Southern California's masters of airlift, part 3: C-15 and C-17 Globemaster III

The last post of my three-part series on the strategic airlifter dynasty produced by Douglas will focus on the last Douglas/McDonnell Douglas strategic airlifter (and by broader extension the last military aircraft to be built by the Long Beach division of Douglas/McDonnell Douglas) to be built, the C-17 Globemaster III. Today, the C-17 is part of the strategic airlift backbone of the US Air Force' Air Mobility Command (AMC), occupying a niche in strategic airlift once occupied by the Lockheed C-141 Starlifter, and it also serves the air forces of a number of US allies around the world, including the UK. However, the roots of the C-17 itself can be traced back to a short-lived effort by McDonnell Douglas to produce a jet-powered C-130 successor for the USAF, and therefore the scope of this post with respect to the C-17 Globemaster III will limit itself to the design, development, flight testing, and early deployment of the C-17 as well as the C-17's ancestor, the YC-15 prototype tactical airlifter.

McDonnell Douglas YC-15, ancestor of the C-17 Globemaster III

The long-term genesis of the C-17 begins in 1972, when the US Air Force issued a requirement for a new STOL tactical airlifter to replace the C-130 able to operate from a 2,000-foot (610 meter) semi-prepared field with a 27,000-lb (12,000 kg) payload. Five companies (Bell, Boeing, Fairchild, McDonnell Douglas, and a Lockheed/North American Rockwell team) submitted designs for the Advanced Medium STOL Transport (AMST) competition, and November 10, Boeing and McDonnell Douglas were selected to build two prototypes each for the AMST contest; the Boeing Model 953 was called YC-14 and the McDonnell Douglas design received the designation YC-15. While the YC-14 was unique in having two turbofans above the wings to create high-velocity airstreams over the inboard section of the wing and over special trailing-edge flaps for high aerodynamic lift (the so-called Coanda effect), the YC-15 layout was more conventional, with four underslung turbojets. The YC-15 made its first flight on August 26, 1975, and a total of 600 flight hours were made by the two YC-15 prototypes. Despite the YC-14 and YC-15 meeting or exceeding AMST requirements, the Air Force found that strategic airlift was of greater importance than tactical airlift, so in December 1979 the AMST program was terminated without either design having been selected for production. The first YC-15 prototype was returned to flying status by McDonnell Douglas in 1996 and flew again on April 11, 1997, being ferried to Long Beach in support of the proposed C-17B five days later. On July 11, 1998, however, the aircraft suffered a No. 1 engine failure and made an emergency landing in Palmdale, California; the USAF deemed the aircraft too expensive to repair and the first YC-15 is now on display at the Air Force Flight Test Center Museum's "Century Circle" display area at Edwards Air Force Base.

Top: Model of the C-17 Globemaster III at the Western Museum of Flight. Photographed by me on May 11, 2019.
Bottom: C-17s flying over the Blue Ridge Mountains in the eastern US in December 2005.

Shortly before the cancellation of the AMST program, in November 1979, the Air Force commenced the C-X program for a new-generation strategic airlifter combining the STOL performance of both the YC-14 and YC-15 with greater operating range. A request for proposals was issued in October 1980, and Boeing, Lockheed, and McDonnell Douglas submitted bids for the C-X context. The McDonnell Douglas design was similar to the YC-15 but had backswept wings, while the Boeing Model 1050 (internally called 'C-16') had three engines, two atop the wings as in the YC-14 and a third in the tail empennage (similar to that of the Lockheed L-1011 TriStar), and two designs offered by Lockheed were based on the C-5 and C-141. On August 28, 1981, the McDonnell Douglas design was selected as the winner of the C-X competition, receiving the designation C-17, and in December 1985, a full-scale development contract was awarded, with the USAF planning to procure 210 C-17s. However, budget constraints meant that the C-17 development program was moving at a slow pace, so the US Air Force gave the green light to a new production run of the C-5 Galaxy, modifying several C-141As to C-141B configuration, and continued purchases of the KC-10 Extender. By April 1990, the procurement for the C-17 was reduced to 120 aircraft, and on September 15, 1991 the C-17 made its first flight, later receiving the official name Globemaster III in 1993. Despite a number of problems during flight tests, including issues with wing loading, the Globemaster III was cleared for operational service in January 1995. Production of the C-17 surprisingly exceeded the originally planned procurement of 210 aircraft, with a total of 279 C-17s being manufactured until 2015 (long after McDonnell Douglas merged with Boeing in August 1997), when the last C-17 was delivered to the Air Force after Boeing shut down the Long Beach factory that Douglas and McDonnell Douglas had used to manufacture the C-74, C-124, C-133, YC-15, and C-17. Since entering service in 1995, the C-17 has seen operational deployment during a number of wars, including the 1999 Kosovo War, the War in Afghanistan, the Iraq War, the French intervention in Mali, among other conflicts. The onset of the C-17 meant that the C-141 Starlifter fleet was replaced by the Globemaster III in May 2006. Besides the US Air Force, the C-17 also serves with the Royal Air Force, Royal Canadian Air Force, Royal Australian Air Force, Indian Air Force, Kuwait Air Force, Qatari Air Force, and United Arab Emirates Air Force. 

Display model of the unbuilt C-17B tactical airlifter

In an interesting footnote, in the late 1990s, a tactical airlifter version of the C-17 was offered to the USAF as the C-17B, utilizing the STOL capability of the YC-15, and a commercial freighter variant of the C-17 was proposed for the civilian freight market as the MD-17 (later BC-17X). However, neither of these proposals progressed beyond the design phase. To this day, the USAF still uses the C-130 as its primary tactical airlifter due to the cancellation of the AMST competition and the failure of the C-17B to win military orders. The Royal Air Force, however, has gone into full bore deploying the new Airbus A400M Atlas as its primary airlifter for both strategic and tactical use after having purchased the C-17 as a backup pending the arrival of the A400M.

