Design and Transonic Wind Tunnel Testing of a Cruise Efficient STOL Military Transport

Lockheed Martin (LM) has teamed with the Air Force Research Laboratory (AFRL) and NASA Langley Research Center to design and validate the efficient transonic cruise performance of a “speed agile” enabled STOL (short take-off and landing) military transport. Speed agility refers to the capability of efficient flight at both low speeds (~70 knots) and at transonic cruise speeds (Mach 0.80). One of the primary challenges associated with this type of aircraft is the efficient, system level integration of the enabling technologies which permit efficient flight at both low and high speeds. This challenge was addressed using computational fluid dynamics (CFD) to design an efficient transonic cruise transport which incorporates the LM and AFRL developed hybrid powered lift system (HPLS) for efficient STOL performance. This paper focuses on the aircraft transonic aerodynamic design using advanced CFD methods, performance validation with NASA National Transonic Facility (NTF) wind tunnel testing of a semi-span powered model at flight Reynolds numbers, and validation of CFD based design tool predictions. Unfortunately test results from this effort were inconclusive as deficiencies in the initial NTF air routing system, which permitted powered testing, caused significant scatter in the test data. These deficiencies have been addressed by NASA with system enhancements incorporated post-test. Ongoing testing and evaluation of these enhancements may lead to a future re-test of the SACD powered model.