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In 1938 Consolidated Aircraft was approached by by United States Army Air Corps to augment the Boeing plant in Seattle in the production of B-17 bombers. However, after touring the Boeing plant Consolidated engineers submitted a design of their own, which would be the most versatile bomber of World War II – the B-24 Liberator. During this blog we’ll trace the development of the Liberator, as well as the many roles it played during the war.
Capitalizing on its success in building large flying boat aircraft in the 1930′s, Consolidated based the design of the Model 32 upon a shoulder-mounted Davis wing. This concept proved highly efficient, giving the Liberator a high aspect ratio, in addition to greater speed, load and range. The fuselage of the Liberator was structured around its bomb bays, with the forward and rear bomb bay compartments split lengthwise with a center line ventral catwalk, which also served as the fuselage’s structural keel beam. A unique feature of the Liberator was it’s bomb bay doors. Instead of having flap type doors, as with the B-17, the Liberator had a set of four tambour-panel metal bomb bay doors, which retracted up the outside fuselage of the plane, closing similar to the slide action of a roll top desk. The reasons for this concept were retraction of the doors along the fuselage minimized drag, allowing the plane to fly over the target area at a high rate of speed, while maximizing ground clearance since the Liberator design was too low to allow the use of conventional bomb bay doors. The aft fuselage was mated to a small wing with two tails, as with the earlier Model 31 flying boat. The Liberator also had the distinction of being the first USAAF bomber to incorporate a tricycle landing gear system.
Designated by Consolidated as the B-24 in 1939, the Liberator began operations with the RAF the following year as a transport flying equipment and civilian ferry pilots between Canada and Britain. The Liberators serving inPB4Y P this role were modified with the removal of armament and the placement of passenger seats and a revised cabin oxygen and heating system. Liberators also tipped the scales in the Battle Of The Atlantic. The delivery of Very Long Range (VLR) Liberators to the RAF Coastal Command in 1941 drastically increased the range of the RAF patrol force, closing the Mid Atlantic Gap, an area of the Atlantic in which U boats could operate free from air attack due to the limited range of existing patrol aircraft. These B-24s were stripped of non-essential armament in order to save weight and carried additional fuel tanks in the bomb bay to extend the range of the plane. By 1942 these Liberators carried ASV (Air to Surface Vessel) radar, which coupled with the Leigh searchlight mounted under the wing, achieved a stunning rate of success against the U boats, with many U boat crews choosing to charge their batteries during daylight when they could see approaching aircraft.
The B-24′s first combat missions as a bomber were flown by the RAF in the Middle East in early 1942. Though the missions were successful, the RAF never deployed the Liberator in a strategic role over Europe. While the first combat for the Liberator with the USAAF was a failed mission against Wake Island in June 1942, within a week B-24s from an Egyptian base launched a raid against the Ploesti oil fields in Romania. Though small in scope, this raid was a precursor of things to come. This effort was followed up by another mission against Ploesti on August 1, 1943. Operation Tidal Wave was the B-24′s most costly mission. In June 1943, three B-24 groups were detailed from the Eighth Air Force in England to train with two B-24 groups from the Ninth Air Force to conduct the mission. Flying from bases in North Africa, the joint force was to approach the Ploesti complex at low altitude in order to gain surprise over enemy fighters. However, the attack became disorganized after a navigational error alerted the defenders, lengthening the bomb run. Though much of the refinery was destroyed, it was producing at total capacity within a few months. This was achieved at a loss of 54 Liberators of the 177 assigned to the mission. It would take several missions flown by B-24s of the newly formed Fifteenth Air Force to completely destroy the Ploesti refinery the following year.
