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Adive bomber is abomber aircraft thatdives directly at its targets in order to provide greater accuracy for thebomb it drops. Diving towards the target simplifies the bomb's trajectory and allows the pilot to keep visual contact throughout the bomb run. This allows attacks on point targets and ships, which were difficult to attack with conventionallevel bombers, evenen masse.[1] Dive bombing was especially effective against vehicles when integrated into early instances ofBlitzkrieg.
AfterWorld War II, the rise ofprecision-guided munitions and improvedanti-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, includingfighters, improving their effectiveness without the inherent vulnerabilities of dive bombers, which needed air superiority to operate effectively.
A dive bomber dives at a steep angle, normally between 45 and 60 degrees or even up to a near vertical dive of 80 degrees with theJunkers Ju 87, and thus requires an abrupt pull-up after dropping its bombs. This puts great strains on both the pilot and aircraft. It demands an aircraft of strong construction, with some means to slow its dive. This limited the class tolight bomber designs with ordnance loads in the range of 1,000 lb (450 kg) although there were larger examples.
The most famous examples are theJunkers Ju 87Stuka (short forSturzkampfflugzeug, dive fighter), which was widely used during the opening stages ofWorld War II often accompanied with the screaming sound of its sirens, theAichi D3A"Val" dive bomber, which sank moreAllied warships during the war than any otherAxis aircraft,[2][3][4] and theDouglas SBD Dauntless, which sank more Japanese shipping than any other allied aircraft type.[5] The SBD Dauntless helped win theBattle of Midway, was instrumental in the victory at theBattle of the Coral Sea, and fought in every US battle involving carrier aircraft.[6][7]
An alternative technique, glide-bombing (attacks made from an altitude of less than 8,000 feet and at an angle of less than 70°[9]), allowed the use of heavier aircraft, which faced far greater difficulties in recovering from near-vertical approaches, though it required greater use of sophisticated bombsights and aiming techniques, by a specialised member of aircrews, namely abombardier/bomb aimer. The crews of multi-engined dive-bombers, such as variants of theJunkers Ju 88 andPetlyakov Pe-2, frequently used this technique. The heaviest aircraft to have dive-bombing included in its design and development, the twin engineHeinkel He 177, also utilised a glide-bombing approach; the requirement that the He 177 be able to dive/glide-bomb delayed its development and impaired its overall performance.
Dive bombing was most widely used before and during World War II; its use declined during the war, when its vulnerability to enemy fighters became apparent. In the post-war era, this role was replaced with a combination of improved and automatedbombsights, larger weapons and evennuclear warheads that greatly reduced the need for accuracy, and finally byprecision guided weapons as they became available in the 1960s. Mosttactical aircraft today allow bombing in shallow dives to keep the target visible, but true dive bombers have not been a part of military forces since the start of the jet age.
When released from an aircraft, a bomb carries with it the aircraft's trajectory. In the case of a bomber flying horizontally, the bomb will initially only be travelling forward. This forward motion is opposed by thedrag of the air, so the forward motion decreases over time. Additionally,gravity causes the bomb to accelerate after it is dropped. The combination of these two forces, drag and gravity, results in a complex pseudo-parabolictrajectory.
The distance that the bomb moves forward while it falls is known as its range. If the range for a given set of conditions is calculated, simpletrigonometry can be used to find the angle between the aircraft and the target. By setting thebombsight to this "range angle", the aircraft can time the drop of its bombs at the instant when the target is lined up in the sight. This was only effective for "area bombing", however, since the path of the bomb is only roughly estimated. Large formations could drop bombs on an area hoping to hit a specific target, but there was no guarantee of success, and huge areas around the target would also be hit. The advantage to this approach, however, was that it is easy to build such an aircraft and fly it at high altitude, keeping it out of range of ground-based defences.