This post concludes my three-part overview of the airlifter dynasty developed from 1945 to 2015 by Douglas, and later McDonnell Douglas and Boeing. Throughout their operational history, the airlifters produced in the Santa Monica-Long Beach area have played a role in the mobility needs of the US Air Force and Army, including not only transporting troops and tanks to war zones abroad but also ferrying ICBMS to missile silos in the US. Although the factories that produced the C-74, C-124, C-133, YC-15, and C-17 no longer exist, Southern California was able to work in tandem with Lockheed to produce a variety of airlifter designs to create the present-day US air mobility landscape. 

References:

Cox, G., and Kaston, C., 2020. American Secret Projects 3: U.S. Airlifters Since 1962. Manchester, UK: Crécy Publishing.

Norton, B, 2001. Boeing C-17 Globemaster III. Minneapolis, Minnesota: Specialty Press. ISBN 978-1-5800-7040-9.

Norton, B, 2002.. STOL progenitors: The Technology Path to a Large STOL Transport and the C-17A. Reston, Virginia: American Institute of Aeronautics and Astronautics. ISBN 978-1-56347-576-4.

Southern California's masters of airlift, part 2: the C-132 and C-133 Cargomaster

The second post in my multi-post series about Douglas/McDonnell Douglas strategic airlifters focuses on the first-generation of gas turbine-powered heavy-lift transport planes conceived by Douglas in the 1950s (by which time long-range airlift was becoming enshrined as a pillar of US strategic military aviation policy). As explained in my previous post on the C-74 Globemaster and C-124 Globemaster II, Douglas had tinkered with re-engining the C-124 with turboprop engines, producing the YC-124B (aka C-127) prototype turboprop airlifter, but test flights revealed that the operating range of the YC-124 fluctuated with altitudes because the C-124 airframe was unpressurized (although the YC-124B had a pressurized cockpit). Thus, this post will focus on Douglas designs for turboprop-powered heavy-lift aircraft, including the C-133 Cargomaster and the unbuilt C-132 project.   

Top: Desktop model of the C-133 Cargomaster at the Western Museum of Flight
Bottom: C-133B Cargomaster (serial number 59-0529) flying over San Francisco Bay, 1960 

After recognizing the deficiencies of the YC-124B in terms of operating range at varying altitudes, the Douglas Aircraft Company realized that pressurizing the entire C-124 design would require a panoply of design changes, including fixing the auxiliary floors in the down position and latching them to form a tension tie across the fuselage (effectively eliminating the ability to haul outsized cargo), and reskinning sections of the fuselage with thicker-gauge aluminum. Douglas therefore envisaged a new large strategic transport design, the Model 1324 (dubbed 'C-124X' internally by Douglas), which retained the wings of the YC-124B/YKC-124B but differed in having a circular cross-section fuselage. Early designs for the Model 1324 had the nose ramp and tail shape of the C-124, but later proposals had the ramp moved to the tail section to enable air-dropping of cargo. Nine Model 1324 configurations were proposed, all varying in turboprop engine options, wing flap types, and gross weight levels. Despite the improvements in wing and fuselage geometry, the cargo deck of the Model 1324 was far from truckbed height, so on March 24, 1953, the Model 1324 was abandoned in favor of the Model 1333, which had a new shoulder-mounted wing that had a revised airfoil, thickness, twist, and leading and trailing edge sweep angles, as well as the fuselage being lowered to the ground so that the cargo deck was low enough for trucks and military vehicles to be loaded into the aircraft. Other features of the Model 1333 included elimination of the secondary deck, all passenger provisions and pressurization. 

Douglas C-133A (serial number 56-2010) at RAF Lakenheath, Suffolk, England, in May 1969

On August 10, the Model 1333 was given the designation C-133 by the US Air Force, and on April 23, 1956 the C-133 made its first flight; no C-133 prototypes were ever ordered because no other aircraft offering the immediate prospect of the performance and cargo capabilities of the C-133. Operational deployment of the C-133 Cargomaster with the Military Air Transport Service commenced in August 1957, and a total of 50 C-133s (35 C-133As and 15 C-133Bs) were built and deployed. Although the C-133A was not specifically designed to carry ICBMs, the C-133B had rear cargo doors modified to open to the side, making ICBM loading much easier. Douglas in May 1959 offered a variant of the C-133B with improved cargo capacity, an aerodynamically efficient and symmetrically tapered rear fuselage, and four Allison T61 turboprops, known as the Model 1476, but this design did not progress beyond the drawing board. During their service life, C-133s ferried ICBMs to and from missile silos in the US as well as Atlas, Titan, and Saturn rockets to Cape Canaveral to be used to launch Mercury, Gemini, and Apollo manned spacecraft, and they helped transport war material and troops to US bases in Western and Central Europe while proving invaluable in the Vietnam War. The C-133 served with MATS until 1971, when it was replaced by the Lockheed C-5 Galaxy.

Top: A desktop model of the proposed cargo pod-carrying variant of the Douglas Model 1240
Bottom: An artist's conception of the C-132 heavy airlifter in flight

