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|  MIL-T-9720F(USAF)
The fully loaded lift truck shall operate at maxi-
3.5.5 Engine loading.
mum forward speed on a f l a t l e v e l s u r f a c e a n d s h a l l b e c a p a b l e o f s i m u l t a n e o u s
operation of the lift arm and the steering system without stalling the engine.
3.5.6 Safety provision.
Mechanical, hydraulic, and hydrostatic systems
shall incorporate inherent safety features and provisions to protect operating
personnel , e q u i p m e n t , a n d a i r c r a f t .
The lifting mechanism shall be equipped with a hydrau-
3.5.6.1 Failsafe.
lically actuated "Failsafe" device which prevents the lift arms from falling
in the event of hydraulic failure.
3.6 M a j o r c o m p o n e n t s .
The power train shall consist of those units necessary
3.6.1 Power train,
for the application of generated engine power to the drive wheels of the lift
truck. When lnstalled in the lift truck, it shall be-capable of satisfactory
operation in any ambient temperature range from -40 Fahrenheit (F) to +125F.
It shall withstand, without damage, storage temperatures of -80F to +180F.
The lift truck shall be equipped with a hydrostatic drive train which includes
all the components and parts essential for adequate and efficient transmission
of power from the engine to the differential under all conditions specified
The hydrostatic system shall be a closed loop hydraulic system con-
herein.
taining a pump driving motor. heat exchanger and filter.
This system shall
also contain a mechanically actuated rotary by-pass valve to allow the lift
truck to be towed in the event of engine/battery failure.
In the open posi-
tion, the valve shall by-pass the hydrostatic fluid, thereby removing the
resistance of the hydrostatic system from the drive wheels. A foot operated
pedal shall provide a variable speed control for the lift truck.
T h e speed
controls shall also provide inching capability both in the forward and reverse
directions for precise positioning of the load.
The s p e e d c o n t r o l s h a l l b e a
This pedal shall cause forward, reverse, or zero
single acting foot pedal.
movement of the lift truck when depressed while the direction selector handle
Downward pressure
is in either forward, reverse, or neutral, as applicable.
The
on the pedal shall cause movement of the hydrostatic pump swash plate.
lift truck shall be equipped with a dash mounted forward, reverse, neutral
(park) selector handle which selects the direction the lift truck will travel
when the foot pedal is depressed.
This handle shall include a microswitch
feature to prevent the engine from being started unless the handle is in the
neutral (park) position, Movement of the selector handle shall not cause move-
ment of the hydrostatic pump swash, plate.
The selector handle shall be
designed to positively remain in the selected position yet allow the driver to
easily change the selector from one position to another.
With the selector in
a n y p o s i t i o n inadvertent movement of the lift truck in any other direction
shall be prevented.
A feature shall be provided to prevent the direction
selection handle from being moved (shifted) when the foot pedal is depressed.
The transmission and transmission controls shall provide for a smooth and
positive destroking of the pump when the foot pedal is released,
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