The horizontal bomber was thus ill-suited for tactical bombing, particularly in close support. Attempts at using high-altitude bombing in near-proximity to troops often ended in tragedy, with bombs both hitting their targets and friendly troops indiscriminately. In attacking shipping, the problems of inaccuracy were amplified by the fact that the target could be moving, and could change its direction between the time that the bombs were released and the time that they arrived. 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 usingB-17s at altitude in theBattle of Midway, with no hits scored. TheGerman battleshipTirpitz was subjected to countless attacks, many while in dock and immobile, but was not sunk until the British brought in enormous 12,000 lb (5,400 kg)Tallboy bombs to ensure that even a near miss would be effective.
An aircraft diving vertically minimises its horizontal velocity component. When the bomb is dropped, the force of gravity simply increases its speed along its nearly vertical trajectory. The bomb travels a virtually straight line between release and impact, eliminating the need for complex calculations. The aircraft simply aims at the target and releases its bombs. The primary source of error is the effect of wind on the bomb's flight path after release. As bombs are streamlined and heavy, wind has only a slight effect on them and the bomb is likely to fall within its lethal radius of the target.
Bomb sighting becomes trivial, requiring only a straight line of sight to the target. This was simplified as the aircraft was pointed directly at the target, making sighting over the nose much easier. Differences in the path of different bombs due to differing ballistics can be corrected by selecting a standardised bombing altitude and then adjusting the dive angle slightly for each case. As the bomber dives, the aim could be continually adjusted. In contrast, when a horizontal bomber veers offline while approaching the bomb release point, turning to the angle that would correct this also changes the speed of the aircraft over the ground (when there is a wind) and thereby changes the range as well.
In the 1930s and early 1940s, dive bombing was the best method for attacking high-value compact targets, likebridges andships, with accuracy. The forces generated when the aircraft levels out at the bottom of the dive are considerable. The drawback of modifying and strengthening an aircraft for near-verticaldives was the loss of performance. Aside from the greater strength requirements, during normal horizontal flight, aircraft are normally designed to return to fly straight and level, but when put into a dive the changes in forces affecting the aircraft now cause the aircraft to track across the target unless the pilot applies considerable force to keep the nose down, with a corresponding decrease in accuracy. To compensate, many dive bombers were designed to be trimmed out, either through the use of special dive flaps (such asFairey Youngman flaps) or through changes intailplanetrim that must be readjusted when the dive is completed.
TheVultee Vengeance, which was mostly used by the RAF and RAAF in Burma, was designed to be trimmed for diving, with no lift to distort the dive. The drawback was that it flew nose up in level flight, increasing drag. Failure to re-adjust trim made the aircraft difficult or impossible to pull out of a dive.[10]
A dive bomber was vulnerable to low-levelground 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 largerAA (anti-aircraft) shells were fused to explode at specific altitudes, which is impossible to determine while the plane is diving. 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.
Dive brakes were employed on many designs to createdrag which slowed the aircraft in its dive and increased accuracy.Air brakes on modern aircraft function in a similar manner in bleeding off excessive speed.[11]
It is difficult to establish how dive bombing originated. DuringWorld War I, theRoyal Flying Corps (RFC) found its biplane two-seat bombers insufficiently accurate in operations on theWestern Front. Commanders urged pilots to dive from their cruising altitude to under 500 ft (150 m) to have a better chance of hitting small targets, such as gun emplacements and trenches.[12] As this exposed the aircraft and crew to destructive ground fire in their unprotected open cockpits, few followed this order. Some recorded altitude at the top and bottom of their dive in log books and in squadron records, but not the steepness of the dive. It was certainly not near-vertical, as these early aircraft could not withstand the stresses of a sustained vertical dive.[13]
TheRoyal Naval Air Service was bombing theZeppelin sheds in Germany and in occupied Belgium and found it worthwhile to dive onto these sheds to ensure a hit, despite the increased casualties from ground fire. Again, the angle of dive in these attacks was not recorded.[12]
Beginning on 18 June 1918, theRoyal Air Force (RAF), successor to the RFC, ordered large numbers of theSopwith TF.2 Salamander, a single-seat biplane. The "TF" stood for "Trench Fighter", and the aircraft was designed to attack enemy trenches both withVickers .303 machine guns and with 25 lb (11 kg) bombs. Of the 37 Salamanders produced before the end of October 1918, only two were delivered to France, and the war ended before those saw action.[14] Whether the Salamander counts in more modern parlance as afighter-bomber or as a dive bomber depends on the definition of "dive". It had armoured protection for the pilot and a fuel system to attack at low level, but lacked dive brakes for a vertical dive.
