Improved Reliability for Challenger 300 Engines: Honeywell HTF 7000 Service Bulletin AS907-72-9022

December 2024

Honeywell’s SB (Service Bulletin) AS907-72-9022 addresses a reliability improvement for the accessory gearbox bevel gears in specific HTF 7000 turbofan engines used in Challenger 300 aircraft. This bulletin applies to Part No. 3030001-4, Model No. AS907-1-1A, affecting engines with serial numbers prior to 118261.

SB AS907-72-9022 Background

Testing has revealed the accessory gearbox bevel gears, prone to pitting and wear, have not met their expected design life. Analysis also found that under extreme tolerance conditions, insufficient clearance in the towershaft end could lead to increased wear over time.

Improvements

This has prompted a redesign of the bevel gears aimed at reducing stress and optimizing the gear's contact pattern. At the same time, the oil jet for the bevel gear has been modified to ensure proper clearance with the new design. Additionally, the towershaft has been redesigned to improve end clearance, addressing potential wear issues.

SB AS907-72-9022 Required Actions

Honeywell recommends replacing the accessory gearbox bevel gears, bevel gear oil jet, and towershaft at the same time before the engine reaches 7,000 operating hours or at first access to the affected parts.

If you have any questions regarding this or other Honeywell Service Bulletins, please reach out to me at +1 402.730.8767, or via email at Shawn.Schmitz@DuncanAviation.com.

The photo image shows the components changed during Service Bulletin. Tower Shaft, Starter Shaft Bevel Spur Gear, Transfer Tube Lube Jet, Lower Tower Shaft Bevel Gear