Dive bomber

For other uses, see Dive Bomber (disambiguation).

An SBD Dauntless drops its bomb. The dive brakes are extended and are visible behind the wings.

A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target reduces the distance the bomb has to fall, which is the primary factor in determining the accuracy of the drop. Additionally, as the bomb's motion is primarily vertical, the complex parabolic trajectory is reduced to one that is much straighter and easy to calculate - even by eye. The rapid vertical motion of the aircraft also aids it in avoiding fire from anti-aircraft artillery, although diving to low altitude offsets this advantage as it brings the aircraft into range of smaller weapons.

A true dive bomber dives at a steep angle, normally between 45 and 90 degrees, and thus requires a very short pull-up after dropping its bombs. This demands an aircraft of extremely strong construction, and generally limited the class to light bomber designs with ordnance loads in the range of 1,000 lbs. This type of aircraft was most widely used before and during World War II; its use fell into decline shortly afterwards. The most famous examples are the Aichi D3A "Val" dive bomber which sank more Allied warships during World War II than any other Axis aircraft and the Junkers Ju 87 Stuka which was widely used during the opening stages of the war. During pullout, the forces were so great that the crew would often black out, and so the controls of the Ju 87 were automated to avoid loss of the aircraft. This system allowed the Stuka to attack in a steep dive angle and make later pullouts than other aircraft could safely manage, which increased accuracy. Another famous design of the war is the Douglas SBD Dauntless, whose most well known action occurred at the Battle of Midway.

A second and simpler dive bomb technique is to bomb from a much more shallow dive angle, sometimes referred to as glide bombing. Shallower diving angles reduces the benefits in terms of accuracy, but still serves as an aid in keeping the target visible during the bomb run. The Junkers Ju 88 was widely employed in glide bombing and was equipped with special bombsights operated by the pilot for this task. The Heinkel He 177 is often mentioned as having its development upset by the demand that it be able to dive bomb, although this too was an example of glide bombing. Glide bombing should no be confused with the glide bomb, where the bomb glides towards its target while the aircraft remains in level flight. Attachments for this sort of bombing were fitted to examples of the famous Norden bombsight, but in practice this concept proved unworkable.

Technique

Horizontal bombing

When released from an aircraft, a bomb carries with it the aircraft's velocity. In the case of a bomber flying horizontally, the bomb will initially be travelling forward only. This forward motion is opposed by the drag of the air, so the forward motion slows over time. Additionally, gravity provides a constant force on the bomb, accelerating it downward. The combination of these two forces, drag and gravity, results in a pseudo-parabolic trajectory of some complexity. For aiming purposes, the key calculation needed from this trajectory is the distance the bomb will travel forward while it falls, a distance known as the "range". The bomber's task is to fly along a line to the target until it reaches this distance from the target, and drop the bombs at that instant. Even then, if the wind is blowing perpendicular to the line of attack, the bombs will be pushed laterally as they fall, an effect which can be quite extreme, especially from high altitudes. This means that a bombsight or bombardier must be capable of taking the direction and speed of the wind into account as well as the speed of the aircraft and range from target. This is something that is difficult if not impossible to do accurately, at least not on a large and repeatable scale, which led to the Allied bomber forces flying over the target in 1/4 mile-wide formations, and all dropping their bombs together in "strings", theoretically assuring that at least one or two aircraft would drop their bombs onto the target (while ensuring that most of the group wouldn't). This can be thought of as similar to the concept of a machine gun's "cone of fire". It may be difficult to hit a distant and small target with a single aimed shot, but if you fire 100 rounds in a tight pattern around the area of the target, at least one round will likely hit the target. While this technique of bombing leads to large areas of destruction and makes the task of hitting only a single building essentially impossible, it does however mean that the bombs won't be scattered over a random area of the city, increasing the likelihood of hitting the specified target. In practice, weather, the stress of combat, human errors and mechanical errors all contributed to decreasing the accuracy of "precision" bombing. Successful degradation of targets was largely in consequence to the large number of aircraft in the raids, repetitively targeting the objective, and the large numbers of bombs dropped.

In the past, aircraft did not have navigation systems that could direct an aircraft towards an arbitrary point in space. Instead, navigation was carried out in relation to objects on the ground - whether they be visual indications or radio beacons. If one calculates the range for a given set of conditions, simply trigonometry can be used to find the angle between the aircraft and the target when they are that far apart. By setting the bombsight to that angle, the "range angle", the aircraft simply had to approach the target and drop its bombs when the target appeared lined up with the sights. This was only effective for "area bombing", however, since radio equipment wasn't accurate or powerful enough to specify a specific target. Large formations could drop bombs on an area hoping to hit a specific target in the dark, but there was no guarantee and huge areas around the target would be demolished, even worse than with "precision" bombing.

