A comparison of gust loads measured in flight on a swept-wing airplane and an unswept-wing airplane Page: 4 of 17
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NACA RM L52L02 3
The following instruments were installed in each airplane to
obtain information pertinent to the gust loads:
(1) NACA magnetically damped recording accelerometer
(2) NACA airspeed-altitude recorder
(3) NACA 1-second interval timer
The recording accelerometers were damped to 0.7 of critical and had a
natural vane frequency of about 19 cycles per second. Their range for
a full-scale film deflection of 2 inches was from -1 g to 5g. The accel-
erometers were located as near as practicable to the center of gravity of
each airplane. For the unswept-wing airplane, the accelerometer was
located approximately 5.5 feet forward of the normal center of gravity
of the airplane. In the swept-wing airplane the accelerometer was
mounted approximately 2.3 feet forward of the normal center of gravity
of the airplane. Corrections to the measured accelerations due to dis-
placement of the recording instrument from the center of gravity will
be discussed subsequently.
The static-pressure source for the recording airspeed installation
of each airplane was calibrated by the fly-by method (ref. 5), and the
results are given in figure 2 where the static-pressure error is shown
as a function of the indicated Mach number.
The test procedure consisted of 12 side-by-side flights through
clear air turbulence over a fixed course of about 22 miles in the vicin-
ity of Dayton, Ohio. All flights were made in continuous rough air at
an altitude of approximately 1500 feet above terrain. Each flight con-
sisted of four runs, two at 300 miles per hour and two at 450 miles per
hour. The pilots' assignments and the order of the high-. and low-speed
runs were varied randomly to eliminate any consistent combination of
conditions that might affect the results. A minimum of pilot control
was used on all flights. No external tanks were used on either airplane
and the dive brakes remained closed throughout the tests.
EVALUATION AND RESULTS
The acceleration records were evaluated to obtain the maximum value
of acceleration -between any two consecutive intersections of the record
line with the 1 g reference and the distance traveled from each inter-
section to the following peak acceleration. The latter measurement is
considered a measure of the gust gradient distance and is referred to
as such in this report. The evaluation was confined to values of accel-
eration increment greater than 0.3g and 0.45g for the low- and high-speed
runs of the unswept-wing airplane, and 0.25g and 0.35g for the swept-wing
airplane. These thresholds correspond to effective gust velocities of
approximately 5 feet per second.
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Funk, Jack & Mickleboro, Harry C. A comparison of gust loads measured in flight on a swept-wing airplane and an unswept-wing airplane, report, June 29, 1953; (https://digital.library.unt.edu/ark:/67531/metadc59506/m1/4/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.