1. Title of the invention
Repair scheme for oversizedbore diameter of collective bell crank used on ALH.
2. Field of invention
This invention is related to repair of smaller module of Helicopter Transmission System.
3. Use of invention
This invention is used to repair the collective bell crank of Helicopter Transmission System.
4. Prior art
This method is unique. There was no previous facility available. Item was rejected and quarantine for use.
5. Draw backs of prior art
Not applicable, as this is a new method developed for the first time.
6. Comparison between prior art and present invention
Not applicable, as this is a new method developed for the first time.
7. Aim of the invention
Aim of the invention is to repair of collective bell crank and use Helicopter Transmission system

8. Summary of the present invention
This repair scheme is used for repair of bore of collective bell crank which are worn out by the bush (mating parts) assemble on it due to dynamic loads by connecting rods. Collective Bell Crank are installed on lower control system of Integrated Dynamic System of Advanced Light Helicopter (ALH).Collective Bell Crank's bore use to wear out due to rubbing of bush installed in it during use while connective rods are operating for collective motion of helicopter.
9. Brief description
The repair scheme of collective bell crank having operations likeDisassembly of Teflon bushes, machining of bores, CD check, Masking, Nickel Plattingof bores, Assembly of Teflon bushes, Installation of Collective Bell Crank on Helicopter for testing/flying.
10. Statement of invention
This repair method has helped to repair the collective bell crank oversized bores through Nickel Platting& re-use again.

11. Detailed description of invention
The Collective Bell crank is a critical item of ALH Dhruv Transmission system. The function is to control and operate the collective motion of main rotor blade. It has one open cylindrical portion where two bushes are sitting.
Due to continuous movement of collective bell crank on swash plate, the excess wear on inner diameter is found during major servicing. The wear is cause to loosen the bushes or some case rejection of bell crank.

The repair scheme by hard anodizing of CBC(Collective Bell Crank) will give desired strength on surface of inner diameter to withstand the wear caused by it regular movement with longitudinal lever.
The Repair Scheme consists following operation for defective CBC.
1. Pre-machining of inner dia 76 mm to a maximum of 76.10 of full length from both end.
2. Crack detection check locally at machined area as per NDT-015 Standard.
3. Mask all other areas except bore which have been opened to 76.10 mm.
4. Hard Anodizing on bore of dia 76 mm to a length of 70(+l) mm at both side upto 0.1 mm (Min. on dia) as per HPS-201 Issue C Type -3 standard.
5. Installation of CBC on H/c for utilization.

Claims
1. Methods and operations use for repair of CBC for wear.
2. Material composition use to repair CBC by hard anodizing.
3. Drawing for repair scheme of CBC.