Flight performance and propulsion; the introduction of a new master track

Aerospace Engineerin

Helicopter

Aerodynamics, Wind Energy & PropulsionAerospace Engineerin

Cruise Range in Formation Flight

Flight Performance and Propulsio

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

This paper presents a generic trim problem formulation, in the form of a constrained optimization problem, which employs forces and moments due to the aircraft control surfaces as decision variables. The geometry of the Attainable Moment Set (AMS), i.e. the set of all control forces and moments attainable by the control surfaces, is used to define linear equality and inequality constraints for the control forces decision variables. Trim control forces and moments are mapped to control surface deflections at every solver iteration through a linear programming formulation of the direct Control Allocation algorithm. The methodology is applied to an innovative box-wing aircraft configuration with redundant control surfaces, which can partially decouple lift and pitch control, and allow direct lift control. Novel trim applications are presented to maximize control authority about the lift and pitch axes, and a “balanced” control authority. The latter can be intended as equivalent to the classic concept of minimum control effort. Control authority is defined on the basis of control forces and moments, and interpreted geometrically as a distance within the AMS. Results show that the method is able to capitalize on the angle of attack or the throttle setting to obtain the control surfaces deflections which maximize control authority in the assigned direction. More conventional trim applications for minimum total drag and for assigned angle of elevation are also explored.Flight Performance and Propulsio

Exploration of Hybrid Electric Propulsion in Regional Aircraft

Flight Performance and Propulsio

A Control Allocation approach to induce the center of pressure position and shape the aircraft transient response

This paper presents a Control Allocation formulation aimed at altering the dynamic transient response of an aircraft by exclusive means of the aerodynamic effectiveness of its control effectors. This is done, for a given Flight Control System architecture and, optionally, closed-loop performance, by exploiting the concept of Control Center of Pressure, i.e. the center of pressure due to only aerodynamic control forces. Two formulations are proposed, and their advantages and disadvantages presented. The first is based on the straightforward augmentation of the control effectiveness matrix, the second on a weighting matrix to prioritize control effectors. The latter is implemented in three application studies on a box-wing aircraft configuration with redundant control surfaces: a simple pull-up maneuver, a trajectory tracking task, and an altitude holding task in turbulent atmosphere. Results show that the proposed formulation can significantly impact performance metrics that are closely related to the aircraft transient response. In the best case scenario, the aircraft is able to completely cancel the non-minimum phase behavior typical of pitch dynamics, hence achieving a sharp initial response to longitudinal commands. If compared to a standard Control Allocation algorithm, the proposed formulation results in improved tracking precision, better disturbance rejection, and a measurably improved feeling of comfort on board.Flight Performance and Propulsio

Evaluation of Landing Characteristics Achieved by Simulations and Flight Tests on a Small-scaled Model Related to Magnetically Levitated Advanced Take-off and Landing Operations

The goal of this paper is to simulate and measure on a small-scaled model the landing characteristics related to take-off and landing (TOL) operations supported by a magnetic levitation (MAGLEV) system as ground-based power supply. The technical feasibility and the potential benefits of using ground-based power to assist TOLs is also presented, including the design of the ground-based system, and the envisioned operational concept. The details of the developed control system are given, as well as the (i) simulation and (ii) flight test results.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin

Optimal energy management for hybrid-electric aircraft

Purpose: In recent years, increased awareness on global warming effects led to a renewed interest in all kinds of green technologies. Among them, some attention has been devoted to hybrid-electric aircraft – aircraft where the propulsion system contains power systems driven by electricity and power systems driven by hydrocarbon-based fuel. Examples of these systems include electric motors and gas turbines, respectively. Despite the fact that several research groups have tried to design such aircraft, in a way, it can actually save fuel with respect to conventional designs, the results hardly approach the required fuel savings to justify a new design. One possible path to improve these designs is to optimize the onboard energy management, in other words, when to use fuel and when to use stored electricity during a mission. The purpose of this paper is to address the topic of energy management applied to hybrid-electric aircraft, including its relevance for the conceptual design of aircraft and present a practical example of optimal energy management. Design/methodology/approach: To address this problem the dynamic programming (DP) method for optimal control problems was used and, together with an aircraft performance model, an optimal energy management was obtained for a given aircraft flying a given trajectory. Findings: The results show how the energy onboard a hybrid fuel-battery aircraft can be optimally managed during the mission. The optimal results were compared with non-optimal result, and small differences were found. A large sensitivity of the results to the battery charging efficiency was also found. Originality/value: The novelty of this work comes from the application of DP for energy management to a variable weight system which includes energy recovery via a propeller.Flight Performance and Propulsio

Take-off and Landing Using Ground Based Power - Landing Simulations Using Multibody Dynamics

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.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin

Controllability of blended wing body aircraft

Aerospace Engineerin