Convair XF-92
| Convair XF-92 | |
|---|---|
 Convair XF-92A in flight |
|
| Type: | Experimental airplane |
| Design country: | |
| Manufacturer: | |
| First flight: |
September 18, 1948 or December 18, 1948 |
| Commissioning: |
Never put into service |
| Production time: |
Was never mass-produced |
| Number of pieces: |
1 |
The Convair XF-92 (factory name Convair Model 7, Consolidated Vultee Model 115) was an experimental aircraft that was originally planned as a prototype for an object protection fighter aircraft. American US by the manufacturer Convair made in 1948, it represents the first delta wing aircraft with jet propulsion of the USAF . Before the general renaming of all USAF aircraft in 1948 was the project name P-92 .
history
designation
Although the design is commonly referred to as the Convair XF-92 in the literature , the company's official name was Consolidated Vultee Aircraft until 1954 . However, Convair has been used in publications and press releases since Consolidated and Vultee merged in the year. The factory name was initially Model 115, but was eventually added to the sequence of Convair models after World War II as Model 7. One citation also gives "Model 1" as the plant name. The delta wing variant was given the model number 7-002 (pronounced Seven-Balls-Two ), so it is widely believed that the swept wing design was numbered 7-001. Instead of 7-002, the designation 7002 used in the construction drawings is sometimes given.
The non-built interceptor was designated with XP-92 (without suffix), while XP-92A or XF-92A was used for the actually built technology carrier.
Tender
In August 1945, the USAAF asked various companies to propose a new generation of high-performance aircraft, including a long-range escort fighter and an interceptor capable of reaching at least 700 mph (1020 km / h). In the first tender documents for this object protection fighter (Project MX-809) the USAAF demanded a climb time of four minutes to 50,000 ft (15,250 m), after which both enemy bombers and "missiles" should be fought. The latter, however, were more likely to be cruise missiles. The military specifications were revised on November 23, 1945 and then again on February 5, 1946. The final version of the Special Operational Requirement (SOR) finally called for 25.5 minutes of deployment time, divided into a 2.5-minute climb to 47,500 ft, 15 minutes of cruise flight at 535 mph, 3 minutes of combat time at 760 mph and finally a descent phase of 5 Minutes. These were very high requirements for the technical possibilities available at the time.
USAAF received draft projects from Bell, Consolidated-Vultee, Douglas, North American, and Northrop. Since the Vultee design team in Downey had already dealt with such concepts in advance, a whole series of drafts could be submitted to the Air Materiel Command at Wright Field within a short time between October 1945 and May 1946 .
Variant development of the XP-92 interceptor
- First variant with swept wing and "Ramjet"
The Vultee Division of Consolidated Vultee used a design in the form of a special rocket engine with an air inlet in the bow for the first draft. A number of small rockets were planned and fuel was to be injected into the air intake in order to obtain a kind of pseudo ramjet engine. The draft, submitted to the Army on October 13, 1945, continued to provide for wings swept at 35 degrees and a V-tail. Convair described the concept as "a reusable manned missile that is guided to its airborne target by its pilot" ( nonexpendable, inhabited missile with a pilot guiding it to its airborne target ). In addition to the rocket inside the fuselage, another four rockets for initial acceleration with 1200 lbf thrust each were arranged at the stern around the exhaust nozzle. A Westinghouse 19XB turbojet provided propulsion for the final approach to the target and for landing. The energy for the electrical consumers should also be generated during the entire flight.
The Consolidated Vultee engineers initially selected a "jacketed" rocket engine for the XP-92, which was described as a ramjet with internal rocket and ramjet combustion chambers. To increase the take-off acceleration, an additional six liquid rocket engines should be installed. The cockpit was provided in the center of the air inlet in the diffuser cone, which made extensive precautions necessary for a possible emergency exit. This structural design showed a great similarity to the Miles M.52 .
On April 12, 1946, the Army announced that Convair had won the tender for the interceptor and received a US $ 850,000 contract on May 2, 1946 for wind tunnel surveys as part of the MX-813 project. A $ 5.3 million order for a full-scale dummy, a break cell and two XP-92 prototypes followed on June 25th. The design team consisted of CR "Jack" Irvine (chief engineer), his assistant Frank Davis as well as Ralph Schick (responsible for aerodynamics) and Adolph Burstein (head of design).
- Delta wing and ramjet
From the development team, Burstein suggested using a delta wing instead of the planned swept wing. The first evidence of this is provided by a memo dated July 5, 1946 in which it is stated that “a 60 ° delta wing is to be examined this week”. The Convair developers were familiar with the theoretical work on delta wings by Michael Gluhareff at Sikorsky and also knew about the results of Alexander Lippisch's aerodynamic studies , which the USAAF became aware of through Operation Lusty . The Lippisch data, which were then used in the conception of the final design, mainly concerned the investigations of the Lippisch DM-1 in the Langley wind tunnel.
