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National Advisory Committee for Aeronautics, Technical Notes - An Analysis of the Airspeeds and Normal Accelerations of Sikorsky S-42A Airplanes in Commercial Transport Operation

Acceleration and airspeed data taken on four Sikorsky S-hQA air-
planes operated on Caribbean routes and along the east coast of
South America have been analyzed and the results indicate that the
flight loads seem about average in comparison with the flight loads
of other types of airplanes operated on different routes. The limit
gust load factor of the S-haA airplanes will be exceeded, on the average,
once in about 3 X lo7 flight miles. The loads of the Sikorsky S~h2A air-
planes were less conservative than the loads of the Beeing 3-307 airplanes,
both of which were operated in the same general region; this difference
was attributed to the higher ratio of probable speed of maximum accele-
ration occurrence to the design maximum level-flight speed Vé/VL of
the S—hEA airplanes. Caribbean operations of the S-hEA and the 8-307
airplanes are in good agreement with respect to route roughness and do
not show greater route roughness than most of the other routes compared.

Previous analyses (references 1 to 3) present the results obtained
from acceleration and airspeed data taken during commercial transport
operation to show the influence of airplane, route, season, and prewar
and wartime operations on the flight loads and operating speeds. These
papers deal with three different types of airplanes operated on different
routes. Insofar as the flight loads of the airplanes are concerned, the
results indicate that airplane speed in regions of turbulent air is a
significant parameter and that differences are apparent in prewar and
wartime operations. Operations of the Douglas DC-3 type airplanes on
transcontinental routes of the United States have indicated that
variations in the forecasting and dispatching practices of.the airlines
appear to compensate for differences in route roughness. Trans-Pacific
operations of the Martin.M-130 airplanes have indicated greater route
roughness than did operations over transcontinental routes of the
United States orroperations over Caribbean routes.

This“ paper gives the results of an analysis ofv-G data taken
on four Sikorsky S-h2A flying boats operated on Caribbean routes and
along the east coast of South America during the period from 1936 to 1939.
Investigation has been made of the influence of operating speeds and
routes on the flight loads. The available S-1L2A data are summarized
and the flight-load results are compared with the results of analyses
made in the past.