An analog computer study of several stability augmentation schemes designed to alleviate roll-induced instability Page: 2 of 51
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NACA RM A56H30
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
AN ANALX COMPUTER STUDY OF SEVERAL STABILITY
AUGMENTATION SCHEMES DESIGNED TO ALLEVIATE
By Brent Y. Creer
An analog computer study has been made of several stability augmen-
tation schemes designed to reduce the objectionable inertia coupling
effects encountered in rolling maneuvers with the F-IOOA airplane having
the original small vertical tail. These augmenters essentially limited
the roll rate to below the critical value (approximately equal to the
yawing or pitching frequency of the nonrolling airplane) or extended the
critical roll rate, and were a roll-rate limiter, a sideslip limiter,
an augmenter employing feedback proportional to the product of rolling
velocity and pitching velocity to remove an inertia cross-coupling yawing
moment, and combinations of the roll-rate limiter with each of the other
The results of this study showed that stability augmenters using
single feedback_quantities reduced the maximum angle of attack and side-
slip excursions experienced during a roll maneuver to reasonable levels,
but the required servo-control-surface deflection was so large as to
make their use on the example airplane impractical, provided the origi-
nal conventional control surfaces were used. However, with either combi-
nation of augmenter tested, this objection was alleviated but not entirely
The effect of changes in the initial trim normal load factor was
small, except when the angle of attack of the principal axis was large
and the critical rolling velocity was exceeded. Changes in the flight-
test speed and altitude generally required changing the feedback charac-
teristics of all the augmentation systems, except for the sideslip limiter,
where it appears as though a single set of servo feedback characteristics
would suffice for all the speed and altitude conditions tested.
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Creer, Brent Y. An analog computer study of several stability augmentation schemes designed to alleviate roll-induced instability, report, February 19, 1957; (digital.library.unt.edu/ark:/67531/metadc62909/m1/2/: accessed January 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.