In the meantime, Ralph Schick learned that Lippisch was staying at Wright Field and arranged to meet him in Ohio, which was followed in October 1946 by Lippisch in San Diego at Convair. The planned use of the P-92 largely corresponded to that of the Me 163 , which was used in World War II and designed by Lippisch , which was supposed to take over the "point defense" of important industrial facilities as an object protection fighter. The project of the Lippisch P-13a, of which only the DM-1 flew as a non-motorized test vehicle until the end of the war, was planned for this task. All designs had in common that they were equipped with rocket engines so that they could quickly rise to the attack height of the enemy bombers.
An amendment to the contract of November 1946 after Lippisch's visit to San Diego stipulated that the future XP-92 demonstrator should be equipped with a Westinghouse 24C jet engine and four additional rocket boosters. In a later published retrospective, NASA called the XP-92 a "manned surface-to-air missile ". Project work, which originally began at the Vultee facility in Downey, was continued in San Diego after the facility was sold to North American in 1947. The USAAF order in 1946 was for two XP-92s and an additional break cell .
On April 17, 1948, the mock-up was inspected, which now had delta wings instead of swept wings. In June 1948, the Air Force decided that the concept with a rocket engine in the fuselage would be abandoned because conventional propulsion configurations had meanwhile been significantly further developed. In addition, the cost of the entire project was estimated at over US $ 16 million. Until the final project assignment and cancellation of the two commissioned XP-92s, the actual costs were US $ 4.5 million.
Development of the technology carrier XF-92
Convair quickly recognized that the design of the XP-92 posed two major challenges for the engineers, namely a new aerodynamic design as well as a new type of drive system. So it was decided to examine the two problems separately and, on the one hand, to build a test aircraft for aerodynamic issues and, in addition, to examine the propulsion system with the help of ground equipment. In September 1946 the Army agreed to the proposal to test the aerodynamic design using a flying mock-up with a jet drive. For this purpose, the previously commissioned fracture cell was replaced by an aerodynamics test carrier XP-92A with the USAAF serial number 46-682. The demonstrator used the wing and the vertical stabilizer as they should also be used for the planned interceptor. What was changed, however, was the fuselage, which now did not have to accommodate the rocket engines and so could be made much slimmer. A General Electric I-40 (XJ33) engine with a centrifugal compressor was planned as the drive.
Even after the cancellation of the XP-92 project, the Air Force was still interested in testing the performance of delta wings and allowed Convair to continue building the technology platform. Lippisch and other German scientists are said to have been loaned out for a few weeks to help design the delta wing.
Construction of the prototype
In order to save time and money, many parts were used from samples that were already in series production. The main landing gear came from a North American FJ -1, the nose wheel from a Bell P-63 , the J33 engine, the brakes and hydraulic system from a Lockheed P-80 , and the ejection seat from a Convair XP-81 . Most of the construction took place in the old Vultee factory in Downey, California. After its closure in the summer of 1947, the 75% complete cell was transported to the Consolidated plant in San Diego, which led to considerable delays in further construction.
The prototype was completed in October 1947 and was then shipped to San Francisco on the USS Titania (AKA-13). From there it was taken to the NACA Ames Aeronautical Laboratory by truck for wind tunnel tests without an engine . The tests took place there from November 29th to December 23rd. The results largely confirmed the results previously made with smaller models. The return of the machine to San Diego took place on the aircraft carrier USS Boxer (CV-21) . Upon arrival on January 12, 1948, an Allison J33-A-21 and JATO missile devices were installed, but they were probably not used. After the transfer to the Muroc Air Force Flight Test Center by ship and truck, the first taxiing tests showed that the brakes had to be replaced and that the machine generally reacted very sensitively about the longitudinal and transverse axes. The first pilot to fly a jet-powered Delta aircraft was Ellis D. Shannon, who also made the maiden flight with other new Convair designs. On June 9, 1948, he accidentally took off for a short jump for the first time during high-speed taxi attempts, covering about 3 km at an altitude of 15 ft. In the following weeks they were replaced. However, the aircraft showed such strong vibrations around the longitudinal and transverse axes that the pilot Ellis Shannon had to "land" again immediately. While the control system was being improved, the J33-A-21 was exchanged for the newer, somewhat more powerful A-23 variant with water-alcohol injection.
Flight tests as an experimental aircraft
The “real” first flight took place on September 18, 1948 without any particular incident. Instead of the Westinghouse 24C, however, they first built an Allison J33-A-21 18.9 kN (4250 lbf) thrust and finally an Allison J33-A-23 with 23.2 kN (5200 lbf) thrust before further flight tests began. a. Shannon carried out nine more flights by the end of the year, which showed that the machine was easy to handle, but "a bit sensitive to control". The second pilot to fly the XF-92 on December 21, 1948 was Bill Martin, also a Convair test pilot.
By the end of "Test Phase I" on August 26, 1949, 47 flights with a total duration of 20 hours and 33 minutes had been carried out. Then the Air Force received the machine in order to carry out "Trial Phase II". The first USAF pilot was Chuck Yeager , who flew the XF-92A for the first time on October 13, 1949. A test flight on December 28, 1949 ended phase II of the test in which 25 flights with a total duration of 17 hours were carried out, but Air Force pilots continued to fly the machine occasionally for a few years.
