Jim Floyd:RAeS Lecture
The Fourteenth British Commonwealth Lecture
The Canadian Approach to All-Weather
Studies on flutter included extensive investigation of wing modes, fin and rudder modes, and control surface buzz (Fig. 10(a)).
wing was treated as a plate, because of the low aspect
ratio, and the modes were calculated for the complete
aircraft, since it was obvious that it would be impossible
to separate the wing and fuselage in a structure
of this type. Cantilever modes were also calculated,
as a check. Calculations involving the complete aircraft
in the symmetrical case involved 6 degrees of freedom,
plus control effects.
degrees of fin freedom were included in the analysis,
together with the rudder fundamental mode. A wide
range of rudder frequencies was covered to establish
the stiffness required of the control circuit for
types of control surface buzz were considered, the
first being the shock wave boundary layer interaction
problem which occurs at a speed slightly higher than
the wing or fin critical Mach number. An oscillatory
condition arises when the shock waves move rapidly
back and forth across the control surface hinge line,
influenced by the trailing edge shape of the control
surface, and the particular flight manoeuvre being
Ground resonance was an important factor, since with an aircraft the size and weight of the Arrow, the complete dynamic structural characteristics had to be completely investigated on the three-point under-carriage suspension. The tests showed that the aircraft, fuselage, and the wing were better than calculated. However, the fin appeared to be less easily predictable, since there was considerable rudder torsion coupling. Further fin flutter tests have been made to check the predictions.
The modes of interest are easily excited by the controls in flight, and we have done considerable stick tapping in an attempt to obtain records throughout the speed envelope. From this, by telemetry, the time and magnitude of damping are checked. Fig. 10(b) shows the excellent damping recorded from these tests.
eliminate time delays, due to development of unfamiliar
production processes, we did not go in for extensive
use of the newer techniques, such as steel honeycomb,
and used titanium only where its high temperature
properties were required, rather than from a strength
consideration. However, a number of the newer materials
CONVERTED TO HTML,
AND HYPERLINKS ADDED, MARCH 28, 2001.
ONLINE STORE FEATURED ITEM:
|| HOME | STORE | NEW INFO | CONTACT US | ABOUT US ||
© C© Copyright AvroArrow.Org, 2009. Materials may be freely copied and distributed subject to the inclusion of the copyright notice, and credit must be given to AvroArrow.Org. The site is intended for historical and informational purposes. This site contains links to other Internet sites. These links are not endorsements of any products or services in such sites, and no information in such sites has been endorsed or approved by this site.