Convair XF-92
Encyclopedia
The Convair XF-92 was the first American
delta-wing aircraft. Originally conceived as a point-defense interceptor
, the design was later made purely experimental
. However, its design, suitably enlarged, led Convair to use the delta-wing on a number of designs, including the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, Navy's F2Y Sea Dart as well as the experimental XFY
.
Prior to August 1945, the Vultee Division of Consolidated-Vultee looked at the possibility of an swept-wing aircraft powered by a ducted rocket. Years earlier, the company had performed designs which involved liquid-cooled radiator engines. If properly designed, fuel would be added to the heat produced by small rocket engines, creating a "pseudo-ramjet".
In August 1945, the United States Army Air Forces
(USAAF, since renamed "United States Air Force
") issued a proposal for a supersonic interceptor capable of 700 mi/h speeds and reaching an altitude of 50000 feet (15,240 m) in four minutes. Several companies responded, among which was Consolidated-Vultee, which submitted its design on 13 October 1945. This design featured swept wings and V-tail
s, as well as a powerful propulsion system. Besides the ducted rocket, four 1200 pound-forces (5.3 kN) rockets were positioned at the exhaust nozzle, along with the 1560 pound-forces (6.9 kN) 19XB turbojet produced by Westinghouse.
In May 1946 Convair (then still Consolidated Vultee) won with their proposal for a ramjet
-powered aircraft with a 45° swept wing
under USAAF Air Materiel Command Secret Project MX-813. However, wind tunnel
testing demonstrated a number of problems with this design.
Looking for solutions, Convair came across the work of Alexander Lippisch
, who had emigrated to the U.S. as part of Operation Paperclip
. Before and during the war, Lippisch had worked on a variety of delta-wing aircraft, first as low-speed gliders, and later as high-speed interceptors. Lippisch had concluded that the delta-wing was a natural design for supersonic flight, as the highly swept leading edge remained free of the shock wave
off the front of the aircraft. He had plans to develop this as the Lippisch P.13a
, but progressed only to an unpowered glider example, the Lippisch DM-1
.
The P.13 design consisted of two large triangles joined together. One formed the main structure and wing, the other was the vertical stabilizer and cockpit. The only deviation from the triangular layout was a circular air intake at the nose, and rectangular nozzle at the rear. The engine was powered by coal
dust stored in a large rotating cylindrical cage, the odd power source being a solution to the twin problems of lack of petroleum and manufacturing capability in Germany at the time the design was being proposed.
Convair took up Lippisch's work, redesigning it for jet power using the 1560 lbf (6,939.2 N) Westinghouse J30
assisted by a battery of six 2000 lbf (8.9 kN) liquid-fueled rockets. The engine layout was rather portly and would not fit cleanly into the wing of the original P.13 layout, forcing a redesign. The new layout placed the engine in a seemingly oversized cylindrical fuselage, moving the pilot out of the triangular rudder into a separate cockpit centered in the middle of the fuselage, serving double duty as a shock cone for the engine intake. The basic layout of the fuselage was very similar to the Miles M.52
design, although the M.52 did not use a delta wing. The rudder, no longer serving as the cockpit as well, was reduced in size. The new design was presented to the U.S. Air Force in 1946, and was accepted for development as the XP-92.
In order to gain in-flight experience with the delta wing layout, Convair suggested building a smaller prototype, the Model 7002, which the USAAF accepted in November 1946. The design was similar in general layout as the original, but by placing the pilot in a conventional cockpit at the front, instead of centered in the fuselage, the resulting aircraft looked considerably less odd. In order to save development time and money, many components were taken from other aircraft; the main gear was taken from a North American FJ-1 Fury, the nosewheel from a Bell P-63 Kingcobra, the engine and hydraulics were taken from a Lockheed P-80 Shooting Star, the ejector seat and cockpit canopy were taken from the cancelled Convair XP-81
, and the rudder pedals were taken from a BT-13 trainer.
Construction was well underway at Vultee Field in Downey, California
when North American Aviation
took over the Vultee plants in summer 1947. The airframe was moved to Convair's plant in San Diego, and completed in the autumn. In December it was shipped without an engine to NACA
's Ames Aeronautical Laboratory
for wind tunnel testing. After testing was completed, the airframe was returned to San Diego, where it was fitted with a 4250 lbf (18,904.9 N) Allison J33-A-21 engine.
By the time the aircraft was ready for testing, the concept of the point-defense interceptor seemed outdated and the (now redesignated) F-92 project was cancelled. They also decided to rename the test aircraft as the XF-92A.