Heavy casualties resulting from air-to-ground attack on trenches set the minds of senior officers in the newly formed RAF against dive bombing. So not until 1934 did theAir Ministry issue specifications for both land-based andaircraft carrier-based dive bombers. The RAF cancelled its requirement and relegated theHawker Henley dive bomber to other roles, while the Fleet Air Arm'sBlackburn Skua was expected to do double duty: as a fighter when out of reach of land-based fighter support, and as a dive bomber. It had dive brakes that doubled as flaps for carrier landings.[15] TheHawker Henley had a top speed only 50 mph (80 km/h) slower than theHawker Hurricane fighter from which it was derived. The American and Japanese navies and theLuftwaffe chose vertical dive bombers whose low speed had dire consequences when they encountered modern fighters.[13]
TheRoyal Naval Air Service developed dive bombing as a tactic against Zeppelin hangars and formed and trained a squadron at Manchester for this task. On 8 October 1914, aSopwith Tabloid with two 50 lb (23 kg) bombs attacked a hangar at Düsseldorf after a dive to 600 ft (180 m). On 14 November 1914, fourAvro 504s attacked the Zeppelin factory atFriedrichshafen onLake Constance, diving from 1,200 ft (370 m) to 500 ft (150 m) to ensure hits. As Zeppelins were tethered close to stores of hydrogen, results were often spectacular.[12]
The first use of dive bombing by the RFC, which had been urging its pilots to drop bombs at heights below 500 ft (150 m) in order to hit within 150 ft (46 m) of the target since February 1915, was later that year. On 27 November 1915, LieutenantDuncan Grinnell-Milne arrived in hisRoyal Aircraft Factory B.E.2c over railway marshalling yards near Lys in Northern France, to find the target already crowded by other bombers. He dived from 10,000 ft (3,000 m) to 2,000 ft (610 m) before releasing his 20 lb (9.1 kg) bombs. A few weeks later, Lieutenant Arthur Gould dived to just 100 ft (30 m) to hit buildings near Arras.[12]
The Royal Flying Corps developedstrafing with diving aircraft using both machine guns and small bombs as a deliberate tactic. At theBattle of Cambrai on 20 November 1917, 320Mark IV tanks and 300 aircraft, mostlySopwith Camels andAirco DH 5s with 20 lb (9.1 kg) bombs, were used to suppress artillery and machine guns. The cost in pilots was very high, with casualties on some days reaching 30 percent.[16] The initial impact at Cambrai was highly successful. The staff officer to theRoyal Tank Corps Lieutenant-ColonelJ. F. C. Fuller published findings which were later taken up byHeinz Guderian to form the basis for theblitzkrieg tactics of using dive bombers with tanks employed by the Germans in 1939–40.[17]
Second LieutenantWilliam Henry Brown, a Canadian from British Columbia serving with the RFC and flying aRoyal Aircraft Factory S.E.5a, made the first attack on a vessel on 14 March 1918, destroying an ammunition barge on a canal at Bernot near St Quentin, diving to 500 ft (150 m) to release his bombs. He was awarded theMilitary Cross for this and other exploits.[18] Brown's technique was emulated by other British squadrons. But the heavy casualties to unprotected pilots cast a pall over the results and influenced RAF thinking for 20 years.[13]
The Royal Flying Corps was initially impressed with the potential of the dive bomber, but was aware of its suicidal nature. It ran a series of tests at the Armament Experimental station atOrfordness in Suffolk.Sopwith Camels andRoyal Aircraft Factory S.E.5as were used in early 1918 to dive bomb targets from various heights, with different bombs and with and without the use of theAldis gunsight, which had been invented in 1916 to aid pilots to calculate the deflection required to hit a traversing enemy aircraft. In principle, it obviated the need for a vertical dive.[19] The results showed that a vertical dive into the wind sighting along the top of rather than through the sight was best. But they were not considered good enough to justify the expected casualties. The Royal Air Force, which took over both army and naval aviation in April 1918, retired itsSopwith Salamander dive bombers at the end of the war.[14]
