World War I The first heavy bomber was designed as an
airliner.
Igor Sikorsky, an engineer educated in St Petersburg, but born in Kiev of Polish-Russian ancestry designed the
Sikorsky Ilya Muromets to fly between his birthplace and his new home. It did so briefly until August 1914, when the Russo-Balt wagon factory converted to a bomber version, with British
Sunbeam Crusader V8 engines in place of the German ones in the passenger plane. By December 1914 a squadron of 10 was bombing German positions on the
Eastern Front and by summer 1916 there were twenty. It was well-armed with nine machine guns, including a tail gun and initially was immune to German and Austro-Hungarian air attack. The Sikorsky bomber had a wingspan just a few feet shorter than that of a World War II
Avro Lancaster, while being able to carry a bomb load of only 3% of the later aircraft. The
Handley Page Type O/100 owed a lot to Sikorsky's ideas; of similar size, it used just two
Rolls-Royce Eagle engines and could carry up to of bombs. The O/100 was designed at the beginning of the war for the
Royal Navy specifically to sink the German
High Seas Fleet in Kiel: the Navy called for “a bloody paralyser of an aircraft” Entering service in late 1916 and based near Dunkirk in France, it was used for daylight raids on naval targets, damaging a German destroyer. But after one was lost, the O/100 switched to night attacks. The uprated
Handley Page Type O/400 could carry a bomb, and wings of up to 40 were used by the newly formed, independent
Royal Air Force from April 1918 to make strategic raids on German railway and industrial targets. A single O/400 was used to support
T. E. Lawrence's
Sinai and Palestine Campaign. The
Imperial German Air Service operated the
Gotha bomber, which developed a series of marques. The
Gotha G.IV operated from occupied Belgium from the Spring of 1917. It mounted several raids on London beginning in May 1917. Some reached no further than Folkestone or Sheerness on the Kent Coast. But on June 13, Gothas killed 162 civilians, including 18 children in a primary school, and injured 432 in East London. Initially, defence against air attack was poor, but by May 19, 1918, when 38 Gothas attacked London, six were shot down and another crashed on landing. German aircraft companies also built a number of giant bombers, collectively known as the
Riesenflugzeug. Most were produced in very small numbers from 1917 onwards and several never entered service. The most numerous were the
Zeppelin-Staaken R.VI of which 13 saw service, bombing Russia and London: four were shot down and six lost on landing. The R.VIs were larger than the standard Luftwaffe bombers of World War II. The
Vickers Vimy, a long-range heavy bomber powered by two
Rolls-Royce Eagle engines, was delivered to the newly formed
Royal Air Force too late to see action (only one was in France at time of the
Armistice with Germany). The Vimy's intended use was to bomb industrial and railway targets in western Germany, which it could reach with its range of and a bomb load of just over a ton. The Vickers Vimy is best known as the aircraft that made the first Atlantic crossing from St John's Newfoundland to Clifden in Ireland piloted by the Englishman
John Alcock and navigated by Scot
Arthur Whitten Brown on June 14, 1919.
Strategic bomber theory Between the wars, aviation opinion fixed on two tenets. The first was that “
the bomber will always get through.” The speed advantage of biplane fighters over bombers was insignificant, and it was believed that they would never catch them. Furthermore, there was no effective method of detecting incoming bombers at sufficiently long range to scramble fighters on an interception course. In practice, a combination of new
radar technology and advances in monoplane fighter design eroded this disadvantage. Throughout the war, bombers continually managed to strike their targets, but suffered unacceptable losses in the absence of careful planning and
escort fighters. Only the later
de Havilland Mosquito light bomber was fast enough to evade fighters. Heavy bombers needed defensive armament for protection, which reduced their effective bomb payload. The second tenet was that strategic bombing of industrial capacity, power generation, oil refineries, and coal mines could win a war. This was certainly vindicated by the
firebombing of Japanese cities and the two
atomic bombs dropped on
Hiroshima and
Nagasaki in August 1945, as Japan's fragile housing and
cottage industry made themselves easily vulnerable to attack, thus completely destroying Japanese industrial production (see
Air Raids on Japan). It was less evident that it held true for the bombing of Germany. During the war, German industrial production actually
