H-43B MODIFIED EMPENNAGE EVALUATION

Results are presented of a limited comparative evaluation of rotor blade-to-tail clearance and stability and control of the original production H- 43B and one of modified empennage with the vertical stabilizers lowered 14 inches and equipped with 10 inch frangible fiberglas tips. The modified empennage was developed to correct rotor blade-to-tail interference which resulted in anAIRCRAFT GROUNDING AND SUSPENSION OF TESTING. The modified empennage configuration on the H-43B provided increased blade to vertical tail clearance and made the possibility of interference very remote. Flying qualities of this helicopter with the modified empennage were acceptable for service use with the directional stability augmentation system (DSAS) operative at the optimum setting utilized during this test program. Without the DSAS functioning properly, the H-43B with the modified empennage should not be flown except for flight test or pilot familiarization with an instructor pilot aboard. Vibration levels during high speed flight and longitudinal stability (static and dynamic) were improved with the modified empennage configuration, however, several undesirable stability and control characteristics still existed. Despite the stability and control deficiencies, the performance capabilities of the H-43B represent a significant improvement in USAF helicopter rescue capabilities at high altitudes.