The X-13 Vertijet was an early experiment in VTOL (“Vertical Take-Off and Landing”).
"Icons of Aviation History" is a diary series that explores significant and historic aircraft.
X-13 Vertijet, on display at the USAF Museum, Dayton OH
In the 1950s, the US military became intensely interested in “vertical take-off and landing” aircraft, dubbed VTOL. The Navy wanted to be able to pack more planes onto smaller aircraft carriers and to launch jet aircraft from the deck of a surfaced submarine, and the Air Force was looking for combat jets that didn’t need large vulnerable airbases or runways and which could operate from dispersed locations like urban parking lots.
The Ryan aircraft company, which had already developed the Fireball hybrid propeller/jet interceptor for the Navy, was already thinking about the concept. They thought they could produce a lightweight jet fighter which could be launched vertically, like a rocket, using a jet engine that was more powerful than the one used in the Fireball. By 1946, Ryan’s project caught the attention of the Navy, who wrote up a contract to research the technical issues further and if possible to construct a full-scale engineering version for testing and evaluation.
In March 1947, Ryan had three potential designs which they presented to the Navy. All three would be a small (23 feet in length) delta-winged aircraft that would use American-built licensed copies of the British Nene jet engine and would be steered during vertical take off and landing by “reaction control”, moving the exhaust nozzle around to redirect it to the desired position. The Navy gave the go-ahead to produce an unmanned version that would demonstrate the concept’s workability. It was known as “Model 38”. The resulting contraption looked like a bed frame wrapped around a jet engine, but when it first flew in October 1950 it did well enough to impress the Navy into funding further research.
At the end of the Korean War in 1953, however, the US military faced a budgetary axe, and Ryan, afraid that the Model 38 VTOL project would be cut, now approached the Air Force to offer a similar project. And indeed, as Ryan feared, the Navy cut off its funding, and the Air Force began to sponsor the project instead. Two manned research planes were authorized, and they were dubbed the X-13 Vertijet. The project was taken over at Ryan by a new design team.
The new X-13 was not very different from the version that had been planned for the Navy. It was a single-engine delta-wing which would eventually be armed with four 40mm cannon. The test models would be fitted with fixed landing gear so it could be evaluated in normal level flight before moving on to the vertical take-off and landing.
The first test flight was in December 1955, but it ended after just seven minutes when the plane developed a serious oscillation problem. Ryan added several stabilizers to the plane and tried again, and this time everything worked well—the plane was excellent in horizontal flight.
Things moved on to the vertical flight tests, which would use the new British Rolls-Royce Avon engine. For the initial test flights, the alierons and rudder were removed and the X-13 was fitted with wheels at the back of the plane to stabilize it during landings, which led to the nickname “Pogo”. For manned flights, these were replaced by two non-retractable metal “bumpers”.
After several successful unmanned tests, the first manned take-off and landing was in May 1956. The X-13 demonstrated that it could take off vertically from a metal launch tower (which doubled as a transport trailer), turn into horizontal flight to perform its mission, then return and land vertically, hooking itself to a metal wire on the tower which supported its weight on the ground. This was a tricky operation, specially since the pilot could not see the tower during landing and had to be talked in by a ground controller. If necessary, a set of tricycle landing wheels could be attached for a conventional take-off and landing, though this was mostly for testing and it was never seriously proposed that this would be done on an actual mission.
Both of the prototype X-13s carried out test flights, including a demonstration in Washington DC, until the project was ended in 1958.
Overall, the project was a success, and it demonstrated that vertical “non-aerodynamic” flight was a practical possibility. The Pentagon would go on to develop the technology further, but it was the British who introduced the first vertical-takeoff service jet, the AV-8 Harrier (which, unlike the Vertijet, performed its take-offs and landing from the horizontal orientation to give the pilot better visibility). The US would go on to utilize VTOL technology in the F-35 fighter-bomber.
Today the US Air Force Museum in Dayton OH has one of the Vertijet prototypes on display along with its launch tower. The other prototype is on display at the San Diego Air and Space Museum in California.
NOTE: As some of you already know, all of my diaries here are draft chapters for a number of books I am working on. So I welcome any corrections you may have, whether it's typos or places that are unclear or factual errors. I think of y'all as my pre-publication editors and proofreaders. ;)
