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HELICOPTER AIR SERVICE PROGRAM        161

of turbine blades. If an overtemperature has occurred the cost exceed $10,000 per incident.

During the first 6,112 T-58 engine hours, LAA experienced 7 reported overtemperature conditions, or one every 857 engine-hours. The changes in procedures developed at LAA to adjust stator vane to prevent the condition had the following effect : there have been 3 reported overtemperatures in the 28,410 ensuing engine-hours, or 1 every 9,470 hours, an improvement of 11 to 1. The cost in the first 7 conditions reported was $4 per engine-hour, and the improved procedure has reduced this cost to approximately 35 per hour.

LAA's techniques in effecting this improvement have been incorporated into the military T-58 maintenance program as Power Procedure Bulletin No. 140. 

Assuming that the military experience of reported overtemperature conditions paralleled that of LAA, and that the military received the benefit of the "fix," the following figure may be derived as a saving.

Basked upon an estimated 200 military S-61 aircraft operating 400 hours annually, 160,000 engine-hours would be operated annually by the military. The reduction in engine-hour costs of more than $3 ($4 to 35 cents), results in a direct saving of over $480,000.

Engine improvements introduced into military T-58 engines as a result of data and experience obtained from the commercial engine operations at LAA

[[3 column table]]
|   | GE Bulletin No. | Military Instructions technical order No., etc. |
| 1. Flexible shaft wear | CEB-107 | PPPC No.24. |
| 2. Fuel pump spline wear | CEB-98 | PPPC No.6. |
| 3. Front frame accessor drive bearing | CEB-132 |PPC(none). |
| 4. Stage 2 compressor disc crack | CIDIA-4583 | Program 58-B-37 |
| 5. Stage 1 compressor disc bridge | SEI-102 | Procedure Change O/H Manual,Navy. |
| 6. NBR-5 carbon seal | CEB-129 | 58-E-73 |
| 7. Compressor fouling-Power deterioration 7 percent stall limit and clearing procedures come from LAA data and experience. | SEI-101 Revised | Maintenance Manual, Revision, Navy. |
| 8.Stator vane schedule upspeeding | SEI-101 | PPB-140 |
| 9. Fuel control outlet fitting cracks | In process for both commercial and military. |   |
| 10. Overhaul performance improvement items | limits and procedure change (commercial and military) PPB-141. |   |
| 11. Service evaluations:
      A. Misco-coated stage 1 turbine buckets---- Evaluation 72-51-1
      B. Improved actuator mount-plastibule        72-31-10-01,
           lubrication and L-605 mounting feet     70-10-2-02
                                                     Revision 2.
      C. Phase 1A liner-------------------------- 72-42-01 O/H------ 10 
                                              product retrofit; 8 58-C-16
      D. PT deep drawn dampers--------------- At overhaul------ 3 58-R-44.
      E. No.3 bearing cage tang wear--- -----do------ Program No. 58-E-79
      F. No.4 bearing cage tang wear--- -----do------ Program No. 58-E-79

Source: General Electric Co., Small Aircraft Engine Division, Lynn, Mass.