In April 1948 the XF-92A was shipped to Muroc Dry Lake
, later to become Edwards AFB. Early tests were limited to taxiing, although a short hop was made on 9 June 1948. The XF-92A's first flight was on 18 September 1948 with Convair test pilot Ellis D. "Sam" Shannon at the controls. After company testing, the aircraft was turned over to the USAAF on 26 August 1949, with the testing being assigned to Frank Everest and Chuck Yeager
.
Yeager was the first Air Force pilot to fly the XF-92A. On his second flight he dived the aircraft in a 4 g split-S dive, reaching Mach 1.05 for a brief time. When approaching for landing on this flight he continued to pull the nose higher and higher in order to slow the forward speed to avoid the problems from his first attempt. Surprisingly, the aircraft simply wouldn't stall; he was able to continue raising the nose until he reached 45 degrees pitch, flying under control in that attitude to a landing at 67 mi/h, 100 mi/h slower than Convair had managed.
In 1951, the XF-92A was refitted with an Allison J33-A-29 engine with an afterburner, offering a thrust of 7500 lbf (33,361.7 N). The re-engined XF-92A was flown by Yeager for the first time on 20 July 1951. However, there was very little improvement in performance. In addition, there were maintenance problems with this engine and only 21 flights were made during the next 19 months. A final engine change was made to the 8400 lbf (37,365.1 N) J33-A-16.
On 9 April 1953, Scott Crossfield
began a series of flights on behalf of NACA. These tests revealed a violent pitch-up tendency during high-speed turns, often as much as 6 g, and on one occasion 8 g. The addition of wing fence
s alleviated this problem.
None of the pilots had much good to say about the design. Yeager commented "It was a tricky plane to fly, but ... I got it out to 1.05 Mach." Crossfield was more direct, saying "Nobody wanted to fly the XF-92. There was no lineup of pilots for that airplane. It was a miserable flying beast. Everyone complained it was underpowered."
The delta wing's thin airfoil cross section, low weight and structural strength made this a good combination for a supersonic airplane (although the fuselage was of a pre-area rule
design). The large surface area of 425 ft² (39 m²), and the low wing loading
it had as a result, led to excellent low-speed performance as well. Very slow landing speeds could be achieved, at the cost of extremely nose-high landing angles and the resulting poor visibility. The combination of good high-speed and low-speed characteristics was very difficult to achieve for other planform
s. Although the XF-92 itself was not liked, the design concept clearly had promise, and the delta-wing became a "standard" layout on Convair designs through the 1950s and 1960s.
Of particular interest to aircraft designers was the unexpectedly good low-speed behavior Yeager had noticed on his second flight. The aircraft continued to remain controllable at very high angles of attack
(alpha), where a conventional layout would have stalled. The reason for this turned out to be the unexpected creation of a large vortex
over the top of the wing, generated by the airflow between the fuselage and leading edge of the wing at high alpha. The vortex became "attached" to the upper surface of the wing, supplying it with air moving at speeds much greater than the aircraft's forward speed. By controlling the flow in this critical area, the performance envelope of the delta could be greatly expanded, which led to the introduction of canard
s on most delta-wing designs in the 1960s and 1970s. More recently "mini-deltas", in the form of leading edge extension
s, have become common on most fighter aircraft, creating the vortex over a more conventional wing planform.
, Wright-Patterson Air Force Base
, near Dayton, Ohio
.
and Janet Leigh
. Due to the lengthy delay in releasing the film, by the time it appeared in 1957, the XF-92A's role had been left on the cutting room floor. It did appear in the film Toward the Unknown
(1956) starring William Holden, again in the guise of another aircraft, this time, the F-102 Delta Dagger.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
delta-wing aircraft. Originally conceived as a point-defense interceptor
Interceptor aircraft
An interceptor aircraft is a type of fighter aircraft designed specifically to prevent missions of enemy aircraft, particularly bombers and reconnaissance aircraft. Interceptors generally rely on high speed and powerful armament in order to complete their mission as quickly as possible and set up...
, the design was later made purely experimental
Experimental aircraft
An experimental aircraft is an aircraft that has not yet been fully proven in flight. Often, this implies that new aerospace technologies are being tested on the aircraft, though the label is more broad....
. However, its design, suitably enlarged, led Convair to use the delta-wing on a number of designs, including the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, Navy's F2Y Sea Dart as well as the experimental XFY
Convair XFY
|-See also:-References:NotesCitationsBibliography* Allen, Francis J. "Bolt Upright: Convair's and Lockheed's VTOL fighters". Air Enthusiast Volume 127, January/February 2007, pp. 13–20. ISSN 0143-5450....