Colonel, later general,Billy Mitchell arrived in France with the first US Army and Air Force units soon after 6 April 1917 and began to organise the US Army Air Force flying FrenchSalmson 2s, a spotter plane. The laterSalmson 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.[20] Mitchell, by now assistant chief of the Air ServiceUnited States Army, arranged tests with captured German and obsolete US ships in June and July 1921 and repeated over the next two years usingRoyal Aircraft Factory S.E.5as as dive bombers andHandley Page O/400s andMartin NBS-1s as level bombers carrying bombs of different weights up to 2,000 lb (910 kg). TheSMSOstfriesland was sunk and so later were theUSSAlabama,USSVirginia andUSSNew Jersey.[21]
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 results and the USAS considering it as a potent anti-ship weapon. Both naval staffs opposed the view taken by the respective airmen.[22]
In 1919,United States Marine Corps (USMC) pilot Lt. L. H. Sanderson mounted a rifle in front of the windshield of hisCurtiss JN-4 (a training aircraft) as an improvisedbomb sight, loaded a bomb in a canvas bag attached to the aircraft's underside, and made a solo attack in support of USMC troops trapped by Haitians during theUnited States occupation of Haiti. Sanderson's bomb hit its target and the raids were repeated. During 1920, Sanderson familiarised aviators of USMC units on the Atlantic coast with dive bombing techniques.[23] Dive bombing was also used during theUnited States occupation of Nicaragua.[24]
As aircraft grew more powerful, dive bombing became a favoured tactic, particularly against small targets such as ships.[22] TheUnited States Navy overcame its hostility to Mitchell's findings and deployed theCurtiss F8C Falcon biplane from 1925 on carriers, while the Marine Corps operated them from land bases as the Helldiver, a name later reused by Curtiss for other dive bombers.
TheImperial Japanese Navy ordered theHeinkel He 50 in 1931 as a floatplane and carrier-based dive bomber and embarked some on new carriers from 1935 in a developed form as theHeinkel He 66, from which theAichi D1A was further developed in Japan. The Luftwaffe confiscated a Chinese export shipment and ordered more.[25]
Navies increasingly operated carriers, which had a limited number of aircraft available for attack, each with only a small bomb load. Targets were often likely to be small or fast-moving and the need for accuracy made dive bombers essential.[22]
Ernst Udet, a German First World War ace, persuadedHermann Göring to buy twoCurtiss Hawk IIs for the newly reformedLuftwaffe. Udet, then a stunt pilot, flew one in aerobatic displays during the 1936Berlin Olympic Games. Due to his connections with theNazi party, he became the development director of theMinistry of Aviation, where he pushed for dive bomber development.[13]
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 projectedUral bomber,[26] and it could reach the battlefield well ahead of field artillery. Soon the Luftwaffe issued a contract for its own dive bomber design, resulting in theJunkers K 47, which, following extensive trials, would in turn result in theJunkers Ju 87Stuka (a contraction ofSturzkampfflugzeug, literally 'diving combat airplane').[25]
Several early Junkers Ju 87 dive bombers, which first flew on 13 September 1935, were shipped secretly from Germany to Spain to assist GeneralFrancisco Franco's Nationalist rebels in the Spanish Civil War. Several problems appeared, including the tendency of the fixed undercarriage to sink into soft ground and an inability to take-off with a full bomb load. TheCondor Legion's experience in Spain demonstrated the value of dive bombers, especially on the morale of troops or civilians unprotected by air cover.[27] The aircraft did not encounter opposing modern fighters, which concealed its vulnerability from the Luftwaffe. Udet was impressed with the Stuka's performance in Spain, so he ordered that theJunkers Ju 88 medium bomber should also be retrofitted as a dive bomber. He also insisted, against the advice ofErnst Heinkel, that theHeinkel He 177 bomber, ordered in November 1937, be able to dive bomb. The lack of a sufficiently powerful, reliable powerplant fatally compromised its utility, and it never performed in the dive bomber role. The requirement was eventually dropped.[28]
Some 23Breda Ba 65s were flown by Italian pilots also in support of 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 (48 km/h) speed advantage in level flight.[29]
