Airworthiness DirectiveEASA AD US-2020-22-07

Nacelle / Pylons - Excessive Pylon Pitch Vibrations - Rotorcraft Flight Manual - Revision

Published: Nov 11, 2020
Effective: Nov 18, 2020
Deadline: Nov 18, 2020

AI-generated summary of the official EASA document. Verify against the PDF before acting.

What to do

Affected operators must revise the Rotorcraft Flight Manual as specified before further flight, incorporating the new cautions related to vibration events. The revision can be performed by a pilot holding at least a private pilot certificate and must be recorded in the aircraft maintenance records. Comments on the AD are invited until December 18, 2020, but compliance is mandatory by November 18, 2020.

Summary

The Federal Aviation Administration's Airworthiness Directive 2020-22-07 is a final rule affecting all Bell Textron Inc. Model 412, 412CF, and 412EP helicopters. This directive addresses an unsafe condition related to excessive pylon pitch vibrations that have caused cracked main gearbox support cases. The AD mandates revisions to the Rotorcraft Flight Manual to include cautions for pilots regarding vibration events during specific flight conditions.

What changed

This new airworthiness directive requires operators to revise Section 2, Normal Procedures, of the Rotorcraft Flight Manual for affected Bell 412 series helicopters. The revisions add cautions under 'BEFORE TAKEOFF' and 'IN-FLIGHT OPERATION(S)' about handling sudden increases in one-per-rev vertical vibrations linked to forward cyclic and collective inputs at certain rotor RPMs when the skids are in contact with the ground. This AD is an interim action prompted by accident investigations and multiple reports of structural failures.

Why it matters

This AD is critical for aviation professionals because it addresses a potentially catastrophic structural failure of the main gearbox support case caused by vibration issues. Operators and maintenance teams must be aware of the new flight manual cautions to prevent unsafe flight conditions and ensure continued airworthiness. Compliance helps mitigate risks of reduced helicopter control and enhances flight safety for Bell 412 series helicopters.

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New ADs and bulletins for Bell Textron Inc. (Bti) 412, Textron Inc. 412, Textron Inc. 412CF and Textron Inc. 412EP, summarized like this page, every Monday.