In 1943 the B-24 received a significant update with nose turrets installed on the H and J models, which were just entering production. This was a marked improvement over the earlier D model, introduced in USAAF service in early 1942, having a web type front housing with two poke guns. The powered Emerson turret enabled the Liberator to reduce vulnerability to head-on attacks. The H and J models also featured an improved bomb sight and fuel transfer system. The J model offered slight improvements in the bomb sight and autopilot over the H model and became the primary B-24 production model from August 1943 through the remainder of the war. The Liberator became the dominant heavy bomber in the Pacific due to it’s greater range, payload and speed over the B-17, which was phased out by mid 1943. Unlike the operations of the European theater, little strategic bombing was conducted in the Pacific by the Fifth and Seventh Air Forces, with the majority of the missions flown in support of ground forces. As with the RAF, Liberators in the China, Burma, India (CBI) area were used in a transport role. The converted cargo version, designated C-87, was used to airlift cargo over the Himalayas from India to China. This was of critical importance early in the war, as the Liberator was the only USAAF transport immediately available which could fly over the Himalayas fully loaded. A tanker model of the B-24 was also utilized in the CBI area. The C-109 became operational in the summer of 1944 as a support aircraft for Boeing B-29 Superfortress operations launched from Chinese bases. Unlike the C-87, the C-109 was not built on the assembly line, but converted in the field from existing B-24 production. These modifications included the addition of several storage tanks, giving the 109 a capacity of 22,000 lbs. of fuel. When fully loaded these aircraft proved difficult to fly, which dictated leaving the forward tanks empty. While plans originally envisioned a fleet of 2,000 C-109 tankers to support 10 B-29 groups operating from China, the capture of the Mariana Islands offered a much easier location from which to supply raids on mainland Japan.
During its service the Liberator played a number of roles. A dedicated naval version, the PB4Y Privateer, a single-tailed aircraft, was used by the navy in both the Atlantic and Pacific areas. The B-24 was one of the first aircraft to use a precision-guided bomb, as well as jamming radar in flight. From service as a VIP transport to bombing U boats in the Atlantic, the Liberator was there. The B-24 was used by at least six Allied nations with more than a dozen versions produced. When production ended in 1945, the Liberator was both the most diverse and the most produced USAAF aircraft of World War II-with more than 18,500 examples built.
In late 1950, as USAF B-29s were bombing North Korean supply lines in support of UN ground troops, they encountered a swept-winged North Korean aircraft capable of great speed. While the introduction of the MIG-15 caught United Nations forces by surprise, its counterpart would prove to be a legend among jet fighter aircraft.
As early as 1944, North American Aviation had proposed a jet aircraft design to the US Navy, as a result of combat against the early German jet fighters, such as the ME-262. This design, the FJ-1 Fury was, in essence, a jet version of the P-51 MUSTANG. Though its speed was impressive compared to piston-powered fighters, its overall performance failed to meet expectations. However, within a few months, the USAAF approached North American with a requirement for a medium-range, single-seat, high-altitude, jet-powered day escort fighter/fighter-bomber. In early 1945, North American submitted four designs to the Air Corps with North American granted permission to produce three examples of the XP-86 (Experimental Pursuit) aircraft. While the XP-86 was a lighter plane than the Fury, and could attain 582 mph, as opposed to 547 for the FJ-1, the XP-86 could not meet the Air Corps requirement for a top speed of 600 mph. Furthermore, two rival designs, the XP-80 and XP-84 having speeds in the range of the XP-86 were already under development and might result in cancellation of the contract for the XP-86.
North American was able to solve this problem with a leapfrog in technology. The XP-86 was the first American aircraft to take advantage of captured German test data at the end of World War II, which indicated a thin swept wing could greatly reduce drag and delay compressibility problems when an aircraft approached the speed of sound. Further study of the tests revealed a swept wing would solve the speed problem, while a slat on the wing’s leading edge would enhance low-speed stability. Since the 86 was approaching an advanced stage of development, North American’s senior management was hesitant to incorporate a swept wing design. However, after a series of wind tunnel tests, a 35-degree sweep offered the best performance with automatic front slats and an electrically adjusted stabilizer based on the ME-262. As a result of combat experience gained in Korea, the front edge wing slats were phased out in favor of a leading edge chord extending 6 inches from the wing root to 3 inches at the tip.
Though much of the design work was delayed until after the end of World War II, the first F-86 SABRE was completed on August 8, 1947, with the first flight occurring on October 1 of that year. The SABRE was first assigned to the USAF Strategic Air Command in 1949 prior to its deployment to Korea in late 1950. The F-86 set a number of speed records during its early years, an official world speed record of 671 mph in September 1948, a 1951Bendix Trophy for an average speed of 553.76 mph, as well as the first woman, Jacqueline Cochran, to break the speed of sound in May 1953.
