Aircraft Restoration and FAR 21.303
by HG Frautschy
Vintage Airplane, March 1992
The preparation of this article was coordinated with the office of the Aircraft Maintenance Division of the Federal Aviation Administration. Our thanks to the FAA for helping us clear up what has become a confusing issue for many restorers during the past year.
A little over a year ago, an article appeared in Aircraft Technician magazine written by an employee of the FAA in Washington, D.C. The contents of that short article dealing with the restoration of an Aeronca Champ wing spar has caused a number of airplane restorers quite a bit of trouble, as they found that the interpretation of FAR 21.303 had apparently been changed. They were taken by surprise when the FAA appeared to reverse a long standing approval policy, and would not allow the restoration of a spar using aircraft quality wood and the original spar as a guide. As it turns out, FAA management never intended to change their policy. Within this article, we will clear up the confusion regarding what you can and cannot do during the restoration of your aircraft.
Within the FAR's, there are many regulations concerning the maintenance of a Type Certificated airplane, but to a restorer, nothing is more important than FAR 21.303. To refresh your memory, here is the applicable text of that FAA regulation:
FAR 21.303 Replacement and Modification Parts
(a) Except as provided in paragraph (h) of this section, no person may produce a modification or replacement part for sale for installation on a type certificated product unless it is produced pursuant to a Part Manufacturer Approval issued under this subpart.
(b) this section does not apply to the following:
(1) Parts produced under a type or production certificate.
(2) Parts produced by an owner or operator for maintaining or altering his own product. (Emphasis ours HGF)
The key part of that regulation is paragraph b. Without exaggerating, that paragraph is the rule that makes possible the restoration of older aircraft. Without this FAR, it would be very difficult, if not impossible, to make replacement parts for antique and classic aircraft. When an aircraft is restored, there are times -when the engineering data is simply not available, for a variety of reasons - the company may not exist, copies are not available from the FAA, or the current type certificate holder may not be willing to allow the drawing to be released. (These days, the current holder of the Type Certificate generally will claim they are unwilling to release the drawing based on product liability.)
An interesting sidebar must be addressed at this point concerning the currency of an available drawing. Unless an AD has been issued against the particular part in question, the individual restoring that part is obligated to use only the blueprint and any added notes that were in effect at the time his aircraft was manufactured. It would seem a bit ridiculous to require a part to reflect all-, the subsequent changes made to a fuselage structure, for instance, that were required when the Vne of an airplane was later increased by almost 28%. If an AD was issued against that part, then any changes required would also have to be incorporated during the part's restoration. It would also be prudent to review any service letters from the manufacturer that deal the the part in question.
The writer of the above mentioned article further defended his interpretation in a letter to EAA's Washington Representative, Charlie Schuck. He stated that a restorer of a 7 series Aeronca could not replace his spars without using a PMA'd part based on his belief that there was no proof available to determine that the restored spar was equal to or better than the original, unless the part could be compared against the manufacturer's blueprint, which at that time was believed to be unavailable. FAR 43.13 requires that:
43.13 Performance rules (general)
(a) Each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller or appliance shall use the methods, techniques, and practices prescribed in the current . manufacturer's maintenance manual, or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques, and practices acceptable to the administrator, except as noted in FAR 43.16. (Authors note: Emphasis ours. For our purposes, 43.16 has little if do additional impact.) He shall use the tools, equipment and test apparatus necessary to assure completion of the work in accordance with accepted industry practices. If special equipment or test equipment or test apparatus is recommended by the manufacturer involved, he must use that equipment or apparatus or its equivalent acceptable to the Administrator.
(b) Each person maintaining or altering, or performing preventive maintenance, shall do that work in such a manner and use materials of such quality, that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness).
If I haven't lost you yet, here is the point of all this FAR quoting: if you, as an owner/operator of an airplane, decide to make a replacement part for your airplane, such as wooden spar, using FAR 21.303 as the basis, you must show your AI that it has been made in a manner equal to, or better than, the original in a way that is "acceptable" to the FAA in accordance with FAR 43.13. That part of the FAR is the area that is generating the problem. For more than 40 years, it has been acceptable for an aircraft restorer to use the old original wood spar of his airplane as the pattern to make a new one out of aircraft quality spruce. Stating on the Form 337 that the old spar was used as a pattern, that the spar was made from aircraft quality spruce meeting "XYZ" Spec and that all the old fittings were cleaned and inspected was, in the past, considered a manner that is acceptable to the Administrator. Regardless of the statements made to the contrary in the past year, it is still an acceptable method of repairing a wooden sparred light airplane, according to Larry Kephart, Manager of the General Aviation and Commercial Branch.
