In the 1950s, some in naval aviation believed that pure jet aircraft weren’t ready to operate from ships at sea. Some naval aviators and aero engineers wanted the Navy’s carrier air wings to be equipped with aircraft powered by turboprop engines – gas turbines that drive propellers.
This series “Brilliant Mistakes” is devoted to innovations that promised to revolutionize warfare – but didn’t. Ever since humans invented longbows, the stirrup, gunpowder and the airplane, brilliance and innovation have made militaries progressively more lethal.
Sometimes, however, a brilliant idea turns to be a brilliant sidestep. A March 23, 1953 press release by Douglas Aircraft told the world that the innovative new, turboprop-powered A2D Skyshark carrier-based attack plane possessed “the latest design innovations” and would “outstrip all its predecessors in performance.”
The Skyshark had adherents in the Navy who were searching for an alternative to early turbojet engines that performed poorly.
They didn’t find one.
“There was a pretty good-sized group of people who thought turboprop power would be the only answer for carrier aviation, that jets would never do it,” said Hal Andrews, who was an aeronautical engineer in the Navy’s Bureau of Aeronautics (BuAer). “They believed turboprops offered greater reliability and staying power.”
The gas turbine engine has been wonderfully successful in other applications – consider the UH-1 Huey helicopter or the C-130 Hercules airlifter – but even having an all-turboprop carrier air wing was only a very short-lived idea. What lasted longer was the belief that a turboprop plane would be ideal to operate from the Navy’s Casablanca class of relatively small escort carriers. But even if a turboprop warplane had been a good idea, the A2D Skyshark wasn’t.
“It was a dog,” said Andrews.
When Rear Adm. A. B. “Abie” Metzger, BuAer class desk officer for the A2D, inspected a mock-up of the aircraft in September 1947, he shook his head. “The Navy isn’t going to use a big monster like that as a fighter and it probably isn’t much good for attack, either,” said Metzger. The biggest problems with the Skyshark, Metzger later said, were:
- the troubled T40 turboprop engine; and
- the Navy’s reluctance to accept an aircraft so large and heavy.
Pros and Cons
Advocates, including Capt. Seldon B. Spangler, director of the powerplant division at BuAer, had high hopes for the Allison XT40-A-2 turboprop engine, which consisted of two T38 engines linked to a common gearbox and intended to provide 5,100 shaft horsepower.
Conceived as a derivative of the piston-powered AD Skyraider and intended to share common design features with that aircraft, the A2D was a wholly new plane by the time pilot George Jansen completed its long-delayed first flight on May 26, 1950 at Edwards Air Force Base, Calif. The aircraft experienced heavy low frequency vibrations and after only two minutes Jansen had to land on the dry lakebed only five miles from his takeoff point. Flights were resumed the following month and the outbreak of the Korean War on June 25, 1950 highlighted the need for a formidable, carrier-based attack aircraft.
The XA2D-1 Skyshark, with the “X” connoting “experimental” status, had a wingspan of just over 50 feet, weighed 18,720 pounds when fully loaded, and had a maximum speed of 501 miles per hour. In terms of its footprint on a carrier deck, it was a behemoth. Even though the Skyshark had to be grounded for several months later in 1950 while engine problems were addressed, the Navy had ambitious plans and placed orders for 331 production Skysharks.
Flight tests resumed in October 1950 and were plagued by gearbox failures, vibration, bearing failures, overheating of the fuselage around the exhausts, and throttle control issues.
Unfortunately, problems persisted. A flight by what was then the only prototype on Dec. 19, 1950, ended in a crash landing on the dry lake that was fatal to Navy pilot Lt. Cmdr. Hugh Wood.
The second aircraft was delayed, had its engine modified extensively, and still did not perform to specs. Douglas engineer Edward Heinemann was overheard saying that the Skyshark had “grown like topsy” while in development and that a smaller, simpler warplane could carry out the carrier-based attack mission. By the time Jansen had to bail out of a Skyshark on April 5, 1954 – suffering significant injuries – the Korean War was over, Casablanca-class escort carriers were being mothballed, the A2D program was close to termination and Heinemann’s idea for a smaller “hot rod” was gaining prevalence.
In the end, just 12 Skysharks were built and only eight ever flew, including the two that crashed.
At a time when the end of the Skyshark program was not yet formalized, the Navy began testing another new attack plane from the same stable, the lightweight, pure-jet A4D Skyhawk, later called the A-4.
The Skyshark continued flying for many months after the Navy formally terminated the program in August 1954. That month, the Air Force completed the first flight of a new transport, the C-130 Hercules, which has gone on to demonstrate that turboprop power can make a huge contribution. It would be no exaggeration to say that the gas turbine revolutionized rotary wing aviation, as demonstrated in 1955 by the Army’s XH-40, which became the UH-1 Huey.
The A2D contributed to aeronautical knowledge in many ways, but the primary contribution was its powerplant. Although turboprop power rarely proved practical for combat planes – Britain’s Westland Wyvern was the only turboprop attack plane ever to enter operational service or fly in combat, as it did at Suez in 1956 – it became the standard for heavier planes. The XT40, not successful itself, was the forerunner of thousands of Allison turboprop engines used on the C-130, P-3 Orion, E-2 Hawkeye, and many turboprop aircraft.
No turboprop-powered attack aircraft ever flew in combat from a U.S. Navy carrier deck. The North American XA2J-1 Savage, a T40 turboprop development of a piston-engined bomber, was as unsuccessful as the Skyshark, although its test program was mercifully shorter-lived. One of Heinemann’s most brilliant designs, the Skyhawk, made its first flight on June 22, 1954, and by that time pure jet engines were the wave of the future.
In the end, the A2D Skyshark became a footnote in Navy history, doomed in part by problems with its engine, gearbox, and contra-rotating propellers but, in the end, eclipsed by jet-powered aircraft, which turned out to be the wave of the future, after all.