A study of air-to-air refuelling flight test techniques

This thesis presents the results of an investigation of air-to-air refuelling test and evaluation techniques. Currently there exists a compatibility problem due to the existence of two methods, probe/drogue and boom/receptacle refuelling. Air-to-air refuelling by different aircraft types has also lead to design compromises which has caused compatibility problems. The scope of the compatibility problems were first fully appreciated during the Gulf War in 1991. To understand how this situation developed, the history of air-to-air refuelling is presented. Design requirements are also discussed regarding the conversion of transport aircraft into tankers. Hazards due to possible incompatibilities between the tanker and receiver are identified. These hazards are analyzed so that the flight test engineer can prepare an safe and efficient test program. To illustrate the test build-up process, a typical ground and flight test program is presented with emphasis on tanker and receiver compatibility. The envelope compatibility between a tanker and receiver is discussed. Eight possible refuelling envelope combinations are explored for jet powered and propeller powered tankers. Tanker wake and proximity compatibility is discussed including the techniques for the receiver clearance analysis, hose stability, and pressure field effects assessments. Receiver handling qualities test techniques are analyzed for calm air day light conditions. Receiver workload intensifiers are also explored including realistic tanker and receiver configurations, failure states, pilot fatigue, poor weather and turbulence, night refuelling, and combat conditions. Finally, fuel system compatibility is discussed. Flight test results are presented based on the experience of the Canadian Forces CC-130 H(T) tactical tanker with the CF-18 and CF-5 receiver aircraft. Other results are presented based on a literature search.