From the Service Letter:
For airplanes flown in SEVERE Usage as defined in Section 2A-10-00:
• Airplanes that have more than 2,500 flight hours must accomplish this document within 10 flight
hours.
• Airplanes that have less than 2,500 flight hours must accomplish this document within 10 flight
hours upon reaching 2,500 flight hours.
From the Service Manual Section 2A-00-00:
(1) Operating Usage
(a) Severe Usage Environment
1 If the average flight length is less than 30 minutes, then you must use the Severe
inspection time limits.
2 If the airplane has been engaged in operations at low altitudes such as pipeline
patrol, fish or game spotting, aerial applications, police patrol, sightseeing, livestock
management, etc. more than 30% of its life you must use the Severe inspection time
limits.
Back to the SL:
For airplanes flown in TYPICAL Usage as defined in Section 2A-10-00:
• Airplanes that have more than 15,000 flight hours must accomplish this document within 10 flight
hours.