2) Examine the components that follow and look for paint or primer discoloration, blistering, and structural damage:
NOTE: Damage is scoring, metal transfer, and/or
____ displacement of material.
NOTE: Discoloration is green primer that has turned brown
____ or black and/or enamel turned yellow, brown, or black.
a) The outer diameter of the axle sleeve
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747-400 MAINTENANCE MANUAL
b) The inner diameter of the axle
WARNING:_______ THE POWER CABLE OF THE BORESCOPE MUST BE IN A
GOOD CONDITION. IF THERE ARE CIRCUMFERENTIAL
CUTS, FRAYED AREAS, OR RUPTURES TO THE EXTERNAL
RUBBER COVER OF THE CABLE, INJURY TO PERSONS CAN
OCCUR.
c) Examine the green primer on the inner surfaces (bore) of the axle with a borescope. 3) If no damage, discoloration/blistering is found, you can leave the axle in service as it is.
NOTE: No further inspections to the axle are necessary.
____
4) Apply grease/CIC to the axle inner diameter. 5) The wheel interface for the tire pressure indicating system
(TPIS), if it is installed (AMM 32-45-12/401). 6) Install the wheel and tire assembly (AMM 32-45-02/401). 7) If damage to the axle is found, remove and replace the
axle.
8) If the paint/primer shows only a small discoloration on the OD and ID of the axle do the heat damage inspection when the airplane goes back to the primary base.
NOTE: Do not land the the airplane more than three times
____ before you do the complete inspection.
9) Locally strip off the discolored or blistered paint and examine the cadmium (or cadmium/titanium) plating.
NOTE: Such damage can cause cadmium embrittlement of the
____ steel substrate. The damage is not always found by non-destructive tests such as ammonium persulphate etch.
10) Examine the cadmium (or cadmium/titanium) plating.
NOTE: Such damage can cause cadmium embrittlement of the
____ steel substrate. The damage is not always found by non-destructive tests such as ammonium persulphate etch.
a) Look for a white oxide material, and blistered or melted (balled up) cadmium plating.
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11) If the plating shows signs of heat damage, replace the axle.
NOTE: Cadmium embrittlement of the axle cannot be
____ eliminated through overhaul methods. Boeing suggest the axle be discarded.
12) If the cadmium plating no signs of heat damage, do the Ammonium Persulfate Etch Inspection.
TASK 05-51-17-212-036
3. Ammonium Persulfate Etch Inspection of the Axle
_______________________________________________
A. General
(1) Do this inspection to find if the high strength steel that showed sign of heat damage has changed.
(a) It will look for a change in the temper or heat treat properties.
WARNING:_______DO NOT BREATHE THE FUMES OF THE SOLVENTS OR ETCH SOLUTIONS. DO NOT GET THEM IN YOUR EYES, ON YOUR SKIN, OR ON YOUR CLOTHES. INJURY TO PERSONS CAN OCCUR.
(2) This inspection can occur on the components of the landing gear axles.
(a) Discolored or blistered paint or plating shows that heat has affected the paint or has changed the temper of the axle. 1) When this occurs, the ammonium persulphate procedure must
be applied to the damaged part of the axle.
NOTE: This procedure can be done on the outer surface of
____ an axle while the axle is still on the airplane.
NOTE: This procedure to the inner surface (bore) of an
____ must only be done in the maintenance shop.
B. References
(1)
AMM 32-41-15/401, Landing Gear Brake Unit - Removal/Installation
(2)
AMM 32-42-04/401, Wheel Speed Transducer - Removal/Installation
(3) 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747-400 AMM 飞机维护手册 限制/维护检查(50)
