Tiltrotor Aircraft Conceptual/Preliminary Design And Optimization

As one of the most promising configurations of high speed rotorcraft,conceptual design of tiltrotor is different from helicopter and fixed-wing airplane,and more complicated than these conventional configurations.Conceptual and preliminary design that is the earliest and the most important procedure in aircraft design is supposed to be vigorously performed.A method of tiltrotor sizing is developed based on the weight model and flight performance analysis model.Firstly,an empty weight model for a tiltrotor configuration is developed.On the basis of components classification of weight,tiltrotor vehicle is divided into different groups.Weight of each group is estimated from a parametric equation.Particularly,the tiltrotor wing weight is calculated by the wing size that is predicted based on wing stiffness check.Then,the flight performance analysis model is established based on two rotor aerodynamic models of different level.The first level is modified momentum theory,the second is blade element momentum theory(BEMT)in large angle with Prantdl tip modification.Performance of vertical flight in helicopter mode and forward flight performance in airplane mode are taken account of consideration.Finally,on the ground of the weight model and the flight performance analysis model,a method of parameter sizing and selection for tiltrotor vehicle is presented.The initial parameters of tiltrotor aircraft are sized according to the specified design conditions and missions,then these parameters are adjusted using ratio fuel method to satisfy all design requirements.Some optimization work is also included to obtain the best preliminary parameters sizing proposal.