As the Royal Navy again took control of theFleet Air Arm, it began to receive theFairey Swordfish from 1936 andBlackburn Skuas from November 1938. The Skua had a secondary function[30] of intercepting attacks by unescorted long-range bombers. With four.303 Browning guns and another rear-facing gun, it was expected to defend against air attack with a top speed of 225 mph (362 km/h) at sea level,[15] which was a low-altitude speed comparable with other navies' carrier borne fighters in 1938–39.[31] The Royal Navy's dedicated, pre- and early-war, fleet fighter was theGloster Sea Gladiator. TheImperial Japanese Navy (IJN)Mitsubishi A5M and USNGrumman F3F were nominally faster than the Skua but this speed was achieved at much higher altitudes; at low altitudes the Skua was quite comparable in speed and was also better armed. The Swordfish was also capable of operating as adive-bomber and in 1939HMSGlorious used her Swordfish for a series of dive-bombing trials, during which 439 practise bombs were dropped at dive angles of 60, 67 and 70 degrees, against the target shipHMSCenturion. Tests against a stationary target showed an average error of 49 yd (45 m) from a release height of 1,300 ft (400 m) and a dive angle of 70 degrees. Tests against a manoeuvring target showed an average error of 44 yd (40 m) from a drop height of 1,800 ft (550 m) and a dive angle of 60 degrees.[32] TheFairey Albacore was also designed to act as a dive bomber and was used extensively in this role during World War Two.[33]
The BritishAir Ministry issued Specification 4/34 in 1934 for a groundattack aircraft with dive bombing capability. TheHawker Henley was a two-seat version of theBattle of Britain-winningHawker Hurricane. It was fast, at almost 300 mph (480 km/h) at sea level and 450 mph (720 km/h) in a dive, but development was delayed when Hurricane development took priority. Just 200 were built and it was relegated to target towing.[34] The RAF ordered the US-builtVultee A-31 Vengeance in 1943, but it, too, was similarly relegated to target towing after a brief operation period in secondary theatres.[citation needed]
TheCurtiss SBC Helldiver was a biplane dive bomber that had been taken aboard theUSS Yorktown (CV-5) in 1934, but it was slow, at 234 mph (377 km/h). Fifty ex-US Navy examples were flown toHalifax, Nova Scotia, byCurtiss pilots and embarked on the French aircraft carrierBéarn in a belated attempt to help France, which surrendered while they were mid-Atlantic. Five airframes left behind in Halifax later reached the RAF, which quickly relegated them to the status of ground instructional airframes for the training of mechanics.[35]
The Japanese introduced theAichi D3A Val monoplane as a successor to the biplaneAichi D1A in 1940, with trials aboard the carriersKaga andAkagi. It was to prove a potent weapon against surface ships.[29]
Only theWehrmacht learned from theBattle of Cambrai (1917) in using dive bombers in conjunction with tanks. The writings of Britain's ColonelJ. F. C. Fuller, a staff officer, andBasil 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 the German army officerHeinz Guderian, who created the combination ofPanzers and dive bombers that later proved so potent in Poland and France. The Ju 87Stuka could be used as aerial artillery moving far ahead of the main forces with Panzers to smash enemy strong points without waiting for the horse-drawn artillery to catch up. It was central to the concept ofBlitzkrieg, which required close co-ordination between aircraft and tanks by radio.[17]
The RAF had chosen the single-enginedFairey Battle and the twin-enginedBristol Blenheim as its tactical bombers. Both were level bombers with similar bomb-loads and entered service in 1937. TheUS Army Air Corps (USAAC) adopted theDouglas A-20 Havoc, first flying in January 1939, for a similar role, although originally ordered by France. Many were also supplied to the Soviet Air Force, which also used theIlyushin Il-2 Sturmovik ground-attack aircraft in huge numbers. None of these were dive bombers. 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.[29]
On 10 April 1940, 16 British Royal NavyBlackburn Skuas flying at extreme range fromthe naval air station at Hatston inOrkney led by Lieutenant Commander William Lucy sank the German cruiserKönigsberg in Bergen harbour, whilst trying to prevent theGerman invasion of Norway.[36] On the German side Stukas augmented or replaced artillery support for theWehrmacht's lightly armed parachute and airborne troops.
