82-03-02 DETROIT DIESEL ALLISON: Amendment 39-4305. Applies to all Model 250-C28B engines installed in, but not limited to, Bell Model 206L-1 rotorcraft certificated in all categories.
Compliance is required as indicated, unless previously accomplished. To preclude possible engine power loss resulting from intermittent or spurious activation of the N2 (Electronic) Overspeed Control System, accomplish the following before further flight:
(1) Disarm the aircraft installed engine N2 Overspeed Circuit Breaker by pulling the N2 Overspeed Circuit Breaker and secure by wrapping with tape or placing a Ty-wrap (or equivalent plastic tie strap) around the breaker stem.
(2) Install placard which states: "ENG OVSP CIRCUIT DEACTIVATED" in 1/4" or larger letters adjacent to N2 Overspeed Circuit Breaker. NOTE: The engine electronic overspeed test and the engine electronic overspeed trip system outlined in the rotorcraft Flight Manual will no longer function with the circuit breaker deactivated.
(3) Install a P/N AN814-4DL or Alternate Plug and P/N AS3084-04 Packing in the outlet port of the N2 Overspeed Solenoid Valve. Tighten and safety with lockwire. NOTE: This action further assures deactivation of the N2 (Electronic) Overspeed Control System. Primary overspeed protection is still provided by the mechanical power turbine fuel governor.
Upon request of the operator, an equivalent means of compliance with the requirements of this AD may be approved by the Chief, Chicago Aircraft Certification Office, Federal Aviation Administration, Central Region.
NOTE: Detroit Diesel Allison Commercial Engine Alert Bulletin CEB-A-73-2020 refers to this subject.
This amendment becomes effective February 4, 1982.