A Generalized Approach to Operational, Globally Optimal Aircraft Mission Performance Evaluation, with Application to Direct Lift Control

Abstract

A unified approach to aircraft mission performance assessment is presented in this work. It provides a detailed and flexible formulation to simulate a complete commercial aviation mission. Based on optimal control theory, with consistent injection of rules and procedures typical of aeronautical operations, it relies on generalized mathematical and flight mechanics models, thereby being applicable to aircraft with very distinct configurations. It is employed for an extensive evaluation of the performance of a conventional commercial aircraft, and of an unconventional box-wing aircraft, referred to as the PrandtlPlane. The PrandtlPlane features redundant control surfaces, and it is able to employ Direct Lift Control. To demonstrate the versatility of the performance evaluation approach, the mission-level benefits of using Direct Lift Control as an unconventional control technique are assessed. The PrandtlPlane is seen to be competitive in terms of its fuel consumption per passenger per kilometer. However, this beneficial fuel performance comes at the price of slower flight. The benefits of using Direct Lift are present but marginal, both in terms of fuel consumption and flight time. Nonetheless, enabling Direct Lift Control results in a broader range of viable trajectories, such that the aircraft no longer requires cruise-climb for maximum fuel economy.

A trim problem formulation for maximum control authority using the Attainable Moment Set geometry

“…The toolbox has been used in the past for the Flight Mechanics analysis of the PrP [5,29], its mission performance evaluation [6], and the sizing of control surfaces on its box-wing geometry [18,19]. PHALANX has also been employed in the analysis of different novel aircraft configurations like the BWB [20] and the Delft University Unconventional Configuration (DUUC), featuring the propulsive empennage concept [21].…”

“…Because lift lies perpendicular to the velocity vector, by definition, an increase in lift introduces a centripetal acceleration V ̇𝛾 which is the most direct way to bend the trajectory upwards. The study of control authority in the lift axis is particularly aimed at exploiting one of the most interesting capabilities of the box-wing aircraft configuration: the innovative way of implementing direct lift control (DLC) [5,6].…”

Preliminary Analysis of the Stability and Controllability of a Box-Wing Aircraft Configuration

“…For example, pairs of elevators placed at the root of both wings and activated in counter-phase can minimise the negative lift variation associated with the pitch-up moment typical of wing-tail aircraft, thus increasing safety for manoeuvres close to the ground (e.g., in the case of missed approach). As well, the proper design, the control strategy, and the placement on the two wings of multiple movable surfaces may enable new control techniques, such as pure-pitch or direct-lift [52]. Finally, regarding aspects related to stability and controllability in low speed, that is, for aircraft with high-lift systems deployed, or those related to directional stability, limited information is found in the literature, and no studies have been focused on the influence of considering these important aspects in the overall design of a box-wing aircraft.…”

Impact of Control Allocation Methods on the Design of Control Surface Layouts for Box-Wing Aircraft under Flying Qualities Constraints

“…By using two full-size wings connected at the tips to create a closed shape, the box-wing concept can achieve the lowest possible induced drag for a given span and weight [11][12][13]. This translates to significant performance benefits in the short-to-medium flight range, where climb and descent phases constitute a larger fraction of the total mission profile, and the box-wing low-speed performance benefits can be exploited more proficiently [14,15].…”