5-22 Change 19
Section IV. ANTI-ICING AND BLEED AIR SYSTEMS
Failure to properly install, align, and tighten air
fittings and tubes could result in an engine fail-
Anti-icing and bleed air systems servicing includes
replacing and testing the compressor bleed valve and
anti-icing air valve. In addition, it includes anti-icing valve
5-32. Anti-icing Air Valve.
Disconnect air tubes (23 and 26, figure 5-13)
at the anti-icing air valve (29). Disconnect the air tubes
at the compressor front support only if necessary.
Disconnect the aircraft linkage from the valve
Remove lockwire , loosen jam nut (24), and
unscrew the valve from the diffuser scroll. Discard pre-
formed packing (25).
Apply 100 psig air pressure to the Valve Inlet
with a 0.025 inch orifice installed between the air source
and the valve inlet after installing gauges to monitor the
pressure on both sides of the orifice.
Apply 3.75 pounds maximum force to hold
the lever in the closed position.
Allow air pressure on both sides of the orifice
to stabilize, maintaining pressure at the orifice inlet at 100
If the valve leakage is excessive such that the
pressure downstream of the orifice decreases, replace
the valve and retest.
c. Anti-icing Valve Poppet Seat Replacement.
Replace the Teflon poppet seat of the anti-icing valve as
Remove the cotter pin (17, figure 5-13),
washer (16), and pin (14). Detach the actuating lever (13)
from the valve. Discard the cotter pin.
Remove the lockwire and unscrew the pop-
pet guide (15) from the valve body (22). Separate the
poppet (18) from the body.
Remove the screw (21) and separate the
poppet seat (20) from the poppet.
Clean valve components in cleaning solvent
(3, table 2-2).
Inspect valve components per table 5-2.
Install the replacement poppet seat (20). Re-
tain the seat with screw (21). Stake the screw securely.
(See figure 5-14.)
Insert the poppet and seat into the valve body
(22, figure 5-13) and screw the poppet guide (15) onto
the body. Tighten the coupling nut to 65-75 in. lb. Do not
lockwire at this time.
Align the actuating lever (13) with the hole in
the poppet guide (notch in the lever toward the guide)
and insert the pin (14). Secure the pin with washer (16)
and new cotter pin (17).
Recheck the valve for leakage. Replace
valve assembly if leakage is still excessive.
Place new preformed packing (25) with
backed-off jam nut (24) on anti-icing valve (29). Apply
antiseize compound (item 15.1, table 2-2) lightly to the
threads and install the valve in the diffuser scroll. Do not
tighten jam nut (24).
Connect air tubes (23 and 26) to the valve.
Tighten the coupling nuts to 150-200 in. lb. Tighten jam
nut (24) to 100-150 in. lb. and lockwire (item 10, table
Loosen poppet guide (15) and position lever
(13) parallel with the vertical centerline of the engine.
Tighten the poppet guide to 65-75 in. lb. and lockwire
(item 10, table 2-2).
5-33. Compressor Bleed Valve.
a. Testing. Test the compressor bleed valve while
installed on the engine. Turn off all bleed air.
Pilot and observer use helmets and exten-
sion cord to passenger communication box.
Observer use flashlight to view operation of
the bleed valve.
Run up engine to 100% N2 and observe com-
pressor bleed valve operation. Valve should not be fully
Apply collective until valve is fully closed.
It may be necessary to increase aircraft gross
weight to accomplish run-up. If passengers
are used to increase gross weight, ensure
that seat belts are fastened for all occupants.
Do not have personnel stand on aircraft
skid tubes to increase gross weight.