AGMA 98FTM12

A program to repair gear teeth was initiated for AlliedSignal’sPower by the Hour customers. Repair turnaround times were becomingmore critical as the availability of new gears for the gas turbineengine overhaul and repair depot became scarce. We decided topartner with Air Gear Industries International because they are anFAA/JAA approved repair facility and have had considerableexperience in the refurbishment of aerospace gearing. Most othergear manufacturers did not want to participate because of thepaperwork and liabilities involved in obtaining FAA approval forFAA repairs. Also, because of the small number and variety ofgears, it would not be economical for a production facility toparticipate in this program. Power gears of AGMA quality Q11 – Q13were chosen to begin the program because the need was greatest andit would be the most rewarding even though it would also be themost challenging since minimum stock removal would be paramount toa successful rework. A number of gears from the Coast Guard fleetof helicopters were reviewed and based on knowledge of themanufacturing stock removal, blueprint case depth, and MaterialReview Board actions, it was concluded that most of the gears werereworkable. Working together with Air Gear, an acceptable procedurefor rework ensued including the establishment of inspectionrequirements. The refurbishment procedure was often more involvedthan just reprofiling the gear teeth. It also included honing,chrome plate and regrind of bearing journals, and unbolting andrebolting of two gears. In addition, a marking procedure fortracking and repair limits had to be established. A 150 hour or1000 cycle engine test was also required before final approvalcould be issued. To accommodate AlliedSignal’s requirements forquality and delivery, Air Gear used their specialized grindingmachines which they had developed for gear refurbishment. Thesemachines can be dedicated for individual parts and be available andready whenever a part is received. With a long term commitment fromAlliedSignal, Air Gear could justify dedicating these machines tothe work at hand. With the success achieved in the Coast Guardprogram we have gone forward onto the regional fan jet program, theALF 502/507 engine which has even more stringent requirements forgear tooth stock allowance and profile tolerances.

Edition:

98

Published:

10/01/1998

Number of Pages:

21

File Size:

1 file , 1.1 MB