• Version
• 38 Downloads
• 1.48 MB File Size
• 1 File Count
• December 13, 2016 Create Date
• December 13, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Static Longitudinal Stability and Control of a Convertible Type Airplane as Affected by Articulated and Rigid Propeller Operation

The results of an investigation in the Langley full—scale tunnel
of the static longitudinal stability and control of a convertible-type
airplane (combination helic0pter and airplane) as affected'by articulated-
and rigidspropeller Operation are presented in this paper. The investi-
gation included force measurements for a very large angle-of-attack range
(from. 12° to 90°) of the model with the all—movable horizontal tail
installed and removed. The flight attitudes investigated include normal-
flight conditions with full power applied and the convertible-flight
region at high angles of attack including the transition to the hovering
condition. The effects of.ailavator and stability-flap deflection on
control-surface effectiveness and on hinge moments were determined. The
effects of propeller slipstream on the ailavator effectiveness at a
static condition and at an angle of attack of 90° for low relative veloc-
ity conditions were also deterndned.

The results show that the destabilizing effect of propeller opera-
tion was more pronounced for rigid-prOpeller operation than for
articulated-propeller Operation'because of the reduction in propeller
normal force and the increment of positive pitching moment due to
propeller articulation. The airplane for full-power operation has a
positive-static-margin average of about 5 percent for articulated-
propeller Operation and about 3 percent for rigid-propeller operation
over most of the lift- coefficient range from 0 50 (11.30 angle of attack)
to about 1.90 (29. 00 angle of attack). The all—movable horizontal tail
is sufficiently powerful to trim the airplane throughout the lift-
coefficient range (from 0. 50 to 1. 80) for full-power operation, although
appreciably less deflection is required for trim with rigidppropeller
Operation. The destabilizing effect of full—power Operation at moderate
angles of attack was more pronounced for rigid-propeller operation.

Full-power operation caused an increase in the ailavator effectiveness
from -0. 0050 per degree at a lift coefficient of 0. RB (1L3o angle of
attack) to -O. 0092 per degree at a lift coefficient of 1.8h (29 00 angle
of attack) with articulatedspropeller operation. The effectiveness,
however, was essentially constant at'a value of about -0.0057 per degree
throughout—the lift-coefficient range with rigid-propeller Operation.

Full-power operation for articulated- and rigid-propeller operation
increased the slope of the lift curve to about 0.068 and 0.070 per
degree,'respectively, as compared with the propeller-removed value of
about 0.032 per degree. The airplane can be trimmed with ailavators
alone in the high—angle—of—attack range up to 58° for rigid—prepeller
Operation.