B-24 bomber

Development history

Historical background

In 1938, the United States Army Air Force (USAAF) prepared to authorize United Aircraft Corporation to produce B -17 bomber. After visiting Boeing's Seattle plant, senior executives of the United Company stated that they could develop a better bomber than the B-17. The proposal was approved by the U.S. military.

On February 1, 1939, the U.S. Army Air Force officially issued the C-212 design specification, requiring the development of a speed exceeding 482 km/h, a range exceeding 3,218 km, and a ceiling exceeding 10,668 meters. Heavy bomber. On March 30, the United Company was awarded a contract to manufacture a prototype aircraft. The new aircraft was named the XB-24 bomber, the internal code name of the company 32 bomber. On April 27 and August 10, the National Army Air Force ordered another 7 YB-24 verification aircraft and 38 B-24A bombers for evaluation purposes.

Development history

The prototype XB-24 bomber was delivered in November 1939. The aircraft was equipped with Pratt & Whitney's R-1830-33 double-layer star 14-cylinder piston engine (Takeoff power of 1200 horsepower), equipped with a mechanical two-speed supercharger, self-defense weapons are five 7.62 mm machine guns with nose observation window, upper and lower cabin doors and left and right observation windows. On December 29, the XB-24 prototype completed its maiden flight. The XB-24's range and transition range were longer than those of the B-17, but the speed was slightly slower than that of the B-17C with a turbocharger.

Subsequently, the YB-24 bomber developed by the joint company canceled the slit of the leading edge of the wing on the basis of the XB-24, and added a deicing device. The self-defense weapon includes the front and rear turrets and the observation windows on both sides. Six 12.7 mm machine guns. The UK purchased the first six YB-24 bombers without waiting for the completion of the test, but the British believed that it lacked turbochargers and self-sealing fuel tanks, and only used it as an unarmed transport aircraft. The last YB-24 bomber was equipped with armor and self-sealing fuel tanks, and was submitted to USAAF for evaluation in May 1941.

Put into production and installation

When the US Army Air Force USAAF was still uncertain, the French government was forced to directly order 60 B-24 bombers from the joint company due to the situation. The first export model of B-24 was called LB-30-MF. In 1940, the Royal Air Force (hereinafter referred to as RAF) also ordered 164 B-24 bombers.

After the defeat of France in June 1940, Britain took over the French order. The Royal Air Force’s B-24 bombers used the nickname "Liberator" for the first time, and this name was quickly recognized by the US Army Air Force USAAF. These urgent orders have injected funds into the joint company’s B-24 bomber project and promoted the continued development of the day.

The British Royal Air Force Coast Corps first used B-24 bombers over the Atlantic in June 1941. In the same month, the US Army Air Force also received the first batch of B-24A bombers. Before the delivery of the B-24D bomber, the B-24 bomber as a real heavy bomber had already entered serial production.

At the beginning of 1942, the B-24D bomber developed by the joint company was put into production, and the production of the B-24 bomber series entered a climax.

At the end of 1942, the B-24 bomber series was shipped to the Middle East, Pacific Ocean, In the European theater, the bombing operations against the Axis powers were put into operation.

B-24 bomber series of various types of aircraft in the United States United Company (in San Diego and Worth Man), Douglas Company (in Tulsa), Ford Company (in Willowen) and North American companies (in Dallas) has production on five production lines, of which 7 are the most successful derivative models.

Between 1943 and 1945, the United States manufactured more than 6,678 B-24 bombers of various types, of which about 800 B-24 bombers were sent by the U.S. Army to the Pacific and European theaters as land-based patrol bombers, named For PB4Y. When production ceased on May 31, 1945, a total of 18,482 B-24 bombers of various types had been produced, making them the largest American bomber produced during World War II.

At the end of 1945, the U.S. Army Aviation announced that the surviving B-24 was a post-war surplus, while the U.S. Army kept the PB4Y-1P in active service until 1951. The US Army’s 14th Air Force stationed in China during the war was also equipped with B-24s.

B-24 bombers and B-17 bombers have also become the main force for large-scale strategic bombing of Germany. The B-24 participated in the bombing campaigns against important areas such as Hamburg, Berlin, Frankfurt, and Ruhr. The most famous battle was the large-scale long-range air raid on the Ploiesti oil field by the B-24 bomber group, which caused great damage to the Nazi's energy supply.

Technical features

Overall design

The B-24 bomber is a four-piston propeller aircraft with a conventional layout and a large aspect ratio trapezoidal cantilever with a single wing. Upright oval double vertical tail.

The B-24 bomber has a larger aspect than the Davis airfoil, and is characterized by the cross-section of the wing as close as possible to the drop shape to reduce cruise resistance. Four nacelles are arranged on the wings, and the air intakes of the radiator are on both sides of the engine, so that the nacelle looks like a rare horizontal oval from the front. Each aircraft is equipped with Fuller flaps on the trailing edge of the inner wing to improve low-speed performance, and ailerons on the outer wing.

