MIL-H-18325B(Aer)
range. However, those areas of the aircraft which contain the equipment and the operator of
the equipment shall be maintained at a minimum temperature of +350F? to preclude hindering
normal operation by equipment operator due to excessive cold. For additional information
concerning general installation requirements of armament control systems, see MIL-I-8677(Aer).
Droppable Stores and Associated Release Systems - External and internal installations
3.10.1.4
of droppable stores and associated release systems require satisfactory operation in temperature
ranges of -65°F to +160°F. Specific temperature requirements are determined by the specific
store or release system to be installed. For additional Information regarding general installa-
tion requirements, see MIL-I-8671{Aer).
.
Automatic Flight Control and Stabilization Equipment - The minimum allowable temperatures
3.10.2
for automatic flight control and stabilization equipment shall be -50°F, except that components
installed in the cockpit or cabin of the aircraft shall be Malted to -30°F minimum.
3.10.3
Instruments - The minimum allowable tempemture for all instruments installed in the
cockpit or cabin of the aircraft shall be -30°F.
3.1O.4 Photographic Equipment - Photographic type airplanes shall be provided with adequate heat
for warning cameras and defogging camera lenses and camera windows. The minimum allowable
temperature for photographic equipment shall be +40°F.
Heater Compartments - Provision shall be made to ventilate adequately and continously
3.10.5
the compartment in which combustion type heaters are installed in order to prevent the
accumulation of fuel vapors in the event of fuel leakage. Maximum concentration of fuel vapor
in heater compartments shall not exceed the. limits specified in paragraph 3.6,
Electrical Equipment - Ventilation shall be provided in any compartment
in which
3.10.6
electrical or other types of heat generating equipment are installed in order to
prevent the
development of temperatures exceeding +160°F for periods of 1/2 hour, or 130°F
continuous
under any condition of flight. Battery compartments shall be heated in order to
prevent the
temperature of the compartment from falling below +30°F.
Ground Preheat - Provision shall be made for supplying sufficient heat, either from an
3.11
outside source or from the cabin heating system to maintain the engine and its auxiliary section
at a temperature not exceeding 0°F; transmissions and gear boxes in rotary wing aircraft at 0°F;
and batteries, bombsights, automatic flight control equipment, and the pilot's compartment at
a temperature not less than +30°F with the outside air temperature at -65°F. These provisions
shall be dependent upon the use of ground equipment and shall not depend upon the operation of
the airplane engine or batteries.
3.12 Noise control
Heater Noise - In flight, the noise produced by the heating system shall not increasej
3.12.1
at any frequency within the audible airplane sound spectrum, the total sound level within the
enclosed and heated spaces by more than 2 decibels.
3.12.2 Ventilation Noise - The design and location of ventilator shall be such that in flight
the total sound level in the enclosed spaces is not increased more than 3 decibels when the
ventilator are opened.
3.12.3
Vibrators - Any units, the operation of which is of such nature that noise or vibrations
would be transmitted to the airplane structure, shall be mounted on vibration damping supports
of an approved type.
3.23 Weight - The weight of the heating and ventilating equipment shall be as low as practicable,
consistent with good manufacturing practices for this type of airplane equipment. The combustion
heaters or heat exchange and as much of the duct work as practical shall be readily removable
from the airplane so that the weight of the heating system may be reduced as much as possible
on those airplanes operating in theatres where heating is not required.
3.l4 Controls
Temperature - The cabin or cockpit temperature control may be manual or automatic. The
3.14.1
controls for starting the system in operation shall be as simple as possible and the shut off
control on the heating system shall, if possible, consist of a single control for shutting off .
all the component parts of the Type I heating system or if a Type II system is installed, stopping
all flow of heated air into the occupied spaces. If a Type III system is installed a single
6
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