It would not be possible to complete my discussion of Douglas turboprop-powered strategic airlifters without mentioning a number of Douglas heavy-lift aircraft designs that were conceived in parallel with the C-133 but never reached the hardware phase. In response to the XC-Heavy requirement issued by the US Air Force in early 1951, Douglas proposed a military transport version of twin-boom Model 1240 (similar to the company's Model 1211J turboprop-powered strategic bomber project in having a very high-aspect-ratio swept wing), which had one central and two auxiliary cargo pods under the wing center section. The Model 1240 pod-carrying variant had a wingspan of over 200 feet, and power was to be provided four turboprops and two auxiliary turbojets. The cargo pod-carrying variant of the Model 1240, however, was not proceeded with because the US Air Force judged the price of the design to be a 6.9% drag penalty compared to a conventional cargo plane. Douglas eventually returned to the drawing board to fine-tune its design for the XC-Heavy contest, and after investigating a spree of somewhat smaller designs with new engine options, it opted for a conventional transport design with a shoulder-mounted back swept wing, the Model 1814. On December 5, 1952 the Air Force selected the Model 1814 for full-scale development and designated it XC-132 in April 1953. The C-132 fuselage had a 'double-lobe' cross section to accommodate two decks, the upper part being pressurized forward of the wing-box for the flight crew. The lower part of the fuselage would accommodate all military vehicles, equipment, or special weapons, and provisions were made to anchor the cargo netting to the sidewalls of the bay. The C-132 was 183 feet 10 inches (56.03 meters) long with a wingspan of 186 feet 8 inches (56.90 meters) and the ability to carry 100,000 pounds (45,359 kg) of cargo, while power was to be supplied by four Pratt & Whitney T57 turboprops each delivering a total of 15,000 shp (11,000 kW). Douglas also planned a tanker variant of the C-132 as the KC-132, which was to be 12,689 lb (5,755 kg) heavier than the C-132 with a total fuel load of 290,000 lb (131,542 kg), and one C-132 variant, the Model 1905, was envisaged in December 1955 with a pressurized upper aft deck compartment to accommodate 100 troops and a more powerful version of the T57. In 1953, a full-scale mock-up of the C-132 was built at the Douglas plant in Santa Monica, with inspection of the mock-up conducted in early 1954. Two YC-132 prototypes were ordered, and the T57 turboprop planned for the C-132 was tested aboard a C-124 Globemaster II in October 1956. Plans called for the construction of the C-132 prototypes to begin in May 1957, with final assembly taking place in June 1958, rollout in May 1959 and the first flight in August. However, on March 29, 1957, the US Air Force cancelled the C-132 program before construction of the prototypes could begin due to budget cuts, concerns about the small size of the cargo space relative to the overall size of the aircraft, expected difficulties in loading ICBMs into the C-132, and the cancellation of the T57.  

References:

Cox, G., and Kaston, C., 2019. American Secret Projects 2: U.S. Airlifters 1941 to 1961. Manchester, UK: Crécy Publishing.

Gunston, B., 1991. Giants of the Sky: The Largest Aeroplanes of All Time. Sparkford: Patrick Stephens Limited.

Taylor, C., 2005. Remembering an unsung giant: the Douglas C-133 Cargomaster and its people. Olympia: Firstfleet Publishers. ISBN 978-0977676200.

Southern California's masters of airlift, part 1: C-74 Globemaster and C-124 Globemaster II

The Boeing (McDonnell Douglas) C-17 Globemaster III and Lockheed C-5 Galaxy have served as the workhorses of the strategic airlift needs of the US Air Force since the early 1970s, carrying huge loads of troops, tanks, and other military vehicles to faraway lands in peace or war. However, one important part of the history of US strategic airlift that is sometimes overlooked is the fact that long before the C-5 Galaxy and other US jet-powered strategic airlifters arrived on the scene, many of the first American strategic airlifters comparable to the C-5 Galaxy were being developed in the design offices of the Douglas Aircraft Company in Santa Monica and Long Beach in the 1940s and 1950s. Due to the long history of strategic airlift design by Douglas (and later McDonnell Douglas and Boeing), I've opted to dedicate three posts to strategic airlifter designs from Douglas/McDonnell Douglas/Boeing, of which this post will discuss the first two Douglas heavy-lift aircraft designs, the C-74 Globemaster and C-124 Globemaster II.

Top: Douglas C-74 Globemaster (serial number 42-65404)
Bottom: C-74 Globemaster (serial number 42-65402) in flight 

When the US entered World War II after the Japanese attack on Pearl Harbor in December 1941, the US Army Air Force, sensing grievous losses of Allied merchant ships to U-boats and Focke-Wulf Fw 200 patrol bombers, but also facing the arduous task of capturing Japanese-controlled island chains in the western Pacific to help stem Japanese aggression in the Pacific, stressed the need for a large transport aircraft to carry huge payloads over long distances to war zones in Europe and the Pacific. In January 1942, Douglas commenced design studies for a heavy-lift transport aircraft designated the Model 415, which had a wingspan of 207 feet (63.14 meters), a bug-eye cockpit, and four Pratt & Whitney R-4360 Wasp Major radial engines. The initial Model 415 design would have carried two T9E1 tanks, two 105 mm howitzers, two angle dozers, or three disassembled P-40 Warhawk fighters. The US Army Air Force, however, judged the Model 415 too expensive to procure in quantity, so in February Douglas offered a revised long-range transport design, the Model 415A. The Model 415A design spanned 173 feet (52.84 meters), weighed 33 percent less when fully loaded and used four Wright R-3350 Duplex Cyclones; an alternate layout was conceived with six radial engines (possibly the Pratt & Whitney R-2800 Double Wasp). The USAAF approved the Model 415A design because of the lower unit cost compared to the original Model 415, and in March 1942 Douglas began the process of freezing the Model 415A design, now formally designated C-74; a contract was signed on June 25 for 50 aircraft and one static test article. By April 1943 the C-74 design process was finalized when the R-4360 was substituted for the R-3350, and in early March 1944 manufacture of the first C-74 airframes began at a new Douglas factory in Long Beach. Due to development of the XB-42 Mixmaster tactical bomber and XB-43 Jetmaster prototype jet bomber as well as production of the A-26 Invader attack aircraft, it was not until September 5, 1945 that the C-74 Globemaster made its first flight, by which time World War II was over. The end of the war also meant that the production contract was reduced to the 14 aircraft that left the assembly line. The C-74 was the biggest American landplane to enter production at the time of its first flight, and it had maximum weight of 172,000 lb (78,000 kg), with the ability to carry 125 soldiers or 48,150 lb (21,840 kg) of cargo over a range of 3,400 miles (5,500 km). Eleven C-74s were delivered to the Air Transport Command (later renamed the Military Air Transport Service in 1948) beginning in 1946, and they played a role in airlifting supplies and transporting wounded servicemen during the 1948 Berlin Airlift and the Korean War. The C-74 was subsequently retired from service in 1959, although a few aircraft served with civilian customers for years until 1969. In an interesting footnote, Douglas proposed an airliner version of the C-74 to carry 108 passengers, the DC-7 (not to be confused with the Douglas DC-7 airliner of the 1950s), in response to a requirement by Pan American World Airways. However, the DC-7 was cancelled in 1946 because of rising development costs.