When the Soviet MIG-15 was introduced in November 1950, it outperformed all UN aircraft, such as the straight-winged F-80 and F-84. The MIG was clearly a generation ahead of both types, as well as the F9F PANTHER, flown by the US Navy from carriers offshore. Three squadrons of F-86s were dispatched to the Far East in December 1950. Though the F-86 and the MIG-15 were evenly matched and based on similar design concepts, there were a number of differences. SABRES were more aerodynamically stable and could turn, roll and dive faster than the MIG. The F-86 could also go supersonic in a dive, while the MIG would experience structural damage attempting to do so. The SABRE was also equipped with a radar gunsight, which allowed pilots to quickly aim their .50 caliber guns more accurately-even compensating for speed. The MIG-15s key advantages were faster climbing and acceleration rates, effective handling at high altitudes and being somewhat more maneuverable. Firepower between the two aircraft was a tradeoff, with the SABRE firing more smaller rounds more accurately aimed and the MIG firing less accurate but larger bore (23mm and 37mm) ammunition. Perhaps the deciding factor in the air war over Korea was the quality of pilots. Many of the MIGs were flown by Soviet pilots for about the first year of their deployment. Many of these were aces from World War II and were thus capable pilots. The USAF followed the same philosophy, sending a number of World War II aces to Korea as well. While the Soviet pilots were well trained, the USAF training program at Nellis AFB was both more broad and intense. As Soviet pilots were rotated home, they were replaced by less capable Chinese and North Korean pilots. As the war progressed, this was reflected in the loss ratio between the two aircraft. While the overall loss ratio was in favor of the SABRE of about eight to one by wars end (78 to 687), the loss ratio against Soviet pilots has been disputed in recent years, with a number of former Soviet pilots stating a loss ratio of two to one in favor of the SABRE. The most hotly contested battles were fought over an area near the mouth of the Yalu River known as MIG ALLEY.
After the Korean War, the SABRE was exported to a number of nations to include NATO allies such as the United Kingdom, Canada, West Germany, Greece, Spain, Norway and Turkey, as well as Taiwan, Japan, Pakistan and Saudi Arabia. The last SABRE was retired from the Bolivian Air Force in 1994. Though the SABRE was in service for many years, the high point of its career was in Korea-in which a few brave pilots and planes made the difference in saving a nation.
In late 1945 the USAAF was at a crossroads. While the B-29 Superfortress was a capable platform in carrying the war to Japan, future requirements dictated an aircraft of intercontinental range, in excess of five thousand miles. The Convair B-36 Peacemaker met this requirement, but would not enter service for three more years. Further complicating matters, General Curtis LeMay and several other forward thinking generals were considering a jet powered bomber. However, within a few years, the generals and engineers got together and designed a truly great jet bomber – the Boeing B-52 Stratofortress. During this blog we will tell the story of the B-52, its development and its long service record with the USAF.
In addition to the range requirements of the aircraft, other performance characteristics specified by the Air Material Command in 1946 were a cruising speed of 300 mph. at an altitude of 34,000 ft., with a minimal payload of 10,000 lbs with five or six 20mm. gun turrets. The AMC issued bids later that year with Boeing, Glen L. Martin and Consolidated Aircraft submitting proposals. The Air Force accepted the Boeing proposal, an aircraft powered by six turboprop engines with a range of 3,110 miles. The Boeing plane, designated Model 462, was a straight-winged aircraft with a gross weight of 360,000 pounds – a heavy plane for its day. As a result of the weight issue, the Air Force began to have doubts about the ability of the aircraft to successfully perform its mission. Boeing then offered a smaller follow-up design, Model 464, having four engines and a 230,000 pound gross weight. While the 464 aircraft was deemed acceptable, the Air Force changed its requirements within a few months to a plane having a 400 mph cruising speed, with a 300,000 pound gross weight. Additionally, the Air Force wanted an aircraft with a range of twelve thousand miles, capable of delivering a nuclear weapon. These modifications increased the gross weight of the plane to 480,000 lbs.
