Abstract: System for determining the airspeed of helicopters, having a coupled measuring device to which is supplied by the cyclic and collective control signals, the attitude angles and the rotational velocities about the axes of the helicopter. The measuring device contains two models, namely a first model of the input behaviour of the helicopter motion, on which the cyclic and collective control signals act as input, and a second model of the system behaviour of the helicopter, on which the condition parameters act as input parameters. The estimated state parameters are obtained in an integration stage by integration of the algebraic sum of the outputs of the two models and the output signal of the correction arrangement, from which the values of the the velocity components are supplied to an indication. The integration stage is connected in front of a correction arrangement for the measured parameters of the rotational velocity and the attitude angle.

Abstract: A process for compacting a porous ceramic structural member having a compated shape and an optional size by encapsulation with material of the same type and capable of sintering and subsequently subjected to hot-isostatic pressing; immersing the preformed body in a suspension of a material of the same type in a solvent but which contains no sintering aid and forming a first encapsulating layer; evaporating the solvent; immersing the thus obtained body in a second suspension of a material in a solvent of the same type capable of sintering and which contains one or more sintering aids, and forming a second encapsulating layer; evaporating the solvent; subjecting the thus obtained body at an elevated temperature in an atmosphere of a protective gas for a sufficient period of time to sinter the same; isostatically compacting the body provided with a tight-sintered surface; and mechanically removing the encapsulating layers.