Theinvasion of Poland (September to October 1939) and theBattle of France (May to June 1940) saw the Stuka used to devastating effect. Germanblitzkrieg tactics used dive bombers in place of artillery to support highly mobile ground troops. TheBritish Expeditionary Force had set up strong defensive positions on the west bank of theOise River to block rapidly advancing German armour. Stukas quickly broke the defences, and the Wehrmacht forced a crossing long before German artillery arrived.[27]
On 12/13 May 1940, Stukas flew 300sorties against strong French defensive positions at theBattle of Sedan. This enabled 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 much of the Allied army.[27]
The skies over Sedan also showed the Stuka's weakness when met with fighter opposition; six FrenchCurtiss H-75s attacked a formation of unescorted Ju 87s and shot down 11 out of 12 without loss.[37] The Stuka was even more vulnerable to theHawker Hurricane with its 100 mph (160 km/h) speed edge and eight machine guns, which it first met over France and then in larger numbers in theBattle of Britain (July to October 1940). Losses were such that the Luftwaffe rapidly withdrew Stukas from operations over the United Kingdom. A similar fate befell unescorted RAFFairey Battles over France.[27]
The Stuka had7.92mmmachine guns or20mmcannons mounted in the wings. Some were modified to destroy tanks withheavy calibre, 37mmBordkanone BK 3,7 autocannons mounted ingun pods below the wings. They were very successful in this role in the early days (1941) ofOperation Barbarossa before theRed Army Air Force countered with modern fighters, such as theYakovlev Yak-1 and later theYakovlev Yak-3.[38]
The most successful dive-bomber pilot,Hans-Ulrich Rudel, made 2,530 sorties. He contributed to the sinking of theSoviet battleshipMarat atKronstadt on 23 September 1941 using 1,000 kg (2,200 lb) bombs. Later, flying a tank-buster Stuka with 20mm cannon, he claimed over 100 Soviet tanks destroyed, mostly at theBattle of Kursk in July 1943. The Ju 87GKanonenvogel, equipped with two 37mm BK 3,7 anti-tank guns, as suggested by Rudel, proved to be a lethal weapon in skilled hands. In the Soviet counter-offensive,Operation Kutuzov (July to August 1943), which concluded Kursk, the Luftwaffe claimed 35 tanks destroyed in a single day.[39] Rudel co-wrote a post-war book about his experiences and consulted with the US Air Force.[40]
When Italy joined the war (10 June 1940) on the Axis side, theRegia Aeronautica shippedBreda Ba.65s to North Africa for use against the British but they also proved vulnerable. By February 1941 British fighters had shot down most of the Italian planes.[41] In Morocco on 11 November 1942, AmericanCurtiss P-40 Warhawks shot down 15 Ju 87Ds in one encounter.[42]
TheUnited States Army Air Forces took delivery of a fewNorth American P-51 Mustangs from a British order but, as there were no funds to buy more fighters, they were modified as dive bombers with a new wing and with dive brakes. First flown in October 1942 as theNorth American A-36 Apache, they arrived in Morocco in April 1943 to assist with driving theAfrika Korps out of Africa. The aircraft was very fast at low altitude. 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.[43] The Apache did not fly with the RAF, but served with US squadrons in Sicily, Italy and, by late summer of 1943, was based in India for use over Burma and China. It proved to be an excellent dive-bomber and a good fighter: one ace in Italy shot down five German fighters.[44]
The Royal Navy'sFairey Swordfish andFairey Albacore torpedo-dive bombers andBlackburn Skua fighter-bombers were replaced byFairey Barracuda torpedo-dive bombers, which made repeated diving attacks on the German battleshipTirpitz which lay protected bytorpedo nets in a Norwegian fjord during 1944. On 3 April 1944, inOperation Tungsten, 42 aircraft flying from the carriersHMSVictorious andHMSFurious scored 14 hits with 500 lb (230 kg) and 1,600 lb (730 kg) bombs and put the battleship out of action for over two months.[45]
TheSoviet UnionArmed Forces deployed theArkhangelsky Ar-2 from 1940 to 1944 and thePetlyakov Pe-2 from 1941 to 1954.