Boeing responded by proposing two bombers, Model 464-16 and Model 464-17. Both planes were four engine turboprop designs, with the Model 16 being a nuclear only aircraft carrying a ten thousand lb. payload. The Model 17 bomber was a conventional bomber, able to mount a 9,000 lb. payload. By mid 1947 the Model 17 aircraft was deemed acceptable by the Air Force, except for the range requirement. By now, designated the XB-52, the aircraft offered only marginal performance in speed and range over the Convair B-36, which was about to enter service. The Air Force then postponed the project for six months in order to evaluate its potential. After a series of intense discussions between Boeing and the Air Force, the XB-52 project was back on track in January 1948, with Boeing urged to include the latest aviation innovations in the bomber design such as jet engines and aerial refueling. In May 1948, jet engines were substituted for turboprops which satisfied the Air Force. However, the Air Force still wanted a turboprop design, since jet engines of the era lacked fuel efficiency. October 1948 proved to be a crucial month for the XB-52 project. Boeing engineers George Schairer, Art Carlsen and Vaughn Blumenthal presented a refined turboprop design to Colonel Pete Warden, Director of Bomber Development for the USAF. After reviewing the proposal, Warden asked the Boeing design team if they could prepare a proposal for a four engine turbojet bomber. The following day Colonel Warden scanned the design, requesting an improved version. After returning to their hotel room, Schairer, Carlsen and Blumenthal were joined by Ed Wells, Boeing Vice President of Engineering, in addition to two other Boeing engineers, Bob Withington and Maynard Pennell. After eight hours of intense deliberation, the Boeing team had designed an entirely new airplane. The new concept of the XB-52 had 35 degree swept wings, based on the B-47 Stratojet, with eight engines paired in four pods below the wings with bicycle landing gear and outrigger wheels underneath the wingtips. The XB-52 also had flexible landing gear, which could pivot 20 degrees from the aircraft centerline to compensate for crosswinds upon landing. Warden approved the design the following week and the Air Force signed a contract with Boeing in February 1951 for an initial production run of 13 B-52As.
When the B-52 entered service in 1955, it was assigned to the Strategic Air Command (SAC) to deliver nuclear weapons under the doctrine of massive retaliation. Carrying a 50,000 lb. payload coupled with the capability to fly nearly half way around the globe, the Stratofortress was ideally suited for its role and soon became the standard for future bomber aircraft. Three B-52s from March AFB set a record around the world flight in 1957. However, it had its share of teething troubles, as with all aircraft. For example, the split level cockpit had climate control problems, while the pilot and co-pilot had sunlight exposure on the upper deck, the navigator and observer nearly froze on the lower deck. Early B-52 models were often grounded due to both electrical and hydraulic issues, with the Air Force assigning contractor teams to B-52 bases, troubleshooting problems as they arose.
By the late 1950s, advances in Soviet surface to air (SAM) missile capabilities brought about a major upgrade in the electronic countermeasure capabilities of the B-52. This situation also caused SAC to change its philosophy from high altitude bombing to low level penetration. The switch to low altitude bombing required a number of modifications to B-52 component parts. Such features as an updated radar altimeter, structural reinforcements, modified equipment mounts, an enhanced cooling system, as well as terrain avoidance radar were necessary to support missions flown at altitudes as low as 500 ft. By the end of the decade, B-52 capabilities increased with the addition of the Quail and Hound Dog missile systems. The Quail, a decoy missile, was carried in the aft bomb bay of the B-52 and launched while in flight to the target. The missile was programmed by the crew to match the speed and altitude of the B-52, thus confusing Soviet radar. Each Stratofortress carried four of these, in addition to the regular nuclear payload. North American’s entry, the AGM-28 Hound Dog was an offensive missile launched from the B-52 to carry a nuclear warhead to its target. With a mach 2 speed and an altitude variance of from 500 to 60,000 ft., the Hound Dog was able to penetrate enemy air defenses to a range of 600 miles. The primary drawback of the Hound Dog was its weight. At 20,000 lbs. each, the B52s could only carry two of them with a corresponding fifteen per cent loss of range.
