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Airworthiness Directive 99-24786

recurring
AD 99-24786 · 1999-09-24 · turbine engine

Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series Turbofan Engines

What this AD requires

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney JT9D-7R4 series turbofan engines, that requires an initial and repetitive inspections of certain High Pressure Turbine (HPT) stage 1 and stage 2 disks utilizing an improved ultrasonic inspection method performed at an approved facility when the disks are exposed during a shop visit, and if a crack indicating a subsurface anomaly is found, removal from service and replacement with a serviceable part. This amendment is prompted by the results of a stage 1 HPT disk fracture investigation which has identified a population of HPT stage 1 and 2 disks that may have subsurface anomalies formed during the forging process. The actions specified by this AD are intended to prevent an HPC disk fracture, which could result in an uncontained engine failure, damage to the airplane, and an in-flight engine shutdown.

Repetitive inspection. Re-inspect. The next-due date/hours depend on this aircraft’s time in service — a records report computes it from the logbooks.

Which aircraft AD 99-24786 applies to

MakesPratt & Whitney
ModelsJT9D-7R4, JT9D

Whether AD 99-24786 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:

Method of compliance — The specific action taken (inspected, replaced, modified) and to what revision.
Date — When the work was done.
Aircraft time — Total time in service / tach at compliance — how recurring next-due is computed.
Signature & certificate — The A&P/IA who returned it to service, with certificate number.
Is AD 99-24786 complied with on your aircraft?

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.