AD 74-14-01

74-14-01 HARTZELL PROPELLERS: Amendment 39-1883 as amended by Amendment 39-1924. Applies to Hartzell T10173H()+(), T10176H()+(), T10178H()-(), and () T10282H()+() hard alloy type blades installed on but not limited to Model HC-B3TN-2( ), HC- B3TN-3( ), HC-B3TN-5( ), HC-B3TN-7( ), HC-B3TF-7( ), HC-B4TN-3( ) and HC-B4TN-5( ) propellers which are used on United Aircraft of Canada Limited PT-6A-( ) and AiResearch TPE 331( )-( ) series engines. These propellers are installed on but not limited to Swearingen SA-226 Series, Short SC-7 Series 3, Aero Commander 690 Series and de Havilland DHC-6 300 type aircraft.

Compliance required as indicated, unless already accomplished. Propellers with more than 1000 hours in service, excepting those with replacement blades having less than 1000 hours in service, as of the effective date of this Airworthiness Directive are excluded. Also, the following propellers having the serial numbers listed below are excluded:

PROPELLER MODEL - HC-B3TN-2; S/N - AG-275 and above PROPELLER MODEL - HC-B3TN-3; S/N - BU-4624 and above PROPELLER MODEL - HC-B3TN-5: S/N - BV-2210, BV-2213, BV-2214, BV-2216 and above PROPELLER MODEL - HC-B3TN-7: S/N - CV-7 and above PROPELLER MODEL - HC-B3TF-7: S/N - EX-3 and above PROPELLER MODEL - HC-B4TN-3: S/N - EA-255 and above PROPELLER MODEL - HC-B4TN-5: S/N - CD-62 and above

To detect blade cracks and prevent possible blade failures, accomplish the following:

(a) Propellers with less than 950 hours in service since new as of the effective date of this Airworthiness Directive must be inspected in accordance with Paragraph (e), within the next 50 hours time in service.

(b) Propellers with 950 hours in service, but not more than 1000 hours in service as of the effective date of this Airworthiness Directive must be inspected in accordance with Paragraph (e) prior to the accumulation of 1000 hours in service.

(c) Propellers whose total hours in service are unknown willbe assumed to have less than 950 hours in service since new and thus must be inspected in accordance with the requirements of Paragraph (a).

(d) In the event propellers with more than 1000 hours in service are equipped with replacement blades which have less than 1000 hours in service, such propeller blades must be inspected in accordance with the requirements of Paragraphs (a) or (b), as applicable contingent upon the time in service of the replacement blades.

(e) Inspect blades for cracks or defects in accordance with Hartzell Bulletin No. 105 dated May 22, 1974, or later Federal Aviation Administration approved revision, or an equivalent procedure approved by the Chief, Engineering and Manufacturing Branch, Great Lakes Region. Replace any cracked or defective blades before further flight with blades to which this Airworthiness Directive does not apply, or have been inspected in accordance with this Airworthiness Directive and found satisfactory.

(f) Upon request of the operator a Federal Aviation Administration Maintenance Inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration Great Lakes Region, may adjust the compliance time specified in Paragraph (b), if the request contains substantiating data to justify the adjustment for that operator.

Amendment 39-1883 became effective as of July 2, 1974.

This Amendment 39-1924 becomes effective August 22, 1974.