Experimental warplanes from the Los Angeles basin, part 3: Lockheed and North American penetration fighter designs

The early years of the Cold War saw the US develop a wide variety of jet fighters for a plethora of officially delineated combat missions, including air superiority, long-range interception, escort, and all-weather/night operations. Some, like the F-84, F-86, F-89, and F-94, entered production and operational service, but others remained at the prototype stage only. During my recent visit to the Planes of Fame Museum, I surprisingly happened to notice desktop models of two seldom-known US jet fighter designs of the early Cold War, the Lockheed XF-90 and North American F-93 penetration fighters. Therefore, I have devoted the third post of my multi-post series on prototype warplanes created in the Los Angeles to discussing in detail the XF-90 and F-93.

On August 28, 1945, a few days before the Japanese surrender aboard the USS Missouri, the US Army Air Force issued a requirement for a new-generation penetration fighter able to escort heavy bombers to enemy targets. Intended as a successor to escort versions of the P-51 Mustang that were used to escort B-17s and B-24s over Nazi Germany in World War II, the new jet-powered penetration fighter was to have a combat radius of 900 miles (1,450 km) and high combat performance. Several companies submitted bids to the jet penetration fighter contest, including Convair, Curtiss, Goodyear, Lockheed, McDonnell, Northrop, and North American. Technical details regarding the Convair and Northrop penetration fighter designs are discussed Buttler (2013) and will not be replicated here, although it should be stressed that the Northrop design was a derivative of the XP-79B flying wing fighter. The USAAF selected the McDonnell Model 36 and Lockheed L-167/Model 90, and North American NA-167 designs for prototyping, designating them XP-88, XP-90, and P-86C respectively. After the Air Force became independent of the US Army in September 1947 and adopted the policy of classifying fighter planes as fighters rather than pursuit planes, these designs were redesignated XF-88, XF-90, and F-86C (later YF-93A) in June 1948.

Left: Desktop model of the Lockheed XF-90 at the Planes of Fame Museum

Right: First XF-90 prototype (serial number 46-687) in flight over Edwards Air Force Base, California

Now this brings me to describing the two US penetration jet fighter designs from the Los Angeles basin, of which I will discuss the XF-90 first. The Lockheed XP-90/XF-90 was a sleek jet fighter with a pointed nose and engine intakes similar to that of Lockheed's earlier P-80/F-80 Shooting Star, as well as two 3,000 lb (13.3 kN) thrust Westinghouse J34 turbojets. Armament provisions included six 0.79 inch cannons, eight 5 in (127 mm) HVAR rockets, and 2,000 lb (907 kg) of bombs. The original design of the XP-90 featured a delta-wing, T-tailed configuration, but the US Air Material Command judged the delta wing configuration to produce high drag at lower speeds, so Lockheed reworked its fighter design into a backswept wing machine with a tail empennage like that of the F-86 Sabre. After a mock-up inspection in December 1947, two XF-90 prototypes (serial numbers 46-687/688) were ordered and the first of these flew on June 3, 1949, with the second prototype following suit on April 12, 1950. The XF-90 broke the speed of sound in a dive on May 17, 1950, reaching a speed of Mach 1.2. However, the XF-90 was too big and heavy for the available thrust generated by the Westinghouse turbojets, and RATO boosters were used for most of the takeoffs.

Left: Desktop models of the North American YF-93 at the Planes of Fame Museum

Right: First YF-93 prototype (serial number 48-317) in flight over Edwards Air Force Base, California

The other penetration jet fighter from the Los Angeles area that took flight was the North American YF-93. It was a derivative of the F-86 Sabre that had the air intakes moved to the fuselage sides to  allow the nose to accommodate the radar scanner. Due to its size difference compared to the F-86, the F-93 was powered by one Pratt & Whitney J48 turbojet delivering 6,000 lb (27 kN) of thrust, and it featured a dual-wheel main landing gear and increased wing area. Although originally designated P-86C/F-86C, in September 1948 the Air Force judged the NA-157 design sufficiently distinct to be allocated the new designation YF-93A. Two prototypes (serial numbers 48-317/318) were ordered in June 1948, along with 118 production F-93As (serial numbers 49-001/048, 49-059/068, 49-392/421, 49-1966/1995). The production order was cancelled in February 1949 due to budget cuts, work on the two prototypes continued apace, with the first aircraft flying on January 25, 1950.

