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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 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.