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COBEM 2021
26th International Congress of Mechanical Engineering
Takeoff Speeds Determination Using a Multidisciplinary Optimization Tool
Submission Author:
Carolina Barbosa Coimbra , MG
Co-Authors:
Carolina Barbosa Coimbra, Vinícius Leite de Morais Véras
Presenter: Carolina Barbosa Coimbra
doi://10.26678/ABCM.COBEM2021.COB2021-0060
Abstract
Takeoff performance determination is regulated for commercial aircraft (CFR 14/RBAC §25.105 and §25.107). The requirements for takeoff speeds determination (VR, VLOF, and V2) are defined on §25.107. The problem of takeoff speeds determination is essentially an inverse problem in the sense that typically a V2 (airspeed at 35ft with one-engine inoperative) is given and, based on a performance model, liftoff (VLOF ) and rotation (VR) speeds can be determined. As per §25.107(e)(2), a single VR must be used for both one-engine inoperative (OEI) and all engines operating (AEO) conditions. Thus, the performance model can be used assuming AEO condition to obtain VLOF and V35 (airspeed at 35ft for AEO condition). This paper presents an optimization process to determine the takeoff speed schedule of a commercial jet in compliance with CFR-14 Part-25 regulation. The goal was, assuming OEI, to determine the VR that minimizes the error between the V35 - as predicted by a dynamic simulation of a complete 6DoF aircraft model - and the target speed at 35ft screen height (V2). The optimization workflow was developed using modeFRONTIER as an integration platform, connecting the aircraft model in Simulink with scripts in MATLAB and Python. Analyses were performed for different weights, center of gravity positions, runway heights, temperatures, and V2VS ratios with the engine failure assumed at minimum ground control speed (VMCG). Maneuver margins and minimum unstick speed constraints were implemented in the workflow to assure the certifiability of the solution. Once the VR was determined in OEI condition, it was used to simulate AEO takeoff. Speed and time increments for the rotation to liftoff (RO-LO) and the liftoff to screen height (LO-SH) segments were obtained. The curves of VR, VLOF, and V2 normalized by the stall speed (VS) were also obtained as a function of the climb gradient, in a given condition, as a mean for visually determine the configurations for which the performance can be improved and what the limiting factors may be. In the context of the Covid-19 pandemic, this work was important to fully explore the performance potential of products already in the market, generating additional value for clients and potentially creating new demands. It also works as a proof-of-concept, as it is by itself a use case of modeFRONTIER in an innovative way to solve complex problems in a multidisciplinary approach, providing accurate results with reduced development time and cost.
Keywords
performance, takeoff, speed schedule, Optimization
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