.
Design and development
In August 1945, the United States Army Air Forces
United States Army Air Forces
The United States Army Air Forces was the military aviation arm of the United States of America during and immediately after World War II, and the direct predecessor of the United States Air Force....
(USAAF, since renamed "United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
") issued a proposal for a supersonic interceptor capable of 700 mi/h speeds and reaching an altitude of 50000 feet (15,240 m) in four minutes. Several companies responded, among which was Consolidated-Vultee, which submitted its design on 13 October 1945. This design featured swept wings and V-tail
V-tail
In aircraft, a V-tail is an unconventional arrangement of the tail control surfaces that replaces the traditional fin and horizontal surfaces with two surfaces set in a V-shaped configuration when viewed from the front or rear of the aircraft...
s, as well as a powerful propulsion system. Besides the ducted rocket, four 1200 pound-forces (5.3 kN) rockets were positioned at the exhaust nozzle, along with the 1560 pound-forces (6.9 kN) 19XB turbojet produced by Westinghouse.
In May 1946 Convair (then still Consolidated Vultee) won with their proposal for a ramjet
Ramjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
-powered aircraft with a 45° swept wing
Swept wing
A swept wing is a wing planform favored for high subsonic jet speeds first investigated by Germany during the Second World War. Since the introduction of the MiG-15 and North American F-86 which demonstrated a decisive superiority over the slower first generation of straight-wing jet fighters...
under USAAF Air Materiel Command Secret Project MX-813. However, wind tunnel
Wind tunnel
A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
testing demonstrated a number of problems with this design.
Looking for solutions, Convair came across the work of Alexander Lippisch
Alexander Lippisch
Alexander Martin Lippisch was a German pioneer of aerodynamics. He made important contributions to the understanding of flying wings, delta wings and the ground effect. His most famous design is the Messerschmitt Me 163 rocket-powered interceptor.Lippisch was born in Munich, Kingdom of Bavaria...
, who had emigrated to the U.S. as part of Operation Paperclip
Operation Paperclip
Operation Paperclip was the Office of Strategic Services program used to recruit the scientists of Nazi Germany for employment by the United States in the aftermath of World War II...
. Before and during the war, Lippisch had worked on a variety of delta-wing aircraft, first as low-speed gliders, and later as high-speed interceptors. Lippisch had concluded that the delta-wing was a natural design for supersonic flight, as the highly swept leading edge remained free of the shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
off the front of the aircraft. He had plans to develop this as the Lippisch P.13a
Lippisch P.13a
The Lippisch P.13a was an experimental ramjet-powered delta wing interceptor aircraft designed in late 1944 by Dr. Alexander Lippisch for Nazi Germany...
, but progressed only to an unpowered glider example, the Lippisch DM-1
Lippisch DM-1
|-References:-External links:*...
.
The P.13 design consisted of two large triangles joined together. One formed the main structure and wing, the other was the vertical stabilizer and cockpit. The only deviation from the triangular layout was a circular air intake at the nose, and rectangular nozzle at the rear. The engine was powered by coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
dust stored in a large rotating cylindrical cage, the odd power source being a solution to the twin problems of lack of petroleum and manufacturing capability in Germany at the time the design was being proposed.
Convair took up Lippisch's work, redesigning it for jet power using the 1560 lbf (6,939.2 N) Westinghouse J30
Westinghouse J30
-See also:...
assisted by a battery of six 2000 lbf (8.9 kN) liquid-fueled rockets. The engine layout was rather portly and would not fit cleanly into the wing of the original P.13 layout, forcing a redesign. The new layout placed the engine in a seemingly oversized cylindrical fuselage, moving the pilot out of the triangular rudder into a separate cockpit centered in the middle of the fuselage, serving double duty as a shock cone for the engine intake. The basic layout of the fuselage was very similar to the Miles M.52
Miles M.52
The Miles M.52 was a turbojet powered supersonic research aircraft project designed in the United Kingdom in the mid 1940s. Design work was undertaken in secrecy between 1942 and 1945. In 1946 the Air Ministry prudently but controversially changed the project to a series of unmanned rocket-powered...
design, although the M.52 did not use a delta wing. The rudder, no longer serving as the cockpit as well, was reduced in size. The new design was presented to the U.S. Air Force in 1946, and was accepted for development as the XP-92.
