K-MAX ROTOR BLADE FLIGHT LOADS SURVEY FOR OUT OF ENVELOPE FLIGHT TEST

摘要

Some of the existing K-MAX K-1200 helicopter flight limits used in the Rotorcraft Flight Manual are not physical limits. They were developed and driven by adapting the unlimited dynamic component service life concept for external lift commercial operators. This conservative approach is based on the operational cost of flying at lower power and airspeed, thereby preserving component life. This approach has restricted the existing K-MAX performance capability and the potential for other applications. In the spring of 2007 an instrumented K-MAX test aircraft was used to conduct an out of envelope flight test program with the intent to fly beyond the existing Federal Aviation Administration (FAA) certified flight envelope. The purpose of the flight test was to expand the existing K-MAX flight envelope, to investigate blade loads, and to explore the trade off between blade service life and enhanced flight capability. This paper describes some interesting observations that were obtained from this flight test: i) The K-MAX has achieved the maximum rate of climb of 3,252 ft/min at zero airspeed with the aircraft gross weight of 7,100 lbs; ii) During an aggressive symmetric pull-up and push-over maneuver, a maximum load factor of +3.0g had been achieved at 87 kts forward airspeed and 6,915 lbs gross weight condition; iii) A minimum load factor of -1.58g had been obtained during the push-over phase of the flight, highly unusual for a teetering rotor system.