TheVultee 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. Initial orders were 300 for France, but France fell before they could be delivered. The RAF, with the cancellation of theHawker 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 GeneralWilliam Slim'sBurma campaign bombing Japanese supply routes, bridges and artillery. It operated in theRoyal Australian Air Force andIndian Air Force as well as the RAF. Some were held back for the United States Army Air Forces after theattack on Pearl Harbor, but did not see combat.[10]
Both theImperial Japanese Navy (IJN) and the United States Navy invested considerable effort on dive bombers. Japan started the war with a very good design, thecarrier-borneAichi 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 mainlanding gear (a shortcoming shared by the Stuka).
The main American dive bomber, theDouglas SBD Dauntless, had similar performance to the D3A Val. From December 1942, the Dauntless was replaced with the faster, but more complex and trouble-proneCurtiss SB2C Helldiver. Both American aeroplanes were ubiquitous, with 6,000 Dauntlesses and over 7,000 Helldivers built.[46] Both the SBD and D3A were used atPearl Harbor on 7 December 1941. The Japanese sent 54 D3A Vals carrying 550 lb (250 kg) bombs to attack parked aircraft atWheeler Field andFord Island. A flight of 18 Dauntlesses fromUSS Enterprise arrived over Pearl Harbor just as the Japanese attacked. Seven were shot down and many others destroyed on the ground atMarine Corps Air Station Ewa[47] At the Battle of the Coral Sea, Dauntlesses sank the light carrierShoho and damaged the fleet carrierShokaku together withDouglas TBD Devastator torpedo bombers.[48]
On 5 April 1942, the heavy cruisersHMS Cornwall andHMS Dorsetshire were leavingColombo, Ceylon to join theBritish Eastern Fleet, but had been spotted by Japanese reconnaissance aircraft. They were attacked by a large number of Aichi D3As and both were sunk.[49] On 9 April 1942 theRoyal Navy aircraft carrierHMS Hermes escorted by the destroyerHMS Vampire were attacked by more than 32 Aichi D3As and both were sunk shortly before eight defending RN FAAFairey Fulmars, of806 Squadron, could reach them. The Fulmars shot down four D3As and damaged two while losing two Fulmars to the more numerous D3As.[49][50]
At theBattle of Midway on 4 June 1942, after most of the torpedo bombers had been shot down without a single hit, Dauntlesses fromUSS Yorktown (CV-5) andUSS Enterprise (CV-6) found four Japanese carriers, in the vulnerable stage of refuelling and rearming aircraft for a second strike. TheCombat Air Patrol of formidableMitsubishi A6M Zeros had been drawn away, chasing torpedo bombers and escorting fighters, leaving a clear sky.Soryu andKaga were ablaze within six minutes, whileAkagi, hit only once, suffered fatal damage as the single bomb ignited fuel and bombs in the hangar.[51]
Later on 4 June,Yorktown andEnterprise dive bombers inflicted fatal damage on the fourth Japanese carrierHiryu. Within hours the Imperial Japanese Navy had lost four of its aircraft carriers and many experienced naval airmen, both of which Japan would have difficulty in replacing. Further follow-up raids by SBDs and SB2Us fromMidway and SBDs fromYorktown,Enterprise andUSS Hornet (CV-8) on 5–6 June sank the IJN heavy cruiserMikuma and heavily damaged her sister shipMogami and two escorting destroyers.[52]
The United States Army Air Forces took a version of the Dauntless with a different tailwheel tire and no arrester hook as theDouglas A-24 Banshee. In crates headed for the Philippines, they were diverted to Australia and operated fromCharters Towers in Queensland. The Banshee was unable to contend with JapaneseMitsubishi A6M Zeros. On 26 July 1942, just seven Banshees were sent to intercept a Japanese convoy supplying forces occupying New Guinea. Six were shot down.[13]
