FAA Wants to Limit Fatigue Damage On Aging Commercial Planes

In the Notice of Proposed Rulemaking (NPRM) with a public comment period set to end on July 17, FAA proposes to "require that design approval holders [DAHs, or airplane manufacturers] establish operational limits on transport category airplanes.


Also, as an instructor, he's taught students for years how to calculate the fatigue-related operational life of various aircraft. Even though he's never worked as a specialist in structural fatigues or fractures, Eastlake says that it's always been his impression that operational-life predictions need to be done mathematically. Furthermore, critical pieces of these calculations have to be based on actual aircraft testing. When an aircraft reaches that mathematically calculated point, then it needs to be taken out of service.

It's also part of Eastlake's understanding that extensions of aircrafts' operational lives have been a possibility for years, although they are rare. The main reason for this is that the inspection schedules become too expensive.

As some media outlets reported, FAA estimates that its proposal would cost the industry $360 million. But left out of those accounts is the fact that these costs would be spread over 20 years. The agency also states that "the present value benefits" of the proposal will total $809 million due to accident prevention and a reduction in unscheduled maintenance and repairs, also accrued over the same 20-year time period. Moreover, out of the $360 million in total costs, only 10 percent of that would be incurred by airplane manufacturers. The remainder would be borne by operators.

Normally, one would assume that the $360-million figure should be subtracted from the $809-million figure to arrive at a total $449 million economic benefit over the next two decades. FAA did not respond to Air Safety Week's requests for clarification.

Another part of the NPRM that deserves a public airing, Eastlake says, would enhance current regulations, which only require that manufacturers analyze the fatigue-based operational life of a part that has a single flaw or a single crack. FAA now has proposed a similar but more detailed analysis, with the assumption that one part can have more than one crack.

The full NPRM is in the April 18 Federal Register (FR Doc. 06-3621; Docket No. FAA-2006-24281) starting on p. 19928. It also can be downloaded at http://www.access.gpo.gov/su_docs/fedreg/frcont06.html.

>>Contacts: Jim Hall, Hall and Associates, (202) 312-0600; Chuck Eastlake, Embry-Riddle, (386) 226-6000; Walter Sippel, FAA, (425) 227-2774

When Safety Information Doesn't Get to Operators

In its April 18 proposal on widespread fatigue damage in transport planes (see accompanying story), FAA says that design approval holders (DAHs) sometimes don't release data in a timely matter so airlines can efficiently respond to safety regulations. FAA gives five historical examples of this, which are reprinted below.

Thrust reversers, where it took 10 years to develop some service information airworthiness directive-related items;

Class D to Class C cargo conversions, where one type certificate (TC) holder did not develop the necessary modifications in time to support operator compliance and where several operators were unable to obtain timely technical support and modification parts from supplemental TC holders;

The Reinforced Flight Deck Door Program, where most operators had substantially less than the one-year compliance time originally anticipated because of delays in developing and certifying the new designs;

The Repair Assessment Rule, where some operators were required to develop their own data for FAA approval in order to meet the rule's compliance date; and

The Structural Repair Manuals, where operators are still awaiting DAH action to perform damage tolerance evaluations and establish inspections, even though the DAH committed to completing this activity by 1993.

[Copyright 2006 Access Intelligence, LLC. All rights reserved.]

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