Frank Piasecki, who died Monday at 88, built the second working helicopter in America in 1943 (following Igor Sikorsky) and then invented the tandem-rotor configuration that came to dominate heavy-lifting whirlybirds.

The two-rotor helicopters, which quickly became known as “flying bananas” (or “sagging sausages”) for their jointed fuselages, were the predecessors of today’s Army Chinook and Navy Sea Knight helicopters.

In addition to being one of the fathers of the conventional helicopter, Piasecki worked on a number of other vertical takeoff technologies. Among these was a floating platform dubbed the “Geep” (after Jeep), flying cars for the Army, and a giant combination of a blimp and four helicopters called the “Helistat,” developed to ferry tree trunks from virgin forests for the Forest Service. The Helistat, said to be the largest aircraft in the world at the time, crashed, killing one, during a test 1986 flight at Lakehurst, N.J. at the same airfield where the Hindenburg zeppelin exploded in flames a half-century earlier.

Piasecki grew up outside Philadelphia and worked while still in high school for a company that manufactured autogyros. He studied engineering at the University of Pennsylvania and aeronautics at New York University before opening an aviation consultancy with a Penn classmate. They developed the PV-2, a single-engine helicopter which Piasecki himself demonstrated to military and government officials at Washington’s National Airport in 1943. He later said he financed the trip to the nation’s capital by selling an engagement ring that was returned to him when his fiancée’s father found out what his line of work was.

Piasecki developed his first helicopter for the commuter market, the PV-2, and it came with foldable rotors to fit in a standard garage. The first working model was built mainly of discarded auto parts except for the innovative rotors. It was painted in silver and Maroon, the official Penn colors. But the commuter market, the darling of all the early developers, never emerged. It was with heavy-duty transport helicopters for the armed services that he had success.

The Navy showed special interest in Piasecki’s helicopter because Sikorsky was producing to capacity at the time for the Army. When a 1943 Senate investigation chaired by Harry Truman criticized the service for failing to tap the potential of helicopters, the Navy awarded a contract to Piasecki to develop the original bent-frame tandem-rotor helicopter. With Laurence Rockefeller and A. Felix DuPont as early investors, the Piasecki Helicopter Corp. was founded in 1946.

The early versions were nicknamed “Dogship” because the first test pilots were dogs. Working models came online too late for World War II. But the basic configuration eventually developed into the H-21 “Workhorse,” which, starting in 1953, made the Piasecki Helicopter Corp. the busiest in the nation. Piasecki’s helicopters were the biggest, could lift the most, and carry the most men. They were designed to be used as mobile hospitals in wartime, although they were not actually deployed until Vietnam.

Rockefeller and DuPont soon decided that Piasecki’s talents were stronger as a visionary designer than as an entrepreneur. His replacement as president and chairman, Don R. Berlin, took so many scalps in cost-cutting measures that his administration became known as the “Berlin Hairlift.” Piasecki Helicopter was renamed Vertol Aircraft Corp., and in 1960 merged with Boeing Corp. as its Rotorcraft Division.

After being ousted as president and then chairman of his company, Piasecki formed the Piasecki Aircraft Corp., dedicated to more experimental craft. His hovering “Geeps” were never actually deployed but made for dramatic photos. Piasecki drones trolled with sonar for Soviet nuclear subs. He also designed early tilt-wing aircraft that could take off like a helicopter and speed off like a plane.

He never stopped working on new designs. Most recently, his company was developing a new helicopter with a ducted fan at the rear for extra acceleration, called the “Speed Hawk.”

A gregarious man described as given to table-pounding in meetings, Piasecki also had a gentle side. He had been concertmaster of the University of Pennsylvania Orchestra and liked to break out his violin to serenade family and friends.

He held over 20 patents related to vertical flight, and he was awarded the National Medal of Technology in 1986. Two of his early crafts hang in the National Air and Space Museum, including a Dogship prototype and the first PV-2.

Frank Nicholas Piasecki

Born October 24, 1919, in Philadelphia, Pa.; died February 11 at his home in Haverford, Pa.; survived by his wife, Vivian O’Gara Weyerhaeuser; two daughters, and five sons, two of whom are executives of Piasecki Aviation; and 13 grandchildren.