Is AD 2021-05-51 a recurring Airworthiness Directive?

No — AD 2021-05-51 is a one-time directive. Verify it was complied with in the aircraft's records.

Airworthiness Directive 2021-05-51

Q: Which aircraft does AD 2021-05-51 apply to?

AD 2021-05-51 applies to Pratt & Whitney Division — models PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, PW4090-3, PW4000. Serial/part conditions may narrow it to specific aircraft.

one-time

Official AD 2021-05-51 · FR doc 2021-04747 · 2021-03-09 · turbine engine

Airworthiness Directives; Pratt & Whitney Division Turbofan Engines

What this AD requires

The FAA is adopting a new airworthiness directive (AD) for certain Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofan engines. This AD was prompted by the in-flight failure of a 1st-stage low-pressure compressor (LPC) blade on a PW4077 model turbofan engine resulting in an engine fire during flight. This AD requires performing a thermal acoustic image (TAI) inspection for cracks in certain 1st-stage LPC blades and removal of those blades that fail inspection. The FAA previously sent an emergency AD to all known U.S. owners and operators of these engines and is now issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-05-51 applies to

MakesPratt & Whitney Division

ModelsPW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, PW4090-3, PW4000

Part-conditional — 52A241, 55A801, 55A801-001, 55A901, 55A901-001, 56A201, 56A201-001, 56A221.

Applies only to engines with a 1st-stage low-pressure compressor (LPC) blade, part number 52A241, 55A801, 55A801-001, 55A901, 55A901-001, 56A201, 56A201-001, or 56A221, installed.

Whether AD 2021-05-51 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 2021-05-51 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.