As the trajectory of the bomb is complex, solving the range is a complex problem. This is normally accomplished by looking up data measured on a bombing range and reduced into table form. Any changes in speed, direction or altitude required all of this to be looked up again. In order to reduce this workload, mechanical calculators were increasingly common during World War II, including the famous Norden bombsight and the less well known British Mark XIV bomb sight and German Lotfernrohr 7. Even with these calculators, accuracy was often poor due to inaccuracies in the ballistics of individual bombs, wind measurements, or setup errors. Moreover, the need to fly in a straight line toward the target made it easy for anti-aircraft artillery to aim at the bomber, which demanded that the aircraft fly higher to avoid fire, and thereby magnified any errors in setup. In spite of enormous efforts, accuracies for horizontal bombing throughout the war was generally measured in thousands of yards. All these points meant that the horizontal bomber was ill-suited for tactical bombing, particularly in close support. To hit any one target, relatively large numbers of bombers and bombs were needed, which were difficult to communicate with in real-time, and which took time to organize and send after a target (which may or may not be obstructed by cloud when they arrived). When they did attempt to bomb a target, the large dispersion and aiming inaccuracies meant that anything within a mile of the target was in danger. Attempts at using high-altitude bombing in near-proximity to troops often ended up in tragedy, with the bombs dropped on "friendly" troops, as well as the enemy. In attacking shipping, the problems of inaccuracy were amplified by the fact that the target was usually moving, and could change its direction between the time the bombs were released and the time they arrived. Thus, the horizontal bomber was of limited use in attacking shipping. Successful strikes on marine vessels by horizontal bombers were extremely rare. An example of this problem can be seen in the attempts to attack the Japanese carriers using B-17s at altitude early in the battle of Midway. No hits were scored. The German battleship Tirpitz was subjected to countless strikes, many while in dock and immobile, and wasn't successfully sunk until the British brought in special, enormous bombs to ensure that even a near miss would do the trick.

Dive bombing

An aircraft diving vertically has no horizontal velocity component. When the bomb is dropped, the force of gravity simply increases its speed along the vertical trajectory. The bomb travels straight downwards between release and impact, eliminating the need for complex calculation and setup of a bombsight. The aircraft simply points at the target and releases its bombs, the only source of error being the effects of winds after release. For bombs, which are streamlined and heavy, wind has only a slight effect, and the bomb is likely to fall within its lethal radius of the target.

Diving perfectly vertically is not simple, for either pilot or airframe. The forces generated when the aircraft levels out at the bottom of the dive are considerable. As the aircraft tilts further down, the horizontal component of its speed reduces, making the trajectory of the bomb once released, closer to a straight line. Bomb sighting becomes trivial; requiring only a straight line sight. Differences in path of different bombs, due to differing ballistics, was corrected by selecting a standardized bombing altitude and then adjusting the dive angle slightly for each case.

Accuracy of the drop depends primarily on the pilot or bombardier's ability to see the target. This was simplified as the aircraft was pointed directly at it, making sighting over the nose much easier. As the bomber dives, the aim could be continually adjusted. But if a horizontal bomber veers offline whilst approaching the bomb release point, there is nothing to be done - turning to the angle that would correct this would also change the groundspeed of the aircraft (at least in the presence of wind) and thereby change the range as well.

So, dive bombing was the only method of attacking high-value compact targets like bridges and ships, with accuracy. It was employed by most naval air services and many land-based air forces as well.

The drawback of optimizing an aircraft for near-vertical dives was loss of performance. During normal horizontal flight, a typical aircraft is in balance between the lift its wings and tail generate, gravity, the force of its engine and drag. When it is put into a near vertical dive, the lift from the wings and horizontal tail are no longer balanced and cause the aircraft to return to level flight, tracking across the target unless the pilot applies considerable force to keep the nose down, with a corresponding decrease in accuracy - meaning that while the nose is pointed straight down, the wings are still trying to "lift" the aircraft. Since there is no longer gravity counteracting this, the aircraft will have a tendency to turn up while diving, moving it across the target as it dives, rather than straight down. To compensate for this, many dive bombers were designed to be trimmed out, either through the use of special dive flaps (such as Fairey Youngman flaps) or through changes in tailplane trim that must be readjusted when the dive is completed. The Vultee A-31 Vengeance used by the RAF in Burma was designed to be trimmed for diving, with no lift to distort the dive. The drawback was having to fly nose up in level flight. Failure to re-adjust trim often made the aircraft difficult or impossible to pull out of a dive.

A dive bomber was vulnerable to low-level ground fire as it dived towards its target since it was often headed in a straight line directly towards the defenders. At higher levels this was less of a problem, as larger AA shells are fused to explode at a certain altitude, which is almost impossible to predict accurately while the plane is diving towards the gunner. In addition, most higher-altitude gunners and gunnery systems were designed to calculate the lateral movement of a target; while diving, the target appears almost stationary. Also, many AA mounts lacked the ability to fire directly up, so dive bombers were almost never exposed to fire from directly ahead, and there were few gunners who could accurately keep their positions and put up effective fire while a group of bombers dived towards them; the natural tendency is to panic and seek cover.

