Aircraft parameter identification techniques have become accepted as indisp
ensable tools in the evaluation of prototype- and derivative aircraft in fl
ight. Applications include estimation of stability- and control derivatives
in the linearized equations of motion, synthesis of nonlinear aerodynamic
and propulsion models in the context of performance certification and incor
poration of information from dynamic flight test manoeuvres in a priori non
linear flight simulation models. A variety of techniques in the time- as we
ll as the frequency domain have been applied in the past. One of the succes
sful techniques is the so-called two-step method (TSM) in which the origina
l state-parameter estimation problem is decomposed into a nonlinear state/p
arameter estimation or reconstruction problem and a subsequent linear param
eter identification problem. In the literature, the first step of the TSM i
s often referred to as 'flight path reconstruction'. The present paper focu
ses on the first step of the TSM. After a derivation of the system models d
escribing the flight path relative to a flat earth as well as a spherical a
nd rotating earth, and observation models for air data and GPS, the flight
path reconstruction problem is introduced. Requirements with respect to typ
e and quality of flight test transducers are discussed. Next follows an ove
rview of different approaches to the solution of the flight path reconstruc
tion problem with emphasis on Kalman filter/smoother and Maximum Likelihood
methods. A new adaptive algorithm is presented, the Modified Recursive Max
imum Likelihood Adaptive Filter (MRML) which is shown to be significantly m
ore robust with respect to initialisation errors than earlier methods. A re
constructibility analysis is presented for different transducer combination
s. Numerical examples are presented based on simulated as well as actual fl
ight test data. Flight results are given of the flight path reconstruction
part of an on-line pseudo real-time application of the TSM. The paper ends
with concluding remarks. (C) 1999 Elsevier Science Ltd. All rights reserved
.