Honeywell issued Service Bulletin (SB) AS907 -72-9067 on December 12, 2016, in regards to the possibility of the LPT2 rotor blades separating on high-time engines (engines with greater than 8,000 hours of service). This may lead to vibration and damage to the turbine section of the engine.
This SB is applicable to all serial numbers of the AS907-1-1A (HTF7000) engines on the Challenger 300 aircraft. Compliance is recommended within 400 operating hours of this initial issue date.
Honeywell has categorized this as a CAT 1 SAFETY SB, meaning it may require urgent action. With that being said, this SB recommends compliance be within 400 engine operating hours.
Compliance of the SB requires the borescope inspection of the LPT2 rotor blades, PN 3035602-1, which have more than 8,000 hours of service. The inspection is looking for wear on the LPT2 rotor blade shroud Z gap contact area; if wear is found that exceeds light maintenance manual limits, operators will be required to replace the LPT2 rotor blades.
If the LPT2 rotor blades, PN 3035602-1, were already replaced prior to 8,000 hours of service, you do not need to comply with this SB.
This can be easily accomplished by Duncan Aviation’s Engine Rapid Response teams or during a regular scheduled maintenance event.