Dive brakes were employed on many designs to create drag which slowed the aircraft increasing accuracy and preventing structural damage. When introduced these were almost exclusive to dive bombers, though the air brakes fitted to modern aircraft function in a similar manner.

Almost a century later it is probably neither possible nor profitable to establish who invented dive bombing. Much would depend upon the definition of dive and the precise angle at which glide becomes dive. What is clear enough is that the Royal Flying Corps on the Western Front found its primitive biplane two seat bombers quite inaccurate. Commanders urged pilots to dive from their cruise altitude to under 500 ft to have a better chance of hitting small targets such as gun emplacements and trenches. As this exposed the aircraft and crew to accurate and destructive rifle fire in their unprotected open cockpits, few chose to follow this order. Those that did recorded altitude at the top and bottom of their dive in log books and squadron records, but not the angle of dive. It is unlikely that it was vertical, since these primitive aircraft could not have withstood the stress of a vertical dive, for long.

The Royal Naval Air Service whose primary target was highly-combustible [Zeppelin]] sheds in Germany and occupied Belgium found it worthwhile to dive onto these to ensure a hit, despite the increased casualties from ground fire. Again the angle of dive was not recorded.

The Royal Flying Corps ordered large numbers of the Sopwith Salamander TF2 a single seat biplane powered by a Bentley BR2 rotary engine just as the war was ending. The TF stood for “Trench Fighter” and it was designed to attack German trenches with both Vickers 0.303 machine guns and 25 pound bombs. Whether it should be considered in more modern parlance as a fighter bomber or a dive bomber again depends upon the definition of dive. It had armoured protection for the pilot and fuel system to attack at low level but lacked dive brakes for a vertical dive. It never saw action.

British experience of the horrendous casualties produced by air to ground attack on trenches set the minds of senior officers in the newly created Royal Air Force against dive bombing. So not until 1934 did the [[Air Ministry}] issue specifications for both a land-based and a carrier-based dive bomber. The RAF Hawker Henley failed to fulfil that role whilst the Blackburn Skua was expected to double as a fighter when out of reach of land-based fighters. It did not dive vertically for long but did have dive brakes which doubled as flaps for carrier landings. The Royal Navy called it a dive bomber.

The British chose to develop dive bombers, which sacrificed bombing accuracy in bombing, for advantages in speed and agility. The Hawker Henley had a top speed only 50mph slower than the Hawker Hurricane interceptor fighter from which it was derived. The American and Japanese navies and the Luftwaffe chose vertical dive bombers whose slow speed had dire consequences when they encountered modern fighters.

History

World War I

The Aichi D1A2, a carrier-borne dive bomber.

The Royal Naval Air Service developed dive bombing as a tactic against Zeppelin hangars, forming and training a squadron at Manchester for this task. On October 8 1914 Flight Lieutenant Matrix flying a Sopwith Tabloid attacked a Zeppelin hangar at Dusseldorf, dropping two 50 pound bombs after diving down to 600 feet. On November 14 1914 four Avro 504s attacked the Zeppelin factory at Friedrichshafen on Lake Constance. The aircraft approached at 1200 ft, diving down to 500ft to release their bombs. As a number of Zeppelins were tethered close to the stores of hydrogen, the damage inflicted was spectacular.

The first use of dive bombing by the Royal Flying Corps was in February, 1915. The Corps had been urging its pilots to drop bombs from heights below 500 ft in order to acheive greater accuracy. On November 27 1915, Lieutenant Duncan Grinnell-Milne flying a B.E.2 attacked the railway marshalling yards near Lys in Northern France. He arrived in his over the target at 10,000 feet, diving through a group of other bombers to release his s 20 pound bombs from 2,000 feet. A few weeks later, Lieutenant Arthur Gould dived to just 100 feet, dropping his bombs on buildings near Arras.

The first dedicated ground attack aircraft was the Sopwith Salamander, which was intended as a fighter and dive bomber. Based on the Sopwith Snipe, it was protected with 600 pounds of armour plate to the front of the aircraft to protect the pilot and fuel supply against small arms fire. A total of 1,400 were ordered, but only two were delivered to France before the Armistice. Production of the Snipe ceased at just 500 aircraft.

The Royal Flying Corps developed ground attack techniques with diving aircraft, using both machine guns and small bombs to damage the targets. The technique was put into play on a large scale at the Battle of Cambrai. On November 20 1917, 300 aircraft, mostly Sopwith Camels and Airco DH.5s carrying 20 pound bombs, flew in support of some 320 Mark IV tanks. The aircraft attempted to supress artillery fire and machine gunners. The cost in pilots during this engagement was very high, reaching 30 per cent.