The 1960s saw a change of doctrine for SAC. With the emergence of both land-based intercontinental ballistic missiles (ICBM), as well as sea-launched (SLBM) missiles from submarines, the manned bomber force became a leg of a nuclear triad. The primary advantage of the missile legs were their relative invulnerability to enemy attack. They were also cheaper to operate than a manned bomber fleet. Both ICBMs and SLBMs offered a quick response to an enemy attack, while a response from manned bombers was more time sensitive. The growing threat from Soviet ICBMs was another factor countering the effectiveness of the manned bomber leg. Due to the potential for conflict in Berlin, Cuba and a number of third world countries, the Kennedy Administration decided to scrap the policy of massive retalation, replacing it with the doctrine of flexible response. Instead of having a large nuclear umbrella with small conventional forces, those forces were increased in order to keep any potential war from escalating to the nuclear threshold. Under the flexible response doctrine, nuclear weapons were to be used in a limited role against selected targets. Thus, the B-52 had a new mission, to loiter on patrol at the edge of Soviet airspace, ready to strike designated targets in a retaliatory role. The Stratofortress was the ideal plane for the job, having the range, speed and payload, as well as an aerial refueling capability.
While the B-52 was designed as nuclear weapon delivery system, it served an entirely different purpose in Viet Nam. In 1964 seventy-four B-52s were modified with external bomb racks, which could carry an additional twenty-four 750 lb. bombs. The following year Operation Rolling Thunder began, in which the USAF commenced bombing missions in both North and South Viet Nam, with the primary role of the Stratofortress to support ground operations in the South. The first mission, Operation Arc Light was conducted by B-52s in June 1965, bombing a suspected Viet Cong stronghold in the Ben Cat District in South Viet Nam. Twenty-Seven B-52s participated in the raid, bombing a one mile by two mile box. Though only partially successful, the raid proved the potential of the B-52 as a ground attack weapon. Later that year, a number of B-52s underwent modifications to increase their capacity for carpet bombing. These raids were devastating to anyone in or near the target areas. B-52s bombed North Viet Nam in late 1972 during Operation Linebacker II. These missions were successful in leading to the peace talks which ended the war, although at a loss of 15 Stratofortresses. During that campaign, B-52 gunners claimed two North Vietnamese Mig-21s – the first hostile aircraft shot down by the plane.
The Stratofortress went on to provide ground support in Operation Desert Storm in 1991, Operation Allied Force in Serbia in 1999, Operation Enduring Freedom in Afghanistan in 2001, as well as Operation Iraqi Freedom in 2003. During its career, the B-52 has proven itself both a durable and an adaptable plane, receiving a number of modifications during its 63 year career. It has dropped bombs, launched missiles, served as an experimental platform, in addition to launching the X-15 rocket plane. Current efforts by Boeing to re-engine the Stratofortress are projected to extend its service life through 2040. One could say of the B-52, it’s the plane that keeps on flying.
The early pioneers of aviation sometimes branched out from other fields before realizing their ultimate success. For example, Glenn Curtiss raced motorcycles and developed small engines prior to his fame in aviation. Both Wiliam Boeing and his family were in the timber business before he founded the Boeing aircraft company. The hero of this blog was no exception, although he achieved his success by a more indirect route.
Andrei Nickolaevich Tupolev was born in Pustomozovo, Russia in 1888. The sixth of a family of seven children, Tupolev developed an early interest in building models and small pieces of furniture – a hobby his parents encouraged. After his graduation from the Tver secondary school in 1908, Tupolev applied to the Moscow Imperial Technical High School (IMTU) pursuing a technical degree. During his time at the technical school, Tupolev met Nickolai Zhukovski, who introduced the subject of aeronautics at IMTU. Zhukovski would serve as both an instructor and a mentor to Tupolev. Perhaps Tupolev’s most significant project at IMTU was the construction of a wind tunnel, one of the first in practical use, from which to test aerodynamic designs. Tupolev was arrested in 1911 for involvement in a subversive student organization. Though Zhukovski interceded on Tupolev’s behalf, he wasn’t successful and Tupolev was placed under house arrest, only allowed to leave to attend his father’s funeral later that year. He was finally released in 1914 and resumed his studies, graduating in 1918 with the degree of Engineer-Mechanic.
