Is AD 2011-21-51 a recurring Airworthiness Directive?

No — AD 2011-21-51 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 2011-21-51 apply to?

AD 2011-21-51 applies to Cessna — models 525C, 525. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2011-21-51

one-time

Official AD 2011-21-51 · FR doc 2011-27596 · 2011-11-01 · airframe

Airworthiness Directives; Cessna Aircraft Company Airplanes

What this AD requires

We are adopting a new airworthiness directive (AD) for certain Cessna Aircraft Company (Cessna) Model 525C airplanes. This emergency AD was sent previously to all known U.S. owners and operators of these airplanes. This AD requires replacing certain lithium-ion batteries installed as the main aircraft battery with either a Ni-Cad or a lead acid battery. This AD was prompted by a report of a battery fire that resulted after an energized ground power unit was connected to one of the affected airplanes equipped with a lithium-ion battery as the main aircraft battery. We are issuing this AD to correct the unsafe condition on these products.

Which aircraft AD 2011-21-51 applies to

MakesCessna

Models525C, 525

Serial-conditional — narrows to serials 0001–0052.

Part-conditional — 9914788-1.

Applies only to airplanes with a lithium-ion battery, Cessna part number (P/N) 9914788-1, installed as the main aircraft battery.

Whether AD 2011-21-51 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 2011-21-51 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.