3436. Instant CG

Paper

Abstract

This paper describes in detail a method to measure the CG of any aircraft at any pitch angle, without having to adjust the aircraft to flight level conditions. This method reduces the time required for weighing, eliminates human error, and eliminates possibility of aircraft damage due to jacking accidents and possibility of injury to weighing personnel. This method is applicable to all aircraft types and configurations. A system of linear equations is solved to compute the CG of the aircraft. The known variables in the system of equations are the pitch angle, oleo extensions and the wheel reactions. The unknowns in the system are the Weight, Arm lengths and CG. The first equation of the system consists of the Moment of all forces computed about the Reference Datum. The remaining equations consist of the functions defining the relation between Arm lengths with respect to the Reference Datum for each wheel and the Oleo extensions of the respective wheels. The pitch angle is measured accurately within one-tenths of a degree, the oleo extensions are measured accurately within one-hundredths of an inch and the wheel reactions within one pound. For each aircraft configuration, we use a GEC custom complex algorithm to compute the arm lengths from the measured oleo extensions. Once the aircraft is rolled onto the GEC platform scales, the reactions are wirelessly transmitted to the GEC handheld equipment through RF. The pitch angle and the oleo extensions are measured and manually entered into the GEC handheld. With these input variables the CG, %MAC and Total Weight of the aircraft are instantaneously computed by the GEC handheld equipment. A test aircraft was weighed both level and off-level to test the algorithm. The computed CG was within 0.1 inches and the %MAC was within 0.1%.