Page 12 - The Future of Aerospace is X - X-Planes 2021

Ryan X-13 Vertijet

The Ryan X-13 Vertijet (company 10,000-pound-force thrust Rolls- trailer and landed by hooking the land-
designation Model 69) was an ex- Royce Avon turbojet. The high- ing wire. Flight tests were performed
perimental vertical take-off and land- mounted delta wing of the aircraft by two test pilots: Ryan’s Chief Test
ing jet aircraft built by Ryan Aeronau- had a wingspan of only 21 feet and Pilot Peter F. “Pete” Girard, and Ryan
tical and flown in the United States in was capped with flat endplates. The Test Pilot W. L. “Lou” Everett.
the 1950s. nose of the aircraft had a hook on the July 28-29, 1957, the X-13 was
The main objective of the project underside and a short pole for gaug- demonstrated in Washington, D.C. It
was to demonstrate the ability of a ing distance from the trailer. The hook crossed the Potomac River and landed
pure jet to vertically takeoff, hover, was used to hang the Vertijet from at the Pentagon.
transition to horizontal forward flight, the vertical trailer bed landing plat- The Air Force chose not to continue
and vertically land. form. After the aircraft was secured development of the Ryan X-13 Vertijet
Just after World War II, Ryan en- vertically, the trailer was lowered to because of the lack of an operational
gineers wondered whether the Ryan/ horizontal and then used to transport requirement.
U.S. Navy FR-1 Fireball, which had the aircraft on the ground. Pitch and The X-13 was designed to investi-
a thrust-to-weight ratio of 1 at low yaw control in hover were provided gate vertical takeoff, horizontal flight
fuel quantities, would take off verti- by vectored engine thrust. Roll con- transition, and return to vertical flight
cally. The United States Navy’s Bu- trol was provided by “puffer” jets for landing. The first prototype of the
reau of Aeronautics in 1947 awarded (also known as “jet reaction control”) X-13 was equipped with temporary
Ryan a contract, originally under the mounted outboard of the wingtip
designation F3R, to investigate the endplates. The first prototype was fit- tricycle landing gear. The X-13 was
development of a vertically launched ted with temporary landing gear and flown conventionally on Dec.10, 1955
jet fighter. This was part of a program made its first horizontal flight on Dec. to test its aerodynamic characteristics.
to evaluate the feasibility of subma- 10, 1955. Later, it made full horizon- The Vertijet was then fitted with a tem-
rine-based aircraft. Ryan conducted tal to vertical attitude conversions porary “tail sitting” rig. On May 28,
remote controlled VTOL tethered rig and back again at altitude. The first 1956, it was flown from the ground in
tests from 1947 to 1950 and a flying prototype then had the landing gear a vertical position to test its hovering
rig in 1951. Ryan was awarded an Air replaced with a tail-mounted frame- qualities. The X-13 VertiJet completed
Force contract in 1953 to develop an work that held it in a vertical attitude its first full-cycle flight at Edwards Air
actual flying jet-powered VTOL air- on the ground. Using this rig, hooking Force Base, Calif., on April 11, 1957,
craft, which was given the designation practice was conducted. The second when it took off vertically from its
X-13. Two prototypes were built. prototype (#54-1620), on April 11, mobile trailer, angled over into a hori-
The Ryan X-13 Vertijet was 23 feet, 1957, made a vertical take-off from zontal attitude, and flew for several Air Force photograeph
5 inches long. It was just large enough the vertically raised trailer, transi- minutes. The X-13 then transitioned Ryan X-13 Vertijet second prototype (#54-1620) about to moor itself to a dual-
to accommodate the single-place tioned to horizontal flight and back to vertical flight and slowly descended role flatbed transport/launch trailer.
cockpit with a tilting seat and the again. It then returned to the vertical back onto its trailer and landed.
Hiller X-18