If you use material that is sold to you as conforming to an accepted industry standard, say, for instance, a Military Specification (Mil Spec) such as MIL-S-6073, you are under no further obligation to ensure that the manufacturer or supplier has indeed complied with that specification. As a matter of personal information and in the interest of self-preservation, you will most likely inspect your purchase as you do any other part of your airframe, but you, as the restorer, do not have to certify that the product meets the Mil Spec, if it is so identified. By using material that is aircraft quality by virtue of it meeting an accepted industry standard, you have met the major criteria for your part to be approved for a return to service by your AI.
Remember, however, that no one without a PMA can supply an individual with a piece of wood described as a "Spar". Unless the item was manufactured under a PMA, you simply have a piece of wood with which you may be able to restore your spar. Also, unless it is identified as meeting the Mil Spec for wood, it is not even a piece of wood that you can legally use on a Type Certificated airplane. Unless that airplane is ,maintained with materials that conform to the FAR's, its Airworthiness Certificate is in jeopardy.
By replacing the damaged spar, you have executed a major repair, so your AI must approve the repair, and he will need to know that the material was aircraft quality (it should be identified on the material itself and on your invoice), and what criteria was used to restore the part, i.e. original factory drawings, the original part, and any other supporting documentation. It should be noted that one of the tests in question, a "Brashness Test" (a test determining the toughness of a sample of wood), is currently included as a requirement within MIL Spec MIL-S6073. (MIL-S-6073 superseded AN-S-6 in 1950.) This testis called out in later Champion specifications detailed on the Champion, but not Aeronca prints of the same part.
Supporting documentation can take a variety of forms, including the original part. Needless to say, the nature of the part will determine if it can be safely reproduced. It does not seem likely, for instance, that anyone, even someone with the knowledge, is going to be sandcasting anew crankcase for his or her 65 horsepower Continental. But based on the track record of aircraft restorers for the past 40 or more years, it does not appear to be unreasonable to expect that a new rudder, or a new elevator, could be constructed using the old one as a pattern, using the same materials as the original as defined in the maintenance manual. The same can be said for the wooden spar of an older airplane. This type of repair has been safely done on light airplanes for many, many years. No one is going to be more concerned with the safety of his or her own airplane more than an aircraft restorer, and his or her expertise coupled with the knowledge of his or her AI has, for a number of years, been sufficient to ensure the safe reconstruction of these older airplanes. Many of these airplanes were hand-built, necessitating the individual fitting of an elevator, for instance, to a stabilizer. Certainly, as production methods became more sophisticated, parts were made that fit better and allowed interchangeability, but the basic fact that a human craftsman produced the part has not changed for over a generation. (Many may argue that only very recently has that method begun to give way to automation in light aircraft production.) The FAA publishes a number of helpful books on the subject, and one is considered one of the more comprehensive manuals on the subject. Advisory Circular 43.13-1A and -2A, Acceptable Methods Techniques, and Practices Aircraft Inspection and Repair was just updated and reissued within the past couple of years, and it contains a wealth of acceptable methods to maintain your airplane.
One additional item should be clarified. It is not legal for an A&P or an AI to manufacture a part and then sell it to you for use on your plane - that would violate the FAR governing the issuing of Parts Manufacturing Approval. Paragraph (b) of FAR 21.303 was put in place to allow the restoration of an airplane, but not as a method to allow individual A&P's or AI's to circumvent the rules governing PMA's. An A&P or AI can, however, supervise the work done by a owner/operator during the reconstruction of a part. Remember that if the work constitutes a major repair, a Form 337 must be produced and signed off by an AI.
There have also been questions concerning the "legality" of a part reproduced in this manner. In the past, the statement has been made that a part made this way is a "bogus" part. A bogus part is one the origin of which cannot be traced, or is not made in accordance with the FAR's. Since the construction and installation of the part would have to be approved by an AI, and then subsequently by the FAA if a Form 337 was required, the part would then be an approved part for installation on that particular model and serial number aircraft. The approval would not extend to any other aircraft of that model in the same manner as a PMA, since it is a one time approval, but other restorers could use the same information to present to their AI for an approval of a similar installation.
To put all this in perspective, it should be pointed out that the ability to restore our aircraft using FAR 21.303 as the basis for restoring a part is a right that should be guarded by not abusing the rule. By carefully producing a part for your own airplane, and following appropriate FAA and industry standards, it seems reasonable that many parts for your airplane can be safely restored. Remember that in the first place, these components were created by craftsmen and are made up with few complicated, difficult to manufacture parts. Be careful though. It should be obvious which parts are not appropriate to attempt a recreation of. Most, if not all restorers, would not give serious thought to reproducing an engine part, for instance. Using good judgment and tapping the expertise of the FAA books, such as AC 43.13-1A and -2A will make it possible to maintain an older airplane in excellent condition, and FAR 21.303 allows us to use our collective capabilities to properly restore a part to better than new condition.