625. Integral Aircraft Weighing Systems

Paper

Abstract

It is now possible to determine the gross weight and center of gravity of an airplane with integrally mounted transducers and instrumentation. This paper will discuss the general system requirements needed to make an effective and accurate measurement of weight and C.G. The necessary performance requirements for the major components in the system, such as the transducers and the computer, will be established. The errors, which must be minimized in order to provide an accurate and reliable system, will be discussed.
Having established the criteria for an effective system, the general methods of approaching this problem will be considered. The methods to be considered will include only those concepts that are presently in use or under development. This will include a brief discussion of such concepts as the measurement of oleo strut pressure, direct force measurement, and axle deflection. Of the concepts considered, the axle shear deflection system, as developed by BLH Electronics, Inc., offers the best possible solution to the fulfillment of the established criteria.
The BLH system, designated as OBAWS (On-Board Aircraft Weighing System), will be described in sufficient detail to make the reader familiar with the concepts of the system. This will include a description of the unique shear-deflection transducers which represent an important break-through in that they respond to vertical shear forces only. As a result, the system does not respond or react to side forces.
Finally, transducer installation problems are discussed followed by a description of BLH installation tooling and how it is used.