The B-24 bomber has a sturdy fuselage with an all-metal semi-hard shell structure. The nose is a glass grille-style navigator and bombardier cabin. Behind is the cockpit. The large bomb bay in the middle of the fuselage can hold up to 3.6 tons of bombs. The bomb compartment is divided into a front compartment and a rear compartment by a partition, and a narrow passage runs through the bomb compartment. In order to reduce the resistance when the bomb bay door is opened, the bomb bay door of the B-24 bomber does not adopt the conventional hinged form, but adopts a form similar to the upward contraction of the garage door. There are observation windows on both sides of the middle and rear of the fuselage, which can be sealed by baffles. The tail position of the aircraft is the tail turret, which is responsible for the rear sector defense. The B-24 bomber uses a front three-point landing gear. The low landing gear is stowed in the front fuselage, and the main landing gear is stowed outwards into the wings.

Power system

After the B-24D bomber was put into mass production by United Aircraft Corporation, the engine used was Pratt & Whitney’s turbocharged R-1830-43 engine, driving 3.531 meters The propeller of the Hamilton Standard Company.

In order to increase the range of the B-24D bomber, a huge integral fuel tank was designed inside the wing, making it the first "wet wing" (integrated wing fuel tank) military aircraft in the United States. However, in actual combat, it was discovered that the "wet wings" were at high risk of fire after being hit, and then they were replaced with separate self-sealing fuel tanks.

Weapon system

The B-24C bomber is equipped with a Martin 250CE-3 electric turret at the rear of the cockpit, and a joint A-6A hydraulic turret at the rear, each turret There are 2 machine guns on board, plus the nose, belly, and side machine guns. The B-24C has 8 12.7 mm machine guns. Although the number is small, the firepower is much stronger than that of the 7.7 mm machine gun.

The B-24D bomber retains the design of the B-24C bomber's rear Martin turret and the combined A-6A tail turret. Starting with the production of the 71st Type D, the down-firing machine gun under the rear abdomen of the fuselage was replaced with a Bondix remote-controlled electric turret. This turret is a semi-retractable type with a built-in twin-mounted 12.7 mm machine gun. The self-defense firepower of the B-24 bomber includes front and rear turrets, upper and lower turrets, and multiple machine guns on the fuselage. The layout of the machine guns and turrets takes into account the defense range and machine gun firing range.

Performance data

B-24 bomber reference data: (B-24D type)

Derivative model

After August 1942, other services also modified anti-submarine bombers, full-range escorts, reconnaissance aircraft, transport aircraft, VIP planes, trainers, fuel transport aircraft and other special models based on the B-24D. , And even converted into fighter-bombers, resulting in the total output of various types of B-24 bombers reaching more than 19,000.

XB-24: The prototype of B-24.

YB-24: Another prototype of the B-24, which is different from the XB-24 in that the leading edge of the wing, the horizontal tail and the vertical tail are added On the pneumatic deicing device.

B-24A: The first production model.

B-24C: Mass-produced machine, the back and tail of the machine are modified with American Martin double gun turrets, and the sides of the fuselage and belly are also changed to 0.5 inch caliber Active machine guns, but only nine were produced for crew training. The back and tail of the C-type aircraft are modified with American Martin gun turrets.

B-24D: This machine is a mass production model, and it is also a US military service model. The US Navy model is PB4Y-1, and the British model is Liberator 3 and 5 machine. In addition to retaining the original equipment of the B-24C, the ordnance equipment of this aircraft has changed the two movable machine guns on the nose to a 0.5-inch caliber, and installed a double-gun spherical retractable turret on the belly. A four-thousand-pound bomb rack is installed below the inner sides of the left and right wings, and fuel tanks are added to the outer wings and the front bomb bay to increase the range. A total of 2,738 B-24D series aircraft have been produced.

B-24E: That is, the Liberator IV is the same as the B-24D, which is manufactured by the North American factory.

XB-24F: Modified from B-24D-CO 41-11678, installed with a thermal deicing system, tested by NACA at Moffett Airport in California, 1942 Delivered on May 13. The deicing system has not been formally adopted either.

B-24G: The first machine went offline in March 1943. The first batch of B-24Gs were equipped with R-1830-43 engines. The first batch of 25 B-24G-NT batches was very similar to the B-24D, but did not have a belly machine gun. A total of 430 B-24Gs were manufactured in North America, and the last one rolled off the assembly line in June 1944. Subsequently, North America switched to B-24Js like other companies.

B-24H: B-24D with nose turret installed.

B-24J: The turbocharger of the B-24J has an electronic control system, which replaces the manual control system previously installed on the engine control panel.

XB-24K: Changed to a single vertical tail and rudder, a test machine.

B-24L: This type of machine is equipped with a Stinger light turret, and a ring-shaped turret is used to replace the ventral spherical turret, which reduces the total weight by one thousand pounds.

B-24M: In 1943, United Aircraft Corporation and Volti Aircraft Corporation merged and reorganized into Convair Aircraft Corporation to produce B-24M. This machine is the same as the B-24L, but is equipped with a light electric-driven tail gun tower. A total of 6,725 were produced, making it the last of the B-24 combat models. The B-24M is improved on the basis of the B-24J, and the main difference is the tail turret.

B-24N: is a single-tail rudder type machine. The nose and tail are remote-operated gun towers, and only a small amount of production is available.

