(d)  
Close ENG 1 & WING VALVE circuit breaker, open ENG 2 & WING VALVE (left wing valve) circuit breaker, and repeat steps (b) and (c) for right valve control circuit.

(e)  
Close ENG 2 & WING VALVE circuit breaker, place wing anti-ice control switch in ON position, and check that both valve open lights glow brightly and both valves remain closed.

(f)  
On landing gear module M338, press GRD SENSING TEST switch and check that both valve open lights glow brightly for 1 to 3 seconds and then continue to glow dim as long as test switch is held and both wing anti-ice valves open.

(g)  
Release GRD SENSING TEST switch and check that both valve open lights continue to glow dim for 1 to 3 seconds and then glow bright, and both wing anti-ice valves close.

(h)  
Return wing anti-ice control switch to OFF position.

(4)  
Test Ground Overheat Protection Circuit

(a)  
Remove wing TAI ground overheat thermal switch from left wing TAI manifold. (Ref 30-11-21 R/I). Reconnect electrical connector to thermal switch.

(b)  
Hold wing anti-ice control switch in GRD-TEST or TEST position. After both valve open lights dim indicating both valves open, heat thermal switch to 200 + 10/-0°F (thermal switch P/N 975-0062-001 or 3000-46-28) or 257 + 10/-0°F (thermal switch P/N 975-0062-002 or 3000-46-27) with Temp Cal heater, allow approximately 2 minutes heating to ensure thermal switch is heat-soaked, and check that both valve open lights go bright after 1 to 3 seconds and both valves close.

(c)  
Allow thermal switch to cool to ambient temperature then check that both valve open lights return to dim and both valves open.

(d)  
Release wing anti-ice control switch and reinstall thermal switch (Ref 30-11-21, R/I).

(e)  
Repeat steps (a) thru (d) for right thermal switch.

(f)  
Determine if there is any further need for electrical power on the airplane, if not, remove external power.

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Oct 20/84  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  30-11-0 Page 503 

C.  Duct Leakage Test
(1) 
 General

(a)  Wing leading edge distribution ducts can be leak tested using either engine bleed, APU, or an external air supply. Air supply above 2000F will cause the ground overheat thermal switch to cycle the wing anti-ice control valve.

(2)  
Prepare to Test Duct Leakage

(a)  
Remove wing leading edge lower access panels.

(b)  
Pressurize pneumatic duct.

1)  If APU air is used: a) Close engine bleed and air conditioning pack valves. b) Check that manifold isolation valve switch is either in OPEN or AUTO
position. 2) If engine bleed air is used, operate engines at idle speed to keep air temperature as low as possible. 3) If external air is used: a) Connect air supply to ground pneumatic connection. (Air supply should be
sufficient to provide a minimum of 7-psi manifold pressure). b) Apply external electrical power. c) Close engine bleed and air conditioning pack valves. d) Check that manifold isolation valve switch is in either OPEN or AUTO
position.
(c)  
Extend wing leading edge flaps and slats.

1)  If APU or external air supply is used, refer to Chapter 27, Wing Leading Edge Flaps and Slats.

(d)  
Check leading edge manifold and ducts for loose or broken brackets.

(3)  
Test Duct Leakage

(a)  
Hold wing anti-ice control switch in GRD TEST or TEST position, as applicable.

(b)  
Check distribution manifold and ducts for cracks, holes, and diffused leakage. Diffused leakage is allowable at duct seals and joints. Jet blasts are not permissible. Test for leakage by feeling in near vicinity of area being subjected to test.

WARNING:  CARE SHOULD BE EXERCISED NOT TO PLACE HANDS DIRECTLY ON HEATED DUCTS. DUCTS MAY REACH APPROXIMATELY 2000F IN NORMAL OPERATION AND UP TO 4500F IF OVERHEAT PROTECTION FAILS. SERIOUS BURNS CAN RESULT FROM DIRECT CONTACT WITH DUCTS.

(c)
Check leading edge flap skins for proper sealing (no leakage) at joints.

(d)  
Check leading edge flap and slat skin openings for diffused airflow and that openings are free of sealant and foreign matter.

CAUTION:  BLOCKED SKIN OPENINGS ALLOW ACCUMULATION OF WATER WHICH ACCELERATES SKIN CORROSION.

(e)  
Release wing anti-ice control switch.

(4)  
Restore Airplane to Normal

(a)  
　
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