In 1918 Zhukovski and Tupolev petitioned the Soviet government to establish an aerodynamic research organization. In December 1918 their request was granted and the Central Aero/Hydrodynamics Institute or TsAGI was established. TsAGI grew rapidly from an initial staff of six to nearly thirty engineers and technicians by mid 1919. In 1921 Tupolev was elected by the staff at TsAGI to be Zhukovski’s deputy or Comrade To The Director. The following year he began work on his first aircraft, designated the ANT 1, using Tupolev’s initials for the name. Because he advocated the use of light metals in aircraft, such as duraluminium, pioneered by Junkers in Germany, Tupolev met with opposition from the timber industry, promoting the construction of wooden aircraft. Although he won the battle for an all-metal aircraft, the ANT 1 was built of mixed metal and wood. It was a single seat cantilever monoplane, with a 25′ wingspan. The ANT 1 first flew in late 1923 and was a successful design. In 1927 the ANT 2, the Soviet Union’s first all-metal plane flew, proving both the durability and practicality of light metal construction. The ANT 2 was powered by an air cooled 100 hp. Bristol Jupiter engine and could accommodate two passengers in the cabin with an open cockpit for the pilot.
In the 1930′s Tupolev traveled to Germany, France, Britain and the United States to gain insight into the aircraft technologies of those nations. He encouraged the Soviet government to purchase a license to manufacture Wright Cyclone engines, which were the basis for a series of Soviet built air-cooled engines, as well as the liquid-cooled Hispano Suiza engine from France. Tupolev’s design bureau produced a number of large scale aircraft, such as the ANT 20, named after the famous Russian poet Maxim Gorky. The ANT 20 was an extremely big plane for its day, having a fuselage 107′ long with a wingspan of 207′. The Maxim Gorky was powered by eight engines, six in the wing and two above the fuselage. The passenger compartment was subdivided into four cabin areas. The ANT 20 first flew in 1934 and made several foreign tours, of great propaganda value to the Soviet state. However, the Maxim Gorky crashed in May 1935 as a result of a mid air collision with a fighter performing aerobatic maneuvers during a Moscow airshow. Tupolev’s next major effort was the development of the ANT 25. The ANT 25 was first proposed in 1931 as a long range bomber. The 25 plane was somewhat smaller than the Maxim Gorky, with a 44′ long fuselage coupled with a 112′ wingspan. It had a crew of three: pilot, copilot, and a navigator who doubled as a radio operator. The long tapered wings of the plane contributed to its range by storing its fuel tanks, which accounted for 52 % of its take off weight. After several test flights in 1934-36, two ANT 25s made transpolar flights from Moscow to Pearson Field, Oregon and San Jacinto, California in June 1937. Both planes had enough fuel to reach Panama, but were denied permission by the Mexican government to overfly its territory.
The World War II era was a difficult one for both Tupolev and his design bureau. He was arrested in 1937 for passing aviation secrets to foreign governments, a charge which was totally baseless. Both he and his staff were imprisoned until released in July 1941. Tupolev and his team worked round the clock designing and improving Soviet aircraft for the demands of war. In 1945 Tupolev was given the demanding task of reverse engineering the Boeing B-29 Superfortress. Though the Soviet Union was not yet at war with Japan, four of the Boeing planes could not make it back to their Marianas bases and were forced to land near Vladivostok, on the Soviet Pacific coast. Stalin ordered three of the planes sent to Moscow with the fourth unit retained for quality control purposes. Tupolev was to have direct control of all aspects of engineering and production. Any requests made by his staff were given top priority, which greatly reduced production time. In just 20 months, the first Soviet B-29 (TU-4) flew above the 1947 May Day parade, to the astonishment of western observers.
Tupolev went on to produce a number of other Soviet aircraft, such as the TU-16 Badger, the Soviet Union’s first major jet bomber, the TU-104 jetliner, a civil variant of the Badger, as well as the TU-95 Bear, the world’s only turboprop bomber. Tupolev’s crowning achievement came in 1968, when, as promised, his design bureau flew the worlds first supersonic transport (SST) on December 31 of that year – some two months ahead of the Concorde. Though Tupolev experienced many hardships throughout his life, his dedication to the field of aviation produced some of the worlds premier aircraft.
This blog is the third of a series about the heroes of aviation.