Insight into the factors affecting the safety of take-off and landing of the ship-borne helicopter

Despite the important role and highly frequent appearance of the helicopter in modern ship operations, the flight mission with take-off and landing of helicopters to ships, especially ships with small-sized decks, could be very challenging and potentially hazardous. Many researches on ship-helicopter dynamic interface (DI) have been conducted, and significant progress has been made. In this paper, a comprehensive and systematical review of the factors affecting the flying qualities of ship-borne helicopter and pilot workload during taking off and landing is derived from these efforts to date. The factors from two aspects, including the ship environment and the pilot-helicopter interface, are covered to address how these factors affect the helicopter handling qualities and pilot workload, primarily focusing on aerodynamic issues. The insight into these factors is not only of great significance for conducting take-off and landing tasks safely but also helpful to establish suitable fidelity criteria and guidelines for the modelling and simulation of the ship-helicopter DI environment.

Three-Surface Model with Redundant Longitudinal Control: Modeling, Trim Optimization and Control in a Preliminary Design Perspective

Notwithstanding the interest in the three-surface concept shown by aircraft designers, this configuration was not thoroughly investigated in conjunction with the adoption of two-elevator surfaces, on both canard and tail. In fact, the inclusion of an additional elevator produces a redundant longitudinal control which can be specifically exploited to target trim optimization. The same redundancy can be also employed to improve the flying qualities of the three-surface aircraft. In this paper, after introducing a simple flight mechanics model, ideal for preliminary design and analyses, the advantages of this configuration are explored. Firstly, the problem of finding the elevator deflections of canard and tail for minimum drag in trim is formulated and solved. Secondarily, the updating of a two-surface back-tailed airplane into an equivalent three-surface one is demonstrated, showing the potential improvement in cruise performance. Finally, the controls are employed through a smart control law for achieving better flying qualities.

Control law design to improve the unexpected pitch motion in slow down turn maneuver

The highly maneuverable fighter aircraft is exposed to unexpected pitch motion such as over-Nz (normal acceleration) and Nz-drop characteristics in transonic and supersonic flight conditions with moderate angle of attack. These characteristics not only degrade flying qualities by destabilizing the aircraft but also threaten flight safety by increasing the structural load. This article proposes an additional augmentation control in the incremental nonlinear dynamic inversion structure, which feeds back the error of pitch angular acceleration to mitigate unexpected pitch motion in slow down turn maneuver. We evaluate the stability, flying qualities, and robustness of the proposed control system by performing the frequency-domain linear analysis and the time-domain numerical simulations based on the mathematical model of advanced trainer aircraft. As a result of the evaluation, the additional augmentation control further improves flying qualities and deceleration performance of the aircraft by decreasing over-Nz and Nz-drop characteristics in high-Nz maneuvering in the transonic flight condition as well as ensuring the stability and robustness of the control system against the major uncertainty factors of the aircraft system compared to the existing transonic pitching moment compensation (TPMC) control in which the predefined scheduling for Nz feedback is used.

GROUND BASED VARIABLE STABILITY FLIGHT SIMULATOR

This paper discusses the development of a ground based variable stability flight simulator. The simulator is designed to meet the pilot training requirements on flying qualities. Such a requirement arose from a premier Flight-Testing School of the Indian Air Force. The simulator also provides a platform for researchers and aerospace students to understand aircraft dynamics, conduct studies on aircraft configuration design, flight mechanics, guidance & control and to evaluate autonomous navigation algorithms. The aircraft model is built using open source data. The simulator is strengthened with optimization techniques to configure variable aircraft stability and control characteristics to fly and evaluate the various aspects of flying qualities. The methodology is evaluated through a series of engineer and pilot-in-the-loop simulations for varying aircraft stability conditions. The tasks chosen are the proven CAT A HUD tracking tasks. The simulator is also reconfigurable to host an augmented fighter aircraft that can be evaluated by the test pilot team for the functional integrity as a fly-through model.

Preliminary parameters design for a long endurance unmanned helicopter with low rotor-disc loading

This paper investigates the design of a long-endurance unmanned helicopter (LEUH) with low rotor disc loading (LRDL) and low rotor speed (LRS). Due to the flaws in flying qualities caused by the LRDL and the LRS, this paper establishes a flying quality evaluation model in which handling qualities (FQs) and flight control (FC) are introduced into the distributed multi-objective collaborative optimization (DMOCO) of the helicopters. The comprehensive design optimization on preliminary parameters of the LEUH in wind shear is also carried out. Numerical simulation results show that the LRDL and the LRS technologies are successfully applied to LEUH, with the FQs and the flight performance considered. Compared with A160 LEUH, the payload load ratio is significantly improved.