<title>Prediction of the Angular Vibration for Airborne Electro-Optical Systems</title>

Abstract

The design of airborne electro-optical systems requires the knowledge of angular vibration as well as the conventional linear vibration of aircraft structures. Rather than predicting the angular vibration subject to aerodynamic and acoustic excitations, an attempt is made here to relate the angular vibration directly to the linear vibration response. With the Bernoulli-Euler beam used as a theoretical model, a relationship has been derived between the linear and angular vibration power spectral density functions. From this relationship together with the angular vibration energy already predicted by Lee and Whaley (AFFDL-TR-76-55, Wright-Patterson AFB, Ohio, 1976), we can now predict the angular power spectral density at an arbitrary aircraft location. Tested on the typical flight test data of RF-4C and F-15 fighters, CH-3E helicopter, and B-52 bomber, the predicted angular power spectral density lies within ±10 db of the measurement over the whole frequency range. Though crude, such a prediction is useful in the preliminary design stage, whereby one can quickly and simply obtain a first-order estimate of angular vibration from the prescribed linear vibration environment.