Top: Desktop model of the C-124 Globemaster II
Bottom: C-124A Globemaster II (serial number 49-241) unloading military equipment at an airbase in South Korea, early 1950s

After World War II, Douglas conceived several proposals for large military transport aircraft to utilize features of the C-74 Globemaster within an airframe that could haul heavy military equipment. The first two design studies, the Models 1036 and 1040 conceived in June 1946, were high-wing designs with deep, rectangular-sided fuselages and rear opening clamshell doors beneath an extended upper fuselage. The Model 1036 had a wingspan of 172 feet 3 in (62.50 meters), while the Model 1040 spanned 208 feet 9 in (63.63 meters). These proposals were followed in 1947 by the Model 1105, which came in two variants, the 164 foot (50 meter) span Model 1105A-T with two vertical stabilizers and four R-4360s driving two pusher propellers and the conventional 209 foot (63.7 meter) span Model 1105A-C. In the end, Douglas opted for progressive development of the C-74, envisaging several C-74 derivatives with rear ramps, turboprop engines, or bigger fuselages ('XC-74X', Model 1040, Model 1041, Model 1106, Model 1110, Model 1113, Model 1114, Model 1119, Model 1122, Model 1128, and Model 1129). By November 1947, the ultimate progressive C-74 development, the Model 1129, which had a deeper fuselage and bow doors as well as conventional cockpit, was submitted to the Air Force and approved for full-scale development, receiving the designation C-124 and the official name Globemaster II. The fifth C-74 airframe (serial number 42-65406) was used in the construction of the C-124 prototype, which first flew on November 27, 1949. The first production C-124 was delivered the US Air Force on April 23, 1950, and a total of 448 C-124s were built, serving USAF strategic airlift needs during the Korean and Vietnam Wars. Two C-124 variants were built, the baseline C-124A (Model 1196) and the C-124C (Model 1317) with uprated Wasp Majors, new propellers, and a few other minor changes; the C-124B (Model 1197) would have had revised R-4360s but did not reach the hardware phase. The C-124 also was used to transport Thor intermediate-range ballistic missiles to England, and it also was involved in Operation Deep Freeze to supply US military bases in Antarctica.

 

Douglas YC-124B Globemaster II

In the early 1950s, Douglas began to investigate fitting the C-124 Globemaster II with turboprops, and two turboprop-powered C-124 variants were conceived, the Model 1182 with four Pratt & Whitney T34 turboprops and the Model 1183 with four Allison T40s. Three variants of the Model 1183 were devised, the Model 1183B and Model 1183E tankers, and the Model 1183D transport. The Model 1182, for its part, was originally designated YC-127, but was later redesignated YC-124B. Besides the turboprops, the YC-124B had a pressurized cockpit, the vertical stabilizer's fabric surface made from metal, and larger horizontal stabilizers. The first flight of the YC-124B took place in February 1954, and test flights showed it to have greater airspeed than the baseline C-124. However, the main drawback with the YC-124B was that its turboprop engines only operated efficiently at high altitude, but also its range being half of the C-124C at 12,000 feet (3,691 meters) and the cabin being unpressurized. Douglas proposed a tanker version of the Model 1182 as the KC-124B, to replace the KC-97s in service with the US Air Force because the KC-97 was slower than the B-36 and B-47 but also the upcoming B-52 Stratofortress, but the KC-124B never progressed beyond the drawing board. 

References:

Berlin, E., 2000. Air Force Legends Number 206: Douglas C-124 Globemaster II. Simi Valley: Steve Ginter. 

Cox, G., and Kaston, C., 2019. American Secret Projects 2: U.S. Airlifters 1941 to 1961. Manchester, UK: Crécy Publishing.

Williams, N., 2020. Air Force Legends Number 223: Douglas C-74 Globemaster. Simi Valley: Steve Ginter. 

Supersonic research aircraft from El Segundo: The Skystreak and Skyrocket

The story of Charles E. "Chuck" Yeager's historic flight over the Mojave Desert in southern California on October 14, 1947 in the Bell X-1 supersonic research aircraft remains one of the most pivotal milestones in the history of not just post-World War II aviation, but also that of aviation development in southern California. However, the United States Air Force that sponsored development of the X-1 was not alone in encouraging the construction of experimental aircraft to investigate flight at transonic/supersonic speeds. Around the time that the Air Force commenced development of the Bell X-1, the US Navy launched their own program for a supersonic research aircraft in the late 1940s. During my visit to the Planes of Fame Museum in Chino, California, on April 13, 2019, I happened to come upon one of the three airframes of the Douglas D-558-2 Skyrocket supersonic rocket-powered research aircraft. Given that the US Navy's own supersonic research aircraft never received Navy designations, and they are at times overshadowed in the public eye by the X-1 and X-15, I though it would be very convenient to discuss in-depth the Navy's efforts in production research aircraft to investigate flight in the supersonic flight regime.

    Douglas D-558-1 Skystreak

In the mid-1940s, around the time that Bell was working on the XS-1 (later X-1) supersonic research aircraft, the US Navy and National Advisory Committee for Aeronautics (NACA) jointly initiated a research program to investigate the aerodynamic challenges of transonic and supersonic flight. This scheme, designated D-558 by Douglas, was originally to proceed in three phases: (1) a jet-powered transonic/supersonic research aircraft; (2) mixed rocket/jet-powered design; and (3) design of a combat plane. The first phase of this program was designated D-558-1 (christened Skystreak), and six aircraft were ordered by the Navy (to be fitted with nose and side air inlets and varying wing airfoil sections), while the second phase was called D-558-2 (christened Skyrocket). However, on January 27, 1947, the original D-558 blueprint was revised whereby the D-558-1 order was reduced to three aircraft (BuNos 37970/37972) with a single nose inlet, and the D-558-2 design conceived as a sleek, airplane with backswept wings. Three D-558-2 aircraft (BuNos 37973/37975) were ordered as substitutes for the final three D-558-1s that had been canceled. Construction of the first D-558-1 Skystreak began in 1946 and was finished in January 1947, with the first flight taking place on April 14. The Skystreak set a world speed air record of 641 miles per hour (1,031 km/h) on August 20, which was broken five days later by the second D-558-1, which had made its first flight that month. The design of the Skystreak featured a streamlined fuselage with a nose inlet (made from magnesium) and straight wings (made of aluminum), and power was supplied by Allison J35 turbojet. The first Skystreak made a total of 101 flights before being handed over to the NACA flight test unit at Edwards Air Force in April 1949. The second D-558-1 flew a total of 46 flights (27 by Douglas and the Navy, 19 by NACA) before it crashed on takeoff on May 3, 1948, due to compressor disintegration, killing test pilot Howard Lilly. The third D-558-3 began flying in 1949 and conducted a total of 81 flights until June 10, 1953, when it was retired by NACA. Like the X-1, the Skystreak was instrumental in providing a library of data on the fundamentals of transonic and near-supersonic flight, taking the US Navy closer to entering the supersonic age.

