New rules governing the nation's increasing number of aging aircraft have been proposed by the Federal Aviation Administration.
If approved, the rules would bring about a significant change in the agency's policy regarding older planes.
The new rules would mandate specific safety modifications once the aircraft reach either a certain age or a certain number of flights.
At present, the safety of passengers depends on frequent aircraft inspections aimed at detecting such problems as cracking, corrosion and other forms of metal fatigue.
Frequent inspections did not prevent the Aloha Airlines accident last year, when a 19-year-old 737 jet had a section of its fuselage disintegrate during a flight, resulting in the death of a flight attendant.
"What the Aloha situation taught us is not to rely so heavily on the inspection method and the human factor," an FAA spokesman said.
The National Safety Transportation Board placed primary blame for the Aloha accident on the airline's maintenance program, and accused the FAA of not adequately monitoring such maintenance.
The airline and others dispute this conclusion, arguing that the type of cracks in the airline's fuselage that led to the accident are an industry-wide problem with aging jets.
To address the problem, the FAA is starting with Boeing 727s, 737s and 747s. Other types of jet will be addressed later this year.
"The rules for other planes will show the same change in philosophy," the FAA spokesman said. "Two separate task forces are coming up with the specifics."
Under the new system, Boeing 727 jets will have to be modified when they reach 20 years or 60,000 flight cycles (takeoffs and landings), whichever comes first. For 737s, the figures will be 20 years or 75,000 cycles, and for 747s they will be 20 years or 20,000 cycles.
The Aloha jet was closing in on 90,000 flight cycles.
The FAA rules will only cover U.S. carriers and will affect about 115 planes.
Modifications designed to reduce the possibility of major structural failure will vary according to the type of jet.
Among the potential changes are either structural reinforcement or replacement of wings, landing gear, fuselage, tail assembly and doors. Airlines would be given four years to complete the modifications.
The number of aging airplanes continues to grow, with the average age of American jets pushing 13 years.
Jets are built, theoretically, to last indefinitely--if they are properly inspected and maintained--though the economic cost to assure operational safety through more frequent inspections goes up after a certain period of service.
According to the FAA, the "economic design goal" of a plane is the length of time it can be in service before becoming too costly to be flown safely.
The economic design goal for the Boeing 727, 737 and 747 jets is 20 years, with the number of flight cycles varying according to the plane.
Location Is Important
Under the present system, airlines can use their aircraft for as long as they meet safety standards. But the longer planes are in service, the greater the chance of metal fatigue, corrosion and other problems.
Where the plane is used is another factor, since the NTSB says that corrosion is highly dependent on the environment.
For example, planes used near salt air or sulphur-producing factories develop corrosion problems before reaching the fatigue limits of their structures. These jets, to avoid safety risks, might need extra maintenance.
How much of the cost of making such modifications will be passed on to passengers through higher fares is unknown.
According to FAA estimates, the total financial impact of the modifications to airlines will exceed $140 million over the four-year period. And there will be ongoing costs for the carriers as their planes grow older.
Some carriers may prefer to buy new jets which, it has been argued, save the carriers money in the long run through greater fuel efficiency.
However, just because one airline buys new jets to replace older ones does not mean that the older aircraft will not be used elsewhere. Such jets may be sold, leased or chartered to other carriers--domestic and foreign--that cannot afford to buy new planes.
The likelihood of older planes continuing in operation rather than being retired is a key reason for seeking a mandatory retirement age for jets.
The FAA estimates that there are 1,700 jets worldwide in the 727 series, 1,100 in the 737 series and 680 in the 747 series. American aircraft are only a small part of the total.
For example, the FAA indicated that 20 American-operated 747s would be involved in the initial four-year period.
With the furor over aging planes, some airlines have even begun to cite the youth of their jets in advertisements.
And a bill has been introduced in the Senate that would require carriers to prominently display in each plane its age and the date of its most recent FAA inspection.
While this proposal is not considered very practical as a decision-making factor for passengers--who, after all, would already be on the flight when they see the age displayed--it does indicate the growing concern over aircraft age.
Putting the age of aircraft onto the airlines' computer reservations systems has also been discussed. Interested passengers would be able to ask about the age of planes on a particular flight.
You can send comments on the FAA's proposed new aging-aircraft rules to the Federal Aviation Administration, Transport Airplane Directorate, Docket 89 NM-60-AD, 17900 Pacific Highway South, C-68966, Seattle, Wash. 98168. The deadline is Friday.