Airworthiness Directive · Amendment 39-18175 · Turbine section
Bell Helicopter Textron Canada Limited
This AD applies to the following helicopters, certificated in any category:
(1) Bell Model 206L-1 with an Engine Upgrade Kit part number (P/N) 206-706-520-101 installed;
(2) Bell Model 206L-3, serial number (S/N) 51001 through 51612, except those with a Rolls-Royce 250-C20R engine installed under Supplemental Type Certificate (STC) No. SR00036SE; and
(3) Bell Model 206L-4, S/N 52001 through 52313, except those with a Rolls-Royce 250-C20R engine installed under STC No. SR00036SE.
We are adopting a new airworthiness directive (AD) for certain Bell Helicopter Textron Canada Limited (Bell) Model 206L-1, 206L-3, and 206L-4 helicopters. This AD requires installing a placard and revising the limitations section of the rotorcraft flight manual (RFM). This AD was prompted by several incidents of third stage engine turbine wheel failures caused by excessive vibrations at certain engine speeds during steady-state operations. The actions of this AD are intended to prevent turbine failure, engine power loss, and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
Within 30 days:
(1) Install placard P/N 230-075-213-117, or equivalent, on the instrument panel directly below the dual tachometer.
(2) Revise the Operating Limitations section of the Rotorcraft Flight Manual (RFM) by inserting a copy of this AD into the RFM or by making pen and ink changes as follows:
(i) In the Power Plant section, beneath the Power Turbine RPM header, add: Avoid continuous operations 71.8% to 91.5%.
(ii) In the Placards and Decals section, add: “AVOID CONT OPS 71.8% TO 91.5% N2” with the location identification “Location: Instrument Panel.”
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
