Jacob Ijff

Abstract: In this work, an efficient aircraft landing simulation strategy is proposed to develop an efficient and reliable hard-landing monitoring procedure. Landing stage is the most dangerous moment during operation cycle of aircraft and it may cause structural damage when hard-landing occurs. Therefore, the occurrence of hard-landing should be reported accurately to guarantee the structural integrity of aircraft. In order to accurately determine whether hard-landing occurs or not from given landing conditions, full nonlinear structural dynamic simulation can be performed, but this approach is highly timeconsuming. Thus, a more efficient approach for aircraft landing simulation which uses a hierarchical aircraft landing model and an extended inertia relief technique is proposed. The proposed aircraft landing model is composed of a multi-body dynamics model equipped with landing gear and tire models to extract the impact force and inertia force at touch-down and a linear dynamic structural model with an extended inertia relief method to analyze the structural response subject to the prescribed rigid body motion and the forces extracted from the multi-body dynamics model. The numerical examples show the efficiency and practical advantages of the proposed landing model as an essential component of aircraft hard-landing monitoring procedure.

Abstract: A novel take-off and landing system using ground-based power is proposed in the EU-FP7 project GABRIEL. The main feature of this system is the complete removal of the landing gear from civil aircraft. The proposed system has the potential to reduce aircraft weight, emissions, and noise. A feasibility study of the structural design of the connection mechanism between aircraft and ground system has been performed by simulating the landing procedure on a moving ground system. One of the key challenges is the landing on a moving ground system under high crosswind conditions. The main focus in the current research is the calculation of the critical dynamic loads on both aircraft and ground system for a wide range of landing conditions (sink rate, velocity differences between aircraft and ground system, etc.). For comparison, conventional landing procedures with a traditional landing (TL) gear have also been simulated. The aerodynamics of the aircraft is represented by an accurate empirical model. The r...

Abstract: The paper describes the facilities and test procedures used in a series of wind-tunnel and full-scale flight investigations of the effectiveness of flight spoilers currently existing on wide-bodied transport jet aircraft when used as trailing vortex hazard alleviation devices. Examples of the results of such studies include the variation of trailing wing rolling-moment coefficient with downstream distance behind a B-747 airplane model with various segments of its flight spoilers deflected 45 deg, and comparisons with models without spoilers deflected. It is concluded that the existing flight spoilers on the B-747 are effective as trailing vortex attenuators.

Abstract: A novel take-off and landing system using ground based power is proposed in the EUFP7 project GABRIEL. The proposed system has the potential benefit to reduce aircraft weight, emissions and noise. A preliminary investigation of the feasibility of the structural design of the connection mechanism between aircraft and ground system has been performed by simulating the landing procedure on a moving ground system. One of the key challenges is the landing on a moving ground system under high crosswind conditions. The main focus in the current research is the calculation of the impact loads on both aircraft and ground system for a wide range of landing conditions (sink rate, velocity differences between aircraft and ground system, etc.). For comparison, conventional landing procedures with a traditional landing gear have also been simulated. Two different aerodynamic models (empirical and vortex lattice method) have been used and compared in the simulations for verification and validation purposes. The results of this research study are a set of load cases and operational constraints that can be used for the structural design of the ground system and modifications to the aircraft. Detailed values are presented in the paper.

Abstract: 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.