MIL-F-18372(Aer)
3.1.2.6 Power Control Override Previsions - Provisions shall be made to permit direct pilot
effort to be applied to a control valve in the event the valve becomes jammed or frozen. In other
words any spring or load relieving device between the pilot and the valve, which is designed to
prevent excessive loads being applied to the valve, shall become a solid link before full pilot
control travel is reached.
3.1.5 Additional Requirements For Secondary Flight Control
3.1.3.1 Manually Operated Trim Control System - When manually operated trim control systems
are used, it shall be possible to obtain the necessary control with a minimum amount of input motion
consistent with acceptable operating forces.
3.1.3.2 Power Operated Trim Control SystemS - Where power units are provided for operating the
trim surfaces or devices, even where more than one speed is provided, the rate, or rates, of appli-
cation shall be such that preciseness of control is obtained for landing, take-off and in-flight
conditions without creating a hazard.
3.1.3.2.1 Emergency Systems - Where failure of a power operated trim control system would result
in marginal or undesirable control characteristics, a completely separted emergency power system, or
means to override the failed power system, shall be provided.
3.1.3.3 Irreversibility - The control system for each triming surface or device shall be
irreversible, and shall maintain a given setting until changed by the pilot. It is desired that
the irreversible mechanism be as near to the trim tab, or trimming device, as is practicable,
preferably in the linkage which connects to the tab horn, to minimize free play at the surface and
maintain rigidity in the control.
3.1.3.4 Synchronization - Where two (2) controllable trim surfaces are used on the elevators,
they shall be mechanically interconnected.
3.1.3.5 Pilot's Controls - The location and actuation of the pilot's controls shall be in
accordance with MIL-STD-203. Controls shall be clearly marked to indicate their purpose and
direction of motion.
3.1.3.5.1 Position Indicator - Suitable indicators shall be provided to indicate the neutral
position and the range of travel of each trim device. Where movable surfaces are used for trimming,
the sensing devices for the indicator shall be operated by the surface or a mechanical link directly
connected to the surface. A position sensing device is not required on the surface if the system
is entirely manual, unless an electrical instrument type indicator is used. On manual type systems
a mechanical type indicator on or near the cockpit control is considered satisfactory.
3.2 Additional Desire And Installation Requirements For Fixed Wing Aircraft
3.2.1 Primary Flight Controls
3.2.1.1 Friction - The requirements relative to friction in the primary flight control systems,
shall be in accordance with the contract requirements.
3.2.1.2 Pilot's Controls
3.2.1.2.1 Longitudinal - Longitudinal controls shall be by means of a stick, or wheel. Forward
movement of the stick or wheel and column shall cause the aircraft to nose down, and aft movement
shall cause the aircraft to nose up. The range of movement of the longitudinal control shall be a
maximum of 14". The extreme aft position shall be not more than 9" from the neutral position.
3.2.1.2.2 Lateral - The lateral control shall be by means of a stick or wheel. Movement of the
stick to the right, or clock-wise rotation of the wheel, shall cause the aircraft to roll to the
right; movement of the stick to the left, or counter-clockwise rotation of the wheel, shall cause the
aircraft to roll to the left. The range of movement of the lateral control stick shall be a maximum
of 7" to the right and 7" to the left of the neutral position. The rotation of the control wheel shall
be a maximum of 110° clock-wise and 110° counter-clockwise.
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