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Convair XF2Y Sea Dart: The Seaplane with a Jet Engine

Written by Colin Fifer

We’ve all seen seaplanes: those slow, propellor-driven ones with clunky pontoons jutting out where wheels ought to be. Now imagine that in wartime dogfights with fighter jets. That’s what the Navy had in mind back in the 1950s.

The Navy probably had a sleeker design and a more effective function in mind than your typical seaplane—after all, you won’t see an aircraft break the sound barrier lugging those cumbersome pontoons around. But the idea of being able to use the other 70% of the earth’s surface as an airfield for fighter jets swayed military opinion enough to make them invest in developing water-borne aircraft technology.

However, after years of research, test flights, and setbacks, the Navy got an idea that never left the ground. The prototypes remained an intriguing “what if?” in the minds of aircraft enthusiasts and military theorists. After all, it is fun to think about how “The Seaplane Jet Fighter That Never Was” could have turned out if not for a few factors.

So strap in and get ready for a bumpy ride. Today, we’re looking at the Convair XF2Y “Sea Dart.”

https://commons.wikimedia.org/wiki/File:F2Y_Sea_Dart_2.jpg#/media/File:F2Y_Sea_Dart_2.jpg

Water-Borne Aircraft

To understand how the Navy arrived at the idea of a sea-based supersonic jet fighter, we first have to look at the history of this type of plane.

Water-borne planes played an influential role in the development of aircraft. From the early days of aviation in the early 20th century, public and private industry alike relied on aquatic planes for the simple fact of convenience: surfaces of water were more abundant than airfields and required no construction.

Up through World War II, water-borne aircraft carried out reconnaissance, shipping, bombing, and coastal patrol missions. Many countries on both sides of the war put water-based planes to effective use. But, perhaps, no more effective than in the Pacific Theater.

The island-hopping warfare between the U.S. and Japan forced both sides to adapt their military aircraft technology. Seaplanes became a simple way to launch missions without the hassle of building runways on tiny islands or the worry of defending them from bombing or potential reinvasion.

By the end of the war, however, both sides had built enough airfields on suitable islands across the Pacific to accommodate fighter jets and other aircraft that required takeoff and landing on land. That, combined with the rapid development of new aircraft models, was pushing the mindset in the aerospace field past the need for water-borne aircraft. 

https://commons.wikimedia.org/wiki/File:F2Y_at_rest.jpg#/media/File:F2Y_at_rest.jpg

Developing at the Speed of Sound

The sole holdout to this line of thinking was the U.S. Navy. Even though supersonic planes (planes that could break the sound barrier) were at the cutting edge of aircraft development, and even the U.S. Air Force was incorporating them into their arsenal after World War II, the Navy found itself constrained to subsonic aircraft because of the limitations that came with flying from an aircraft carrier.

Supersonic aircraft needed too much runway to take off and operated at too great of speeds for aircraft carriers to accommodate them safely. As the end of the 1940s neared, the U.S. Navy faced a choice: remain with outdated subsonic planes or find a way to accommodate supersonic jets in their capabilities.

It was with the second goal in mind that the U.S. Navy opened up a contest to create a water-borne supersonic jet fighter.  

A San Diego-based company called Convair impressed Navy higher-ups with their proposal. In 1951, the Navy awarded them the contract. The team at Convair’s hydrodynamic research laboratory had proposed a simple plan. Why not take an existing aircraft they had already developed and throw some water skis on it?

That’s exactly what they did. Convair had already produced the Delta Dagger as part of the backbone of the Air Force’s defense against Soviet strategic bomber fleets (thanks, Cold War militarization!). The initial prototype Convair presented to the Navy was the same plane, just with water skis on the bottom and a few modifications to prevent water damage.

The Navy loved it. They ordered two prototypes, and, soon after, before they had even done a test flight, twelve more production models.

https://commons.wikimedia.org/wiki/File:XF2Y-1_off_San_Diego_1954-55_NAN1-81.jpg#/media/File:XF2Y-1_off_San_Diego_1954-55_NAN1-81.jpg

Bumpy Start

When the test flights started, Convair quickly realized they faced some significant obstacles. To understand the problems the Sea Dart had, let’s look at its design.

The XF2Y was a delta-wing aircraft, meaning its wings formed the same shape as the Greek letter delta (or a triangle to you non-Greek speakers out there).

The water skis on the bottom of the plane were retractable. Since they were not buoys, they could not keep the aircraft out of the water standing still. This meant that, when stationary, the plane was floating on its belly with its wings touching the water.

The water skis presented another problem: since they were not hydrofoil—a surface that creates lift in the water, much like airplane wings do in the air—they only provided lift to the plane in a similar way that recreational water skis do to people. They needed significant forward momentum to get the hull clear of the water.

This meant that the retractable water skis could only be extended once the plane had reached ten miles an hour or more. Starting with its belly submerged and dragging the back of its wings in the water made for a bumpy take off for the Sea Dart.

The vibrations made the plane difficult to control. And that was on calm waters.

Convair did not give up on their sea fighter, though. To combat the instability in the water, they replaced the two water skis with a single, non-retractable V-shaped ski down the middle of the plane’s belly. Though this improved the vibration problem, the plane’s performance was still not satisfactory.

A test pilot could only push the Sea Dart past the sound barrier one time during a shallow dive. Failure to reach those speeds during level flight kept the XF2Y from being classified as a supersonic plane.

https://flic.kr/p/cnQY9d

Grounded Before Take-off

Continual development and test flights of the plane continued. However, as the 1950s progressed, the Sea Dart’s fortunes did not. This was because of a few reasons.

In 1954, during a test flight of the Sea Dart, the press and spectators watched on as this oddity of a plane performed a low-level, high-speed fly by… then crashed. The impact killed the test pilot and all but disintegrated the plane. Subsequent test flights were suspended until redesign and safety checks could be carried out on the other prototypes.

As development sputtered along, advances in other areas of aerial technology outpaced the Sea Dart.

Thanks to the influence of the U.K. Royal Navy, the U.S. Navy implemented angled flight decks and automatic landing signals on their aircraft carriers. These steps greatly increased the safety and effectiveness of taking off and landing supersonic jets from carriers.

Following news of these advances, the U.S. Congress approved the construction of four new aircraft carriers with these designs implemented. This rendered the Sea Dart an ineffectual, watered-down option when compared to its counterparts.

By 1957, the Navy discontinued the program and retired the planes that had already been built. However, five years later, the Sea Dart would be pulled out and dusted off one last time, in name only.

In 1962, the Pentagon overhauled its naming system for aircraft. The XF2Y model was now the F-7A. Even though all surviving Sea Darts were housed in museums across the country, they now went by new names. This made the F-7A the only Navy plane to be renamed after being retired.

The remaining four Sea Darts are still on public display today. The Smithsonian in Washington, D.C.; the Air and Space Museum in San Diego; the National Museum of Naval Aviation in Pensacola, and the Florida Air Museum in Lake Linder International Airport all have the honor of housing the seaplane jet fighter that never was. 

Sources

http://www.aviastar.org/air/usa/convair_seadart.php

https://airandspace.si.edu/collection-objects/convair-xf2y-1-sea-dart/nasm_A19730275000

https://en.wikipedia.org/wiki/Convair_F2Y_Sea_Dart#Development

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