   

Top: Douglas D-558-2 Skyrocket (BuNo 39374) at the Planes of Fame Museum
Bottom: Third Douglas D-558-2 Skyrocket (BuNo 39375) at Edwards Air Force Base

Even while tests flights of the Skystreak were ongoing, the El Segundo Division of Douglas proceeded in earnest with development of the D-558-2 Skyrocket, which had a sleek, streamlined fuselage with a pointed nose and backswept wings and horizontal stabilizers. Like the Skystreak, the fuselage of the Skyrocket was made of magnesium and the wings and tail empennage were constructed from aluminum alloys. Although the Skyrocket was initially configured with a flush cockpit canopy, it was clear that visibility from this cockpit design was poor, so it was reconfigured with a raised cockpit with conventional angled windows. The first flight of the D-558-2 took place on February 4, 1948, with test pilot John F. Martin at the controls, and the first and second Skyrocket airframes initially flew using a single Westinghouse J34 turbojet only, but were later modified to include a Reaction Motors LR-8 four-chambered liquid-fuel rocket engine, while the third D-558-2 was completed with both the turbojet and rocket motor. A total of 313 flights were made by the Skyrocket (123 by BuNo 37973, 103 by BuNo 37974, and 87 by BuNo 37975), and the first Skyrocket was modified with air-launch capability and pure rocket power in 1955. One Boeing P2B-1S (patrol version of the B-29 Superfortress), christened Fertile Myrtle (BuNo 84029, previously USAAF serial number 45-21787), was modified to serve as the mothership for the Skyrocket, and the first aerial launch of the D-558-2 from the P2B-1S took place on September 8, 1950. On November 20, 1953 (nearly a month before the 50th anniversary of the Wright brothers' historic flight at Kitty Hawk in 1903), the Skyrocket became the first aircraft to reach Mach 2 when NACA pilot Scott Crossfield took the second D-558-2 into a dive to attain a top speed of Mach 2.005 (1,291 miles per hour, 2,078 km/h). The last flight of the Skyrocket occurred on December 20, 1956, and the three Skyrocket aircraft now reside in air museums, with BuNo 37973 (photographed by me in 2019) now displayed at the Planes of Fame Museum in Chino, California, BuNo 37974 (the only Skyrocket to reach Mach 2) on display at the National Air and Space Museum in Washington, D.C., and BuNo 37975 displayed on a pylon on the grounds of Antelope Valley College in Lancaster, California.

Left: Douglas Model 674; Right: Douglas Model 684

As an important footnote, in 1954, Douglas proposed a high-altitude hypersonic research aircraft, the Model 674, after the US Navy's Office of Naval Research awarded a preliminary contract for Douglas to look into a new-generation high-speed research aircraft. The Model 671 combined the straight wings of the Skystreak with the fuselage and tail empennage of the Skyrocket and was designed to reach an altitude of 1,000,000 feet and a speed of Mach 7. However, the performance benchmarks laid out for the Model 671 were rather too ambitious, and when the US Air Force, US Navy, and NACA announced a competition in December 1954 for a hypersonic research aircraft able to reach Mach 6.7 and 250,000 feet, Douglas unveiled a less ambitious but more radical proposal, the Model 684, which had stubby wings and the horizontal stabilizers and vertical fins arranged in a cruciform manner. The Model 684 was submitted in May 1955 along with the Republic AP-76, Bell D-171, and the North American design, and on September 30, North American's design was declared the winner and designated X-15. Some sources refer to the Model 671 and Model 684 projects as "D-558-3" or "Skyflash", but there is no evidence from Douglas company documents that either of these design was designated as much or given a company name.

Although overshadowed by the Bell X-1 in the public imagination, the Douglas D-558-1 Skystreak and D-558-2 Skyrocket played a role in helping the US Navy enter the supersonic age by providing a huge wealth of data on flight in the transonic and supersonic areas.     

 

Northrop's lost fighter jets: the YF-17 Cobra, F-20 Tigershark, and YF-23 Black Widow II/Spider/Grey Ghost

Everyone is familiar with the F-15 Eagle, F-16 Fighting Falcon, and F-22 Raptor jet fighters for the US Air Force and the F-18 Hornet strike fighter for the US Navy. (The Lockheed F-35 Lightning II was given an out-of-sequence designation after winning the Joint Strike fighter contest in October 2001 because the X-35 was Lockheed Martin's technology demonstrator for the JSF competition, but that's another story.) But whatever happened to the F-17 slot between F-16 and F-18? While Northrop aced a couple of success stories in combat jet development with the F-89 Scorpion all-weather fighter and F-5 lightweight fighter to make up for the cancellation of its flying wing bomber programs, it also produced a handful of jet fighter designs that are less well-known to most people, the YF-17 Cobra and F-20 Tigershark lightweight jet fighters and the YF-23 Black Widow II/Grey Ghost prototype stealth fighter jet. Therefore, I thought it'd be convenient to give an overview of all three "lost" jet fighters created by the Northrop Corporation in the 1970s and 1980s, because these designs remained at the prototype stage only.

