• Version
• 333 Downloads
• 40.14 MB File Size
• 1 File Count
• April 25, 2016 Create Date
• April 25, 2016 Last Updated

Cooperative Programme on Dynamic Wind Tunnel Experiments for Maneuvering Aircraft

There is now considerable interest in highly agile fighter
aircraft, capable of flying at high angles of attack and of
performing rapid, large-amplitude manoeuvres under such
conditions. Such manoeuvres result in highly non-linear
aerodynamic characteristics involving, asymmetric and
unsteady flows, which also usually contain several systems of
vortices. To correctly and efficiently predict such high angle-
of-attack rapid manoeuvres, the structure of these very
complex flows must be properly understood and the resulting
aerodynamic loads must be accurately determined. At the
present time, the best way to achieve this is by conducting
appropriate wind-tunnel experiments, with aircraft models
performing rotary or oscillatory motions, or even - if
feasible - a representative combination of these motions. In
all cases such dynamic experiments should be conducted at
high angles of attack, representative rates, and (for oscillatory
motions) also large amplitudes. The oscillatory experiments
should preferably include not only angular but also
translational motions. The results should include not only
aerodynamic coefficients and static and dynamic stability
derivatives, but also the effect of time histories and detailed
information on the flow fields involved, such as can be
obtained by means of pressure measurements and flow
visualization studies.
One type of dynamic experiment mentioned above, namely
when the aircraft model performs a rotary motion in the wind
tunnel, has been reviewed recently by AGARD FDP Working
Group 11. The results were published in 1991 as AGARD
Advisory Report No. 265 and included, inter alia, a review of
the experimental test rigs (“rotary balances”) used in the
various NATO countries as well as representative rotary test
results. It was pointed out that in the 60 years or so of their
existence the rotary balances were mostly used for obtaining
data required for prediction of the spin characteristics of
aircraft (usually general aviation and fighter aircraft). In most
cases the data were found to be reliable and sufficient for the
purpose for which they were intended.