The impact of aircraft at the Battle of Cambrai was significant. British armoured warfare proponent J.F.C. Fuller, who at the time was a staff officer at the Royal Tank Corps, published a report on the battle. His findings and theories on armoured warfare were later taken up by Heinz Guderian, who helped to formulate the basis of operations that was to become known as Blitzkrieg warfare. These tactics involved deep penetration of the armoured formations supported behind enemy lines by bomb carrying aircraft. Dive bombers were the principle agents of delivery of high explosives in support of the forward units.

Second Lieutenant William Henry Brown, a Canadian from British Columbia flying a SE5a for the RFC, made the first attack on a naval vessel on March 14, 1918. Lt Brown destroyed an ammunition barge on a canal at Bernot near St Quentin, diving to 500 ft tbefore releasing his bombs. On June 22 he was awarded the Military Cross for this and other exploits. Brown`s technique was emulated by other British squadrons, but pilot losses were heavy, influencing RAF thinking on the matter for 20 years.

Interwar era

The Royal Flying Corps was initially impressed with the potential of the dive bomber but aware of its suicidal nature. It ran a series of tests at the Armament Experimental station at Orfordness in Suffolk. Sopwith Camels and SE5As were used in early 1918 to dive bomb targets from various heights, with different bombs and with and without the use of the Aldis sight. This had been invented by Hugh Aldis in 1916 to aid pilots to calculate the deflection required to hit a traversing German plane. In principle, it obviated the need for a vertical dive. .

The results were not considered good enough to justify the expected casualties. The Royal Air Force which took over both army and naval aviation in November 1918, retired most of its Sopwith Salamander dive bombers.

Colonel later General William Mitchell arrived in France with the first US Army and Air Force units soon after April 6 1917 and began to organize the US Army Air Force flying French Salmson 2s, a spotter plane. The later Salmson 4 was to be a ground attack and dive bomber, but production was cancelled at the end of the war. Mitchell became a strong advocate of dive bombers after witnessing British and French aerial attacks .

Mitchell by now assistant chief of the Air Service arranged tests with captured German and obsolete US ships in June and July 1921 and repeated over the next two years using SE5as as dive bombers and Handley Page 0400s and Martin NBS-1s as level bombers carrying bombs of different weights up to 2,000 pounds. The Ostfriesland was sunk and so later were the USS Alabama, USS Virginia and USS New Jersey .

Opposite conclusions were drawn by the RAF and USAS, from two very different tests regarding the usefulness of dive bombers, with the RAF concluding that the cost in pilots was too high to justify the meagre results and the USAS considering that it proved it would become a potent anti-ship weapon. Both naval staffs opposed the view taken by the respective airmen.

In 1919 United States Marine Corps pilot Lt. L. H. Sanderson mounted a carbine barrel in front of the windshield of his Curtiss JN-4 (a training aircraft) as an improvised bomb sight, loaded a bomb in a canvas bag attached to the plane's underside, and made a solo attack in support of US Marines trapped by Haitians during the United States occupation of Haiti. Sanderson's bomb hit its target precisely and the raids were repeated. During 1920 Sanderson familiarized aviators of USMC units at the Atlantic coast with the dive bombing technique Dive bombing was also used during the United States occupation of Nicaragua.

As planes grew more powerful, dive bombing became a favoured tactic particularly against small targets such as ships. The US Navy overcame its hostility to Mitchell`s findings and deployed the Curtiss F8C biplane from 1925 on carriers. The Marine Corps operated the same aircraft from land bases and called it the Helldiver a name used again by Curtiss for more famous dive bombers.

The Imperial Japanese Navy ordered the Heinkel He 50 with a 550 pound bomb load in 1931 as a floatplane and carrier plane and embarked some on new carriers from 1935 as the Heinkel He 66, from which the Aichi D1A was developed in Japan. The Luftwaffe, confiscated a Chinese export shipment and ordered more.

Navies increasingly operated carriers, which had few small aircraft available for any attack, each with only a small bomb load. The target was often likely to be a small fast- moving warship. The need to score a hit made dive bombers essential.

A German First World War ace with 62 victories and friend of Hermann Goering,Ernst Udet persuaded him to buy two Curtiss Hawk IIs to ship to Germany. Udet, then a stunt pilot, flew one in aerobatic displays during the 1936 Olympic Games in Berlin. Due to his connections and Nazi party membership, he became development director of the Reich Air Ministry where he pushed for dive bomber development.