The USAF staged a fly-off of the XF-88, XF-90, and YF-93A in June-July 1950, and the XF-88 was declared the winner of the penetration fighter contest in late July. The McDonnell design was judged superior to the Lockheed and North American designs in terms of handling, maneuverability, and high-speed characteristics, as well as armament stability and ability to operate from existing runways (see Buttler 2013, pp. 75-76). However, the euphoria at the McDonnell Aircraft Corporation over the outcome of the penetration fighter competition was all for naught. On August 22, 1950, just as the XF-88 was about to be cleared for production, the US Air Force gave up on the penetration fighter concept due to changing priorities and a tight defense budget. However, experience gained during the Korean War prompted the USAF to revive the notion of the penetration fighter, leading to General Operational Requirement (GOR) 101 being issued in February 1951 for a long-range escort fighter. McDonnell eventually developed an enlarged version of the XF-88, the F-101 Voodoo, which made its first flight in late September 1954.

References:

Buttler, T., 2013. Early US Jet Fighters: Proposals, Projects, and Prototypes. Manchester, UK: Hikoki Publications. 

Experimental warplanes from the Los Angeles basin, part 2: the Lockheed XP-49 and XP-58 Chain Lightning

The Lockheed P-38 Lightning was one of the outstanding US fighters of World War II, one of only two American twin-engine fighter planes for the US Army Air Force to enter production (the other being the Northrop P-61 Black Widow night fighter). In particular, one of the most famous P-38 missions of the war involved the shootdown of a G4M bomber flown by Admiral Isoroku Yamamoto, the architect of the Japanese attack on Pearl Harbor, and one P-38 pilot, Richard Bong, was the top American fighter ace of World War II, shooting down forty Japanese warplanes. However, with the exception of highly experienced military aviation historians, most people don't think highly often of the fact that Lockheed made two abortive attempts to develop an modernized P-38, the XP-49 and the XP-58 Chain Lightning. During my visits to the Planes of Fame Museum in January 2018 and again in June 2020, I saw a desktop model of the XP-58 inside a glass display cabinet at the museum's Foreign Hangar. My first post in an overview of experimental warplanes built in the Los Angeles basin drawing upon my photos of desktop models taken at air museums in Southern California dealt with the Hughes XF-11 spyplane and its secret D-2 predecessor; thus, the second post of this series will focus on the XP-49 and XP-58 Chain Lightning derivatives of the P-38.

Front angular view of the sole Lockheed XP-49 prototype (serial number 40-3055)

In March 1939, the US Army Air Corps issued Circular Proposal 39-775 and Specification XC-615 for a twin-engine escort fighter with two Pratt & Whitney Twin-Wasp radial engines and fitted with conventional undercarriage. Bell, Bellanca, Brewster, Curtiss, Grumman, Lockheed, and Vought submitted bids for the new fighter design, and Army Air Corps selected the Lockheed L-106 and Grumman G-41/G-45 designs for prototyping, designating them XP-49 and XP-50 respectively. The XP-49 was similar to the P-38 Lightning but differed in having a pressurized cockpit, as well as new nacelles and booms for different engines. It was 40 ft 1 in (12.22 m) long, with a wingspan of 52 feet (15.85 m), a gross weight of 19,948.5 lb (9,049 kg), a maximum take-off weight of 22,000 lb (9,979 kg), and a service ceiling of 37,500 feet (11,430 m). The XP-49 was originally intended to use two either two 2,000 hp (1,491 kW) Pratt & Whitney X-1800 H-block inline engines or two Wright R-2160 Tornado radial engines, but the X-1800 showed disappointing performance during bench tests in 1940 and was cancelled after just one example had been built, while the R-2160 ran into development problems, forcing Lockheed to substitute two 1,600 hp (1,193 kW) Continental XIV-1430 V-cylinder inline engines. Technical problems plaguing the Continental engines meant that the sole XP-49 prototype (serial number 40-3055) did not fly until November 14, 1942, by which time the introduction of P-38 variants with new versions of the Allison V-1710 engine made the XP-49 redundant. Not surprisingly, the low power output of the IV-1430 compared to the X-1800 meant that the XP-49 had dismal speed (406 mph at 15,000 ft) despite good maneuverability and handling, relegating the aircraft to being a mere testbed for the XIV-1430. The XP-49 continued to be tested at Wright Field, Ohio, and was scrapped in 1946.

Left: Desktop model of the Lockheed XP-58 Chain Lightning at the Planes of Fame Museum, Chino, California
Right: The first (and only completed) Lockheed XP-58 prototype (41-2670) in flight over Los Angeles County en route to Muroc Army Air Field. 

