THRUSH AIRCRAFT INC – MODEL S2R R1340
AIRCRAFT MAINTENANCE MANUAL
5-12
Effective: 01/01/08
PRESSURE CHECK SET-UP
Reference Figure 5-5, Manometer Board.
Enough colored water should be in the 1”
tube to extend beyond the curve slightly.
With no pressure on the 1” tube, align the
bottom of the manometer scale (the
zero) with the top of the colored water in
the manometer.
Plug shop air into the shut-off valve with
the shut-off valve closed. Connect the
pressure hose from the shut-off valve to
a wing fuel outlet, and connect the wing
vent line to the manometer inlet side.
Plug the other wing fuel outlet.
PRESSURE CHECK PROCEDURE
Crack the shut-off valve just enough to
hear air flowing through it. An increase
in pressure in the wing will be indicated
by movement of the manometer water
column up the scale side. While extreme
pressure build-up within the tank or fuel
system is prevented by the open-ended
manometer tube, too rapid of pressure
build-up can cause a pressure spike that
can severely damage the wing.
Apply pressure to the fuel tank
very gradually. Do not
pressurize the tank in excess
of 44.0 inches of water or
damage may occur.
When pressure in the tank exceeds 38”,
start checking the tank for air leaks.
Some can be identified by hissing
sounds and/or feeling the air escaping.
Feel sensitivity is increased by wetting
the hands. Leak detection fluid will
identify smaller leaks. Turn the shut-off
valve off before the water column
reaches 44”. The valve may need to be
re-opened to maintain at least 38” while
leaks are detected and solved.
Once all obvious leaks have been
detected and solved, a general check of
all joints and seams should be made
using leak detection fluid or soapy water.
When satisfied that all leaks have been
detected and solved, and with the
manometer reading between 38” and
44”, close the shut-off valve. Start a
stop-watch or note the second hand
position on a watch and note the
manometer reading.
After 5 minutes minimum has elapsed by
the watch, if the manometer reading has
not decreased by more than ¼” the
pressure check is successful. Leakage
greater than this necessitates finding and
solving the remaining leak(s).
Repeat this process until the wing holds
pressure as specified above.
CAUTION
