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: 5 of 24
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NACA TN 3750
Check-flight-maneuver accelerations were evaluated by reading the
appropriate deflections of the acceleration trace greater than a threshold
value of t0.1g. The resulting distributions of the positive and negative
accelerations are given in table III. The total number of record hours,
the amount of time actually spent in check flights, and the flight miles
represented by the distribution are also shown in table III.
Because in some past cases the maneuver accelerations have contri-
buted substantially to the total acceleration history of the airplane,
the combined positive and negative distributions df table III are compared
with the gust acceleration distribution in figure 4. It was found imprac-
tical to evaluate the records for the additional maneuver accelerations
experienced during the regular operational flights since these accelera-
tions were relatively small and difficult to distinguish from the much
larger number of gust accelerations.
Derived gust velocities Ude were calculated by means of the revised
gust load formula of reference 7 for each gust acceleration peak and the
corresponding indicated airspeed and altitude. The resulting frequency
distributions are presented in table IV for class intervals of 4 feet per
second for each flight condition and for the total operation. Only gust
velocities greater than 8 feet per second are given in the table because
the lower values corresponded to accelerations less than the threshold
value of 0.3g. Positive and negative gust velocities were combined as
in table I because the distributions were essentially symmetrical about
zero gust velocity. The frequency of occurrence of gust velocities for
the complete operation is plotted in figure 5. A solid line was faired
through the data points to indicate the trend of the distribution. Gust-
velocity distributions for the short-haul and long-haul operations previ-
ously discussed are also shown in figure 5 for comparison.
Operating Airspeeds and Altitudes
In order to define the operating airspeeds and altitudes for the
feeder-line operations, the indicated airspeed and pressure altitude were
read from the records for each 1-minute interval of flight. The distri-
butions of indicated airspeed obtained from these readings for the climb,
en-route, and descent conditions are shown in figure 6 as portions of the
flight time spent within given airspeed intervals . The distributions of
airspeed for which acceleration increments greater than 0.3g were experi-
enced are also given in the figure to indicate any difference between the
speeds in rough air and the overall speeds.
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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/m1/5/: accessed May 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.