A series of flight tests involving a modified F-106
fighter aircraft towed behind a C-141 cargo aircraft was
completed at NASA’s Dryden Flight Research Center
in February, 1998, under the title of the Eclipse
Project.
1 This paper presents a numerical approach
used to compute tow cable shapes and altitude offsets in
the vertical plane for the towed configuration as a
function of trimmed flight condition. Each solution
was generated in two distinct steps. First the trim
condition of the towed aircraft was found using an
existing aerodynamic database. Correction factors for
this database were extracted from data measured during
untowed steady-state test glides. The second step was
numerical integration of the differential equations
governing cable shape in the presence of distributed
aerodynamic and gravitational loads. The aircraft trim
condition from the first part of the solution provided the
initial conditions needed for the second part.
Computational results for nominal test conditions are
compared with flight test measurements of aircraft
altitude offset, angle of attack, pitch angle, cable pitch
angle, and cable tension. Altitude offsets were
measured using highly accurate differential GPS
receivers. Families of computed cable shapes are
presented as a function of elevator deflection and flight
path angle