Residual Error for In-Flight Thrust Determination

Forces acting on the installed propulsion system are difficult to be defined and even more difficult to be evaluated. The fundamental problem of any in-flight thrust computation is that the methodology employed is always indirect, that is measurements are made of indicators of thrust.

This paper discusses the necessity of in-flight thrust determination (IFTD) and methods of thrust calculation as well as the reasons for the choice of a method.

The residual error (RERR) method is a variant of the gas-path/nozzle method, which does not require an ATF test, and can be used for turbofan engines to extrapolate sea level static (SLS) data to higher pressure ratios found during flights.

The RERR method is described and applied to data expansion and thrust calculation of turbofan engine.