By Nathan Pfau, Army Flier Staff WriterOctober 26, 2017
FORT RUCKER, Ala. -- Before the Osprey, the Harrier and F-35 brought vertical lift to fixed-wing flight, one experimental aircraft was taking its licks to try and perfect this form of flight.
The Ryan XV-5 Vertifan was an aircraft that was ahead of its time, and although the aircraft was deemed a failure, technology from its propulsion system later went on to power the flying behemoths of today, according to Bob Barlow, U.S. Army Aviation Museum volunteer and former Aviator.
The XV-5 was borne out of a need for an aircraft that had the versatility of vertical takeoff combined with the speeds of fixed-wing flight, said Barlow, and thus a program was developed by General Electric in the early 1960s to fit that need, and in 1961 GE won a contract with the U.S. Army to develop its fan-in-wing concept design.
The Vertifan would be powered by two GE J-85 turbojet engines, which functioned as normal engines while in level flight, but while in hover flight, the exhaust gasses from the engines were redirected through a series of ducts to provide power to lift fans that were located in the wings and nose of the aircraft -- one on each wing and one in the nose.
"The system would use bleed air from the engines that were mounted in the back, and would duct the gasses to the fans to spin the fan blades," said Barlow. "This provided advantages in that you didn't have gear boxes or drive shafts or all of the necessary plumbing and lube systems that go with (having engines in the wings), which reduce weight."
Two aircraft were built in the early 1960s and by May of 1964 they were ready for their first test flight, which consisted of only a hover, said Barlow. The first transition from hover flight to forward flight didn't take place until November of that year, and it didn't go as smoothly as planned.
In order to transition from one flight mode to the other, the pilot had to shut down one mode of flight while simultaneously initiating the other, which is where problems arose.
"What the aircraft did was when you started the jet engines, which were in the back, in order to take off vertically, you had a system whereby you would duct the exhaust to the fans and the fans would provide lift," said Barlow. "Once you got to a hover, in order to translate to forward flight you had to start moving forward, and in order to transition, you had to change the system over from shutting off the fan to immediately ducting the exhaust out the back of the jets.
"In the Harrier, there are two nozzles on either side of the aircraft and they pivot gradually to keep the lift going, but this didn't do that," he said. "This was a bang-bang process and there were no automated systems or stability augmentation systems -- the pilot had to do it all."
Because of the high level of skill required for the conversion process, transitioning from vertical flight to forward flight, or vice-versa, was a troubled process, and on April 27, 1965, during a demonstration flight, it resulted in a fatal crash.
"During a high-speed pass, the aircraft nosed over into a 30-degree dive and never recovered," said Barlow. "During the accident investigation, (it was discovered) that the pilot initiated the conversion process at way too high of a speed to be safe. There was a very narrow window of speed in which the pilot could begin the conversion process."
The surviving aircraft was retrofitted with a rescue hoist on the left side of the aircraft to test a possible application for the aircraft in combat situations as a rescue aircraft. The Army wanted an aircraft that could get to someone in need quickly, come to a slow flight hover, lower the cover and hoist up whoever was in need.
During a demonstration of this capability, however, as the pilot arrived and put the aircraft into a low-speed deep descent to get into position, the line from the hoist somehow made its way around the top of the wing, becoming lodged in the lifting fan, which caused the aircraft to lose lift on that side.
"The pilot elected to eject, but the aircraft had passed the safe parameters for an ejection and he was ejected horizontally, resulting in his death," and making this the second fatal mishap for the aircraft, said Barlow.
Remarkably, following the ejection, the aircraft eventually recovered and managed to settle itself onto the ground with minimal damage, he added.
The aircraft was subsequently rebuilt as the XV-5B, which featured a wider track main landing gear, improved cockpit visibility and functionality, and modified intake and control systems.
Although the program was deemed a failure, the XV-5 program did have some positive outcomes.
"Many lessons were learned about control procedure during conversion from one flight mod to another," said Barlow. "Also, the point was driven home that such conversion flight was only to prove practical if automated flight control and stability systems were used."
But the most significant outcome of the program was its role and development of the high-bypass turbofan engine, which led to the development of the TF-39 engine used in Lockheed's C-5 Galaxy aircraft.
The only remaining Vertifan aircraft left in the world now sits on the west lawn of the U.S. Army Aviation Museum.
"It's a pretty awesome aircraft and we're lucky to have it," Barlow said.