WASHINGTON B — WASHINGTON -- The U.S. military services have decided to replace -- but not until 1996 -- a synthetic lubricant linked to a series of UH-1N Huey helicopter crashes that have killed 11 servicemen, even though investigators say they are virtually certain the grease did not cause the accidents.
Although aviation officials in the Air Force and Marine Corps said they see no urgency in replacing the synthetic lubricant, called Syn-Tech grease, some conceded that they eventually want to eliminate recurring doubts about its quality.
"Everybody's comfortable with the grease right now, but with any product, there's room for improvement," a Marine officer close to the accident investigations said last week.
The switch is not expected to begin until 1996, when development of a new, more versatile grease is scheduled to be completed by the Army, the largest user of military helicopters, said Maj. George Rynedance, an Army spokesman.
The Sun reported in late December that questions about the quality of Syn-Tech grease have been raised after the first of four fatal Air Force and Marine UH-1N helicopter accidents occurred in July 1990. These incidents, as well as two emergency landings by Air Force helicopters last year, have been linked to a suspicious mechanical problem involving the main drive shaft of the twin-engine UH-1N, a variant of the Army's single-engine helicopter made by Bell Helicopter Textron Inc. of Fort Worth, Texas.
According to interviews and documents obtained by The Sun, the services never established specifications for the grease, and, until the fatal accidents, relied mainly on contractor assurances that the grease was sufficient to meet the rigorous demands of military flying.
During a review of the grease last year, the lubricants center at Robins Air Force Base, Ga., "indicated a decision had been made not to establish a military specification for the grease due to cost considerations," said an Oct. 3 Air Force report warning of the UH-1N's "high accident potential."
The Navy, which oversees Marine aviation accident investigations, briefly suspended use of Syn-Tech grease after the first UH-1N crash killed two Marines and injured three others. Testing later indicated that the grease, while meeting Bell Helicopter's standards, might not have provided adequate lubrication to the helicopter's drive shaft coupling, located between the UH-1N engines and transmission, the report said.
Air Force analysts reported finding that the grease "most likely" used in a UH-1N that crashed in January 1991, killing two airmen, came from the same 1987 Syn-Tech batch used in the earlier Marine helicopter accident. That batch "was in the last year of shelf life at the time of both mishaps," the report said.
An Air Force laboratory then faulted the quality of two other batches of Syn-Tech grease, including one produced as recently as February 1991. A Navy mishap board also urged the services to buy a higher-quality grease after finding that Bell Helicopter lowered its contamination and temperature standards in 1984, possibly "to make the specification meet the product," the report said.
Last week, military officials said that the UH-1N accidents spurred Air Force and Navy interest in a program launched in October 1990 by the Army Research Development Center at Fort Belvoir, Va., to develop a multipurpose aircraft grease. At Air Force request last year, the Army tested several batches of Syn-Tech grease and then shared detailed plans and specifications for the new grease with the Air Force and Navy.
There has been no request to speed up development of the new grease, officials said.
"It originally was undertaken to reduce the number of proprietary and military greases required for helicopter servicing and maintenance," Major Rynedance said of the Army research. The goal is to develop a single grease, made to strict military standards, that can meet a wide range of temperature and lubrication needs in several kinds of helicopters, he said.
A replacement grease should simplify and standardize some helicopter maintenance procedures across the military, the major added.
The grease, which costs less than $6 a tube, is a synthetic material designed to withstand high temperatures and resist oxidation. It was introduced to the military in 1978 by Syn-Tech Ltd. of Addison, Ill., for use in UH-1N drive shaft couplings, military officials said.
Investigators are continuing to explore several possible mechanical causes for the helicopter accidents, but Marine officials said they are becoming more convinced that misaligned drive shafts are to blame -- even though the reason for alignment problems remains unclear.