U.S. Department
of Transportation

Federal Aviation

St. Louis
Flight Standards District Office

10801 Pear Tree Lane
Suite 200
St. Ann, Missouri 63074


July 2004 




Thought for the month..... If you're too open minded your brains will fall out!

Standard Parts… I think somewhere, every day, there is a discussion among owners and aircraft mechanics on the subject of "standard parts". FAR 21 permits the manufacturing of aircraft parts that conform to an established industry or government standard. FAR 43 (§ 43.13) speaks to the authorization to use permitted parts in type certificated aircraft. The following discussion comes from the Federal Register on the subject of replacement and modification parts in aircraft products. What follows is a digested version of that docket. I recommend that you read the complete text by opening <http://www.faa.gov/avr/sups/62fr9923.txt> for a better understanding of the FAA's intent.

What is a Standard Part? Section 21.303(b) of the Federal Aviation Regulations provides four exceptions to produce parts for sale to install in a type certificated aircraft other than by a Parts Manufacturer Authorization (PMA). One of these exceptions is for standard parts (such as bolts and nuts) conforming to established industry or U.S. specifications. The interpretation of an acceptable U.S. government or Industry accepted specification may include specifications that may be limited to detailed performance criteria, complete testing procedures, and uniform marking criteria. The specification must include all information necessary to produce and conform the part and be published so that any party may manufacture the it. Manufacturers of parts that conform to such specifications are excepted as standard parts.

Section 21.303(b)(4) has come to be understood by the aviation and manufacturing public as meaning a part, the specification for which has been published by a "standard setting organization" or by the U.S. government. Examples of such ``traditional'' standard part specifications include National Aerospace Standards (NAS), Air Force-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Aerospace Standard (AS), and Military Standard (MS).

The qualification and quality control requirements for any part installed on [an aircraft, engine, or propeller] is established by the design approval holder for that product. If a design approval holder utilizes a standard part design in a safety critical application (and/or an application requiring the part to perform outside its specified operating tolerances) but imposes qualification or quality control requirements beyond those of the standard specification for the part, then that altered part would no longer be a ``standard part''.

The marking of a part is the manufacturer's certification that the part conforms to the specification. The ability of the manufacturer to make that certification at the time of manufacture is based on the specification requirements that include production system requirements, test and acceptance procedures, and any additional internal quality control requirements.

Much of the componentry used in electronic devices are manufactured under standard industry practices, often to published specifications developed by standards organizations. Such standards development by these bodies is overseen by the Institute of Electrical and Electronics Engineers (IEEE), the IEEE Standards Committee, as well as the electrical and electronics industry, at large, who depends upon characteristic design standards for consistency in operation and performance.

Section 21.303 deals with the production of parts for sale for installations on type certificated products. However the installation of replacement or modification parts including owner/operator-produced and standard parts must be accomplished in compliance with part 43 of Title 14 of the CFR (Part 43). Substitution of a standard part with other than a standard part would require a demonstration of acceptability in accordance with part 43.

As I said at the beginning of this newsletter, the subject of standard parts will always be a matter of discussion. Some people who believe they are experts on this topic (or any other topic) sometimes have a somewhat liberal concept of what standard parts are. I would caution you that "standard" is not a generic term but rather a measure to conform to. It may be wise not to maintain too open a mind on this issue else your brains may fall out…

Upcoming Events

August 12
Grecian Steak House
1108 W. South By Pass
Kennett, MO
The Successful Cross Country
7-9:30 P.M.

August 18
Wings of Hope Hangar
18590 Edison Av
Spirit of St. Louis Airport
Light Sport Pilot and Light Sport Aircraft
5 to 8:00 P.M

August 19
Mid-Coast Training Center
18 Mark Allen Drive
St. Louis Downtown Airport
Part 135 Safety and Standardization Meeting

August 26
Mid-Coast Training Center
18 Mark Allen Drive
St. Louis Downtown Airport
The Successful Cross Country
7 - 9:30 P.M.

October 23
Mid-Coast Training Center
18 Mark Allen Drive
St. Louis Downtown Airport
8th Annual Helicopter Safety Seminar
9 A.M. to 4 P.M

Register at http//faasafety.gov for E-mail notification of safety seminars in the St. Louis District.

Good Maintenance is no accident
Steven Long
Airworthiness Safety Program Manager
1-800-322-8876 extension 4835