PARIS (Aug. 28, 2001)—Tire makers are pushing the aviation industry to accelerate its use of radial tires, which, they claim, offer safety and long-term cost benefits compared with bias-ply tires that predominate on today´s aircraft.
Though supposedly five times safer than bias-ply equivalents, radials have gained only 15 percent of the world aviation tire market since their launch 20 years ago, Group Michelin Chairman Edouard Michelin said at a news conference during the recent 2001 Paris Air Show.
“If special measures are not taken, the radialization rate will not reach much more than 50 percent 20 years from now,” said Mr. Michelin, who called for “coordinated efforts” by airframe manufacturers, airline wheel makers and regulators to introduce this technology faster.
Michelin has 28 percent of the global market for aviation tires, which it estimated at $415 million in 2000. The French tire group's share of the radial tire market is about 70 percent.
Also at the Paris show, Goodyear announced it had tripled radial aircraft tire production in the U.S. by investing $10 million in an expansion of its aircraft tire plant in Danville, Va.
Tire production began in June for commercial aircraft such as the Boeing 737 and Airbus A320 and military and private planes. The investment is a direct response to the growth of the radial segment of the aviation marketplace.
“Radialization is beginning to happen because of the advantages of radial tires,” Alex Dumm, Goodyear general manager for global aviation products, said in Paris.
But while airframe manufacturers, such as Airbus SAS and Boeing Co., specify radial tires for new aircraft, existing fleets generally only change from bias-ply tires when replacing models. Aircraft typically have service lives of more than 30 years.
Changing to radial tires sometimes involves costly modifications, especially to the aircraft wheel system. Since radials have only one bead wire, they generate more concentrated stresses on the wheel than a bias-ply tire, which can spread loads across three bead wires, said Pierre Desmarets, president of Michelin's aircraft tire business.
But radials' better wear resistance, lighter weight and capacity to take overload mean costs can be offset by lower maintenance, fuel consumption and quicker turnarounds, Mr. Desmarets said at the Paris Air Show.
While new aircraft are equipped with radials, Mr. Dumm conceded that bias-ply tires continue to dominate the aviation marketplace. “This is because of their long record of safety, dependability and performance and the significant cost of qualifying radial tires for aircraft already in service,” he said.
Goodyear´s Flight Radials for commercial aircraft weigh 10 to 20 percent less than comparable bias-ply tires, have reduced rolling resistance and can deliver more landings per tread, Mr. Dumm said. However, bias-ply tires “continue to be preferred by the majority of our customers, and we will continue to develop our bias-ply and radial product offerings to satisfy those customers' needs,” he added.
Goodyear, which claims about 35 percent of the overall aviation tire market, also produces aircraft tires at facilities in Bangkok, Thailand, and Sao Paulo, Brazil—the latter a revival of production after an eight-year hiatus. Michelin makes radial tires at Bourges, France, general aviation tires in Norwood, N.C., and, since early 2000 has produced small aircraft tires at Nong Kae, Thailand.
Simex Aircraft Tire Co., part of the Sime Darby Group of Malaysia, is gearing up to become the third company in the world to manufacture radial aircraft tires for wide-bodied aircraft, Simex Chairman Encik Ahmad Zubir said recently.
Under a deal with Boeing, the airframe manufacturer will advise Simex on its plans to develop radial main tires and nose tires for the Boeing 777, as well as nose tires for Boeing 737 aircraft. Simex also will have technical support from Sumitomo Rubber Industries Ltd. to gain Boeing and Federal Aviation Administration approval for the tire.
Michelin, along with Bridgestone Corp.—the world´s No. 2 supplier of radial aircraft tires—already is certified to supply the Boeing 777, according to an industry source.
Michelin also used the Paris show to debut its NZG-Near Zero Growth-radial developed for EADS, the French aerospace group that is working to restore the Concorde's certificate of airworthiness, which was withdrawn after the crash of an Air France Concorde on July 25, 2000.
The NZG features a high-modulus reinforcement ply material that limits tire tread extension to 3 percent—compared with 6 percent for a nylon-reinforced tire—and makes the tread more cut-resistant, Mr. Desmarets said. The NZG tire is 20-percent lighter than the older tires because it requires fewer plies to deliver the same level of reinforcement.
In destruction tests, the new tires broke into pieces that on average were 400 grams, though there was one piece above one kilogram.
Investigations into the crashed Concorde indicated that a 4-kg chunk of reinforced rubber projected from the tire had hit a fuel tank, leading to a fire and the loss of the aircraft.