Heavy bomber
During World War II, mass production techniques made available large, long-range heavy bombers in such quantities as to allow strategic bombing campaigns to be developed and employed.
Along with the emergence of more accurate precision-guided munitions ("smart bombs") and nuclear-armed missiles, which could be carried and delivered by smaller aircraft, these technological advancements eclipsed the heavy bomber's once-central role in strategic warfare by the late 20th century.
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.
[1] 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.
[2] 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 2,000 lb (910 kg) of bombs.
The uprated Handley Page Type O/400 could carry a 1,650 lb (750 kg) 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.
[7] 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).
Throughout the war, bombers continually managed to strike their targets, but suffered unacceptable losses in the absence of careful planning and escort fighters.
The prime proponent of strategic bombing, Luftwaffe Chief of Staff General Walther Wever, died in an air crash in 1936 on the very day that the specification for the Ural bomber (later won by the Heinkel He 177 which saw only limited use against the Soviet Union and the United Kingdom) was published.
It was based on the successful Short Sunderland flying boat and shared its Bristol Hercules radial engines, wing, and cockpit with a new fuselage.
The Stirling's low operational ceiling of just 12,000 ft (3,700 m)—also caused by the thick wing—meant that it was usually picked on by night fighters; within five months, 67 of the 84 aircraft in service had been lost.
Due to the absence of British heavy bombers, 20 United States Army Air Corps Boeing B-17 Flying Fortresses were lent to the RAF, which during July 1941 commenced daylight attacks on warships and docks at Wilhelmshaven and Brest.
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.
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.
Altogether 850 airmen were killed or captured; only 33 Fortresses returned from the October raid undamaged[13] 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.
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.
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.
[18] 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.
[19] 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.
[20] 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.
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).
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.
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.