The JapaneseYokosuka D4Y Suisei, code-name Judy, began to replace the Vals after a very troublesome development on surviving larger Japanese carriers from March 1943. With a sleekfuselage, retracting landing gear and a powerful licensedDaimler-Benz 601 engine, it could outpace pursuingGrumman 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 newEssex-class aircraft carriers, which each carried 36 of the fasterGrumman F6F Hellcats. TheBattle of the Philippine Sea on 19–20 June 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.[53]
Henceforward attacks were mostly confined tokamikaze.[53] The Japanese were now on the defensive. Japan's industrial output dropped from a peak in 1942, while that of the US increased by a quarter in two years from 1942 to 1944. Japanese wartime production of bombers of all types was just 16% of the US output.
When the RAF were attempting to stop thePanzers ofErwin Rommel'sAfrika Korps in early 1942, a lack of dive bombers proved to be an impediment. 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 RAF used them on Hurricanes in June 1942 against Rommel's tanks. The British Army had used 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; it became an anti-tank weapon.[54] The more powerfulHawker Typhoon, originally developed as a fighter, proved even more effective, carrying eightRP-3 60 lb (27 kg) rockets and producing a similar effect to a naval destroyer's broadside.[55]
On 23 May 1943, aFairey Swordfish destroyedU-752 in the Atlantic, and five days later, aLockheed Hudson ofRAF Coastal Command sankU-755 in the Mediterranean, usingspecialised rockets fitted with iron spikes which were 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.[56]
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 onD-Day and later used by Navy aircraft in the Pacific.[57] By January 1943, American pilots who had been flying in RAFEagle Squadrons before the US entered the war, converted fromSupermarine Spitfires toRepublic 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.[58]
By late 1944, the RAF was able to hit stationary targets with greater accuracy from greater heights inflicting far more damage with less risk. On 12 November 1944, two 5-long-ton (5.1 t)Tallboy bombs were dropped byAvro Lancasters from 25,000 feet (7,600 m) and hit the German battleshipTirpitz at supersonic speeds, sinking it. The Tallboy was developed byVickers designerBarnes Wallis who followed it up with the even larger 10-long-ton (10 t)Grand Slam earthquake bomb which was used to destroyrailway viaducts and bridges, targets that could previously only be damaged in diving attacks. Wallis also designed a bomb that bounced across water to destroy the Eder and Moehne dams, which needed to be hit repeatedly at the same spot under water to be breached but had nets to protect against torpedoes.[59]
Pilots in the Pacific later developed a technique ofskip 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 could still dive towards their targets, they were no longer optimised for steep diving attacks. Through the pioneering efforts by the Luftwaffe'sFritz X and theUSAAF'sAzon, controlled-trajectory bombs evolved into today'ssmart bombs. A bomb can be dropped far from a target's air defences using a guidance system to hit the target, ensuring greater accuracy and minimising risk to the crew.
Jet engines allowed higher speeds which made "toss bombing" possible, a reverse dive bombing method where an aircraft snaps up from low altitude as a bomb is released, throwing it upwards like ashot put.
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