Air Wisconsin

We have petitioned Bombardier for a revision to SB 601R-27-160 and expect that revision prior to the close of commenting for NPRM, August 6, 2012. Our concern is for the vibropeening and cad plating of the pins. Hand vibropeening is difficult to control and cannot be done confidently to ensure the specifications (attached) are met. The specifications are very demanding. Among other details, depth must be between 0.001 and 0.006 and the height must be 0.10. Additionally, there is no method to adequately measure that depth to ensure the specifications have been met. We tried hand vibropeening MLG side stay shafts in the past and it resulted in our having to scrap 8 shafts (total cost $10, 000) because it was obvious the vibropeening did not produce the desired effect. As for the HSTA pins, one ship set is $8,500. A more confident marking method is required to ensure HSTA pins are not rendered unserviceable during marking. Bombardier has informed us that the preferred way remains unchanged: vibropeening per method 2D1 of Aerospace Standard AS 478, but an alternate method will allow use of ink marking, followed by the application of a polyurethane clearcoat The process methods will be detailed to ensure ink and clearcoat durability. The alternate method will be detailed in SB 601R27-160 Revision A. The Airworthiness Directive should be coordinated so that Revision A of SB 601R27-160 can be used by the operators. Trusting that Bombardier will have the SB revision by August 6, I will submit that revision to the NPRM when made available.