In order to gain in-flight experience with the delta wing layout, Convair suggested building a smaller prototype, the Model 7002, which the USAAF accepted in November 1946. The design was similar in general layout as the original, but by placing the pilot in a conventional cockpit at the front, instead of centered in the fuselage, the resulting aircraft looked considerably less odd. In order to save development time and money, many components were taken from other aircraft; the main gear was taken from a North American FJ-1 Fury, the nosewheel from a Bell P-63 Kingcobra, the engine and hydraulics were taken from a Lockheed P-80 Shooting Star, the ejector seat and cockpit canopy were taken from the cancelled Convair XP-81
Convair XP-81
|-See also:-References:NotesBibliography* Ginter, Steve. Consolidated Vultee XP-81 . Simi Valley, California: Ginter Books, 2007. ISBN 0-942612-87-6....
, and the rudder pedals were taken from a BT-13 trainer.
Construction was well underway at Vultee Field in Downey, California
Downey, California
Downey is a city located in southeast Los Angeles County, California, United States, southeast of downtown Los Angeles. The city is best known as the birthplace of the Apollo space program, and is the city where folk singer Karen Carpenter lived and died...
when North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...
took over the Vultee plants in summer 1947. The airframe was moved to Convair's plant in San Diego, and completed in the autumn. In December it was shipped without an engine to NACA
NACA
- Organizations :* National Advisory Committee for Aeronautics, the forerunner of the U.S. federal agency NASA* National Association for Campus Activities, an organization for programmers of university and college activities...
's Ames Aeronautical Laboratory
NASA Ames Research Center
The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...
for wind tunnel testing. After testing was completed, the airframe was returned to San Diego, where it was fitted with a 4250 lbf (18,904.9 N) Allison J33-A-21 engine.
By the time the aircraft was ready for testing, the concept of the point-defense interceptor seemed outdated and the (now redesignated) F-92 project was cancelled. They also decided to rename the test aircraft as the XF-92A.
Operational history
Rogers Dry Lake
Rogers Dry Lake is an endorheic desert salt pan in the Mojave Desert of Kern County, California. The lake derives its name from the Anglicization from the Spanish name, Rodriguez Dry Lake. It is the central part of Edwards Air Force Base as its hard surface provides a natural extension to the...
, later to become Edwards AFB. Early tests were limited to taxiing, although a short hop was made on 9 June 1948. The XF-92A's first flight was on 18 September 1948 with Convair test pilot Ellis D. "Sam" Shannon at the controls. After company testing, the aircraft was turned over to the USAAF on 26 August 1949, with the testing being assigned to Frank Everest and Chuck Yeager
Chuck Yeager
Charles Elwood "Chuck" Yeager is a retired major general in the United States Air Force and noted test pilot. He was the first pilot to travel faster than sound...
.
Yeager was the first Air Force pilot to fly the XF-92A. On his second flight he dived the aircraft in a 4 g split-S dive, reaching Mach 1.05 for a brief time. When approaching for landing on this flight he continued to pull the nose higher and higher in order to slow the forward speed to avoid the problems from his first attempt. Surprisingly, the aircraft simply wouldn't stall; he was able to continue raising the nose until he reached 45 degrees pitch, flying under control in that attitude to a landing at 67 mi/h, 100 mi/h slower than Convair had managed.
In 1951, the XF-92A was refitted with an Allison J33-A-29 engine with an afterburner, offering a thrust of 7500 lbf (33,361.7 N). The re-engined XF-92A was flown by Yeager for the first time on 20 July 1951. However, there was very little improvement in performance. In addition, there were maintenance problems with this engine and only 21 flights were made during the next 19 months. A final engine change was made to the 8400 lbf (37,365.1 N) J33-A-16.
On 9 April 1953, Scott Crossfield
Albert Scott Crossfield
Albert Scott Crossfield was an American naval officer and test pilot.-Biography:Born in Berkeley, California, Crossfield grew up in California and Washington. He served with the U.S. Navy as a flight instructor and fighter pilot during World War II...
began a series of flights on behalf of NACA. These tests revealed a violent pitch-up tendency during high-speed turns, often as much as 6 g, and on one occasion 8 g. The addition of wing fence
Wing fence
Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Not to be confused with wingtip fences, wing fences are flat plates fixed to the upper surfaces parallel to the airflow. They are often seen on swept-wing aircraft...
s alleviated this problem.
None of the pilots had much good to say about the design. Yeager commented "It was a tricky plane to fly, but ... I got it out to 1.05 Mach." Crossfield was more direct, saying "Nobody wanted to fly the XF-92. There was no lineup of pilots for that airplane. It was a miserable flying beast. Everyone complained it was underpowered."
