An approach to estimate aircraft touchdown attitudes and control inputs

More strict aircraft emission criteria are proposed by the European Union and the United States. Moreover, the rapid development of the global aviation transportation market also asks for more fuel-efficient aircraft. An innovative assisted takeoff and landing technology is proposed in the EU FP-7 project GABRIEL with the aim to improve fuel-efficiency of commercial aircraft. The technology is based on the removal of the conventional landing gears and the introduction of a ground based landing system. This result in a significant reduction of the structural weight and thereby aircraft performance and fuel efficiency are improved. Furthermore, both airport noise and congestion can be decreased as the aircraft can reach a higher take-off speed without the need for longer runways. The ground based system has a yaw degree of freedom and therefore, the conventional de-crab maneuver for crosswind landings can be avoided. As a consequence, the possible touchdown attitudes and control inputs will be different from those seen in conventional landing. The flight attitudes and control inputs of aircraft during touchdown can significantly influence the landing impacts. Generally, these parameters are obtained from flight test or empirical data and they are crucial for landing gear design. However, the use of empirical data is not possible for new innovative designs such as the GABRIEL system. This paper proposes a solution to estimate all possible aircraft touchdown attitudes and control inputs based on flight dynamics simulations and Monte Carlo evaluation. Turbulence is accounted for based on the von Karman turbulence model. The GABRIEL system is used as a test case and 100 sets of stochastic turbulence are implemented. The resulting flight attitudes and control inputs are presented for different control strategies and compared to the results of landing simulations with a conventional landing gear.