Is AD 99-29612 a recurring Airworthiness Directive?

No — AD 99-29612 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 99-29612 apply to?

AD 99-29612 applies to Bell Helicopter Textron, Inc. — models 412, 412EP, 412CF. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 99-29612

one-time

AD 99-29612 · 1999-11-16 · airframe

Airworthiness Directives; Bell Helicopter Textron, Inc. Model 412, 412EP and 412CF Helicopters

What this AD requires

This amendment adopts a new airworthiness directive (AD) applicable to Bell Helicopter Textron, Inc. (BHTI) Model 412, 412EP, and 412CF helicopters. This action requires inspecting and measuring the thickness of certain main rotor yoke assemblies. This AD also requires adding 500 hours time-in-service (TIS) to the total time for main rotor yoke assemblies that measure below 0.478-inch thickness and noting the measurement and added TIS on the component history card or equivalent record. This amendment is prompted by a report of an emergency landing due to severe main rotor vibration on a BHTI Model 412 helicopter. Subsequent fatigue analysis indicates that the main rotor yoke assembly (yoke) does not have the anticipated service life when manufactured below 0.478-inch thickness. The actions specified in this AD are intended to prevent a fatigue failure of the yoke, loss of a main rotor blade, and subsequent loss of control of the helicopter.

Which aircraft AD 99-29612 applies to

MakesBell Helicopter Textron, Inc.

Models412, 412EP, 412CF

Serial-conditional — narrows to serials 33001–33213, 34001–34036, 36001–36204, 46400–46499.

Part-conditional — 412-010-101-123, 412-010-101-127.

S/N 33001-33213, 34001-34036, and 36001-36204 apply to Model 412/412EP; S/N 46400-46499 apply to Model 412CF. Applies only when main rotor yoke assembly P/N 412-010-101-123 or -127 is installed.

Whether AD 99-29612 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 99-29612 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.