MIL-F-18372(Aer)
less than 7/16 dia. Male shank type rod end bearings are preferred over female types.
3.1.1.18.2 Supports - All push-pull tubes shall be supported by suitable levers, bellcranks, or
rollers. To prevent possible binding of the system due to misalignment or deflection, self-aligning
anti-friction bearings shall be used in all terminals. Suitable precautions shall be taken to prevent
jamming or undesirable wear of parts resulting from rotation of the tube about its axis.
3.1.1.18.3 Tubes - Tubes shall have a minimum wall thickness of .035 inch and shall be seamless
except that steel tubes, seam-welded by the electrical resistance method, may be used. Consideration
shall be given to the natural frequency of vibration of the tubes with respect to the vibrations set
up in the aircraft.
3.1.1.18.4 Flexible Controls - Flexible push-pull type controls shall not be used.
3.1.1.19 Torque Systems
3.1.1.19.1 Slip Joints - All torque control systems shall incorporate splined joints or equivalent,
as necessary, to prevent binding of the system due to deflections of the aircraft structure.
3.1.1.19.2 Supports - All torque tubes shall be mounted on anti-friction (preferably self-aligning)
bearings.
3.1.1.19.3 Tubes - Tubes shall have a minimum wall thickness of .035 inch and shall be seamless,
except that steel tubes seam-welded by the electrical resistance method, may be used. Consideration
shall be given to the natural frequency of vibration of the tubes with respect to vibrations set up
in the aircraft.
3.1.1.19.4 Universals - All torque tube control systems shall incorporate universals as necessary
to prevent binding of the systems due to misalignment of supports or deflection of the aircraft
structure.
3.1.1.20 Differential Controls - A control system in which differential motion is obtained shall
incorporate stops to prevent the cranks from reaching a locking or reversing position unless specifically
required for the proper operation of the system.
3.1.1.21 Control Surface Stops - In aircraft, such as VP and VR types, employing large, heavy
surfaces, stops shall be provided at each surface.
3.1.1.22 Adjustable Stops - All adjustable stops shall be positively locked or safety wired in the
adjusted position. Jam nuts (plain or self locking type) are not considered adequate as locking devices
for this application.
3.1.1.23 Stability Augmenting Devices - Devices installed for the purpose of augmenting stability
shall be so designed that the failure of such a device will not cause discontinuity of the flight
control system or any other flight hazard. The system shall be designed so that, under normal operating
conditions, there is no adverse reflection on the pilot's primary controls.
3.1.1.24 Other Devices - Other devices such as spring bungees tension regulators, bob weights,
dampers, etc., shall be so designed that their failure shall not cause discontinuity of the control
system, or any other flight hazard. Positive locks or safety wire shall be provided at all attachment,
where there is a possibility of the components in spring cartridge, dampers, etc., becoming detached
as a result of inadvertent rotation of the components.
3.1.2 Additional, Requirements For Primary Flight Controls
3.1.2.1 Type I System - In the design of flight control systems the reliability, strength, and
simplicity of the system shall be of paramount consideration. Whenever push-pull tube systems are
used they shall be so arranged that all the tubes are in tension for the greater load for which the
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