TY - JOUR

T1 - Nonlinear six-degree-of-freedom aircraft trim

AU - Elgersma, Michael R.

AU - Morton, Blaise G.

PY - 2000/1/1

Y1 - 2000/1/1

N2 - When computing numerical trim solutions, it is difficult to know if all possible trim solutions have been found. This paper presents closed-form formulas for computing all possible trim values for six-degree-of-freedom nonlinear aircraft models. The models include gravity, nonlinear angular-rate terms, and tabular aero functions. However, the models are linear in four functions of the four inputs (thrust, aileron, elevator, rudder). The four independent control inputs lead to a four-dimensional trim set. In the subsonic case where the Mach dependence of the aero functions can be ignored, the four-dimensional trim set is parameterized by (pitch angle, roll angle, angle of attack, sideslip angle) giving at most two real trim values for each set of fixed values of these four parameters. When the Mach dependence of the aero functions needs to be considered, the four-dimensional trim set is parameterized by (speed, angle of attack, sideslip angle, and heading angular rate) giving up to eight trim values for each fixed set of values of these four parameters. The advantage of these closed-form computations, over more numerical methods, is that they give all possible solutions values.

AB - When computing numerical trim solutions, it is difficult to know if all possible trim solutions have been found. This paper presents closed-form formulas for computing all possible trim values for six-degree-of-freedom nonlinear aircraft models. The models include gravity, nonlinear angular-rate terms, and tabular aero functions. However, the models are linear in four functions of the four inputs (thrust, aileron, elevator, rudder). The four independent control inputs lead to a four-dimensional trim set. In the subsonic case where the Mach dependence of the aero functions can be ignored, the four-dimensional trim set is parameterized by (pitch angle, roll angle, angle of attack, sideslip angle) giving at most two real trim values for each set of fixed values of these four parameters. When the Mach dependence of the aero functions needs to be considered, the four-dimensional trim set is parameterized by (speed, angle of attack, sideslip angle, and heading angular rate) giving up to eight trim values for each fixed set of values of these four parameters. The advantage of these closed-form computations, over more numerical methods, is that they give all possible solutions values.

UR - http://www.scopus.com/inward/record.url?scp=0033884172&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033884172&partnerID=8YFLogxK

U2 - 10.2514/2.4523

DO - 10.2514/2.4523

M3 - Article

AN - SCOPUS:0033884172

SN - 0731-5090

VL - 23

SP - 305

EP - 311

JO - Journal of Guidance, Control, and Dynamics

JF - Journal of Guidance, Control, and Dynamics

IS - 2

ER -