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• December 12, 2016 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - An Analysis of the Normal Accelerations and Airspeeds of a Four Engine Airplane Type in Postwar Commercial Transport Operations on Trans-Pacific and Caribbean - South American Routes

Normal-acceleration and airspeed data taken on several transport
airplanes of a four-engine type during postwar commercial operations on
trans-Pacific and Caribbean - South American routes of the same airline
are analyzed. The results indicate that the acceleration increment
corresponding to the limit-gust-load-factor increment may be exceeded,
on the average, twice in about 5.6 x 106 flight miles for the Caribbean -
South American operations and twice in about 2 x 109 flight miles for the
trans-Pacific operations. The larger accelerations for the Caribbean -
South American operations appear to result about equally from the lower
operating weight, more severe gusts encountered, and higher airspeeds in
rough air. The possibility of a trend toward a more severe flight load
and gust history for postwar commercial transport airplanes, as indicated
by previous work, is not substantiated by the present results. The never-
exceed speed used by the airline, 250 miles per hour, may be exceeded, on
the average, once in about 105 flight miles for the Caribbean South
American operations and once in about 106 flight miles for the trans-
Pacific operations.

Data on imposed flight loads, operating speeds, and gusts experi-
enced by commercial transport airplanes that were operated during the
prewar period have formed the basis for gust load design requirements.
With the introduction of new airplane types during the postwar period and
changes observed in operating practices, appreciable doubt existed that
postwar flight histories could effectively be predicted on the basis of
prewar data. A program was initiated, therefore, to obtain statistical
data‘ from which imposed flight loads, operating speeds, and gust history
of postwar commercial transport airplanes could be-deduced.

The results of an analysis of the first postwar sample of normal
acceleration and airspeed data obtained from the V-G program have been
reported in reference 1. To the extent that the results of that analysis
could be taken as being representative of postwar operations, a trend was
indicated toward more severe imposed flight loads and gust encounters for
postwar commercial transport airplanes.