Is AD 2011-20-51 a recurring Airworthiness Directive?

No — AD 2011-20-51 is a one-time directive. Verify it was complied with in the aircraft's records.

Airworthiness Directive 2011-20-51

Q: Which aircraft does AD 2011-20-51 apply to?

AD 2011-20-51 applies to Pratt & Whitney Canada — models PT6A-15AG, PT6A-27, PT6A-28, PT6A-34, PT6A-34AG, PT6A-34B, PT6A-36, PT6A. Serial/part conditions may narrow it to specific aircraft.

one-time

Official AD 2011-20-51 · FR doc 2011-26840 · 2011-10-17 · turboprop engine

Airworthiness Directives; Pratt & Whitney Canada PT6A-15AG, -27, -28, -34, -34AG, -34B, and -36 Series Turboprop Engines

What this AD requires

We are adopting a new airworthiness directive (AD) for Pratt & Whitney Canada PT6A-15AG, -27, -28, -34, -34AG, -34B, and -36 series turboprop engines. This emergency AD was sent previously to all known U.S. owners and operators of these engines. This AD requires the removal of affected part manufacturer approval (PMA) replacement Timken Alcor Aerospace Technologies, Inc. (TAATI) first stage reduction sun gears and the interacting planet gears, from the propeller reduction gearbox assembly. This AD was prompted by failures of certain PMA replacement first stage reduction sun gears, manufactured by TAATI. We are issuing this AD to correct the unsafe condition on these products.

Which aircraft AD 2011-20-51 applies to

MakesPratt & Whitney Canada

ModelsPT6A-15AG, PT6A-27, PT6A-28, PT6A-34, PT6A-34AG, PT6A-34B, PT6A-36, PT6A

Serial-conditional — narrows to serials PC5-091–PC5-176.

Part-conditional — E3024765.

Applies only to engines that have had maintenance performed on the power section module involving first-stage reduction sun gear replacement since February 3, 2010, with a Timken Alcor Aerospace Technologies (TAATI) PMA replacement first-stage reduction sun gear, P/N E3024765, S/N PC5-091 through PC5-176, installed. The serial range given is for the sun gear, not the engine.

Whether AD 2011-20-51 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 2011-20-51 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.