An analysis of airspeed, altitude, and acceleration data obtained from a twin-engine transport airplane operated over a feeder-line route in the Rocky Mountains Page: 7 of 24
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NACA fN 3750
the smaller gusts for the feeder-line operation probably resulted from
the larger amount of turbulence at the lower altitudes over the mountainous
terrain. In addition, little effort was probably made to climb above this
turbulence because of the short duration of most of the flights. (See
fig. 1.) The lower frequency of the larger gusts for the feeder-line
operation may have resulted from more conservative operating practices
in regard to such factors as severe weather avoidance.
It was also noted that the gust-velocity data indicated very little
variation in gust frequency with an increase in pressure altitude for the
altitude range covered by the data. This characteristic of the present
data apparently resulted from the essentially constant flight altitude
above terrain for all flight conditions. In many cases, mountain peaks
near the flight path extended above the cruising altitudes for the present
" Figure 2 indicates that the frequency of gust accelerations for the
feeder-line operation is approximately 3 times greater than that for the
short-haul operation and 30 times greater than that for the long-haul
operation. Differences between the frequency of gust accelerations for
various operations are primarily due to variations in the gust experiences,
wing loadings, and the airspeeds flown in rough air. Since neither the
gust experience, particularly for the larger gusts (fig. 5), nor the air-
speeds in rough air (table II) were excessive for the feeder-line operation,
its relatively high gust acceleration frequency is due almost entirely to
the low wing loading of the airplane (table II).
Table I indicates that the number of gust accelerations experienced
per mile of flight during the en-route portion of the present operation
was greater than the number experienced in climb and approximately equal
to the number experienced during descent. This result is in contrast to
other operations (refs . 1, 2, 8, and 9) where the number of gust accelera-
tions per mile of flight was less for the en-route condition than for
either the climb or descent condition. The number of gust accelerations
per mile for each flight condition was largely determined by the airspeeds
for the climb, en-route, and descent conditions since, as previously noted,
little variation in gust frequency with increasing altitude was evident
for the feeder-line operation. This is apparent in table I which indicates
that the average airspeeds and acceleration frequencies for the en-route
and descent flight conditions are approximately similar.
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Copp, Martin R. & Fetner, Mary W. An analysis of airspeed, altitude, and acceleration data obtained from a twin-engine transport airplane operated over a feeder-line route in the Rocky Mountains, report, October 1956; (https://digital.library.unt.edu/ark:/67531/metadc56182/m1/7/: accessed May 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.