Left: Desktop model of the Northrop YF-17 at the Western Museum of Flight
Right: Northrop YF-17 during flight testing, 1974

The first "lost" Northrop jet fighter design that is worth discussing is the Northrop YF-17 Cobra. In the late 1960s, the US Air Force initiated the Lightweight Fighter (LWF) competition for a lightweight jet fighter to replace the F-5 Freedom Fighter/Tiger II, at the behest of the so-called "Fighter Mafia" led by Pierre Sprey, Everest Riccioni, and John Boyd. Boeing, General Dynamics, Lockheed, Northrop, and Vought responded with proposals for the LWF competition. Since 1965 Northrop had initiated design studies for advanced versions of the F-5E Tiger II, including the N-300 proposal with a longer fuselage, two General Electric GE15-J1A1 turbojets each delivering 9,000 pounds (40 kN) of thrust, small leading-edge root extensions (LERXs), and a slightly elevated wing. and the N-530 proposal with a greater wing area, two GE 15-J1A5 turbojets delivering 13,000 pounds (58 kN) of thrust, a trapezoidal wing planform and nose section, and LERXs that tapered into the fuselage under the cockpit and enabled maneuvering at angles of attack exceeding 50° by providing about 50% additional lift. By January 1971, Northrop conceived a revised version of the P-530 design with cannons mounted on the upper part of the fuselage, designated P-600, to meet the LWF requirement parameters. The P-600 had two General Electric YJ101 turbojets each delivering 14,400 pounds (64 kN) of thrust, two rudders with a 45° cant, and a fly-by-wire electronic control augmentation system (ECAS) that utilized ailerons, rudders, and stabilators for primary flight control. The General Dynamics and Northrop designs were selected for prototyping by the Defense Department and designated YF-16 and YF-17 respectively. The design of the P-600's LERXs resembled a cobra, hence the YF-17's unofficial name, Cobra. The YF-17 made its first flight on June 9, 1974, nearly five months after the F-16, and two prototypes were built (serial numbers 72-1569/1570). After a fly-off contest between the F-16 and YF-17, on January 13, 1975, Air Force Secretary John L. McLucas declared the F-16 the winner of the LWF competition, citing low operating costs, greater range, and higher maneuver performance in the supersonic flight regime. Despite losing the LWF competition, Northrop would later team with the St. Louis division of McDonnell Douglas to use the YF-17 Cobra design as the basis for a new-generation lightweight jet fighter for the US Navy, the F-18 Hornet, which flew in 1978, and the first prototype YF-17 was sent to NASA Dryden Research Center (now Neil Armstrong Flight Research Center) for base drag studies in May-July 1976. The first and second YF-17 prototypes are now preserved at the Western Museum of Flight in Torrance, California, and Battleship Memorial Park in Mobile, Alabama, respectively.

Left: Sole remaining F-20 prototype (serial number 82-0064) at the California Science Center, Los Angeles

Right: F-20 prototype (serial number 82-0062) in flight

Years after losing the LWF competition to General Dynamics, Northrop began work on an advanced version of the F-5E Tiger II with one General Electric F404 turbofan engine under the designation F-5G in response to the FX program initiated in the late 1970s for a new fighter jet for export that could outperform the F-5E. After a series of back-and-forth moves by the Defense Department to support and then defer the FX program, the F-5G was cleared for full-scale development and four prototypes (serial numbers 82-0062/0065) were ordered. The first F-5G prototype made its first flight on August 30, 1982, and recognizing the advanced nature of the F-5G compared to past F-5 variants, Northrop requested that the F-5G be redesignated F-20, and this request was approved by the Defense Department in late 1982 (Northrop initially wanted the F-5G to be redesignated F-19, but it later changed its mind and requested that F-19 be skipped in favor of F-20 due to possible confusion with the Mikoyan-Gurevich MiG-19 fighter). In March 1983, the F-20 was officially named Tigershark and a number of countries, including Bahrain and South Korea, expressed customer interest in the F-20. With Northrop looking at incorporating avionics upgrades, an expanded fuel tank, and fiberglass composite materials into the planned production F-20, plans were made to have the fourth Tigershark prototype built to include fully operational equipment. Although the Tigershark performed well during test flights, Northrop's hopes for securing production orders for the F-20 from foreign customers were stymied by several US allies in Europe, East Asia, and the Middle East buying the F-16 but also a Congressional investigation in 1984 on the merits of the F-20 compared to the F-16, and the fact that European countries were offering combat jet designs of their own to foreign customers. Meanwhile, the first and second F-20 prototypes crashed during flight testing, with the first aircraft being lost during a demonstration flight in South Korea on October 10, 1984, and the second prototype crashing at Goose Bay in Labrador, Canada, in May 1985; both crashes were found to have been caused by the pilots losing consciousness due to excessive g-forces. By late 1986, Northrop canceled the F-20 program without any orders from foreign customers, and the fourth F-20 prototype (serial number 82-0065) was only half-complete when the Tigershark program was terminated. The third F-20 prototype (the only one to survive the flight test program) is now on display at the California Science Center at Exposition Park in Los Angeles.

Left: Second YF-23 prototype (serial number 87-8701) at the Western Museum of Flight in Torrance, California

Right: The first YF-23 prototype (serial number 87-8700) in flight over the Mojave Desert, California 

 