Now it should be possible to discuss the one P-38 derivative of which I saw a desktop model at the Planes of Fame Museum, the XP-58 Chain Lightning. In April 1940, Lockheed began work on an advanced version of the Lightning (company designation L-121 in return for the US Army Air Corps allowing for the export of the P-38 Lightning to France and the UK. The initial L-121 proposal was to use two Continental IV-1430 V-cylinder inline engines, and it was offered in single- and two-seat versions, the former with the P-38's armament and the latter armed with two tail boom-mounted 0.50-inch machine guns. The two-seat version was chosen for further development and designated XP-58, but concerns about the viability of the IV-1430 prompted Lockheed to re-engine the XP-58 design with two Continental X-1800 (H-2600) engines. The Model 20-14 design of September 1940 had a second forward-firing 20-mm cannon and the tail boom guns were replaced by a remote-controlled dorsal turret with two 0.50-inch machine guns. One XP-58 prototype was ordered with the serial 41-2670. Extensive details about redesign of the XP-58 are discussed in Angelucci & Bowers (1987), Francilion (1982), and Norton (2008), so thus not need repeating here. Lockheed explored the Pratt & Whitney XH-2470, Continental XH-2860, and Pratt & Whitney R-2800 Double Wasp as possible powerplants for the Chain Lightning after Pratt & Whitney shelved development of the H-2600 due to disappointing performance during test runs. The R-2800 was seen as a perfect choice by Lockheed, but the USAAC judged the XP-58's performance estimates with the R-2800 inadequate, suggesting that the Wright R-2160 Tornado be substituted for the Twin Wasp; Lockheed agreed to this recommendation and also revised the rear-firing armament of the XP-58 to include one ventral turret with a 0.50-inch machine gun. A second prototype was ordered by the Army Air Force in May 1942 with extra fuel capacity. Throughout the first two years of US involvement in World War II, the USAAF mission requirements for the Chain Lightning became superfluous, with the escort fighter role of the XP-58 being reworked into a ground attack machine and finally a bomber destroyer. With the Chain Lightning redesigned as a bomber destroyer, Lockheed proposed that the first prototype use four forward-firing 37-mm cannons, with the second having a 75-mm cannon and two 0.50-inch machine guns. When the R-2160 ran into development problems and was cancelled in February 1943, the XP-58 was equipped with two Allison V-3420 V-cylinder liquid-cooled engines. Only the first XP-58 prototype was finished, but without any armament and fitted with dummy dorsal and ventral turrets, and it first flew on June 6, 1944 (the same day as the D-Day invasion). By now, the need for a bomber destroyer had vanished, and the sole XP-58 became relegated to a non-flying instructional airframe in early 1945.

As a side note, in 1942 Lockheed proposed a redesigned version of the XP-58, under the designation L-134. Unlike the Chain Lightning, the L-134 lacked tail booms and instead had a conventional twin-tail empennage, and it had two piston engines inside the fuselage between the pilot and rearward-facing gunner driving counter-rotating pusher propellers. The nose was armed with six machine guns in three pairs, and the dorsal and ventral rearward-firing gun turrets were retained (Buttler and Griffith 2015, p. 68). There was also a version of the L-134 that would have had canards, judging from Lockheed documents. However, the L-134 was destined to remain a paper project only.      

References:

Angelucci, E., and Bowers, P.M., 1987. The American Fighter. Sparkford, UK: Haynes Publishing.

Buttler, T., and Griffith, A., 2015. American Secret Projects 1: Fighters, Bombers, and Attack Aircraft, 1937 to 1945. Manchester, UK: Crecy Publishing.

 

Francillon, R.J., 1982. Lockheed Aircraft since 1913. London, UK: Putnam & Company.

Norton, W., 2008. U.S. Experimental & Prototype Aircraft Projects: Fighters 1939–1945. North Branch, MN: Specialty Press.

