How Murphy Stroke a Test Pilot in Private and on Duty: A Case Study

LTC Markus Ruedinger, Experimental Testpilot USNTPS, German Airforce, WTD 61 Manching, Germany

Abstract

The problem really begins for a testpilot when you give Murphy the opportunity to hit you in an aircraft both in private and on duty.

This paper features case studies about a planned dive recovery flight test with an Eurofighter and a normal aerobatic training flight with a civil experimental aerobatic biplane, which got more interesting than planned and finally led to a landing outside of the cleared flight envelope. The last case study is about a refueling trial with the Tornado aircraft, during which a pod malfunction almost caused a severe accident.

During the 45° inverted dive recovery test at 40.000 ft in the Eurofighter the maximum permissible Mach
number was exceeded due to circumstances, which were not taken into consideration at all and were not known to the aircrew and key flight test personnel on the ground. First, flight test instrumentation indications on the ground were different from those in the aircraft leading to different abort criteria and therefore ambiguous terminology. Second, the test setup was made exactly into a jetstream, which hit the area exactly on that day. This led to true dive angles being much greater than those indicated on various displays.

During a normal aerobatic training flight a 5g dive recovery from a hammerhead ended up with having the entire control stick loose in the hands. The stick broke at the very bottom during the pull. The aircraft at that time was still in a 70 deg dive in 1.500 ft above ground. Finally the aircraft was recovered at 500 ft AGL with the help of the aircraft trim. The question then came up what to do next; the options were to either bail-out or to try a landing in this heavily degraded aircraft configuration. Finally the aircraft could be landed safely, however, the circumstances for the landing were very unique.

The last case study deals with a normal air-to-air refueling test, which ended up with having the entire refueling basket including 4 feet of the hose stuck on the refueling probe. The reason was a pod malfunction, which was indirectly indicated to the fuel operator on the tanker; however, this indication was nowhere documented nor the consequences described. Thereafter the appropriate documentations were amended and procedures established.