variavel0=<b>Gustavo di Fiore dos Santos</b> - difiore@embraer.com.br Embraer - Empresa Brasileira de Aeronáutica S.A.
<b>João Roberto Barbosa</b> - barbosa@mec.ita.cta.br Instituto Tecnológico de Aeronáutica
<b>Abstract.</b> In-flight thrust determination is important for the aircraft manufacturer because the aircraft drag must be precisely known. It depends on the drag the determination of the load carrying capacity of the aircraft. Since for level and steady flight drag equals thrust, measuring thrust is the same as measuring drag. Methods that might be considered for in-flight thrust determination (IFTD) and uncertainty analysis for turbofan engines are presented. Four IFTD methods are presented, three of which are standard in aircraft industry and are documented in SAE AIR 1703 as F/AP, F/mRootT, the Residual Error Method. The authors propose the fourth, named Specific Thrust Method. This paper includes also full uncertainty analysis assessment as per SAE AIR 1678. It is also intended to provide appropriate background information to gain a perspective of the major aspects and processes that might be used for the determination of in-flight thrust and its uncertainty. A case study is analyzed, reflecting a flight test program that illustrates the practices and results for determination of in-flight thrust for a modern turbofan engine.
<b>Keywords.</b> IFTD, Residual Error, Performance, Uncertainty, Engine.