Experimental warplanes from the Los Angeles basin, part 1: the Hughes D-2 and XF-11

Howard Hughes (1905-1976), the wealthy yet reclusive and eccentric aviator who would capture the public's imagination when he starred in the 2004 film The Aviator, is forever remembered for building the H-1 that set a new landplane speed record (352 mph) in September 1935 as well as the largest-ever flying boat, the 320-foot span the H-4 Hercules (popularly called the Spruce Goose), that had the biggest wingspan of any airplane until the 385-foot span Scaled Composites Stratolaunch space launch platform took to the skies in April 2019. Hughes also served as head of TWA from the late 1930s until 1966. During my visits to the Planes of Fame Museum in January 2018 and June 2020, I saw a model of the Hughes XF-11 prototype photo-reconnaissance aircraft in a glass display cabinet at the Jet & Air Racers Hangar, but I also happened to notice a desktop model of the XF-11's top-secret and seldom-known ancestor, the D-2 prototype attack/fighter aircraft. Given that the Hughes D-2 is one of the most enigmatic US warplane designs of the World War II era, but also the fact that the XF-11 shared much of its heritage with the D-2, I thought it would make sense to devote the first post out of a number of planned blog posts on prototype warplanes from the Los Angeles area to the D-2 and XF-11.

Left: Hughes company artwork showing notional Hughes A-37 attack aircraft bombing a German factory

Right: Artist's rendering of the proposed A-37 attack version of the D-2

The story of the mysterious D-2 goes back to 1937 when Howard Hughes envisaged a design for a twin-engine, twin-boom interceptor in response to the X-608 specification by the US Army Air Coprs for a twin-engine fighter plane. The design, which was similar in layout to the Lockheed P-38 Lightning that won the X-608 competition, was stated by Hughes himself in a 1947 testimony before the US Senate to have been stolen by Lockheed, although many others refute this claim. Although the Hughes design lost to the P-38 Lightning, beginning in the summer of 1939 the Hughes Aircraft Corporation began work on a new aircraft design, the D-2 (aka DX-2), which was to be made of Duramold, a plastic-bonded plywood molded under heat and pressure. The D-2 design was floated by Hughes personnel as having the potential to be used as either a light bomber or heavy fighter. The D-2 design was initially to have a tailwheel but the landing gear arrangement was changed to a tricycle undercarriage as in the P-38, with the main wheels retracting into the tail booms and a nose wheel retracting and folding 90 degrees into the nose. The originally intended powerplant for the D-2 was to have consisted of two Wright R-2160 Tornado liquid-cooled radial piston engines, but developmental problems with the Tornado caused Hughes to substitute two Pratt & Whitney R-2800 Double Wasp radials. By March 1941, the D-2 design was relegated to its role as a convoy protector with a 2,600 mile (4,284 km) range, 450 mph (724 km/h) top speed, and seven .50-cal machine guns. In response to an August 1941 Army Air Force requirement for a convoy protector able to escort bombers for distances of up to 2,000 miles (3,218 km), Hughes proposed the D-3 with two four-gun turrets, design estimates of which were submitted to the Air Material Division on January 13, 1942. Power was supplied by two Allison V-3420 V-cylinder inline piston engines, and four variants of the D-3 were under consideration: the D-3 bomber convoy-protector, D-3F fighter, D-3H interceptor, and D-3R bomber convoy-destroyer (Buttler and Griffith 2015, pp. 59-60).

Top: Hughes D-2 under construction at the Hughes factory in Culver City, late 1942

Bottom: The completed D-2 at Harper Dry Lake in front (left) and side (right) views

 

Although Duramold was a potential remedy for shortages of strategic metals, it was difficult to work with, so the US Army Air Force judged Duramold to be insufficiently robust, rejecting the D-2 for use as a fighter plane in November. However, in early 1942, the AAF reversed course and decided that the Duramold construction of the D-2 could be suited for high aerodynamic performance, so Hughes was given the go ahead to build one D-2 prototype. The D-2 was 57.8 feet (17.6 meters) long, with a wingspan of 60 feet (18.3 meters), a gross weight of 31,672 pounds (14,366 kg), a top speed of 433 mph (697 km/h) at 25,000 ft (7,620 m), a cruising speed of 274 mph (441 km/h), and a service celling of 36,000 ft (10,973 m). Armament included 2,200 lb (998 kg) of bombs and ten .50-cal machine guns (six on the nose, four positioned above each other in a turret in the rear of the fuselage nacelle). In June 1942, the USAAF reserved the XP-73 designation for the D-2 fighter version, but in July, it envisioned the D-2 more in its role as an attack aircraft, so recommended designating it XA-37 (Norton 2008, p. 192). (Neither designation was officially used for the D-2.) Construction of the D-2 commenced in secret and even though the USAAF wanted to spend $500,000 on the D-2's construction, Hughes turned down the offer, instead investing $3 million to build the D-2 with his fortune. Still lacking a definite role, the D-2 was completed at a facility in Harper Dry Lake near Barstow, California, and after a few modifications to the control surfaces following some technical problems in ground tests, it made it first flight on June 20, 1943, with Hughes himself at the controls. The D-2 accumulated nine hours of flight testing, but issues with control surfaces prompted Hughes to propose an improved version of the D-2 with a new wing spanning 92 feet (28 meters) and larger bomb bay, the D-5. However, many in the USAAF remained disinterested in the D-2 and D-5, largely due to Hughes' erratic behavior and a collective feeling that his company didn't have the capacity to undertake series aircraft production, so on August 13, the AAF decided not to take any further action regarding the D-2 or D-5. On November 11, 1943, the D-2 was being modified to D-5 standard at its hangar in Harper Dry Lake when the hangar housing it was destroyed by a lightning strike (some claim Hughes deliberately burned the aircraft and hangar).

