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National Advisory Committee for Aeronautics, Technical Notes - Maximum Pitching Angular Acceleration of Airplanes Measured in Flight

Existing flight—test data on pitching angular accelerations have
been compiled. The sources from which the data were taken were manu-
facturer's reports, NACA papers, and unpublished tests which were con-
ducted at the Langley Aeronautical Laboratory; The compilation has
been made for conventional airplanes that had moments of inertia which
ranged from 535 to 572,000 slug-feete. 'All the data available are for
Mach numbers below 0.80.

In addition to the compilation, an analysis was made of the data
to establish methods for determining maximum pitching accelerations.
The methods presented follow several elementary approaches and include
variables which are usually available at the design stage.

Knowledge of the maximum values of pitching angular accelerations
to which an airplane may be subjected is necessary in the structural
design of various airplane components. For example, critical loads
occur on the horizontal tail either when maximum negative angular
accelerations are combined with maximum positive load factors or when
maximum positive angular accelerations 'are combined with maximum nega-
tive load factors.

Analytical methods such as those given in references 1 to h are
available which may be used to Obtain maximum values of pitching
accelerations. These methods are based on either (1) a prescribed load-
factor variation, (2) a maximum constant rate of force application, or
(3) a maximum constant rate of elevator motion. At the design stage,
however, any of these methods are complicated by the problem of deter-
mining several aerodynamic quantities to a high degree of refinement for
use in the equations of motion.

The purpose of this paper is to present existing flight-test data
on maximum pitching accelerations that have been collected during the
past 19 years and to analyze these data by elementary concepts in which
consideration is given to the possible effects of airplane geometry,
Weight, load factor, and rapidity of maneuver. The results may be used
in the preliminary design of an airplane.