Balancing Weight Centered between Two Screws Figure 518/TASK 71-00-00-991-343- 33 (SHEET 3)
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(25) Note the correspondence of the screws in g.cm.
(Ref. Fig. 515/TASK 71-00-00-991-334)
Example:
- P06 = 412 g.cm.
- P04 = 303 g.cm.
- P05 = 361 g.cm.
(26) On a polar graph, take a g.cm scale and plot the corresponding
weights on the corresponding blade positions.
(27) Select 2 screws and draw 2 circles as follows:
(a) One circle with the end of the first vector as center and the length of the second vector as radius.
(b) On circle with the end of the second vector as center and the length of the first vector as radius.
(28) From the end of the first vector, draw a parallel to the second vector leading to the point of intersection of the two circles.
(29) The vector connecting the origin of the polar graph and the point of intersection of the two circles equals the vectorial sum of the two previous balancing screws. Example: (Ref. Fig. 519/TASK 71-00-00-991-349) The sum of P04 in position No. 3 and P06 in position No. 23 is 166 g.cm at 101 degrees.
(30) Add the vector found to the next balancing screw. Example 166 g.cm at 101 degrees and a P05 screw in position No. 12 give 236 g.cm at 229 degrees.
(31) Once the total initial weight installed on the engine has been calculated (for example: 236 g.cm at 229 degrees) the correction weight calculated in step (19) must be added. Example: 479 g.cm at 296 degrees.
(32) Proceeding as above, on a polar graph, add up these two vectors. Example: (Ref. Fig. 520/TASK 71-00-00-991-350)
- Initial weight = 236 g.cm at 229 degrees
- Calculated weight = 479 g.cm at 296 degrees
- Total weight = 609 g.cm at 275 degrees.
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Weight Calculation Example (Addition of Screw Weights)
Figure 519/TASK 71-00-00-991-349
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Example of Addition of Initial Weight and Correction Weight
Figure 520/TASK 71-00-00-991-350
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(33) Remove the initial screws and replace them by P07 screws.
(34) Then determine the screws and positions corresponding to the total weight in following figures: (Ref. Fig. 516/TASK 71-00-00-991-335) and (Ref. Fig. 517/TASK 71-00-00-991-337) and (Ref. Fig. 518/TASK 71-00-00-991-343) Example: 610 g.cm at 275 degrees. (Ref. Fig. 516/TASK 71-00-00-991-335)
- This figures indicates that the 275-degree position is between blades No. 9 and No. 10.
- The 610 g.cm correction weight corresponds to two P04 screws (604 g.cm). (Ref. Fig. 517/TASK 71-00-00-991-337, 518/TASK 71-00-00-991-343)
- The spinner therefore requires two P04 screws in positions No. 9 and No. 10, which represents exactly 604 g.cm at 275 degrees.
- The rest of the screws on the spinner will be P07.
Subtask 71-00-00-750-055
C. Vectorial Analysis
NOTE : If the vibrations registered during the next flight, after the
____ one-shot plot procedure, remain unsatisfactory the vibration level can be improved by calculating the correction factors (sensitivity, phase lag) specific to the engine to be balanced.
(1) Record the flight registered vibrations. Example: Assume that these vibrations, after addition of 479 g.cm at 296 degrees, are:
at 96 percent of N1 3.0 mils at 340 degrees at 84 percent of N1 2.0 mils at 320 degrees at 64 percent of N1 1.0 mils at 330 degrees
(2) Calculate the sensitivity and phase lag as well as the new balancing weight to be installed as follows:
CAUTION : WE RECOMMEND TO USE GSEM No.11 PRIOR TO USING THE DISKETTES
_______ IN ORDER TO PREVENT ANY HANDLING ERROR LEADING TO DESTRUCTION OF THE DATA.
CAUTION : THE PROGRAM WAS DESIGNED TO OPERATE ON IBM PC TYPE OR
_______ COMPATIBLE COMPUTERS, USING IBM DOS AND EQUIPPED WITH AN EGA OR VGA GRAPHIC CARD.
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