Dive bombing would allow a low-cost Luftwaffe to operate effectively in the tactical role. Against small targets, a single-engine dive bomber could achieve four times the accuracy at one tenth of the cost of a four engine heavy bomber, such as the projected Ural bomber. . It could reach the battlefield well ahead of horse-drawn field artillery. Soon the Luftwaffe issued a contract for its own dive bomber design, resulting in the gull-winged Junkers Ju 87 Stuka (a contraction of Sturzkampfflugzeug, literally "diving combat airplane").

Several Junkers Ju87 dive bombers, which first flew in on September 13 1935 powered initially by a Rolls-Royce Kestrel engine were shipped secretly from Germany to Spain to assist General Francisco Franco`s Nationalist rebels in the Spanish Civil War. Several problems, such as the tendency of the fixed under-carriage to sink into soft ground and an inability to take-off with a full bomb load appeared. Condor Legion experience in Spain demonstrated the value of dive bombers especially on morale of troops or civilians without countervailing air cover. .

The aircraft did not encounter opposing modern fighters, which concealed from the Luftwaffe its true vulnerability. On August 15 1939, just before their use in Poland, 13 Ju87s crashed into the ground in formation at Sagan, during an air display, as the result of a lowering cloud base.

Some 23 Breda Ba 65s were flown by Italian pilots also to support Nationalist Forces. First flown in 1935, it was a single-seat dive bomber carrying the same bomb load as the Stuka with a 30 mph speed advantage in level flight, due to its retractable under-carriage.

Udet was so impressed with the Stuka`s performance in Spain that he ordered that the Junkers Ju88 medium bomber should also be retrofitted as a dive bomber. This required 50,000 modifications, increasing its weight by 5 tons and reducing speed by 120 mph. He also insisted against the advice of Ernst Heinkel that the Heinkel He 177 heavy bomber, ordered in November 1937, be able to dive bomb. This required that two Daimler Benz 601 engines be welded together in each of two wing nacelles, fatally compromising its reliability. It never performed in the dive bomb role.

As the Royal Navy again took control of carrier-borne dive bombers in the new Fleet Air Arm it began to receive Blackburn B24 Skuas from November 1938. Royal Navy doctrine was that it needed a navigator to cross ocean wastes and that it could operate as a fleet interceptor fighter since it would not meet land-based fighters. With four 0.303 Vickers guns and another rear-facing it was supposed to defend ships against air attack despite its top speed of just 225mph at sea level.

The British Air Ministry issued a specification 4/34 in 1934 for a ground attack aircraft with dive bombing capability. The Hawker Henley was a two seat version of the Battle of Britain winning Hawker Hurricane. It was fast at almost 300 mph at sea level and 450 mph in a dive but had neither dive brakes nor automatic level out. Development was delayed and it was plagued by over-heating of its Merlin engine. Just 200 were built and it was relegated to target towing where its pace enabled it to match the speed of German bombers whilst towing a drone. . Instead the RAF came to rely on the US-built Vultee A41 Vengeance but only from 1943.

The Curtiss SBC-4 Helldiver a biplane dive bomber had been taken aboard the USS CV5 Yorktown in 1934 but was slow at 234 mph, flat out. Fifty, a gift from the US Navy were flown to Halifax, Nova Scotia by Curtiss pilots and embarked on the French aircraft carrier Bearn in a last ditch attempt to help France, which surrendered whilst they were in mid-Atlantic. Diverted to Martinique only five, left behind in Halifax reached the RAF in time to serve in the Second World War.

The Japanese introduced the Aichi D3A Val monoplane as a successor to the biplane D1A in 1940 with trials aboard the carriers Kaga and Akagi. It was to prove a potent weapon.

Only the Wehrmacht understood the lesson of the battle of Cambrai 1917 of using dive bombers in conjunction with tanks. The writings of Colonel J.F.C. Fuller a staff officer and Basil Liddell-Hart a military journalist propounded the concept of mobile tank forces supported by ground-attack aircraft creating a breakthrough. These were eagerly studied by Heinz Guderian who created the combination of Panzers and Junkers Ju 87s which proved so potent in Poland and France. The Stuka could be used as aerial artillery moving far ahead of the main forces with Panzers to smash enemy strongpoints without waiting for the horse-drawn artillery to catch up. It was central to the concept of Blitzkrieg which required close co-ordination between aircraft and tanks, by radio.

Carl L. Norden a Dutch-born Swiss-educated engineer who had emigrated to the US was working with Sperry Gyroscope on a mechanical computer system linked to an aircraft autopilot which promised a huge improvement in bombing accuracy. In tests on October 14 1931, aircraft equipped with the Nordern bomb sight hit the battleship USS Pennsylvania with half the bombs. It seemed that dive bombers would be unnecessary if level bombers could achieve such results in war conditions. The RAF was also keen to acquire Norden sights but despite much diplomatic effort failed until 1942 when it was rejected due to operational problems with the gyroscope.