Influence
Area rule
The Whitcomb area rule, also called the transonic area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.75 and 1.2....
design). The large surface area of 425 ft² (39 m²), and the low wing loading
Wing loading
In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly,...
it had as a result, led to excellent low-speed performance as well. Very slow landing speeds could be achieved, at the cost of extremely nose-high landing angles and the resulting poor visibility. The combination of good high-speed and low-speed characteristics was very difficult to achieve for other planform
Planform
In aviation, a planform is the shape and layout of a fixed-wing aircraft's fuselage and wing. Of all the myriad planforms used, they can typically be grouped into those used for low-speed flight, found on general aviation aircraft, and those used for high-speed flight, found on many military...
s. Although the XF-92 itself was not liked, the design concept clearly had promise, and the delta-wing became a "standard" layout on Convair designs through the 1950s and 1960s.
Of particular interest to aircraft designers was the unexpectedly good low-speed behavior Yeager had noticed on his second flight. The aircraft continued to remain controllable at very high angles of attack
Angle of attack
Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...
(alpha), where a conventional layout would have stalled. The reason for this turned out to be the unexpected creation of a large vortex
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...
over the top of the wing, generated by the airflow between the fuselage and leading edge of the wing at high alpha. The vortex became "attached" to the upper surface of the wing, supplying it with air moving at speeds much greater than the aircraft's forward speed. By controlling the flow in this critical area, the performance envelope of the delta could be greatly expanded, which led to the introduction of canard
Canard (aeronautics)
In aeronautics, canard is an airframe configuration of fixed-wing aircraft in which the forward surface is smaller than the rearward, the former being known as the "canard", while the latter is the main wing...
s on most delta-wing designs in the 1960s and 1970s. More recently "mini-deltas", in the form of leading edge extension
Leading edge extension
A leading edge extension is a small extension to an aircraft wing surface, forward of the leading edge. Different kinds of extensions have been used for different reasons.-Leading edge slats:...
s, have become common on most fighter aircraft, creating the vortex over a more conventional wing planform.
Aircraft on display
XF-92A Dart, s/n 46-682, is on display in the Research & Development Gallery at the National Museum of the United States Air ForceNational Museum of the United States Air Force
The National Museum of the United States Air Force is the official museum of the United States Air Force located at Wright-Patterson Air Force Base northeast of Dayton, Ohio. The NMUSAF is the world's largest and oldest military aviation museum with more than 360 aircraft and missiles on display...
, Wright-Patterson Air Force Base
Wright-Patterson Air Force Base
Wright-Patterson Air Force Base is a United States Air Force base in Greene and Montgomery counties in the state of Ohio. It includes both Wright and Patterson Fields, which were originally Wilbur Wright Field and Fairfield Aviation General Supply Depot. Patterson Field is located approximately...
, near Dayton, Ohio
Dayton, Ohio
Dayton is the 6th largest city in the U.S. state of Ohio and the county seat of Montgomery County, the fifth most populous county in the state. The population was 141,527 at the 2010 census. The Dayton Metropolitan Statistical Area had a population of 841,502 in the 2010 census...
.
Specifications (XF-92A)
Popular culture
An unusual application of the XF-92A was as a movie model, stepping into the role of the "MiG-23" in the Howard Hughes film, Jet Pilot (1957 film), starring John WayneJohn Wayne
Marion Mitchell Morrison , better known by his stage name John Wayne, was an American film actor, director and producer. He epitomized rugged masculinity and became an enduring American icon. He is famous for his distinctive calm voice, walk, and height...
and Janet Leigh
Janet Leigh
Janet Leigh , born Jeanette Helen Morrison, was an American actress. She was the wife of actor Tony Curtis from June 1951 to September 1962 and the mother of Kelly Curtis and Jamie Lee Curtis....
. Due to the lengthy delay in releasing the film, by the time it appeared in 1957, the XF-92A's role had been left on the cutting room floor. It did appear in the film Toward the Unknown
Toward the Unknown
Toward the Unknown is a 1956 movie about the dawn of supersonic flight filmed on location at Edwards Air Force Base. Starring William Holden, Lloyd Nolan and Virginia Leith, the film features the screen debut of James Garner. It was directed by Mervyn LeRoy and written by Beirne Lay, Jr...
(1956) starring William Holden, again in the guise of another aircraft, this time, the F-102 Delta Dagger.
See also
External links
- Curry, Marty. "XF-92A". Dryden Flight Research Center, 16 May 2006. Retrieved: 4 September 2006. Numerous images of the XF-92.
- XF-92A history
- Convair delta history including the MX-82. http://kolyan.net/foto2006/october/10/planes_201.jpg http://img12.imageshack.us/my.php?image=convairxf92mockup105661.jpg
