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Douglas A2D Skyshark: The U.S. Navy's Idea of an Engine Swap During the Cold War

Engine swaps will always be awesome. Something about taking an existing vehicle, gutting everything under the hood, and swapping it for more powerful hardware appeals to us in a visceral way. But this isn't just true of cars and motorcycles. It can apply to airplanes too.
Douglas A2D Skyshark 16 photos
Photo: United States Navy
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Lord bless it for being an absolutely mad machine, but the Douglas A2D Skyshark falls under this category. This is the story of the turboprop attack plane whose engine preferred rapid disassembly over functioning correctly. Of course, that's not the only gripe pilots and ground crew had of the Skyshark. The infernal, eardrum-destroying noise is also firmly on that list. But to understand why the Navy contracted Douglas to swap a turboprop into the airframe of a Skyraider, we need to remember the state of naval aviation after World War II.

In the years immediately after the capitulation of the Axis powers, an interesting dynamic took shape in the air forces and navies in both Eastern and Western countries. One in which piston-engine aircraft had already seen its last days of battlefield superiority in favor of novel gas turbine engines. Much of this new technology was scrounged by the French, British, Americans, and Soviets in the months following the fall of the Third Reich.

The breakneck pace of aeronautical development may not have slowed during the mid-to-late 40s, but that wasn't always true about the aircraft carriers meant to ferry military planes around. Even up until the Korean War of 1950 to 1953, most American aircraft carriers utilized wooden flight decks, sometimes with a thin layer of armor overtop. With far larger, heavier jet airplanes due to enter operational service any day, it was clear some form of intermediary aircraft was needed to bridge the gap between prop planes and turbojet aircraft.

More to the point, small Casablanca-class escort carriers in commission since 1943 needed something on their decks to counter aerial threats of ever-increasing technological prowess. The Douglas Aircraft Company of Santa Monica, California, was the team to answer the Navy's request. By June 1945, Douglas was just finishing the first production run of AD Skyraider single-engine piston attack planes when the U.S. Navy's Bureau of Aeronautics issued this peculiar design proposal.

Douglas A2D Skyshark
Photo: National Museum of Naval Aviation
A timeless classic in its own right, it's easy to view the AD (A-1) Skyraider as a sort of A-10 Warthog of the Korea/Vietnam era. In fact, the A-10 was developed around the idea of taking the concept of the Skyraider and applying it to modern technology. A stocky, rugged, dependable airframe powered by the same Wright R-3350 radial engine as the B-29 Superfortress that dropped atom bombs over Japan, the Skyraider could carry as just many bombs by weight as a quad-engined B-17.

Not to mention, Skyraiders were known throughout the years to tank insane levels of punishment from anti-air defenses and keep on fighting. There are even a few instances of "Spads," as they were nicknamed, turning North Vietnamese MiG-17s into a paste with their cannons in dogfights. It was just the kind of airframe the Navy wanted to fit with a turboprop engine for light escort carrier service.

Like an old Chevy truck waiting for an LS swap, Douglas employed the Allison Engine Company of Indianapolis, Indiana, to supply a turboprop powerplant for what became the A2D program. Coincidentally, Allison is actually a corporate brother to Chevrolet under General Motors. Instead of creating an entirely novel engine for the Skyshark, Allison opted for a different solution, the T40. Essentially, the T40 was two Allison T38 turboprops bolted together and driven via a shared reduction gearbox and two separate clutches, like a twin-rotor RX-7 with wings or something.

From the moment the first XT40 fired to life for the first time in June 1948, it plagued its engineers with mechanical problems and failures galore. Of course, the fancy twin-clutch transmission was a frequent cause of headaches. The fact the engine used similar vacuum lines to what you'd find on a Ford Flathead V8 wasn't much benefit either. It seemed in this primordial era of turbine engines, not much of anything was a known science just yet.

Douglas A2D Skyshark
Photo: National Museum of Naval Aviation
That's why it might be easy to write all the T-40's early issues as teething problems, except for the infernal sonic boom noise emitted by the T-40's twin contra-rotating propellers when they spun up to operating RPMs. No amount of R&D was going to fix that problem. Coincidentally, that was the same problem that doomed the Republic XF-84 Thunderscreech program that used the same engine. It can only be assumed that engineers figured 5,100 shaft hp on offer with the T40 would make everything worthwhile. The rest of the Skyshark's airframe was also subject to changes to match the new engine.

Exhaust ports needed to be fabricated on either side of the Skyraider's airframe to accommodate the T40's engine's business end. These ports added an additional 830 lbs in residual thrust. The wings and control surfaces were also enlargened and made thicker to support the aerodynamic forces of the higher speeds the Skyshark could now achieve. What resulted was a stocky, 18,720 lb (8,491 kg) bull of an airframe that could touch just under 500 mph (804 kph) at service altitude and climb at 7,960 ft/min (40.4 m/s). For an attack plane in the early 1950s, that wasn't bad at all.

It all sounds great on paper, especially for something built to launch from smaller aircraft carriers with shorter runways. Except, this performance only happened when the T40 engine worked properly. Something that, shocker, seldom ever happened. Sometimes, things even went catastrophically wrong. As was the case when the first Skyshark prototype crashed when one of the compressors failed. This alone shouldn't have brought the plane down. But a further failed transmission clutch prevented power from being redirected to the remaining compressor.

The crash instantly killed Cdr. Hugh Wood, the Navy test pilot behind the controls on December 19th, 1950, only months after its first flight in March of that year. In short, the engine inside Cdr. Wood's aircraft had slowly but surely destroyed itself piece by piece over the course of the flight, leading to the fatal accident. In subsequent examples, the Skyshark's reduction transmissions sported automatic de-clutching systems to prevent such accidents from occurring again. The extra R&D needed for this redesign added a staggering 16 months to the Skyshark's development.

Douglas A2D Skyshark
Photo: Gaijin Entertainment
The finished engine wasn't fitted to a Skyshark airframe until 1953, by which point the Korean War was already nearly its close, and Casablanca-class escort carriers meant to fly the new plane had already begun decommissioning. Couple that with a better understanding of how to make turbojets work reliably on carrier-borne Navy fighters by the mid-1950s, and the days were all but numbered for the ten pre-production A2D-1s built. Four of them never even flew.

And so, the A2D Skyshark faded into obscurity. Today, only a single example remains. It's on display at the San Diego Air and Space Museum Annex at Gillespie Field in San Diego, California. In most respects, that should have been the end of the Skyshark's story. But all of this changed on May 29th, 2019, with update 1.89 to Gaijin Entertainment's online vehicle combat game War Thunder.

On this day, the A2D was added to the game with a battle rating (BR) of 7.0 in air-realistic battles. The plane's been one of the most desirable premium American aircraft at its BR since its release. War Thunder pilots routinely laud the Skyshark for its supreme rate of climb and a hard-hitting arsenal of bombs ranging from 250 to 2,000 lbs. Coupled with 20 HVAR rockets, two Mk.13-6 torpedoes, and four 20 mm T31 autocannons, the Skyshark is one of the most fun premium planes to fly in the game. Its AN/APS-19 airborne target detection radar is pretty good too.

It just goes to prove that even if a military plane fails in real life, there's always a possibility it's still genuinely fun in the world's biggest vehicle combat game. Whether you're willing to shell out the in-currency to make it happen is another matter entirely.

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