increased, despite a sustained Allied bombing campaign. It was clear that the B-17C model was not combat ready and that its five machine guns provided inadequate protection. Combat feedback enabled Boeing engineers to improve the aircraft; when the first model B-17E began operating from English airfields in July 1942, it had many more defensive gun positions including a vitally important tail gunner. Eventually, U.S. heavy bomber designs, optimized for formation flying, had 10 or more machine guns and/or
cannons in both powered turrets and manually operated flexible mounts to deliver protective
arcs of fire. These guns were located in
tail turrets, side gun ports either just behind the bombardier's clear nose glazing as "cheek" positions, or midway along the rear fuselage sides as "waist" positions. U.S. bombers carried
.50 caliber machine gun, and dorsal (spine/top of aircraft) and ventral (belly/bottom of aircraft) guns with powered
turrets. All of these machine guns could defend against attack when beyond the range of fighter escort; eventually, a total of 13 machine guns were fitted in the B-17G model. In order to assemble
combat boxes of several aircraft, and later combat wings formed of a number of boxes,
assembly ships were used to speed up formation. Even this extra firepower, which increased empty weight by 20% and required more powerful versions of the
Wright Cyclone engine, was insufficient to prevent serious losses in daylight. Escort fighters were needed but the RAF interceptors such as the
Supermarine Spitfire had very limited endurance. An early raid on Rouen-Sotteville rail yards in Brittany on August 17, 1942, required four Spitfire squadrons outbound and five more for the return trip. The USAAF chose to attack aircraft factories and component plants. On August 17, 1943, 230 Fortresses attacked a ball-bearing plant in Schweinfurt and again two months later, with 291 bombers, in the
second raid on Schweinfurt. The works was severely damaged but at a huge cost: 36 aircraft lost in the first raid, 77 in the second. Altogether 850 airmen were killed or captured; only 33 Fortresses returned from the October raid undamaged With the arrival of
North American P-51 Mustangs and the fitting of drop tanks to increase the range of the
Republic P-47 Thunderbolt for the
Big Week offensive, between February 20–25, 1944, bombers were escorted all the way to the target and back. Losses were reduced to 247 out of 3,500 sorties, still devastating but accepted at the time. The
Consolidated B-24 Liberator and later version of the Fortress carried even more extensive defensive armament fitted into
Sperry ball turrets. This was a superb defensive weapon that rotated a full 360 degrees horizontally with a 90-degree elevation. Its twin
M2 Browning machine guns had an effective range of . The Liberator was the result of a proposal to assemble Fortresses in Consolidated plants, with the company returning with its own design of a longer-range, faster and higher-flying aircraft that could carry an extra ton of bombs. Early orders were for France (delivered to the RAF after the fall of France) and Britain, already at war, with just a batch of 36 for the USAAF. Neither the USAAF nor the RAF judged the initial design suitable for bombing and it was first used on a variety of VIP transport and maritime patrol missions. Its long range, however, persuaded the USAAF to send 177 Liberators from Benghazi in Libya to bomb the Romanian oilfields on August 1, 1943, in
Operation Tidal Wave. Due to navigational errors and alerted German flak batteries and fighters, only half returned to base although a few landed safely at RAF bases in Cyprus and some in Turkey, where they were interned. Only 33 were undamaged. Damage to the refineries was soon repaired. By October 1942, a new
Ford Motor Company plant at
Willow Run Michigan was assembling Liberators. Production reached a rate of over one an hour in 1944 helping the B-24 to become the most produced US aircraft of all time. It became the standard heavy bomber in the Pacific and the only one used by the RAAF. The SAAF used Liberators to drop weapons and ammunition during the
Warsaw Uprising in 1944. The
Avro Manchester was a twin-engine bomber powered by the ambitious 24-cylinder
Rolls-Royce Vulture, but was rapidly redesigned for four
Rolls-Royce Merlin engines due to technical problems with the Vulture which caused the aircraft to be unreliable, under-powered and hastened its withdrawal from service. Reaching squadrons early in 1942, the redesigned bomber with four Merlin engines and longer wings was renamed
Avro Lancaster; it could deliver a load of bombs or up to with special modifications. The Lancaster's bomb bay was undivided, so that bombs of extraordinary size and weight such as the 10-ton
Grand Slam could be carried.