The third and final "lost" Northrop jet fighter to be discussed is the Northrop/McDonnell Douglas YF-23 stealth air superiority fighter. In 1981, the US Air Force initiated the Advanced Tactical Fighter program for a stealthy air superiority fighter to replace the F-15 Eagle in response to the Soviet Union's new MiG-29 and Su-27 jet fighters. The ATF requirement called for supercruise capability (sustained supersonic flight without the need for afterburners), survivability, and ease of maintenance, and several aerospace companies, including Lockheed, Boeing, General Dynamics, McDonnell Douglas, Northrop, Grumman and Rockwell International, submitted bids for the new aircraft by July 1986. Lockheed later decided to form a team with Boeing and General Dynamics to develop whichever of their proposed designs was selected, while Northrop followed suit by forming a team with McDonnell Douglas should its design be chosen. In October 1986, under the "fly-before-buy" principle, the USAF selected the Lockheed/Boeing/General Dynamics and Northrop/McDonnell Douglas designs for prototyping, and these designs were designated YF-22 and YF-23 respectively. The YF-23, like the F-22, had chines along the nose, but utilized diamond-shaped wings as well as vertical stabilizers angled 50 degrees from vertical position. S-duct engine air intakes were provided to allow air to flow into the jet engines. The two YF-23 prototypes were painted in different colors, the first prototype (serial number 87-8700) being painted in charcoal gray and nicknamed "Black Widow II" in honor of the Northrop P-61 Black Widow night fighter of World War II, while the second prototype (serial number 87-8701) was painted in two shades of gray and nicknamed "Spider" and "Grey Ghost".* The first YF-23 had two Pratt & Whitney F119s, while the second YF-23 used two General Electric F120s. The first flight of the YF-23 took place on August 27, 1990, piloted by Alfred "Paul" Metz (who later became the test pilot for the first service test F-22 Raptor in 1997), while the second prototype flew on October 1990. A fly-off contest between the YF-22 and YF-23 continued into late 1990, and on April 23, 1991, the Air Force declared the YF-22 the winner of the ATF competition. The YF-23 was faster and stealthier, while the YF-22 was more maneuverable, but development experience played the final role in the outcome of the ATF contest; the Northrop company was busy with development of B-2 Spirit stealth bomber, and McDonnell Douglas was reeling from the cancellation of the A-12 Avenger II carrier-based stealth attack aircraft. Lockheed, by contrast, had built the F-117 Nighthawk under budget and on time, so the USAF must have decided that the YF-22 offered lower technical risks (Jenkins and Landis 2008; Miller 2005). The YF-23 prototypes were transferred to NASA Dryden Flight Research Center (now NASA Armstrong Flight Research Center) at Edwards AFB with their engines removed. One of the aircraft was to be used by NASA for studying techniques for the calibration of predicted loads to measured flight results, but those plans never materialized, and the first YF-23 prototype is now on display at the US Air Force Museum in Dayton, Ohio, while the second YF-23 is now displayed at the Western Museum of Flight in Torrance, California.

*The different names applied to the YF-23 prototypes reflected the different naming conventions by the YF-23 manufacturers for their jet fighters. Northrop named its fighters after arachnids and other deadly animals, while the St. Louis division of McDonnell Douglas named its fighters after evil spirits.

 

In an interesting footnote, McDonnell Douglas submitted a design for a lightweight stealth fighter based on the YF-23 for the Joint Strike Fighter competition of the 1990s. It was similar to the YF-23 in the tail empennage design but differed in a having wings reminiscent of the McDonnell F-101 Voodoo escort fighter, and utilized a reheated turbofan, with a remote gas-driven fan to augment lift in STOVL mode. However, the McDonnell Douglas proposal was rejected in favor of the Boeing and Lockheed Martin designs for JSF prototyping by the Pentagon in late 1996, and the Boeing and Lockheed Martin technology demonstrators for the JSF became X-32 and X-35 respectively, flying in late 2000 (the Lockheed Martin design won the JSF contest on October 26, 2001, and subsequently developed into the F-35 Lightning II, but that's another story). Northrop Grumman in the early 2000s conceived a long-range fighter-bomber version of the YF-23 (internally known as "FB-23") as an interim stopgap design pending the arrival of a planned replacement for the B-52H and B-1B (now called the B-21 Raider), but this design remained on the drawing board.

Although Northrop had accomplished something to make up for the cancellation of its jet flying wing bomber programs in the late 1940s by producing the F-89 Scorpion and F-5 Freedom Fighter/Tiger II, the 1970s to early 1990s sapped away Northrop's fortunes in the fighter jet business, either because of technical and aerodynamic considerations or fierce competition from other aircraft for the export market. Nevertheless, the YF-17, F-20, and YF-23 constitute Northrop's willingness to adapt to leaps and bounds in aviation technology during the late Cold War as well as geopolitical circumstances, and the design philosophy of the YF-17 is still prevalent in the F-18 Hornet naval strike fighter. 

References:

Chong, T., 2016. Flying Wings & Radical Things: Northrop's Secret Aerospace Projects & Concepts 1939-1994. Forest Lake, MN: Specialty Press.

Jenkins, D.R. and Landis, T.R., 2008. Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Press.

Miller, J., 2005. Lockheed Martin F/A-22 Raptor, Stealth Fighter. Hinckley, UK: Midland Publishing. 

The US Navy's airborne whale of a whale: Douglas A-3 Skywarrior

The United States Navy in the Cold War years deployed its significant share of carrier-based tactical warplanes, the most recognizable of which were the F3H Demon, F-8 Crusader, F9F Panther/Cougar series, F-4 Phantom II, A-4 Skyhawk, A-1 Skyraider, A-7 Corsair II, and A-6 Intruder. However, the early years of the Cold War bore witness to one unsung hero of carrier-based jet aviation: the Douglas A3D/A-3 Skywarrior. Although not as well-known as the B-47 Stratojet or B-52 Stratofortress, the Skywarrior was the chief airborne warrior queen of the US Navy from 1956 until the deployment of ballistic missile-armed nuclear submarines, and gave the Navy the ability to launch nuclear strikes on enemy territory from large carriers over long distances.

In the late 1940s, the US Navy feared that the US Air Force would control the American nuclear weapons stockpile. To address this concern of, the Navy decided to build a nuclear-armed strategic bomber of its own, the North American AJ/A-2 Savage twin-engine strategic bomber. However, the Savage was a piston-engine warplane, and gas turbine engines made it obsolete by the time it reached service in 1950. With General Curtiss Lemay, the head of Strategic Air Command (SAC), engaged in a lobbying blitz to have Congress divert funds for nuclear weapons delivery systems to US Air Force strategic bombers, the US Navy in January 1948 issued its OS-111 requirement for a jet-powered strategic bomber to operate from the planned USS United States aircraft carrier that could carry either a 10,000 lb (4,500 kg) bomb load or a nuclear weapon. Because the United States would allow the Navy to conduct nuclear strikes on large parts of the globe that the USAF could not reach with its existing bomber fleet, it was crucial to prevent the US Navy from being finished as a major service in case the Air Force got a hold on all US nuclear weaponry. A total of seven companies from submitted bids for the OS-111 requirement: Convair, Curtiss-Wright, Douglas, Fairchild, Lockheed, North American, and Republic (Zichek 2009 is consulted for details of these submissions). Of these proposals, the Convair proposal had three Westinghouse J40 turbojets (two under the wings and third buried in the rear fuselage), while the Douglas (El Segundo) D-593 had two underwing Westinghouse J40 turbojets and the Douglas (Santa Monica) Model 1181 was powered by three J40 tubojets (two in the wing roots and a third in the rear fuselage), whereas the Lockheed L-187 encompassed various designs ranging from swept-wing jet- and turboprop-powered aircraft to a jet-powered flying wing, and North American's RD-4554 was studied in conventional and flying wing layouts (Butler 2010, 2021). (A number of alternate layouts for the Convair design and the Model 1181 were worked out without the third turbojet in the rear fuselage, and one alternate Convair design for the OS-111 had two J40s buried in the wing roots.) The Curtiss-Wright P-558 and Douglas D-593 were picked for further study in late 1948, and by the spring of 1949 a few modifications were made to the D-593 and P-558 designs, and the D-593 was considered the most favorable design by the Navy.