Desktop models of the Hughes D-2 (left) and XF-11 prototype reconnaissance aircraft (right) in a glass display cabinet at the Planes of Fame Museum, Chino. The differences between the two in size and rearward extent of the fuselage nacelle are evident.

Even before the D-2 was destroyed by fire, in early August 1943, President Franklin D. Roosevelt's son, Colonel Elliot Roosevelt, toured the Los Angeles area conversing with US aircraft companies to develop a dedicated photo-reconnaissance aircraft. He was greeted by Hughes, who took him on a tour of the D-2. Roosevelt was so impressed by the D-2 design that the White House asked USAAF General Henry "Hap" Arnold to approve full-scale development of a reconnaissance version of the D-5 design. To address concerns about duramold construction by the US Army Air Force, the design was revised so that the wings and tail booms would be of all-metal construction, with only the fuselage being of duramold construction (Hansen 2012, p. 541). On October 6, 1943, the USAAF issued a letter of intent to purchase 100 of the D-5 reconnaissance version under the designation F-11, and a contract was signed on May 5, 1944, for two prototypes (serial numbers 44-70155/70156) and 98 production machines (44-70157/70254). (Prior to 1948, all reconnaissance aircraft were designated with the letter F, but after the USAAF became the US Air Force, F was used to denote fighters and the Air Force substituted R for F when denoting reconnaissance planes.) The XF-11 was 65 ft 5 in (19.9 m) long, with a wingspan of 101 ft 4 in (30.9 m), a height of 23 ft 3 (7.09 m), a top speed of 450 mph (725 km/h), and a service ceiling of 42,000 ft (12,802 m). The aircraft had an empty weight of 39,278 lb (17,816 kg), a maximum weight of 58,315 lb (26,451 kg), and a 5,000 mile (8,047 km) maximum range with 2,105 gallons (7,968 L) internal fuel. Besides having a bigger wingspan and using metal in construction of the wings and tail booms, it also differed from the D-2 in that the fuselage nacelle only extended to the middle of the wing's center section, and power was supplied by two Pratt & Whitney R-4360 Wasp Major radials. The front of the fuselage and left tail boom contained photographic equipment, and one of the crew members could serve as a photographer by crawling past the pilot and into the aircraft's nose to service the cameras in flight.

Left: The first XF-11 prototype (44-70155) takes off for its ill-fated first flight, which nearly cost Howard Hughes his life

Right: Top view of the second XF-11 prototype (44-70156) with single rotation propellers

The first XF-11 was originally scheduled for November 1944 with production plans for 10 aircraft a month. However, delays were encountered almost immediately, supporting the USAAF's belief that the Hughes Aircraft Corporation wasn't up to series aircraft production. By mid-1945, the XF-11 had not yet flown, and with World War II winding down, the F-11 production contract was canceled on May 26, 1945, but construction of the two prototypes continued. The first prototype, completed in April 1946, featured Hamilton Standard counter-rotating propellers. After receiving minor damage during taxi testing, it took off for its maiden flight on July 7, 1946. One hour and 15 minutes into the flight (contravening the USAAF's requirement that the first flight last 45 minutes), the rear set of propellers went into reverse pitch, and the aircraft lost altitude, crashing into a golf course in Beverly Hills. Hughes himself escaped the burning wreckage, but suffered severe burns, a displaced heart, a punctured lung, and broken ribs, so he was hospitalized for several months. The second XF-11 prototype (44-70156) was subsequently completed with single rotation Curtiss Electric propellers (legend has it that Hughes masterminded these modifications from his hospital bed). It first flew on April 4, 1947, with Hughes himself at the controls; the first flight of the second prototype was smooth and flawless, and in November the aircraft was delivered to Wright Field, Ohio. Test flights at Eglin Air Force Base in Florida lasted from December 1947 to July 1949, and even though the second XF-11 displayed good performance, in-flight access of the camera equipment was difficult and some of the aircraft's systems were unreliable. After the Air Force became independent of the Army in 1947, it changed the designation lettering for reconnaissance aircraft from F to R, meaning that XF-11 became XR-11. By now, however, the intended operation role of the XF-11 was taken up by B-29s and B-50s modified for reconnaissance, so the XF-11 became irrelevant. The second XF-11 was flown to Sheppard Air Force Base in Wichita Falls, Kansas, on July 26, 1949, serving as a ground training aid. It was finally stricken off the USAF inventory in November and eventually scrapped.

