INVESTIGATION OF SPECIAL GROUND EFFECT MACHINE CONFIGURATIONS
HILLER AIRCRAFT CORP PALO ALTO CA
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The evaluation was continued of 2 unique GEM configurations diffuser-recirculation and diffuser-plenum. The prime emphasis was to investigate and document the performance and stability characteristics of the 2 concepts, and to determine means of achieving the required positive stability characteristics. The investigation was accomplished with 2-dimensional model tests and supporting mathematical studies. The stability was demonstrated with 3-dimensional, free-flight model tests. Static 3-dimensional model tests documented the performance of an inherently stable configuration of the original concept. The 3-dimensional model static test data of the diffuser-plenum GEM indicates that a performance of 3.26 air horsepower per square foot of gap area can be attained at a planform loading of 20 psf. The off-design hover performance is also presented. Data is presented which describes the characteristics of the diffuser edge seal and exit gap as components of the GEM. This data describes the hover performance, the pitch and heave stability characteristics, the lifting efficiency, the diffuser pressure rise and a continuity parameter, which is the ratio of diffuser exit flow to the flow supplied to the diffuser.
- Fluid Mechanics