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AIR6007 - IN-FLIGHT THRUST DETERMINATION FOR AIRCRAFT WITH THRUST VECTORING

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Document Number: AIR6007
Project Initiation: 09-23-2008
Project Number:
Revision Number:
Sponsor Name: Raymond F. Ball
Title
IN-FLIGHT THRUST DETERMINATION FOR AIRCRAFT WITH THRUST VECTORING
Scope
Thrust vectoring presents new in-flight thrust determination challenges that are only briefly touched on in previous AIR reports. Two of the new engine testing challenges are the requirement for multiaxis thrust measurement and the collection of exhaust gases when engine altitude test facilities (ATF) are required. Engines for commercial applications are usually only concerned with calibrating thrust in the axial (thrust/drag) axis. Most aircraft that utilize thrust vectoring, especially for control/maneuverability, must calibrate engine thrust not only in the thrust/drag axis but also in the vertical (normal/lift axis plus pitching moment) or lateral components (side axis plus yawing moment) for single axis thrust vector systems depending on the vectoring direction; for multiaxis thrust vector systems, the thrust/drag axis as well as longitudinal and lateral thrust components must be calibrated. In addition, if thrust is to be used for an aircraft control function, the accuracy requirement for each component will be strictly imposed. In an ATF, collection of exhaust gas from a nozzle that may be moving relative to the facility exhaust collector will be an issue. A variable geometry collector may be required and if manual relocation of the collector is required, a significant penalty in test time and cost will be incurred. Another major challenge for military thrust vectoring engine systems will be the definition of an appropriate control volume. The control volume for nonvectoring commercial applications is generally drawn around the nacelle and part of the pylon thus assuming that thrust effects on the rest of the airplane are minimal. For thrust vectoring military installations, the engine and nozzle are usually tightly integrated with the airframe and throttle dependent thrust effects (known as jet interference effects) are known to spread over much of the configuration and have significant effects on lift and drag. These challenges (and others) must be addressed for successful determination of in-flight thrust of thrust vectoring engine installations. The purpose of this document is to provide guidance on in-flight thrust determination of engines that are impacted by intentional or unintentional thrust vectoring. For simplicity and coherence of purpose, this document will be limited in scope to multi-axis thrust vectoring nozzles or vanes attached to the rear of the engine; single-axis thrust vectoring and unintentional thrust vectoring (fixed shelf or deck configuration) are special cases of this discussion.
Rationale
Nozzle thrust vectoring has become a major contributor to military aircraft performance and control. This SAE Aerospace Information Report is intended to provide guidance on the impacts of thrust vectoring on in-flight thrust determination.
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