1446. Ground Attitude Weighing of the YAH-64


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R G Farr: 1446. Ground Attitude Weighing of the YAH-64. 1981.



Hughes Helicopters, Inc. Has developed a method for weighing the YAH-64 Advanced Attack Helicopter in the ground attitude on electronic platform scales, and by calculation, determining the longitudinal center-of-gravity in the level flight attitude. This method was selected because it is safer, easier, faster, and provides accurate results. During the Phase I development of the YAH-64, the conventional 3-point compression load cell system was employed with unimpressive results. Problems experienced in rotating and leveling the aircraft at three points raised questions regarding the supporting system stability and its lack of handling safety. In addition, the alignment of the loads on the cells without side load and other influenced became a time-consuming chore to obtain accuracy and repeatability. The primary purpose of this paper is to present the derivation of equations necessary to rotate the YAH-64 measured center-of-gravity form ground attitude to level flight. Included is a discussion on the desirability and reasons for using the ground attitude as a primary weighing method, the problems encountered and their solutions. The presentation also includes a discussion on the accuracy of the developed equations with relation to vertical center-of-gravity and aircraft geometry. A method is also presented of a simplified graphical solution for use by field personnel. This procedure can also be used to determine vertical center-of-gravity by measurement when two attitudes are used in weighing the aircraft.


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