The RAF chose as its tactical bombers the single Rolls-Royce Merlin-engine Fairey Battle and the twin engine Bristol Blenheim. Both were low-level light bombers with similar bomb-loads and entered squadron service in 1937. The US Army Air Corps (USAAC) adopted the Douglas B20 Havoc first flying in January 1939 for a similar role, although early shipments were to France and after the Fall of France to the RAF who called it the Douglas Boston. Many were also supplied to the Soviet Air Force, which also used the Ilyushin Il2 Sturmovik ground-attack aircraft in huge numbers. But this usually attacked with cannon in a shallow dive as its bomb sighting was so poor. No Allied Air Force operated a modern dive bomber at the outbreak of the Second World War, although both the Royal Navy and the US Navy had shipboard dive bombers.

World War II

European theater

Three Blackburn B24 Skuas flying from HMS Ark Royal on September 26 1939 had the first aerial victory over the North Sea when, in their fighter role, they shot down a Dornier Do 18 flying boat. On April 10 1940 16 Blackburn B24 Skuas flying at extreme range from the naval air station at Hatston, Orkney led by Lieutenant Commander William Lucy sank the German cruiser Koenigsberg in Bergen harbour, whilst trying to prevent the German seaborne invasion of Norway.

The invasion of Poland the Low Countries and France saw the Stuka used to devastating effect. The British Expeditionary Force had set up strong defensive positions on the west bank of the Oise River to block rapidly advancing German armour. Attacks by Stukas quickly broke the defence, and combat engineers were able to force a crossing long before German artillery arrived.

Massive aerial attacks in 13 May 1940 against strong French defence positions at Sedan in the Battle of France, allowed German forces to make a fast and unexpected breakthrough of the French lines, eventually leading to the German advance to the Channel and the cutting off of large parts of the Allied army.

The Stuka soon showed its weakness in the Battle of Britain where great numbers were lost in attacks on ships in the Channel and radar stations on the south coast of England. The Hawker Hurricane with almost 100mph speed advantage could easily rip the Stuka apart with its eight machine guns. The Stuka had not met such opposition before and was rapidly withdrawn. The same fate befell RAF Fairey Battles over France.

The Stuka had 7.92mm machine guns or 20mm cannons mounted in the wings. Some were modified to destroy tanks with 37mm cannons mounted below the wings. They were very successful in this role in the early days of Operation Barbarossa before the Red Army Air Force countered with modern fighters, such as the Yakovlev Yak 1 and later Yakovlev Yak 3

The most successful dive bomber pilot was Hans-Ulrich Rudel who made 2,530 sorties. He sank the Soviet battleship Marat with another Stuka at Kronstadt on September 23 1941 using 1,000 pound bombs. Converting to a tank buster 20mm cannon Stuka, he claimed over 100 Soviet tanks destroyed, mostly at the Battle of Kursk in June 1944.- each side`s claims were notably larger than battlefield wreckage would suggest. Rudel co-wrote a post-war book about his experiences and consulted with the US Air Force.

When Italy joined the war on the Axis side Breda Ba 65s were shipped to North Africa for use against the British. But by February 1941 most had been shot down by British fighters.

The North American P51 Mustang was developed for the RAF when the president of North American Aviation, “Dutch” Kindleberger promised to produce a better fighter than the Curtiss P40 Tomahawkand just as quickly as setting up an assembly line for the Tomahawk. He was as good as his word. Once the original Allison engine was replaced by a Packard-built Rolls-Royce Merlin the Mustang became the best long-range fighter of World War 11. Chief Naval Test Pilot Captain Eric Brown, tested the Mustang at RAE Farnborough and famously remarked. ” If I were in a dogfight, I'd prefer to be flying the Spitfire. The problem was I wouldn't like to be in a dogfight near Berlin, because I could never get home to Britain in a Spitfire!".

When the Lend-Lease contract with Britain used up its funds, some Mustangs were delivered to the United States Army Air Force. There were no funds to buy more fighters but there was an appropriation for a dive bomber. So the Mustang modified with a new wing and dive brakes but with the Allison engine first flew as the North American A36 Apache in October 1942 and arrived in Morocco in April 1943 to assist with driving the Afrika Korps out of Africa. It was very fast at low altitude, only 40 mph slower than the contemporary Supermarine Spitfire MKX11 which had the much more powerful Rolls-Royce Griffon engine. Sadly it was also accident-prone, achieving the highest casualty rate during training of any USAAF aircraft and was officially restricted to no more than a 70 degree dive.

The Apache did not fly with the RAF but served with US squadrons in Sicily, Italy and by late summer of 1943 were based in India for use over Burma and China. It proved to be an excellent dive bomber and a good fighter creating one ace in Lieutenant Michael T.Russo in Italy who shot down five German fighters

Royal Navy's Fairey Barracudas which had replaced the Fairey Swordfish as a torpedo bomber but could also dive bomb made repeated dive attacks on the German battleship Tirpitz which lay protected by torpedo nets in a Norwegian fjord, during 1944. On April 3 1944, in (Operation Tungsten) 42 aircraft flying from carriers HMS Victorious and HMS Furious scored 14 hits with 500 pound and 1600 pound bombs and put the battleship out of action for over two months.

