Innovative Method for the Estimation of Closure Velocity between RAT Driven Drogue and IFR Probe Air to Air refueling Flight Trials

Air-to-air refueling for a fighter platform is a force multiplier in terms of increasing its combat radius and payload carrying ability. Adapting for such a facility especially for an aircraft under design and development is a challenging task. It requires rigorous ground and flight testing to meet the certification standards. One of important flight test parameter that needs to be validated for structural impact load calculations and certification needs is the closure velocity. The air-to-air refueller was equipped with a Ram-air-turbine powered drogue and chute system. An innovative methodology of estimating the closure velocity between the drogue of the mother aircraft and the in-flight refueling probe of the receiving aircraft was evolved. The method was employed and validated during the air-to-air refueling trials of a prototype fighter platform. The intention of this paper is to explain the methodology employed and deliberate the results obtained with respect to the air-to-air refueling certification.