An analysis of the airspeeds and normal accelerations of Boeing S-307 airplanes in commercial transport operation Page: 11 of 29
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NACA TN No. 11 1
prewar calculated flight envelope is well within the
design gust envelope, whereas the calculated flight
envelope for the war period exceeds it over a fairly
large speed range..
The differences between the two pericds can, of
course, be explained in terms of the two factors pre-
viously discussed, namely, the greater turbulence
experienced during the war period (due to restricted
forecasting and/or relaxed dispatching techniques)
and the higher speeds maintained during the war period
in regions of-turbulence. It would be desirable to
determine the separate-effect of each of these factors
but such a determination cannot ba.made on the basis of
the present data. As additional information from other
transport airplanes becomes available, however, the
knowledge gained thereby may be expected to permit a
suitable assessment of each of the foregoing factors.
Additional information regarding operations during
the prewar and war periods may be obtained from the
effective-gust-velocity envelopes of figures 8 and 9.
These envelopes have been used to determine the average
number.of hours required to experience an effective
gust.velocity greater than 30 feet per second at
different airspeeds for the prewar and the war periods.
The results are presented in figure 10. The differences
in operating practices in the two periods are emphasized
in this figure. For example, in the prewar period, an
effective gust velocity greater than 30 feet per second
would be experienced an average of ;once in 20Q,C00 hours
at the normal cruising speed (200 nmph) of the S-507 air-
plAne, and at the same speed during the war period, an
average of once in 2,000 hours. These values suoDort
the conclusion already drawn that during the war period,
the airplanes were flown into regions of turbulence at
higher speeds than during the prewar period.
The conclusion that flights were made through more
turbulent air during the war period is also strengthened
on the basis of figure 10. Eixaminaion of the probable
seeds (145 mph for the prewar period and 16-5 mph for
Sthe war period) shows that for the prewar period an
effective gust velocity of 50 feet per second would be
experienced at the probable seed once in 4C30 hours,
and for the war period, once in 140. hours. That is,
not only were the airplanes flown in turbulent air at
higher speeds, but the- were also flown into regions of
greater turbulence during the war period.10
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Peiser, A. M. & Walker, W. G. An analysis of the airspeeds and normal accelerations of Boeing S-307 airplanes in commercial transport operation, report, September 1946; (https://digital.library.unt.edu/ark:/67531/metadc55014/m1/11/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.