From the beginning, the designers also thought of using the XF-92A in supersonic flight. According to the calculations at the time, it should be able to exceed Mach 1 in level flight. The pilots, however, judged the machine to be non-supersonic, so after the end of "Phase II" it was brought back to the factory in January 1950 to swap the engine for a J33-A-29 with an afterburner that provided 33.4 kN (7500 lbf) of thrust has been. Then there was also an extended hull to accommodate the afterburner. The machine was also painted completely white for better visual tracking. Convair estimates that the top speed at sea level should increase from 552 to 718 mph and the climb time at 30,000 ft should decrease from 12.4 to just 3.4.
After the 14-month conversion phase in San Diego, the machine returned to Muroc, whereupon Yeager carried out the first flight with the new engine on July 21, 1951. Before the XF-92A was transferred to the NACA and became the subject of further research into the stability of the delta wing, it completed a further 21 flights over 11 hours and 21 minutes. The results of the flight program turned out to be disappointing overall, since Mach 1 could only be exceeded in orbit flight, which was achieved at least once with Everest as the pilot. In late 1951, the XF-92A was briefly considered as a proof-of-concept demonstrator for the planned F-102 . However, because of the expected high costs, a decision was made against this further use.
The Air Force ended the testing program in February 1953 and gave the aircraft to the NACA . Convair then changed the engine again and installed a J33-A-16 that delivered 37.4 kN (8400 lbf) of thrust. The subsequent flights, carried out by Scott Crossfield from April 1953, showed a tendency towards nose pitch-up in fast turns. As a remedy, boundary layer fences were temporarily installed, but they could not offer any effective remedy.
On October 14, 1953, the machine was damaged by failure of the nose wheel strut on landing. The Air Force and NACA agreed not to carry out a repair because the first flight of the YF-102 was scheduled only 10 days later. The decommissioning after a total of 62 flight hours and 118 flights was so inevitable; The machine was listed in the Air Force inventory until March 1954. The project cost was US $ 4.5 million.
Consequential effect
Long before its final decommissioning, the experience gained with the XF-92A was used in the design of the F-102 , F-106 fighter aircraft and the B-58 strategic bomber . During the flight tests of the XF-92, the delta wing was convincing, showing exceptionally stable flight characteristics and good-natured stall behavior in the low speed range, especially in thin air . The high rigidity of the wing, paired with a thin profile cross-section and large fuel capacity, was seen as a major advantage of this design.
Frank Davis, Ralph Schick and Adolph Burstein from the American Institute of Aeronautics and Astronautics received the National Aircraft Design Award in 1981 for their contributions to the development of the delta wing .
Whereabouts
After it was taken out of service in 1954, the XF-92A was also used as a prop in two feature films. The film recordings made at Edwards Air Base were first used in the film Toward the unknown , released in August 1956, with William Holden . A year later, the Howard Hughes-produced feature film Jet Pilot hit theaters. After the filming, the XF-92A was shown at several Air Force exhibitions across the country. It then went into the possession of the University of the South in Sewanee ( Tennessee ) for a few years, before finally being shown in the National Museum of the Air Force exhibition at Wright Patterson AFB .
Technical specifications
| Parameter | Data |
|---|---|
| crew | 1 |
| length | 12.99 m |
| span | 9.55 m |
| Wing area | 39.5 m² |
| height | 5.37 m |
| Empty mass | 4,118 kg |
| Takeoff mass | 6,626 kg |
| drive | 1 × Turbojet Allison J33 -A series with a maximum of 33.4 kN thrust |
| Top speed | 1,156 km / h |
| Service ceiling | 15,450 m |
literature
- Dennis R. Jenkins, Tony R. Landis: Experimental & Prototype US Air Force Jet Fighters , Specialty Press, 2008, ISBN 978-1-58007-111-6 , pp. 122-129
- Bill Yenne: Convair Deltas - From SeaDart to Hustler , Specialty Press, 2009, ISBN 978-1-58007-118-5 , pp. 24-37
- Hans-Ulrich Meier (Ed.): The swept wing development in Germany until 1945 - Die deutsche Luftfahrt Vol. 33 , Bernard & Graefe Verlag, 2006, ISBN 3-7637-6130-6
Web links
- Photos of the XF-92 on the NASA Dryden website (accessed February 8, 2014)
- Brief history on nasa.gov (accessed February 8, 2014)
Individual evidence
- ^ Bill Yenne: Convair Deltas , Specialty Press, 2009, p. 28
- ↑ Dennis R. Jenkins, Tony R. Landis: Experimental & Prototype US Air Force Jet Fighters , Specialty Press, 2008, p. 126
- ^ Hans-Ulrich Meier: The arrow wing development in Germany until 1945 , Bernard & Graefe Verlag, 2006, p. 354
- ↑ Jenkins / Landis p. 124