Gust Loads On Aircraft

This book provides an authoritative and practical presentation of the determination of gust loads on airplanes, especially continuous turbulence gust loads. The text emphasizes the basic concepts involved in gust load determination and enriches the material with discussion of important relationships, definitions of terminology and nomenclature, historical perspective, and explanations of relevant calculations. Coverage begins with discrete-gust idealization of the gust structure and moves to continuous-turbulence gust loads. Also considered are loads combination and design criteria, gust-response equations of motion, spanwise variation of vertical gust velocity, nonlinear systems, and analysis of gust-response flight-test data.

Two jet-propelled airplanes were flow at different speeds in rough air to investigate the effects of compressibility on applied gust loads at Mach numbers up to 0.68. The results indicated that no compressibility correction to the slope of the lift curve was necessary.

Aeroelastic phenomena arising from the interaction of aerodynamic, elastic and inertia forces, and the loads resulting from flight / ground manoeuvres and gust / turbulence encounters, have a significant influence upon aircraft design. The prediction of aircraft aeroelastic stability, response and loads requires application of a range of interrelated engineering disciplines. This new textbook introduces the foundations of aeroelasticity and loads for the flexible aircraft, providing an understanding of the main concepts involved and relating them to aircraft behaviour and industrial practice. This book includes the use of simplified mathematical models to demonstrate key aeroelastic and loads phenomena including flutter, divergence, control effectiveness and the response and loads resulting from flight / ground manoeuvres and gust / turbulence encounters. It provides an introduction to some up-to-date methodologies for aeroelastics and loads modelling. It lays emphasis on the strong link between aeroelasticity and loads. It also includes provision of MATLAB and SIMULINK programs for the simplified analyses. It offers an overview of typical industrial practice in meeting certification requirements.

A model of a hypothetical canard airplane, which was designed to be of the same size and general aerodynamic characteristics as a Boeing B-247 airplane, was tested in the N.A.C.A. gust tunnel at one wing loading, one forward speed, one gust velocity, and three gust gradients. The purpose of these tests was to determine the reactions of the model and to compare them with the results of unpublished tests on an equivalent model of the Boeing B-247 airplane.

A flight investigation has been conducted of an automatic gust-alleviation system designed primarily to improve riding comfort in rough air. The gusts were sensed by a vane located on a boom ahead of the airplane. The wing flags moved in response to the vane in such a way as to counteract the change in wing lift due to the gust and a portion of the elevator moved to counteract pitching moments due to flap deflection. In the final configurations, inboard portions of the wing flaps also moved in such a way as to counteract the change in angle of attack at the tail due to the gust. The result indicate alleviation of normal acceleration of up to about 60 percent at the natural frequency of the airplane (0.6 cycle per second) and about 40 percent at 2 cycles per second. A further increase in riding comfort was achieved by a simultaneous alleviation of pitching velocity. For this particular airplane, gusts having frequencies greater than 1.5 cycles per second at a speed of 130 knots had little effect on riding comfort. Brief tests were also made of a configuration intended for reducing structural loads and of a configuration utilizing an accelerometer as the gust sensor. The gust alleviation capabilities of these configurations were somewhat less than that of the optimum configuration with vane-type gust sensor.