Brown Chevrolet In Philadelphia went out of business during World War II, but passersby could see lights in the dealership's windows at night. And if they peered inside, they could watch Frank Piasecki and his band of moonlighting engineers constructing one of the world's earliest helicopters.

When he died on February 11, at age 88, Piasecki was leading his company, Piasecki Aircraft, through flight tests of a new winged helicopter. Though virtually blind after his second stroke, in 1994 -- associates would read to him from technical manuals -- Piasecki remained what he had been for more than 70 years, an aviation innovator.

Piasecki was born in Philadelphia, in 1919, a birth year he shared with the helicopter's predecessor, the autogyro. In 1936, he and a partner, Harold Venzie, recruited University of Pennsylvania classmates to launch the P-V Engineering Forum. The members worked day jobs -- Piasecki was employed by a company designing a stainless-steel plane -- and designed helicopters at night.

Their first product, the PV-2, was only the second helicopter flown successfully in the United States. "We had to scrounge for parts," recalls Don Meyers, a key member of the forum and an engineer at its later incarnations, Piasecki Helicopter and Piasecki Aircraft. "We used the fuselage of a small lightweight airplane and a one-way clutch from a Studebaker, as well as parts we had made to our design. The first flights were just a few inches off the ground. Four or five of us would stand around ready to grab hold of it in case it got out of control. Frank practiced that way for quite a while before he flew it at any altitude."

The Army was already buying helicopters from Igor Sikorsky, whose company to this day plays Coke to Piasecki Aircraft's Pepsi (NYSE:PEP). "The Navy got interested, but they wanted a helicopter with much more payload," recalls Frank Mamrol, an engineer who joined the forum, in 1942, while still in high school. "Frank responded with the PV-3, nicknamed the Flying Banana. Sikorsky's design called for a single rotor. Frank's used two, which allowed the vehicle to carry larger loads, such as troops and heavy equipment, without throwing off the center of balance."

In 1945 the Navy placed an order for 20 helicopters; to handle the growth, Piasecki required additional capital. "We had to get outside investors, so we lost financial control of the company," says Meyers. "The new owners wanted to spend the company's resources on bigger contracts for what they were already building. Frank wanted to develop new products." In 1955, Piasecki Helicopter was sold to Boeing. Piasecki and some others left to form Piasecki Aircraft.

"Pi always had new ideas," says Joe Cosgrove, director of program requirements at Piasecki Aircraft. "Depending on who's counting, he came up with between 25 and 30 industry innovations." (In 1986, Piasecki was awarded the National Medal of Technology.)

Piasecki was also a gifted marketer. Meyers recalls the CEO and some others towing the PV-2 to Washington to show it off to the media. To attract publicity, "they stopped at a gas station and pretended to fill it up with gas and then fly it away.

"He was a good salesman," says Meyers. "He was a great engineer."