Douglas A3D Skywarrior (BuNo 135422) at Naval Air Station Jacksonville, Florida, mid-1950s

On April 23, 1949, the USS United States was cancelled by US Defense Secretary Louis Johnson due to budget cuts. Although the Navy top brass was disappointed at the cancellation of the United States-class carriers, the US Navy continued with the OS-111 competition, issued a new weight requirement to make a winning design able to operate from the Midway-class carriers. Douglas came out with a lighter version of the D-593 design, the D-593-8, and by July the Navy declared the D-593-8 the winner of the OS-111 competition. The Douglas design, officially named Skywarrior by the Navy, was designated XA3D-1 and a contract for two prototypes (BuNos 125412/125413) was signed. The first flight of the Skywarrior took place on October 28, 1952, and the aircraft was cleared for service on March 31, 1956. In the meantime, the Westinghouse J40 engines used on the A3D prototypes were to prove unreliable, and Douglas selected the more powerful Pratt & Whitney J57 turbojet to power all service test and production A3Ds. A total of 282 Skywarriors were built, and production of the A3D continued until 1961. As a strategic bomber, the Skywarrior could carry 12,800 lb (5,800 kg) of free-fall conventional bombs and mines, including one free-fall nuclear weapon. Navy crews dubbed the Skywarrior the "Whale" because of its size and less-than-slender appearance. On September 18, 1962, the A3D was redesignated A-3 under the new Tri-Service aircraft designation system. By the end of the 1950s, the strategic bomber role of the Skywarrior was rendered obsolete due to the introduction of the Polaris submarine-launched ballistic missile and the ballistic missile submarines designed to carry them. However, many A-3s would be modified to serve tactical reconnaissance, electronic warfare, and tanker roles. The Skywarrior also happened to form the basis of the Douglas B-66/RB-66 Destroyer medium bomber for the US Air Force, which first flew in June 1954 and of which 294 were built. Like the Skywarrior, the B-66 served as both a bomber, reconnaissance platform, and EW platform during its operational career, but it differed in having ejection seats.

Top: Douglas EKA-3B Skywarrior (BuNo 142251) on display at the USS Midway Museum, San Diego
Bottom: Douglas EKA-3B (BuNo 147663) in flight, 1971

Although the A-3 Skywarrior's career as a nuclear-armed strategic bomber was rather brief given the introduction of SLBMs, it represented a quantum leap forward in the US Navy's efforts to acquire a long-range airborne nuclear weapons delivery system for use from large carriers. Even in situations where the Americans did not use a carrier-based plane to drop a nuclear weapon in anger, the A-3's airframe gave it operational flexibility to be used for electronic warfare, reconnaissance, and tanker missions during the Vietnam War and Operation Desert Storm. 

Now all this brings me to discussing one A-3 Skywarrior I saw on the deck of the USS Midway during my visit to the USS Midway Museum in April 2017. Although the A-3 Skywarrior fell out of use as a nuclear-armed strategic bomber after the Polaris SLBM was introduced, the Vietnam War paved the way for the Skywarrior to be used as a tanker aircraft (KA-3B), reconnaissance aircraft (RA-3B), and electronic warfare aircraft (EA-3B, EKA-3B, ERA-3B). The KA-3B had all bombing equipment replaced by a probe-and-drogue system for refueling aircraft, while the EA-3B featured a pressurized compartment in the former weapon bay for one Electronic Warfare Officer and three ESM operators. The RA-3B, on the other hand, had the weapons bay modified to accommodate 12 cameras plus photoflash bombs, and increased pressurization enabled the camera operator to enter the weapons bay to check the cameras. The EKA-3B version that I saw at the USS Midway Museum was designed for a dual tanker/EW role, with the tail turret replaced by a tail fairing with electronic countermeasures (ECM) equipment. A total of 85 A-3Bs were converted to KA-3B iteration, and 34 of them were modified to EKA-3B standard. During the Vietnam War, EA-3Bs and EKA-3Bs were used to jam North Vietnamese radars, as well as refuel tactical aircraft operating over Vietnamese airspace. After the Vietnam War, most of the EKA-3Bs were converted back to KA-3B configuration, and the EKA-3B was replaced in active service by the Grumman KA-6D Intruder (tanker version of the A-6 attack aircraft). The EA-3B was also used during the Cold War for electronic intelligence against Warsaw Pact member states in Eastern Europe, and it served long enough to take part in Operation Desert Storm in early 1991, before being retired from service on September 27 of that year.

References:

Buttler, T., 2010. American Secret Projects: Bombers, Attack, and Anti-Submarine Aircraft 1945 to 1974. Hinckley, UK: Midland Publishing.

Buttler, T., 2021. American Secret Projects 4: Bombers, Attack, and Anti-Submarine Aircraft 1945 to 1974. Manchester, UK: Crécy Publishing.

Francillon, R. J., 1979. McDonnell Douglas Aircraft since 1920, Volume I. Annapolis, MD: Naval Institute Press. 

Gunston, B., and Gilchrist, P., 1993. Jet Bombers: From the Messerschmitt Me 262 to the Stealth B-2. Oxford, UK: Osprey Publishing. ISBN 1-85532-258-7.

Heinemann, E., 1987. "A Whale of an Airplane." Naval Aviation News 70 (November/December 1987): 18–21.

Zichek, J.A., 2009. The Incredible Attack Aircraft of the USS United States, 1948–1949. Atglen, PA: Schiffer Publishing. ISBN 978-0-7643-3229-6.

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.