Intelligent Black Box Verification, Validation, and Accreditation for Rotorcraft Performance Modeling

The paper addresses process and tool development in support of qualification assessments of performance models. Details are provided regarding developing enablers in the fields of data science, uncertainty quantification, and machine learning. Performance models are delivered for assessment in all different shapes, for different purposes, with different pedigrees. All or parts of these models may be proprietary. Some models are delivered without documentation and pedigree, referred to as black box models. Traditionally these gaps in information, if possible, are filled by time-consuming, resource-intensive work of subject matter experts (SMEs). New processes and tools are proposed for reducing this burden and providing direction for SME efforts. The new approach is exercised for validation of an AH-64 performance model. Efforts contrast new applications of high-powered computational tools with the long-accepted SME-driven methods to establish value and increase capabilities. Results indicate that emerging methodologies can provide valuable guidance without SME involvement.

Effectiveness of the Compound Helicopter Configuration in Rotorcraft Performance Increase

The article presents the results of calculations applied to compare flight envelopes of varying helicopter configurations. Performance of conventional helicopter with the main and tail rotors, in the case of compound helicopter, can be improved by applying wings and pusher propellers which generate an additional lift and horizontal thrust. The simplified model of a helicopter structure, consisting of a stiff fuselage and the main rotor treated as a stiff disk, is applied for evaluation of the rotorcraft performance and the required range of control system deflections. The more detailed model of deformable main rotor blades, applying the Galerkin method, is used to calculate rotor loads and blade deformations in defined flight states. The calculations of simulated flight states are performed considering data of a hypothetical medium class helicopter with the take-off mass of 6,000kg. In the case of both of the helicopter configurations, the articulated main rotor hub is taken under consideration. According to the Galerkin method, the elastic blade model allows to compute blade deformations as a combination of the blade bending and torsional eigen modes. Introduction of additional wing and pusher propellers allows to increase the range of operational speed over 300 km/h. Results of the simulation are presented as time-runs of rotor loads and blade deformations and in a form of disk distribution plots of rotor parameters. The simulation method can be useful in defining requirements for a high speed rotorcraft.

Flow Control on Helicopter-Rotor Blades Via Active Gurney Flap

The Active Gurney Flap (AGF) is a small, flat tab cyclically deployed and retracted at lower surface of the rotor blade near its trailing edge. It is expected that the device may improve performance of modern helicopters. The main goal of presented investigations was to develop research methodology and next to use it in studies on phenomena occurring in the flow around helicopter-rotor blades equipped with AGF. Conducted CFD simulations aimed at validation of the developed methodology as well as at significant supplementing and extension of results of experimental research. Simplified sensitivity analysis has been conducted aiming at determination of geometric and motion-control parameters of the AGF, optimal from point of view of helicopter-performance improvement. Fully three-dimensional simulations of the rotor flight aimed at determination of flight conditions, in which the use of Active Gurney Flaps could significantly improve the rotorcraft performance.

Effect of active Gurney flaps on overall helicopter flight envelope

ABSTRACTThis paper presents a study of the W3-Sokol main rotor equipped with Gurney flaps. The effect of the active Gurney is tested at low and high forward flight speeds to draw conclusions about the potential enhancement of the rotorcraft performance for the whole flight envelope. The effect of the flap on the trimming and handling of a full helicopter is also investigated. Fluid and structure dynamics were coupled in all cases, and the rotor was trimmed at different thrust coefficients. The Gurney proved to be efficient at medium to high advance ratios, where the power requirements of the rotor were decreased by up to 3.3%. However, the 1/rev actuation of the flap might be an issue for the trimming and handling of the helicopter. The current study builds on the idea that any active mechanism operating on a rotor could alter the dynamics and the handling of the helicopter. A closed loop actuation of the Gurney flap was put forward based on a pressure divergence criterion, and it led to further enhancement of the aerodynamic performance. Next, a generic light utility helicopter was built using 2D aerodynamics of the main aerofoil section of the W3 Sokol blade along with a robust controller, and the response of the rotorcraft to control inputs was tested. This analysis proved that the 1/Rev actuation of the Gurney did not alter the handling qualities of the helicopter, and as a result, it can be implemented as a flow control mechanism for aerodynamic enhancement and retreating blade stall alleviation.

Helicopter Mission Analysis Using a Multidisciplinary Simulation Framework

This paper describes the work done and strong interaction between the Technology Evaluator (TE), Green Rotorcraft (GRC) Integrated Technology Demonstrator (ITD) and Sustainable and Green Engine (SAGE) ITD of the Clean Sky Joint Technology Initiative (JTI). The GRC and SAGE ITDs are responsible for developing new helicopter airframe and engine technologies respectively, whilst the TE has the distinctive role of assessing the environmental impact of these technologies at single flight (mission), airport and Air Transport System levels (ATS). The assessments reported herein have been performed by using a GRC-developed multidisciplinary simulation framework called PhoeniX (Platform Hosting Operational and Environmental Investigations for Rotorcraft) that comprises various computational modules. These modules include a rotorcraft performance code (EUROPA), an engine performance and emissions simulation tool (GSP) and a noise prediction code (HELENA). PhoeniX can predict the performance of a helicopter along a prescribed 4D trajectory offering a complete helicopter mission analysis. In the context of the TE assessments reported herein, two helicopter classes are examined namely a Twin Engine Light (TEL) configuration for Emergency Medical Service (EMS) and Police missions and a Single Engine Light (SEL) configuration for Passenger/Transport missions. The different technologies assessed reflect three simulation points which are the ‘Baseline’ Year 2000 technology, ‘Reference’ Y2020 technology, without Clean Sky benefits, and finally the ‘Conceptual’, reflecting Y2020 technology with Clean Sky benefits. The results of this study illustrate the potential that incorporated technologies possess in terms of improving performance and gas emission metrics such as fuel burn, CO2, NOx as well as the noise footprint on the ground.