As a side note, it is astounding to note that the XF-11 became a political football long after reaching the hardware phase. Technical and managerial problems during development of the XF-11 but also the H-4 flying boat prompted the Truman Committee and Brewster Committee to investigate the XF-11 and H-4 programs in 1946-1948, precipitating the Hughes-Roosevelt hearings of August 1947 (Hansen 2012, pp. 530-536). Senator Owen Brewster claimed that Howard Hughes received $40 million from the War Department without delivering any of the F-11s on contract, but Hughes insisted that Brewster had been motivated by his connections to Pan American World Airways, the rival to Hughes' TWA. Despite making counter-claims, Brewster's reputation suffering as a result of the hearing, and he resigned from the Senate at the end of 1952.

The story of the D-2 and its big descendant the XF-11 is a reminder the promising military applications offered by the Hughes Aircraft Corporation's novel aircraft designs, yet it duly reflects the eccentric nature of Howard Hughes himself, considering that the reclusive aviator felt he could finance construction of the D-2 and XF-11 with his own money with little financial input from the US military top brass.

References:

Buttler, T., and Griffith, A., 2015. American Secret Projects 1: Fighters, Bombers, and Attack Aircraft, 1937 to 1945. Manchester, UK: Crecy Publishing.

Hansen, C., 2012. Enfant Terrible: The Times and Schemes of General Elliott Roosevelt. Tucson, AZ: Able Baker Press.

Norton, W., 2008. U.S. Experimental & Prototype Aircraft Projects: Fighters 1939–1945. North Branch, MN: Specialty Press.

Yenne, B., 1990. The World's Worst Aircraft. New York: Barnes & Noble Books.

Lockheed A-12: SR-71's precursor

The Lockheed SR-71 Blackbird is remembered as the fastest military aircraft ever produced, attaining top speeds of Mach 3 and holding the speed record for the fastest speed by a manned air-breathing plane (2,193 mph, achieved on July 28, 1976). However, most fans of the SR-71 Blackbird may not be aware that not all Blackbirds built were SR-71s, because the first iteration of the Blackbird to be constructed was the A-12. While visiting the California Science Center in July 2019 to mark the 50th anniversary of the Apollo 11 moon landing and the San Diego Air and Space Museum in August of that year, I had the chance to glance up two examples of the A-12, both of them mounted on pedestals outside their respective museums.

Top: A-11 design (left) and initial A-12 design (right) (after Robarge 2012) 

Bottom left: First A-12 (serial number 60-6924) on takeoff from Area 51 for its first official flight, April 30, 1962

