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FAA Issues New Advisory Circular for Vintage Aircraft

July 2, 2009 — In a move intended to help keep vintage aircraft safely maintained, restored and flying, the FAA has issued new Advisory Circular AC 23-27, Parts and Materials Substitution for Vintage Aircraft, dated May 18, 2009. The AC, created by the FAA’s Small Airplane Directorate in Kansas City, Missouri, was a joint effort by the FAA in consultation with industry representatives including EAA and EAA’s Vintage Aircraft Association.

The publication gives guidance to both owner/restorers and FAA aviation safety inspectors when collecting information needed for an FAA approval when parts or materials used in the original construction of the type-certificated airplane are no longer available, or newer, more appropriate materials are now common and would be more appropriate to be used when repairing or replacing components.

EAA regularly works with the Directorate on matters related to small aircraft certification, including the recent Part 23 Process Certification Review. This AC, an outgrowth of the FAA’s recognition that obtaining exact original parts and materials was becoming problematic for aircraft restorers and owners, is one example where the agency has reached out for industry input to resolve a problem and EAA stood ready to help. When asked to comment about the process of creating the AC, Kim Smith, the manager of the Directorate, highlighted the cooperation the FAA received: "It is a great accomplishment to proactively work together and make it easier for owners to enhance the safety of their vintage aircraft."

The advisory circular details the level of information needed to document a part or material substitution, and while it is not intended as a “how to” manual, it does give specific examples of the types of changes that can be made with a simple logbook entry. Examples shown in appendix 1 include the use of ANSI specifications for bearing substitutions, or the use of generator or alternator belts made to an SAE specification.

Also detailed is the AC is the use of the same series of batteries in a particular airplane. If your airplane takes a series 35 battery, but your vintage aircraft is not on the PMA list, you do not have to obtain an STC to install the battery, as long as it weighs the same (plus or minus one pound) and it’s form and fit allows you to install it without modification to the original installation. Installation of a same series battery is a minor alteration, and becomes a simple logbook entry with the information needed in the entry spelled out in the advisory circular.

In appendix 2, clear guidance is also given regarding the substitution of 4130 steel instead of older, milder steel specifications in both non-structural and structural applications. Of course, structural modifications or repairs are still considered major repairs requiring FAA approval, typically done via an FAA Form 337.

Only gliders, or fixed-wing aircraft powered by reciprocating engine(s) which are unpressurised and have a certificated weight of 12,500 pounds or less, and which were certificated before January 1, 1980 (and follow-on type certificated models of the same aircraft) as well as those certificated under Group 2 Memos, (and ATC aircraft certificated by the Department of Commerce) are eligible for parts and material substitutions using AC 23-27 as approved data. Also, the change cannot cause a perceptible change to the certification basis for that particular airplane.

It is expected that this AC will be a living document, amended as new examples of parts and materials substitutions come to the attention of the FAA. While there is no set schedule for the revisions, the FAA’s Small Airplane Directorate is responsible for the creation and oversight of the AC. If you have suggestions regarding the incorporation of other parts and material substitutions, send them to:


FAA Small Airplane Directorate
Attn: ACE-100/AC23-27 comments
910 Locust
Kansas City, MO 64106-2641

We’d also like to see a copy of your comments; send the Vintage Aircraft Association a copy of your note. You can e-mail them to us at vintageaircraft@eaa.org.

You can download a PDF copy of Advisory Circular 23-27 here.

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