(3)  
To know the depth of a blend at the leading or trailing edge, you must measure from the initial edge contour (the edge contour when the blade was manufactured).

 NOTE: A blend is an area where damage was repaired and made smooth.
____ To find the initial edge contour, use a straight edge.
 (a)  
You must add together the depth of each blend that is at the same position.

 (b)  
If the total depth of the blend is at its maximum limit from the initial edge contour, no more blends are permitted.

 (c)  
Do not measure from a raised material surface.

 (4)  
Blends directly opposite each other on leading and trailing edges are also added together and must not be more than the maximum depth of one leading or trailing edge blend.

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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
(5)  
Maximum depth blends which are on the leading and trailing edges must be separated by a minimum distance equal to the mean chordal length of the blade. Refer to AMM 72-31-02/801 for the mean chordal limits.

 (6)  
If two heavily repaired blades are adjacent, move the blades and their matched moment blades so that the damaged blades are installed symmetrically around the rotor. This will keep the engine vibration to a minimum.

 (7)  
The blending instructions in this procedure will make sure that damage at the surface and below the surface is removed. It is very important that the blending procedures are followed carefully when the repairs are done in the shop or on the wing. It is necessary to examine the repaired areas with Eddy Current or Flourescent Penetrant Inspection to make sure all surface damage has been removed.

 (8)  
If there is damage on the fan blade adjacent to the core inlet, it is necessary to examine the engine for Birdstrike (Foreign Object Damage) (AMM 72-00-00/601).

 C.  
This procedure for the inspection of the 1st-stage fan blades is divided into the tasks that follow:

 (1)  
General (this part of the procedure).

 (2)  
1st-Stage Fan Blade Airfoil Inspection of Surface Damage and Cracks.

 (3)  
1st-Stage Fan Blade Part Span Shroud Inspection for Damage.

 (4)  
1st-Stage Fan Blade Airfoil Inspection for Bends and Curl.

 (5)  
1st-Stage Fan Blade Platform Inspection for Damage.

 (6)  
1st-Stage Fan Blade Root Inspection for Damage.

 (7)  
Fluorescent Penetrant Inspection of the Airfoil and Shroud for Cracks.

 (8)  
Eddy Current Inspection of the Leading and Trailing Edges for Cracks.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
TASK 72-31-02-206-018-N00
 2. 1st-Stage Fan Blade Airfoil Inspection of Surface Damage and Cracks (Fig.601)
___________________________________________________________________
 A. General
 (1)  
This inspection is done when it is necessary for a detailed inspection during a regular engine inspection check, such as made necessary by the Maintenance Program, or when you think there is foreign object damage.

 B.
Equipment

 (1)  
Protective mat - Rubber Manufacturer's
 Association, Grade SC43, neoprene sponge, 1
 inch thick, approximately 5x6 feet with warning
 streamers attached (3 required).

 (2)  
Light source

 (3)  
Mirror

 (4)  
Gloves or a lint-free cloth

 C.
Access

 (1)  
Location Zone
 412 Engine 1 - LPC Hub
 422 Engine 2 - LPC Hub
 432 Engine 3 - LPC Hub
 442 Engine 4 - LPC Hub

 D.
Examine the Fan Blade Airfoil for Surface Damage and Cracks (Fig. 602).
　
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