Airworthiness Directive 99-01-08
one-timeAirworthiness Directives; Pratt & Whitney JT8D and JT3D Series Turbofan Engines
What this AD requires
This amendment adopts a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT8D and JT3D series turbofan engines. This action requires operators to remove and replace with serviceable parts, certain stage 7 through stage 15 high-pressure compressor (HPC) disks identified by part number and serial number. This amendment is prompted by a report of an uncontained failure of a stage 8 HPC disk during a takeoff roll that resulted in damage to the airplane. The actions specified in this AD are intended to prevent the failure of a high-pressure compressor disk due to Cadmium embrittlement, resulting in uncontained engine failure and damage to the airplane.
Which aircraft AD 99-01-08 applies to
Applies only to engines with stage 7 through stage 15 high-pressure compressor (HPC) disks installed that match the specific part number/serial number combinations listed in AD Appendix 1 (disk P/Ns visible in source text include 701407, 701507, 766007, and 774407, among others across stages 7-15; the full appendix table is truncated in the source text). Installed on but not limited to Boeing 707, 727, and 737 series airplanes and McDonnell Douglas DC-8, DC-9, and MD-80 series airplanes.
Whether AD 99-01-08 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.
How AD compliance is recorded
A valid compliance record (14 CFR 43.9) states:
Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.
Look up a tail number →Read the full directive (Federal Register)Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.