Evaluation of B-52 structural response to random turbulence with stability augmentation systems.

A theoretical evaluation of the structural performance of benefits to be expected after installing a state-of-the-art stability augmentation system (SAS) on the B-52 is presented. The new system is expected to provide additional stability in the airplane rigid body motions and the low-frequency structural vibration modes. The mathematical model used in this study included rigid body motions, a large number of normal vibration modes, control surface rotations, and the SAS transfer functions. The dynamic response of the airplane to random atmospheric turbulence was determined using harmonic analysis techniques with provisions made to include the effects of nonlinearities due to SAS saturation. Quantitative estimates of the changes in airplane structural response indicate that fatigue-damage accumulation rates and peak-load amplitudes, due to atmospheric turbulence, can be significantly reduced without degrading the flutter margin.