On Jan. 31, a jury in Baltimore's U.S. District Court awarded $3.65 million to the families of two men killed in 1981 when their helicopter, an Army AH1 Cobra equipped with the teeter-rotor system, crashed on a military training flight near Patuxent Naval Air Test Center.

The jury found that Bell Helicopter Textron, the manufacturer of the Cobra, was liable for the compensatory damages because of a design that permitted the hub of the helicopter's rotors to bump, then break the mast holding the rotors, thus dooming the helicopter and its occupants. Bell is appealing.

In reaching its decision, the jury rejected Bell's reliance on the government-contractor defense. That evolving defense generally holds that if a manufacturer builds to government specifications or, in some cases, has its specifications accepted by the government, the manufacturer is shielded from liability.

But that defense may be eroding in the face of a series of accidents in which design flaws are suspected. Crashes of two types of helicopters -- the Cobra and the Boeing Vertol Chinook -- have claimed 269 lives in recent years, including 46 in a 1982 crash in Mannheim, West Germany.

The government-contractor defense has been invoked in at least half a dozen military-aircraft accident cases working their way through courts around the country -- including mast-bumping cases involving teeter-rotor Bell helicopters and the Mannheim crash. The defense has been successful in some cases, and most attorneys specializing in the area think that the underlying questions will find their way to the Supreme Court.

"It's a very unsettled area of law," said Washington attorney Michael Pangia. He recently won a $450,000 decision against LTV Corp. involving the crash of a Navy aircraft in 1980 that killed the pilot. LTV's government-contractor defense was rejected by the judge in Baltimore's U.S. District Court. The decision is under appeal.

The government is protected against paying anything more than survivor benefits when an individual on active duty is killed, regardless of cause. If the fatal accident happens in a military aircraft, plaintiffs' attorneys sue the manufacturers while the Pentagon sits on the sidelines.

A major question is how safe military aircraft can be expected or required to be. Any airplane, in the words of aviation lawyer Donald W. Madole, is "a tissue of compromises" between performance and safety. Every extra gadget, every redundant system, may add safety but also adds weight and thus reduces performance or payload.

"Keep in mind," a Pentagon specialist said, "that when we are designing a plane that is going to get up in the air in a hurry to intercept people coming our way, sometimes we have to make decisions about that plane, and the effect is that it is not as safe as the civilian thing."

In civilian airliners, federal law mandates "the highest level" of safety. The manufacturer has total control over the design and shares with the airline (and its insurers) total liability. On a military aircraft, however, the armed services play a large role in determining the appearance and performance, but have no liability.

"The military contracting officer has the ultimate authority," an aerospace industry specialist said. "It's the one relationship where, if the government says 'Jump,' you say, 'How high?' "

That view is not universally held. Military contractors are coming under increasing scrutiny for their quality control and billing practices. Congress is demanding performance guarantees for some military procurements. Nonetheless, the question of control blurs the question of reponsibility.

The issue is significant for taxpayers, because if liability payments in military-aviation accidents become as universal as in civil plane crashes, "It is logical that things will cost more," said George Galerstein, chief legal counsel for Bell Helicopter Textron. Other aerospace industry specialists voiced the same view.

However, it has not happened yet, according to a Pentagon specialist who asked not to be identified. "Insurance is not a big-ticket item in our analysis of the costs," he said. "We would really start getting into questions about alternative ways to do this if the contractor said, 'Hey, I can't get any insurance at all and I'm not willing to bet my company.' "

The Pentagon does indemnify contractors in "areas with unusually hazardous risks or nuclear materials," the specialist said, but the Reagan administration has opposed legislative proposals that would extend indemnification further.

The Cobra helicopter accident at Patuxent illustrates how the legal issue can turn.

Bell's Galerstein and John Green, an Odessa, Tex., attorney who represented the plaintiffs, agreed in separate interviews that a critical element in the Baltimore jury's verdict is the fact that Bell never formally filed with the Army an Engineering Change Proposal (ECP), a recommendation to modify the rotor system to reduce the possibility of mast bumping. There had been studies by Bell and the Army indicating that the possibility of mast bumping could be reduced through modification.

However, Galerstein said, Bell did everything but send the formal letter because the Army had said it was not interested in paying for a modification. "While it is true we did not put the piece of paper in," Galerstein said, "we did everything a reasonable man would expect."

Green said, "I feel that if Bell had submitted an ECP we might have had different results. Then they Bell could have said, 'We did all this, but the Army didn't correct it.' "

Last September, before the Baltimore trial but after the mast-bumping controversy had broken in the Fort Worth Star-Telegram, Galerstein wrote an article in Aviation Litigation Reporter entitled "The Need for National Product Liability Legislation."

He wrote: "For all intents and purposes, the manufacturer has given up on having courts and juries understand his plight. When courts allow lay juries to decide whether an extremely complicated mechanism, about which there are valid, professional differences of opinion, was properly designed some 20 years ago, whether there was at that time based upon today's standards the proper apportioning of safety, performance, costs and utility, the manufacturer rolls his eyes in despair."