PROCEDURES USED TO ENSURE STRENGTH, ENDURANCE AND DAMAGE TOLERANCE OF MIL HELICOPTER FUSELAGES (Mi-26, Mi-28, etc.)

1. With a few exceptions, fuselages are made up of thin-walled components because of their considerable dimensions and low loads applied to them in operation. Since fuselages are of very irregular structure, separate components being the weak elements are of great concern in providing the required stability. The important factor of weight saving is design modification during the experimental stage. Based on this approach, the weight of the Mi-26 helicopter fuselage has been reduced by 14%. 2. The possibility to obtain fatigue evaluations very fast eliminates many obstacles on the way to weight saving. The method of spiral loading used at out plant makes it possible to get quite a full and comprehensive insight into the load carrying capacity in a matter of 10-20 days and to offer weight-saving solutions. This method is based on features inherent in helicopters, i.e. the weight of the airframe is relatively small (12-13% of the gross weight), and the weights of other components are concentrated in small volumes. Rather a small quantity of computer-controlled force-exciters (76 for the Mi-26 helicopter) allows to simulate all the required combinations of limit loads quite accurately. Successively applying load combinations at each loading level and gradually increasing them, complete information on the loading level for all analytical cases and load carrying capacity at the level no lower than the one when the first failure occurred can be obtained.