Tip Jet

Tip jet refers to the jet nozzles located at the tip of some helicopter rotor blades. The objective is to spin the rotor, much like a Catherine wheel firework.

Some tipjets rely solely on compressed air, provided by a separate engine, to create jet thrust. Others use an afterburner type system to burn fuel in the compressed air at the tip (tip-burners) to enhance the thrust. Some are ramjets or even a complete turbojet engine. Some are rocket tip jets that run off stored propellant such as hydrogen peroxide.

Tipjets replace the normal shaft drive and have the advantage of placing no torque on the airframe, so no tail rotor is required.

During the Second World War a German, Friedrich von Doblhoff, suggested powering a helicopter with ram jets. The first jettip powered helicopter was the WNF 342 V1 in 1943. After the war two WNF 342 prototypes ended up with the Americans and Doblhoff joined McDonnell Douglas who subsequently produced the McDonnell XV-1. The engineer who had actually produced the tip jet engines, August Stephan, joined the Fairey Aviation company of the United Kingdom which used them in their Fairey Jet Gyrodyne and Fairey Rotodyne aircraft first flying in 1954 and 1957 respectively.

Eugene Michael Gluhareff was an early pioneer of tipjets.

In engine-out scenarios the presence of tipjets on the rotor increases the moment of inertia, hence permitting it to store energy, which makes doing a successful autorotation landing somewhat easier. However, the tipjet also very typically generates significant extra air drag, which demands a higher sink rate and means that a very sudden transition to the landing flare must occur for survival, with little room for error.