Robinson revises service letters on maintenance course, stabilizer Robinson has published an update to two service letters for owners and operators. The first is related to the component maintenance course for the R66, R44, and R22, and the second covers the symmetrical horizontal stabilizer retrofit kit for the R66. R22 SL-81D, R44 SL-67D, R66 SL-25D: Component Maintenance Course R66 SL-45H: Symmetrical Horizontal Stabilizer Retrofit Kit