Bottom right: A-12s lined up on the tarmac at Area 51, 1960s

For technical starters, at first glance, A-12 may look like a military designation, because the letter A in the US Defense Department's Tri-Service designation system for aircraft denotes attack aircraft. However, "A" in A-12 actually stood for Archangel, meaning that A-12 was the shortened form of Archangel-12. The Lockheed Skunk Works headed by Clarence "Kelly" Johnson had given the U-2 Dragon Lady the project codename Angel, and when CIA official Richard Bissell in 1957 asked US aerospace companies to look into designs for an advanced reconnaissance plane to replace the U-2, Lockheed chose to apply the project codename Archangel to design studies for a superfast U-2 successor, because those spyplane proposals were all intended to fly at altitudes above 90,000 feet at Mach 3, faster and higher than the U-2, which could only fly as fast as a subsonic jet bomber and early generation jet fighters. As aircraft designs evolved and changes to the configuration were made, the various Archangel studies became known as A-1, A-2, et cetera. By early 1959, Kelly Johnson unveiled two Archangel designs with diamond shaped delta wings, the A-10 with General Electric J93 turbojets and length of 109 feet, and the A-11 with two Pratt & Whitney J58 turbojets and a length of 116 feet (Robarge 2012, pp. 4-5). The A-11's rival design, the Convair FISH (First Invisible Super Hustler), had a much smaller radar cross section, and for this reason CIA official Edwin Lang rejected the A-11 design as not having a small enough radar cross section despite the immaturity of the technology planned for the FISH. Therefore, Johnson reworked the A-11 design with two J58s arranged in individual nacelles buried in the middle of the wings and twin canted fins to create the A-12. Lockheed submitted the A-12 design to a joint DoD-CIA-USAF panel at the Pentagon in July 1959, and Convair submitted their rival design, the Kingfish, with had two internally mounted J58s. Although the CIA favored the Kingfish because it had a much smaller RCS, the Convair company was facing cost overruns in development of the B-58 Hustler supersonic bomber, and because Lockheed had built the U-2 under budget and on time, the US Air Force persuaded the CIA to pick the A-12 instead, and on August 28, the A-12 was chosen as the successor to the U-2. The A-12 eventually was given the CIA codename Oxcart, and the CIA placed an order for twelve A-12s (serial numbers 60-6924/6939), the first of which flew on April 26, 1962 at Groom Lake, Nevada (flown by test pilot Lou Schalk. The A-12 fleet began deployment in May 1967 from Kadena Air Base in Okinawa, Japan, with operational overflights over North Vietnam. A number of A-12 sorties were conducted over North Korea, two of which took place when North Korea seized the warship USS Pueblo in early 1968. By now, budgetary constraints caused A-12 operations to be discontinued on May 1968, with the A-12s being retired in June. It would not be until 1982 that the CIA publicly disclosed details of the A-12 program.

Top: A-12 "Titanium Goose" (serial number 60-6927) preparing to refuel from a KC-135

Bottom left: Side view of the A-12 "Titanium Goose"; bottom right: Cockpit of the "Titanium Goose" in front view 

Now the overview of the A-12's development life brings my attention to the two above-mentioned examples of the A-12 that I have seen in person. The first one to be discussed, and the most jaw-dropping one, is the A-12 with the serial number 60-6927, which is on display at the Roy A. Anderson Blackbird Exhibit & Garden within the California Science Center. This aircraft, delivered in November 1963, was the only A-12 of its kind to be built in a two-seat trainer configuration, with the rear cockpit (accommodating the flight instructor) being raised and slightly offset relative to the front cockpit for the pilot. Instead of J58s, the A-12 trainer used the less powerful Pratt & Whitney J75 turbojets, and In case of an emergency, the flight instructor would take control of the aircraft. The appearance of the cockpit configuration led to 60-6927 being nicknamed "Titanium Goose" by the popular press. The "Titanium Goose" was transferred to the Military Aircraft Storage and Disposal Center in April 1977 years after being retired, and in August 2003 it was made an aviation exhibit at the California Science Center.

Lockheed A-12 serial number 60-6933 on display at the entrance to the San Diego Air and Space Museum in Balboa Park, San Diego, California. 

The other A-12 airframe that I saw during my travels that is worth discussing is the A-12 serial number 60-6933. This aircraft was the tenth A-12 to be built and delivered to Groom Lake, with delivery taking place in 1964. A number of traits are evident in this airframe that served to distinguish the A-12 from the later SR-71 Blackbird, including provisions for the pilot only, a slightly shorter fuselage, and the shape of the chines that were designed to deflect radar returns. Because the A-12 was intended to fly over enemy targets when penetrating enemy airspace, it could carry a better camera and far more spy instruments (the SR-71, by contrast, had SIGINT sensors and a side-looking airborne radar). Although the A-12 was made primarily from titanium to withstand heat friction at Mach 3, it also made use of radar-absorbent plastic composites on the edges of the wings to absorb radar waves. Ironically, even though individual airframes of most US military aircraft are consigned to the boneyards after retirement to be either scrapped or used for test purposes, all A-12s that were retired (five aircraft having been lost in accidents), including 60-6933 and 60-6927, made their way into museums.

Together with the SR-71, the A-12 represents the determination of the American aerospace industry to take spy plane technology to new heights during the Cold War by braving the technological challenges to developing a reconnaissance aircraft that could efficiently fly at high altitudes in the Mach 3 flight regime when flying over enemy territory. Due to the high value of the titanium alloy used in the A-12's construction, it is miracle that none of the A-12s retired from active duty were ever destroyed by the breaker's torch, and these planes will forever remain testaments to the ingenuity of Lockheed engineers in coming up with bold new ideas for future aircraft design.

