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Airworthiness Directive 98-26821

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AD 98-26821 · 1998-10-07 · airframe

Airworthiness Directives; McDonnell Douglas Helicopter Systems Model 369D, 369E, 369FF, 500N, AH-6, and MH-6 Helicopters

What this AD requires

This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369D, 369E, 369FF, 500N, AH-6 and MH-6 helicopters. This action requires visual inspections of the overrunning clutch retainer, carrier, housing, and pin for wear from spinning of the bearing outer race. This amendment is prompted by a report of inflight vibrations and subsequent investigations of three other overrunning clutches, which indicated wear of the bearing carrier due to spinning of the bearing outer race. The actions specified in this AD are intended to detect wear of other clutch components, excessive vibration which could lead to failure of the overrunning clutch, wear on the bearing carrier, and subsequent loss of power to the helicopter rotor drive system.

Which aircraft AD 98-26821 applies to

MakesMcdonnell Douglas Helicopter Systems

Whether AD 98-26821 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 98-26821 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.