Pacific theater

United States Navy Curtiss SB2C Helldiver dive bomber

The Vultee A31 Vengeance was developed in the US as a private venture dive bomber for export. It first flew in March 1941. It had a zero incidence wing which was perfect for vertical dives as there was no lift from wing or tailplane in a dive. But it had to fly in a nose up attitude to maintain level flight, which made landings difficult. First orders were 300 for France, but France fell before they could be delivered. The RAF, with the failure of the Hawker Henley and having noted the success of Stukas in Poland took delivery, instead. It was considered too vulnerable to German fighters for use in Europe or North Africa but large numbers flew in Burma from March 1943. It flew close support for General William Slim`s Burmese campaign bombing Japanese supply routes, bridges and artillery. It operated in the Royal Australian Air Force, Indian Air Force and Fleet Air Arm as well as the RAF. Some were held back for the Army Air Force after Pearl Harbor, but did not see combat.

Both the Imperial Japanese Navy (IJN) and the U.S. Navy invested considerable effort on dive bombers. Japan started the war with a very good design, the Imperial Navy's carrier-borne Aichi D3A ("Val"). As the war progressed the design became outdated due to its limited speed, due in part to the limited horsepower of its power plant and to the greater drag of its fixed main landing gear (a shortcoming shared by the Stuka).

The main U.S. dive bomber the Douglas SBD Dauntless had similar performance to the D3A Val. Later in the war the Dauntless was replaced with the faster, but more complex and trouble-prone Curtiss SB2C Helldiver from December 1942. Both airplanes were ubiquitous, with 6,000 Devastators and over 7.000 Helldivers built.

Both aircraft were used at Pearl Harbor on December 7 1941. The Japanese sent 54 D3A Vals carrying 550 pound bombs to attack parked aircraft at Wheeler Field and Ford Island. A flight of 18 Dauntlesses from the carrier USS Enterprise arrived over Pearl Harbor just as the Japanese attacked. Seven were shot down and many more destroyed on the ground at Marine Corps Air Station Ewa

At the Battle of the Coral Sea, Dauntlesses sank the light carrier Hosho and damaged the fleet carrier Shokaku together with Douglas TBD Devastator torpedo bombers.

On April 9 1942, the Royal Navy aircraft carrier HMS Hermes escorted by the heavy cruisers HMS Cornwall and HMS Dorsetshire, and destroyer HMS Vampire were returning to base at Trincomalee, Ceylon at full speed after they had been spotted by a plane from the Japanese battleship Haruna}. They were attacked by more than 32 Aichi D3As and all sunk before defending RAF Fairey Fulmars could reach them. Two Fulmars and five D3As were shot down and four damaged.

At the Battle of Midway on June 7 1942 after most torpedo bombers had been shot down without a single strike, Dauntlesses from US carrier Yorktown found four Japanese carriers, in the vulnerable stage of refuelling and rearming aircraft for a second strike. The Combat Air Patrol of formidable Mitsubishi Zeros had been drawn away, chasing torpedo bombers, leaving a clear sky. Soryu and Akagi were ablaze within six minutes whilst Kaga hit only once exploded as the bomb ignited fuel and bombs in the hangar.

Within hours the Imperial Japanese Navy had lost most of its fleet and many experienced naval airmen, both of which Japan would have difficulty in replacing.

The Army Air Force took a version of the Dauntless with a different tailwheel tire and no arrester hook as The Douglas A24 Banshee. In crates headed for the Philippines, they were diverted to Australia and operated from Charters Towers in Queensland. It was unable to contend with Japanese Mitsubishi Zeros. On July 26 1942 just seven Banshees were sent to intercept a Japanese convoy supplying forces occupying New Guinea. Six were shot down.

The Japanese Yokosuka D4Y Suisei code-name Judy began to replace the Vals on surviving larger Japanese carriers from March 1943. With a sleek fuselage, retracting landing gear and a powerful licensed Daimler-Benz 601 engine, it could outpace pursuing Grumman F4F Wildcats. To maximise speed and range, the Japanese had dispensed with armour protection and self-sealing fuel tanks which proved to be very costly when the US Navy deployed the new Essex-class aircraft carriers which each carried 36 of the faster Grumman F6F Hellcats. The Battle of the Philippine Sea on June 19-20 1944 was a failure in terms of Japanese carriers hit, but the losses of Vals and Judies and their crews were enough to destroy the Japanese navy`s ability to strike by air ever again.

