General design and construction requirement. The
valve shall conform to the applicable specification sheet. (For example
see MIL-V-81995/1, MIL-V-81995/2, MIL-V-81995/3, and MIL-V-81995/4.)
Acceptable design. The valve shall be suitable for
operational use with an engine starter utilizing a pneumatic energy
source, and Its design shall be amenable to production processing methods.
Design of each unit shall be consistent with good aircraft accessory
practices. Careful consideration shall be given in the design of the .
unit to simplify servicing. inspection (testing), and overhaul. The
necessity of using special tools and fixtures for maintenance and overhaul
shall be kept to a minimum.
Interchangeability. Each article of the same part
number manufactured in accordance with this specification shall be
physically and functionally interchangeable with articles bearing the
same contractor part number.
Components. The valve shall consist of a mechanism
(such as a butterfly) for controlling airflow through the valve, a
pneumatic pressure regulating or on-off actuating power device, a solenoid-
operated pilot valve for control of the actuator, and position indicators.
Fail-safe features. The valve shall automatically
close in the event of loss of electric power or pneumatic energy source.
External openings. All air vents or case openings
shall be protected by suitable means against passage of round objects of
3/16-inch or greater in diameter.
Adjustments. No external adjustment means shall be
provided and no adjustments shall be required during installation of the
valve. All adjustments are to be made at the time of manufacture or
overhaul. If devices for making adjustments are installed within components,
suitable locking and sealing means shall be provided to indicate when an
unauthorized adjustment has been made.
Drainage. The valve shall incorporate provisions
for drainage or be designed to prevent water from accumulating within
the unit. Drainage shall be such that any condensed or accumulated
water will not cause malfunction or delay in operation if frozen.
Direction of flow. The direction of airflow through
the valve shall be prominently and permanently marked on the valve
Pneumatic bleed. The source of air pressure used to
actuate the valve shall be integral with the valve and shall be located
on the upstream side of the valve. Bleed ports and passages shall be as
large as is practical to preclude blockage by contamination.