The Hiller X-18 was an experimental cargo transport aircraft of one engine meant the airplane would crash. Thrust control was
designed to be the first testbed for tiltwing and V/STOL (vertical/ through throttle changes, which were too slow for acceptable height
short takeoff and landing) technology. and roll control.
Design work started in 1955 by Stanley Hiller Jr., and Hiller On the 20th and final flight in July 1961, the X-18 had a propel-
Aircraft Corporation received a manufacturing contract and fund- ler pitch control problem when attempting to convert to a hover at
ing from the U.S. Air Force to build the only X-18 ever produced. 10,000 feet and went into a spin. The crew regained control and
To speed up construction and conserve money, the plane was landed, but the X-18 never flew again. However, ground testing
constructed from scavenged parts including a Chase YC-122C of the tiltwing concepts continued. Eventually a VTOL Test Stand
Avitruc fuselage, and turboprops from the Lockheed XFV- was built on which the X-18’s vertical takeoff and landing and
1 and Convair XFY-1 Pogo experimental fighter programs. The hover control was to be tested. One engine run was successfully
tri-bladed contra-rotating propellers were a giant 16 feet across. conducted to the full 15-foot wheel height on the VTOL Test Stand.
The Westinghouse turbojet engine had its exhaust diverted upwards The program was cancelled on Jan. 18, 1964 before further VTOL
and downwards at the tail to give the plane pitch control at low Test Stand testing could be conducted, and the X-18 was cut up
speeds. Hiller nicknamed their X-18 the Propelloplane for public for scrap.
relations purposes. The program proved several things that contributed to further
Preliminary testing occurred at Moffett Field Naval Air Station, tilt-wing VSTOL technology programs:
Calif. The first flight (hop) was on Nov. 11, 1959, followed by the 1. Cross-shafting between the engines was necessary in order
first real flight on Nov. 24, 1959, with Hiller test pilots George to avoid loss of control in the event of an engine failure.
Bright and Bruce Jones. Further test flights were held at Edwards 2. Direct propeller pitch control was necessary for precise
Air Force Base, Calif., ultimately recording 20 flights. height and lateral control during VTOL and hover.
A number of problems plagued the X-18 including being sus- This knowledge was employed in the successful development Air Force photograph
ceptible to wind gusts when the wing rotated, acting like a sail. In and flight tests of the Tri-Service XC-142A, tilt-wing VSTOL Hiller X-18 on testing platform with fully rotated wings.
addition, the turboprop engines were not cross-linked, so the failure transport.

X-5, from 11
stability and control data with the wings at a 59 got into a spin during an X-5 flight, but recov- brakes, you got quite a nose down pitch. Well, istics were due to the aircraft’s design, rather
degree sweep angle. Other tests with the X-5 ered safely. Tragically, Maj. Raymond Popson now it would be very unacceptable. But in a than the variable wing sweep. But while the
included drag studies behind an F-80 and B-29, was lost in a spin accident with the Air Force’s research airplane you put up with it because concept of changing the wings’ sweep angle
and acting as a chase plane for a B-47 flight. X-5 (50-1839) on Oct. 13, 1953. The wings it’s all you’ve got.” The final NACA X-5 flight was shown to have promise, the mechanism
The NACA flights in the X-5 also showed were in the 60 degree position, and, unlike the was made on Oct. 25, 1955, by a new High- itself, which required the wings move back and
the design’s shortcomings. Crossfield noted others, Popson could not recover in time. Speed Flight Station pilot, Neil A. Armstrong. forth as their angle changed, was not practical.
later, “The X-5 was not a comfortable airplane On April 23, 1954, Walker made his last X-5 During the pilot checkout flight, a landing gear The solution to this, developed by NACA engi-
to fly. It had a low-slung engine. So there was flight, and two new pilots were assigned to the door separated. The aircraft was subsequently neers at Langley, was to move the pivot points
a misalignment of the drag axis, and the prin- program. They were Stanley P. Butchart and grounded. In all, the first X-5 had made 122 of the wings outside the fuselage.
cipal axis, and the thrust axis, and all of that. John B. “Jack” McKay. They continued mak- NACA flights. Variable sweep wings became a design
So it could get into some interesting maneuvers ing stability and control research flights from The results of the X-5 were mixed. It pro- feature in aircraft beginning in the 1960s and
and motions, and that sort of thing.” Its big- June 1954 into October 1955. Butchart later vided verification of wind tunnel predictions continuing into the 1980s. These included the
gest problem, he added was that “...it was a said about the X-5’s poor spin characteristics, about drag reductions and performance im- F-111, the F-14 and B-1 in the U.S., the Su-22
terrible airplane in a spin. It took a long time “You just had to know that and stay away from provements from variable sweep wings. The and Su-24 attack aircraft and the Tu-22M and
to get that airplane out of a spin.” On Oct. 21, it.” He also noted a special characteristic of the X-5 pilots also found that the variable sweep Tu-160 strategic bombers built in the (then)
1952, Walker entered a spin at 36,000 feet, and aircraft: “The speed brakes on the X-5 were up wings gave a tactical advantage over conven- Soviet Union, and the European Tornado strike
required 18,000 feet to recover. Crossfield also front [on the nose]. When you opened the speed tional aircraft. The poor stall/spin character- aircraft and interceptor.
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