R (e) Calculate differences between removed blades and spare blades as
R below:
R D1 - D'1 = 185 - 175 = 010 cm.g (04 in.g) = F1
R D2 - D'2 = 160 - 020 = 140 cm.g (55 in.g) = F2
R D3 - D'3 = 140 - 025 = 115 cm.g (45 in.g) = F3
R D'4 - D4 = 195 - 025 = 170 cm.g (67 in.g) = F4

R (f) Determine the direction of corrections as follows:

R NOTE : When D is greater than D' the balance weight should be

____ R added close to the heavier blade. When D is lighter than R D' the balance weight should be added close to the lighter R blade.
R 1_ For blades No. 1 and 19, D1 is greater than D'1 and the
R balance weight should therefore be added close to the heavier
R blade: No. 1.

R 2_ For blades No. 18 and 36, D2 is greater than D'2 and the
R balance weight should therefore be added close to the heavier
R blade: No. 18.

R 3_ For blades No. 21 and 3, D3 is greater than D'3 and the
R balance weight should therefore be added close to the heavier
R blade: No. 21.

R 4_ For blades No. 35 and 17, D4 is less than D'4 and the balance
R weight should ore be added close to the lighter blade: No. 17.

R (g) Construct vectorial diagram as follows:
R (Ref. Fig. 408/TASK 72-21-00-991-342, 409/TASK 72-21-00-991-343)

R 1_ On a polar diagram draw vectors corresponding to moment weight
R difference calculated in (e) and orientated as in (f).
R (Ref. Fig. 409/TASK 72-21-00-991-343)

R 2_ Draw the resultant Fr representing the correction required
R from F1, F2, F3 and F4.

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R  NOTE : In this example, Fr is approximately 405 cm.g (159____ 
R  in.g) and orientated close to the balance screw No. 18. 
R  NOTE : When resultant imbalance direction is between 2 holes,____ 
R  the screw given in fifth column of referenced figures 
R  must be placed in the nearest hole. 
R  (h) Select balance screws as follows: 
R  (Ref. Fig. 410/TASK 72-21-00-991-344) 
R  1_  Find in the tables the values of the resultant Fr calculated
R  in paragraph (g). This indicates which balance screw must be 
R  installed. The screw in the fifth column of the table must be 
R  installed at location calculated in paragraph (g). 
R  NOTE : In this example, for a resultant Fr of 405 cm.g (159____ 
R  in.g), one centered screw P01 installed in hole No. 18 
R  and two lateral screw P02 installed in holes No. 17 and 
R  No. 19 provide a correction returning the fan to its 
R  initial balance condition. 
R  NOTE : Balance screws are identified by a number corresponding____ 
R  to their moment weight (P01-P02-P03-P04-P05-P06-P07) 
R  engraved on screw head. As it may be difficult to read 
R  the numbers due to erosion and pollution, the 
R  relationship between the screw reference and screw 
R  length is shown in. 
R  (Ref. Fig. 411/TASK 72-21-00-991-345) 
R  (2) Install balance screws. TORQUE the screws to between 65 and 75 lbf.in 
R  (0.73 and 0.84 m.daN). 
R  (3) Install the spinner rear cone (Ref. TASK 72-21-00-400-006). 
R  (4) Install the spinner front cone (Ref. TASK 72-21-00-400-005). 
R  (5) Remove the rubber mat from the air intake cowl. 
R  NOTE : If resultant imbalance FR defined in paragraph (g) is greater____ 
R  than 400 cm.g (157.5 in.g), do a vibration survey test after 
R  the static correction.

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R R  Balance Screws Figure 411/TASK 72-21-00-991-345
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 E 56-5B E E E R NOTE : You can do a vibration check (Ref. TASK 71-00-00-710-009) when

____ R you replace the fan blade(s) or when you install the same fan R blade set again. The results of the survey will show if it R necessary to do the fan trim balance or if the installation is R correct.
R 5. Close-up
________
R Subtask 72-21-00-869-080
R A. Make sure that the work area is clean and clear of tool(s) and other R items.
R Subtask 72-21-00-942-078
　
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