Regulatory Report

Fatigue life guidance

"This AC [advisory circular] provides information on approval of continued operational flight with known cracks in the structure of small airplanes, regardless of certification basis," the Federal Aviation Administration (FAA) announced January 18, 2005, in the Federal Register (FR Doc E6-450).

The document in question is AC 23-13A, titled "Fatigue, Fail-Safe, and Damage Tolerance Evaluation of Metallic Structure for Normal, Utility, Acrobatic, and Commuter Category Airplanes." Scattershot throughout the text are implications for maintenance:

"Provide data for inspection and maintenance instructions and guidance information to the operators. The data should include inspection methods, inspection thresholds and intervals."

And, ominously, the AC mentions that redundant structure has failed to prevent accidents: "There are well-documented cases in which a design thought to be fail-safe was not, and the design failed to prevent a catastrophic failure."

All of which bears on the fatal December 19, 2005 crash of a Chalk Air Gulfsteam G-73 seaplane, in which the spar broke from metal fatigue and the right wing separated from the airplane, resulting in a crash that killed all 20 aboard (see AM, Feb. 2005, p. 22). Whether or not this airplane met the criteria set forth in this AC is a matter for the National Transportation Safety Board accident investigators to determine. But, obviously, if the aircraft met the provisions of this AC, that is a matter of grave concern. And if it did not, which standards were not met, and is it because they were not required at the time the G-73 was modified?

What is to be done with aging general aviation airplanes

A summit on the continued airworthiness of the general aviation fleet will be held March 22-23, the FAA announced January 27, 2005, in the Federal Register (FR Doc E6-102). According to the announcement, "The average airplane in the [GA] fleet of the United States is approximately 35 years old. We expect the average age to continue to rise. By the year 2020, the average [GA] airplane will be almost 50 years old."

There have been several fatal accidents attributed to aircraft age, and the FAA said it is concerned about "service difficulty experience and reporting, modification and inspection programs, and continued field support from type certificate holders."

A technical panel will discuss these and other issues. The meeting will start at 8 a.m. each day at the Doubletree Hotel Overland Park, 10100 College Blvd., Overland Park, Kansas. Further details are in the announcement.