References:

Landis, T.R., and Jenkins, D.R., 2005. Lockheed Blackbirds (Warbird Tech Series, Volume 10), Revised edition. Minneapolis, MN: Specialty Press. 

Robarge, D., 2012. Archangel: CIA's Supersonic A-12 Reconnaissance Aircraft, 2nd edition. Washington, D.C.: Central Intelligence Agency.

Convair C-131/R4Y Samaritan

The Convair company is best known in US aviation history for developing famous bombers and flying boats, including the PBY Catalina, PB2Y Coronado, B-24 Liberator (including the RY, C-87, and C-109 transport versions and PB4Y-1 patrol version), B-32 Dominator, B-36 Peacemaker, and PB4Y-2 Privateer. However, shortly after World War II, Convair dipped its toes into the development of civil and military transport planes, including the creation of turboprop-powered airliners rivaling the UK's Vickers Viscount. During my visits to the Yanks Air Museum in Chino and the March Field Air Museum in Riverside, I happened to come upon two examples of a twin-engine piston-powered plane similar to appearance to the C-54 Skymaster. Eventually, it would be clear to me that the twin-engine plane wasn't a Douglas plane, but instead the C-131 Samaritan, a military version of the Convair CV-240/340/440 airliner series.

                                                    

Top: Convair C-131F (originally R4Y-1) BuNo 141000 in flight, 1970s

Bottom left: Convair C-131B (serial number 53-7184) of the New Mexico Air National Guard, 1950s 

Bottom right: T-29A trainer (serial number 49-1941 at RAF Burtonwood, Lancashire, 1957

The Convair C-131 Samaritan had its genesis in the Convair CV-240 piston engine airliner that first flew on March 16, 1947 and entered service in February of the following year. The US Air Force expressed interest in the ConvairLiner series and asked Convair to build two military versions of the aircraft, the C-131 Samaritan transport and the T-29 Flying Classroom trainer. The C-131, like the CV-240/340/440 series, had two Pratt & Whitney R-2800 Double Wasp radial piston engines each delivering 2,400 horsepower, but it featured provisions for either 39 troops or 20 stretchers and 7 seats. The T-29, on the other hand, featured 14 fully equipped stations for students or instructors and one radio operator's station, with each student having access to a map table, Loran scope, altimeter, and radio compass panel. The T-29 made its first flight on September 22, 1949, and the first T-29A was delivered in March 1950, with the initial T-29A version having an unpressurized fuselage and later versions (T-29B, T-29C, and T-29D) featuring a pressurized fuselage; production of the T-29 totaled 365 planes. The T-29's purpose was to instruct bombardiers, navigators, and radio operators for Air Force planes. There was a planned bomber training version of the T-29 with a transparent nose, the T-32, but this design was not built. The C-131 Samaritan, meanwhile, did not reach USAF service until 1954, and it was primarily used for medical evacuation and personnel transportation, with a few C-131s being retained for training and testing. The Samaritan was ordered by the US Navy under the designation R4Y, and the first of 36 R4Ys was delivered in 1952. The R4Y had a seating capacity of 44 passengers and it was assigned to Navy and Marine Corps squadrons as logistic and administrative aircraft. One C-131 was used in 1959 for training astronauts as part of the first US manned spacecraft program, Project Mercury. The C-131s were retired from active USAF units in the late 1970s, but the Air National Guard and Navy continued to operate the aircraft until 1990.

Left: Convair C-131D (serial number 54-2808) on display at the March Field Air Museum, Riverside, California 

Right: Convair C-131F (originally R4Y-1) BuNo 141013 on display at the Yanks Air Museum, Chino, California

The Samaritan that I saw at the Yanks Air Museum was originally built as an R4Y-1 with Navy BuNo 141013 and delivered to the US Navy on January 3, 1956. It served with the Navy for 26 years before being retired to the Military Aircraft Storage and Disposal Center in 1982, where it remained until May 26, 2004, when it was transferred to the Yanks Air Museum with the civil registration N9030V. Following the Defense Department's creation of the Tri-Service designation system for all US military aircraft on September 18, 1962, the R4Y-1 was re-designated C-131F, while the R4Y-1Z and R4Y-2 versions became VC-131F and C-131G respectively. On the other hand, the C-131 Samaritan on display at the March Field Air Museum is of the C-131D version and bore the US Air Force serial number 54-2808, with its first flight on July 28, 1954, and delivery to the Air Force on October 19. It served as a VIP transport initially with the Military Transport Command and later the Tactical Air Command until May 31, 1989, when it was retired from USAF service.