharger. When the waste gate is open, exhaust gases leave the engine through the exhaust pipe, and when it is closed, they leave through the turbine. 

Watt.  The basic unit of power in the metric system. One watt is the amount of power needed to do one joule (0.7376 foot- pound of work) in one second. One watt is 1 ⁄ 746 horsepower. 

Wet-sump engine.  An engine that carries its lubricating oil supply in a reservoir that is part of the engine itself. 

Wet-sump lubrication system.  A lubrication system in which the oil supply is carried within the engine itself. Return oil drains into the oil reservoir by gravity. 

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. 

Windmilling propeller.  A propeller that is rotated by air flowing over the blades rather than powered by the engine. work. The product of a force times the distance the force is moved. 

Worm gear.  A helical gear mounted on a shaft. The worm meshes with a spur gear whose teeth are cut at an angle to its face. A worm gear is an irreversible mechanism. The rotation of the shaft, on which the worm gear locks the spur gear so its shaft cannot be rotated. 

Wrist pin.  The hardened steel pin that attaches a piston to the small end of a connecting rod. 

Yaw.  Rotation of an aircraft about its vertical axis. 

Zero-lash valve lifter.  A hydraulic valve lifter that maintains zero clearance in the valve actuating mechanism. 

