DOWNWASH TESTS OF THE DUAL TANDEM DUCTED PROPELLER VTOL RESEARCH AIRCRAFT CONFIGURATIONS TO EVALUATE ENGINE INLETS, PROTECTION DEVICES AND STUDY AERODYNAMIC INTERFERENCE
KELLETT AIRCRAFT CORP WILLOW GROVE PA
Pagination or Media Count:
A full scale half-model simulation of a dual tandem ducted propeller VTOL aircraft was tested under the severe environment caused by operation simulating vertical flight in close proximity to sand and crushed stone covered terrain. Four engine inlet protection devices were evaluated in this series of tests. A wing-like deflector device was tested in two configurations of different chord lengths. A full inlet screen and a blocked half-screen inlet protection device were also tested. It was found that due to its location in the upflow region, the full screen tended to collect particles and thereby aggravated inlet ingestion. The blocked half-screen and the deflector devices significantly reduced ingestion, but were not sufficiently effective to positively prevent engine damage. Tests over crushed stone caused significantly worse inlet ingestion and airframe damage problems than those experienced over sand.