XB-24P: The XB-24Q manufactured by Ford is the last type. It is equipped with a radar remote control tail gun tower. This device was later used on the B-47 jet bomber. .

CB-24: The model was changed to a public model for dismantling the armed forces, used for army identification and weather forecasting.

TB-24: type machine, formerly known as AT-22 trainer, is a B-24D type machine with dismantled weapons and equipment, and six sets of teaching aids are set up for training B- Engine power operation and flight crew of 29 and B-32 aircraft.

C-109: The fuel carrier modified by the B-24, which can carry 2900 gallons of fuel, adopts a single-point fuel supply and delivery system, and is equipped with Automatic anti-flammability protection device, part of which is equipped with a foldable fuel tank. This aircraft is designed to transport fuel for flying over the hump route. It is used for B-29 bombers that take off from bases in my country and attack Japan.

T-7: It is a long-range reconnaissance aircraft modified by the B-24. It has a camera cabin specially equipped with eleven cameras in five shooting windows. This includes a three-lens camera that simultaneously photographs areas with a range of 30 degrees vertically and on the left and right. It shoots at an altitude of 30,000 feet, covering 40 square miles. Some firearms and protective armor are still on board.

XB-41: Experimental combat escort aircraft, modified from B-24D, equipped with a total of 14 0.5-inch caliber machine guns, divided into the upper and lower sides of the fuselage , With 12420 rounds of ammunition, but due to overweight and insufficient horsepower, it did not invest in production.

Service dynamics

Flying in battle

During the Second World War, the B-24 bomber participated in the battle and dropped a large number of bombs on Germany. In the later stages of the war, B-24 bombers were more heavily invested in the Far Eastern theater, not only performing strategic missions, but also participating in tactical strike operations. The B-24 bomber was also used in local conflicts such as the Vietnam War of Resistance against France and the Korean War.

The B-24 bomber was the most produced large-scale bomber in the United States during World War II, and it was also the most-used large-scale aircraft type. The B-24 bomber is the main aerial bombing force on the vast naval and air battlefields in Europe, as well as Africa and Asia.

In 1942, the United States provided the Chinese Kuomintang government with B-24 bombers. After the Second World War, a large number of B-24 bombers were provided as surplus materials to allies of the United States, including the Chinese Kuomintang government at that time.

Uprising Operation

On June 26, 1946, the 8th Battalion of the Kuomintang Air Force pilot Liu Shanben, the co-pilot Zhang Yiyi, the flight mechanic Tang Shiyao, and the correspondent Tang Yuwen flew a US-made B aircraft. The -24 bomber took off from Chengdu and flew to Yan'an, marking the first time the Kuomintang Air Force flew to the Liberated Area.

On December 16, 1948, Lieutenant Pilots of the 8th Battalion of the Kuomintang Air Force Yu Bo, Hao Guiqiao, ChenJiuying, lieutenant navigators Zhou Zuozhou and Zhang Zuli piloted an American-made B-24 bomber to take off from Nanjing. After takeoff, he was preparing to bomb the Nanjing University Field Airport and the Presidential Palace. Due to the failure of the bombing system, all five bombs fell to the Yanzi outside Nanjing. At that time, Chiang Kai-shek was in the Air Force Club at the University Field Airport to condolences to the Air Force soldiers, and he was panicked when he heard the explosion. After dropping the bomb, the bomber flew to Shijiazhuang, which was occupied by the Chinese People's Liberation Army.

On February 3, 1949, lieutenant pilots Zhang Yunong, Ren Yongshou, Huang Youshou, and Huang Wengang of the 8th Battalion of the Kuomintang Air Force stole a US-made B-24 bomber and forcibly took off from Shanghai and flew to Peking Nanyuan Airport to revolt .

On the night of May 11, 1950, three B-24 bombers of the Kuomintang Air Force invaded Shanghai. The anti-aircraft artillery unit of the Chinese People's Liberation Army shot down a B-24 aircraft and crashed in Tangqiao Town, Pudong.

Overall evaluation

The B-24 bomber is a heavy bomber between the B-17 bomber and the B-29 bomber. Compared with the B-17 bomber, the B-24 bomber has a larger ammunition capacity, a longer range, a higher ceiling, and a slightly faster speed. However, in terms of maneuverability, stability and damage resistance, the B-24 The bombers are slightly inadequate, so the B-24 bombers are not as well-known as the B-17 bombers for large-scale air strikes.

In the middle and late stages of World War II, the manufacturers of the B-24 bombers did not formulate strict and unified production standards, which caused great inconvenience to battlefield maintenance and seriously affected the attendance rate of the B-24 bombers. . However, the B-24 bomber has excellent long-distance performance. The modified PB4Y-2 anti-submarine patrol aircraft can patrol the Pacific for 16 hours. Therefore, the B-24 aircraft was converted into a maritime reconnaissance aircraft, anti-submarine aircraft, transport aircraft, and photographic reconnaissance aircraft, and became the most versatile and produced aircraft in World War II. Both in the European battlefield and the Pacific battlefield, the B-24 bomber played an important role. (Review of "International Outlook")