Barnes Wallis, deputy chief aircraft designer at
Vickers, spent much time thinking about weapons that might shorten the war. He conceived his “Spherical Bomb, Surface Torpedo” after watching his daughter flip pebbles over water. Two versions of the '
bouncing bomb' were developed: the smaller Highball was to be used against ships and attracted essential
British Admiralty funding for his project. A flying torpedo, of which half was
Torpex torpedo explosive, it was developed specifically to sink the
Tirpitz which was moored in Trondheim fjord behind torpedo nets. Development delays in the 'bouncing bomb' meant that another Barnes Wallis invention, the 5-ton
Tallboy was deployed instead; two Tallboys dropped by
Avro Lancasters from
altitude hit at near-
supersonic speed and capsized the Tirpitz on November 12, 1944. Upkeep, the larger version of the
bouncing bomb, was used to destroy the Mohne and Eder dams by Lancasters from the specially recruited and trained
No. 617 Squadron RAF, often known as "the Dam Busters", under Wing Commander
Guy Gibson. In March and April 1945, as the war in Europe was ending, Lancasters dropped Grand Slams and Tallboys on U-boat pens and railway viaducts across north Germany. At Bielefeld more than of railway viaduct was destroyed by Grand Slams creating an earthquake effect, which shook the foundations. The
Boeing B-29 Superfortress was a development of the Fortress, but a larger design with four
Wright R-3350 Duplex-Cyclone engines of much greater power, enabling it to fly higher, faster, further and with a bigger bomb load. The mammoth new Wright radial engines were susceptible to overheating if anything malfunctioned, and technical problems with the powerplant seriously delayed the B-29's operational service debut. The aircraft had four remotely operated twin-gun turrets on its
fuselage, controlled through an
analog computer sighting system; the operator could use any of a trio of Perspex ball stations. Only the
tail gunner manually controlled his gun turret station in the rear of the airplane. B-29s were initially deployed to bases in India and China, from which they could reach Japan; but the logistics (including transport of fuel for the B-29 fleet over the
Himalayan range) of flying from these remote, primitive airfields were complicated and costly. The island of
Saipan in the
Marianas was assaulted to provide Pacific air bases from which to
bomb Japanese cities. Initial high-level, daylight bombing raids using
high-explosive bombs on Japanese cities with their wood and paper houses produced disappointing results; the bombers were then switched to low-level, nighttime
incendiary attacks for which they had not originally been designed (one variant, the B-29B was specially modified for low altitude night missions by removal of armament and other equipment). Japan burned furiously from the B-29
incendiary raids. On August 6, 1945, B-29
Enola Gay dropped an
atomic bomb on Hiroshima. Three days later, B-29
Bockscar dropped another on Nagasaki. The war ended when Japan announced its surrender to the
Allies on August 15, and the Japanese government subsequently signed the official
instrument of surrender on September 2, 1945.
After World War II heavy bomber After World War II, the name
strategic bomber came into use, for aircraft that could carry
aircraft ordnances over long distances behind enemy lines. They were supplemented by smaller
fighter-bombers with less
range and lighter bomb load, for tactical strikes. Later these were called
strike fighters,
attack aircraft and
multirole combat aircraft. When North Korea attacked South Korea in 1950 the USAF responded with daylight bomber raids on supply lines through North Korea. B-29 Superfortresses flew from Japan on behalf of the
United Nations, but the supply line for North Korea's army from the Soviet Union was physically and politically out of reach: North Korea for the most part lacked worthwhile strategic targets of its own. The Soviet-backed Northern forces easily routed the South Korean army. The distance to North Korea was too great for fighter escorts based in Japan, so the B-29s flew alone. In November,
Mikoyan-Gurevich MiG-15s flown by Soviet pilots started to intercept the US bombers over North Korea. The MiG-15 was specifically designed to destroy US heavy bombers; it could out-perform any fighter deployed by United Nations air forces until the capable F-86 Sabre was produced in greater numbers and brought to Korea. After 28 B-29s were lost, the bombers were restricted to night interdiction and concentrated on destroying supply routes, including the bridges over the Yalu river into China. By the 1960s, manned heavy bombers could not match the
intercontinental ballistic missile in the
strategic nuclear role. More accurate
precision-guided munitions ("smart bombs"),
nuclear-armed
missiles or
bombs were able to be carried by smaller aircraft such as
fighter-bombers and
multirole fighters. Despite these technological innovations and new capabilities of other contemporary
military aircraft, large strategic bombers such as the
B-1,
B-52 and
B-2 have been retained for the role of
carpet bombing in several conflicts. The most prolific example (in terms of total bomb tonnage) is the
U.S. Air Force B-52 Stratofortress during the 1960s–early 1970s
Vietnam War era, in
Operation Menu,
Operation Freedom Deal, and
Operation Linebacker II. In 1987 the Soviet
Tu-160—the heaviest supersonic bomber/aircraft currently in active service—entered service; it can carry twelve long-range cruise missiles. The 2010
New START agreement between the United States of America and the
Russian Federation defined a "heavy bomber" by two characteristics: • range greater than • equipped for long-range nuclear "
air-launched cruise missiles" (ALCMs), defined as an
air-to-surface cruise missile of a type
flight-tested from an aircraft or deployed on a
bomber after 1986. ==List of heavy bombers==