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National Advisory Committee for Aeronautics, Report - Estimation of the Maximum Angle of Sideslip for Determination of Vertical Tail Loads in Rolling Maneuvers

Recent experiences have indicated that angles of sideslip
in rolling maneuvers may be critical in the design of vertical
tails for current research airplanes having weight distributed
mainly along the fuselage. Previous investigations have
indicated the seriousness of the problem for the World War II
type of airplane. Some preliminary calculations for airplanes
of current design, particularly with weight distributed primarily
along the fuselage, are made herein.

The results of this study indicate that existing simplified
expressions for calculating maximum sideslip angles to determine
the verticalrtail loads in rolling maneuvers are not generally
applicable to airplanes of current design. A general solution
of the three linearized lateral equations of motion, including
product-of-inertia terms, will usually indicate with sufiicient
accuracy the sideslip angles expected in aileron rolls from
trimmed flight. In rolling pullouts, however, where the pitch-
ing velocity is large, consideration of cross-couple inertia
terms in the equations of motion is necessary to obtain the side-
slip angles accurately. The inclusion of the equation of the
pitching motion seems desirable along with the lateral equations
of motion in order to obtain the influence of pitching in the
cross-couple inertia terms of the lateral equations. Pitching
oscillations started during rolling maneuvers will be influenced
by cross-couple inertia moments in pitch and may cause large
variations in angle of attach: which afiect the horizontal-tail
loads.

Large angles of sideslip and resultant large vertical-tail
loads have been encountered in a flight of a high-speed
swept-wing research airplane and with models of two designs
flown by the Langley Pilotless Aircraft Research Division.
All three configurations rolled abruptly while pitching up.
In the flight of one model, the vertical tail, which was de-
signed by conventional methods, was lost during the rolling
maneuver. The motion for all flights appeared to be essen-
tially a rolling about the X body axis while at high angles of
attack.