Airframe & System Upgrades

Rotor Hub-Shaft Nut
SB number : SB EC135-63-023
Applicable to version(s) : According to Service Bulletin
Reduces the wear of the spacer tube
Airbus Helicopters Deutschland proposes the installation of an improved rotor hub-shaft nut. The torque applied on the rotor mast during the installation process is presently counteracted by the friction force generated in the contact area of mast nut and lower mast bearing. The new design increases the preload on the rotor mast bearing in order to reduce relative movements between spacer tube and inner ring of upper mast bearing. This helps to reduce the wear of the spacer tube.
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+0.54 kg

On Request

On Request


  • Reduction of spacer tube wear, results in lower DMC rate
  • Inspection interval of the spacer tube is increased from 1600 Fh to 2000 Fh
  • No special tools required for re-torque of new mast nut
  • Reduced risk of chip occurrences after mast nut re-torque


Valid for all S/N. Compliance is optional. It is recommended to accomplish this Service Bulletin within the framework of the next periodical inspection of the spacer tube in accordance with AMM, 63-21-00,6-2 since this is part of the Service Bulletin. For obtaining the new 2000 FH inspection interval the spacer tube needs to be in the highest limits according to MSM (63-21-00, 6-2) [11].

Airframe 8 Hour(s)

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