Henceforward attacks were mostly confined to kamikaze . The Japanese were now on the defensive. Japan's industrial output dropped from a peak in 1942 whilst the US increased by a quarter in two years. Japanese wartime production of bombers of all types was just 16% of the US output.

Decline

After World War II, the rise of precision-guided munitions and improved anti-aircraft defences – both fixed gunnery positions and fighter interception – led to a fundamental change in dive bombing. New weapons such as rockets allowed for better accuracy from smaller dive angles and from greater distances. They could be fitted to almost any aircraft including fighters, improving their effectiveness without the inherent vulnerabilities of dive bombers, which needed significant air superiority to operate effectively.

When the RAF were attempting to stop the Panzers of Erwin Rommel`s Afrika Korps in early 1942, its lack of dive bombers was an impediment to success. However, the British Government's Chief Scientist, Henry Tizard formed a panel of experts which recommended using rockets. A rocket has a much flatter trajectory than a bomb allowing it to be launched with reasonable accuracy from a shallow dive, and could be fitted on existing aircraft. The British Army used them on Hurricanes in June 1942 against Rommel`s tanks. They went on to use rockets against low-flying bombers during the Battle of Britain by enlarging the tube from 2 inches (51 mm) to 3 inches (76 mm) and fitting high explosive warheads. The more powerful Hawker Typhoon originally developed as a fighter proved even more effective, carrying eight RP3 60 pound rockets and providing the same impact as a naval destroyer`s broadside.

On May 23, 1943, a Fairey Swordfish destroyed U752 in the Atlantic, and five days later, a Lockheed Hudson of RAF Coastal Command sank another U-boat in the Mediterranean. These rockets were fitted with iron spikes and fired at a shallow angle into the sea. Once under water, they curved upwards and punctured the pressure hull below the waterline, disabling or sinking the submarine.

Caltech developed the 5-inch (130 mm) High Velocity Aircraft Rocket (HVAR) with a 24-pound (11 kg) warhead for the US Navy. It was rushed to Europe for use on D-Day and later used by Navy planes in the Pacific. By January 1943, American pilots who had been flying in RAF Eagle Squadrons before the US entered the war, converted from Supermarine Spitfires to Republic P-47 Thunderbolts to form the USAAF 4th Air Fighter Group. At over 4 long tons (4.1 t) unladen, one of the biggest single engine fighter bombers of the war, it could carry ten 5-inch (130 mm) HVARs.

By late 1944, the RAF was able to hit stationary targets with greater accuarcy from greater heights inflicting far more damage with less risk. On November 12, 1944, two 5-long-ton (5.1 t) Tallboy bombs were dropped by Avro Lancasters from 25,000 feet (7,600 m) and hit a German Tirpitz at supersonic speeds easily sinking the battleship. The Tallboy was developed by Vickers designer Barnes Wallis, who also designed two versions of a bomb that skipped across water. US pilots in the Pacific later developed a technique of skip bombing which required flying at low level and dropping a spherically-nosed conventional bomb onto the sea, at a shallow angle, which then bounced back into the air.

Although new aircraft still dived into their targets, they were no longer optimized for the steep diving attacks used in WWII. Through the pioneering efforts by the Luftwaffe's Fritz X and the USAAF's Azon, controlled-trajectory bombs evolved into today's smart bombs and have largely reduced the need for dedicated attack platforms. A bomb can be dropped far from a target's air defence using a guidance system to hit the target, ensuring greater accuracy and minimizing risk to aircraft. Bomb sights also led to "toss bombing" abilities, a reverse dive bombing method where an aircraft pulls up from a low altitude as a bomb is released, throwing it upwards in a long trajectory.

References

Notes

Citations

Bibliography

• Angelucci, Enzo and Paolo Matricardi. World Aircraft: World War II. Volume II (Sampson Low Guides). Maidenhead, UK: Sampson Low, 1978. ISBN 0-562-00096-8.
• Brown, David. Warship Losses of World War II. Arms and Armour, London, Great Britain, 1990. ISBN 0-85368-802-8.
• Casey, Louis. Naval Aircraft. Secaucus, New Jersey: Chartwell Books Inc. 1977. ISBN 0-7026-0025-3.
• Parshall, Jonathan (2005). Shattered Sword: The Untold Story of the Battle of Midway. Dulles, Virginia: Potomac Books. ISBN 1-57488-923-0. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) Uses recently translated Japanese sources.
• Worth, Richard. Fleets of the World War II. New York: Da Capo Press, 2001. ISBN 978-0-306-81116-6.

External links

• "Dive Bombing at Target Assures Accuracy" April 1933, Popular Mechanics - early article on dive bombing for general public
• "Diving Artillery" , April 1942, Popular Science good article on the basics of dive bombing with illustration and rare photos
• Tail Brake on Do-217E Controls Its Diving Speed, November 1942, Popular Science
• battle Dive bombers compared Flight article of 1940