DOWNWASH TESTS OF THE DUAL TANDEM DUCTED PROPELLER VTOL RESEARCH AIRCRAFT CONFIGURATIONS TO EVALUATE ENGINE INLETS, PROTECTION DEVICES AND STUDY AERODYNAMIC INTERFERENCE

摘要

A full scale half-model simulation of a dual tandem ducted propeller VTOL aircraft has been tested under the severe environment caused by operation simulating vertical flight in close proximity to sand and crushed stone covered terrain. The model was the same as used in similar previous downwash effects programs, except that various propeller positions and inlet configurations were investigated. Four engine inlet protection devices were evaluated in this series of tests. Based on previous promising results, 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, butnwere not sufficiently effective to positively prevent enginen%ndamage. Tests over crushed stone caused significantly worse inlet ingestion and airframe damage problems than those experi¬enced over sand. Aerodynamic interference tests were also conducted. Single (Isolated du and power settings. Propeller blade stress investigations werenct) as well as tandem propeller configurations were Investigated at various propeller blade settings, propeller duct heights, distances between ducts