Sunday, June 22, 2014

WW II Navy Dive Bombing
Two Seconds Short of Suicide

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As a squadron of U.S. Navy dive bombers, flying at 12,000 feet, closed in on a Japanese target the sky ahead would fill up with bursting anti-aircraft shells as the Japanese defenders ranged in their guns. A high speed run in to 10,000 feet placed the squadron almost two miles high over the target in the midst of the bursting anti-aircraft shells. 

Manila Bay sky full of anti aircraft missiles
The leader signaled attack and rolled over into a vertical two mile dive, followed at 3 second intervals by the 12 planes of the division. As pilot of the seventh plane in the formation Chuck Downey steepened his dive until he hung suspended from his shoulder straps, hands busy of the control stick and throttle, feet working on the rudders. Chuck looked straight down at the six planes below him with their dive flaps deployed. He was aware of them but did not see them… his eyes were focused on the Japanese warship below him, his target. He was also aware of anti-aircraft shells bursting around him but he did not see them…all that mattered was the target he was lining up in his sights…

 “All of a sudden there was a huge flash. Everything blew up in my face about 400 feet in front of me … the whole thing just blew.” The Helldiver in front of Downey had exploded, hit by anti-aircraft fire. It had been flown by Johnny Manchester, a new young pilot nicknamed “School Boy.”

“There was nothing there, no airplane, pilot, gunner, bomb, load of gas,” Downey recalls. “It was all just gone, no smoke, no nothing. The whole thing just blew … and I just kept diving through it.” His attention remained focused on his target as he passed through the cloud of fragments clicking like hail against his fuselage. He planted his bomb on the bridge of a Japanese cruiser, his target, and pulled out of his dive low over the water.

 Dive bomber pilots experienced many such challenges throughout the Pacific War as they participated in sinking 175 Japanese warships,more than any other weapon. Time after time in a six months tour of sea duty the pilots would fling themselves seaward, charging through a barrage of Japanese anti-aircraft fire and tracer bullets. Casualties were to be expected.

Both Downey and Manchester were 19 years old, teenagers hurling 8 tons of Helldiver out of the sky, delivering 2,000 pounds of bombs straight down into the inferno of fire shielding the target.

When World War II began in the Pacific, the weapons the Japanese Navy brought into battle outclassed the United States Navy in every category except one. The SBD Dauntless dive bomber surpassed Japan’s Val dive bomber in speed, range, bomb load, and diving accuracy. This one weapon provided the tactical edge that proved decisive at the Battle of Midway on June 4, 1942 snatching victory from defeat. This changed the course of the war in the Pacific, and possibly saved England and Russia from defeat at the hands of the Axis partners of Germany, Japan and Italy in 1942.
Battle of Midway Painting by Captain R. Rasmussen
(The torpedoes with which our submarines and torpedo planes were equipped were defective during the decisive years of 1942 and 1943, a time when the outcome of the war with Japan was still in doubt. In all of 1942 only 1 seaplane tender and two destroyers were sunk by submarines, 14 minor warships in 1943.1

Our Navy’s most effective offensive weapons were the Marines on the ground and the dive bombers in the air. We did not have reliable torpedoes until September 1943, almost two years after Pearl Harbor.)

Post war historians not only failed to examine the superior qualities of dive bombing as a weapon, they even displayed an ignorance of the technique. Their emphasis was on what happened, ignoring details of how and why the dive bombers succeeded.

The dive bomber was the first “smart” bomb. Dive bomber pilots were programmed in the ready room aboard the carrier. They were launched from the deck and directed over sea and land to targets. Once over the target they tipped over from 10,000 feet or higher and visually locked in on the target. The difference between the piloted plane and modern-day guided munitions was that the pilot of a dive bomber pulled out after releasing the bomb.

In diving at 300 knots the two-mile dive took 30 seconds as the aircraft plummeted seaward, and the image of the target grew ever larger in the windscreen.

 As the war progressed bombs were released at 1,000 feet before pulling out. At 506 feet per second this was only two seconds before impact. 2

The only difference between our Navy’s dive bombers and the Japanese Kamikaze was these two seconds. The only difference between the WW II dive bomber and the Tomahawk missile was these same two seconds. We were the first “Smart Bombs” and the Japanese were the first to employ aircraft as suicide weapons.

Ideally our dive bombing aircraft, in a vertical 90 degree attitude, plunged along a 70 degree flight path because of the remaining lift on the wings. Without some lift the aircraft would not be able to pull out of the dive.

In a well-executed dive the pilot would hang suspended from his shoulder straps, looking straight down. The target, at 24 knots would travel 1,214 feet while a plane dived from a two mile altitude. Wind was also a factor. The aircraft was literally flown down the dive path at constant speed, using ailerons and elevators to continually adjust the point of impact until release of the bomb and a high gravity pull out at about 1000 feet, two seconds before impact.

Helldiver Painting by Tom Freeman

The post WW II U.S. Strategic Bombing Survey documented the futility of indiscriminate area bombing, 3 and the necessity for pinpoint accuracy that is now employed. The dive bomber showed the way.

   Even pilots of other services have a minimal understanding of dive bombing. All military pilots have put aircraft in vertical dives, and many have dropped bombs from a diving plane, but our Navy’s dive bombing was different from the diving attacks of conventional aircraft.

  The unique features engineered into the SBD and SB2C enabled the pilot to fly a controlled vertical flight from 10,000 feet or more to sea level, tracking a moving target ship as small as 40 feet wide which was taking evasive action. Of these features the most important was the split wing perforated dive flaps or “dive brakes”. These were opened on the trailing edge of the wings to slow down the dive and allow more abrupt pull outs. Wings were strengthened to withstand the high G forces. A yoke was designed to throw the bomb clear of the aircraft’s propeller as the bomb was dropped in a vertical dive.

A Slim Target for Japanese Gunners

Neither the Stuka nor the Japanese Val was designed for bombing with extremely steep dive paths4. Both had fixed landing gear, and a dive brake that deployed 90 degrees below the main wing spar. Elevator tab adjustments were necessary to trim the aircraft. This meant that the aircraft in a dive could assume a vertical flight attitude but, because of the lift aerodynamics, the flight path would not exceed 65 degrees.

German Stukas JU 87
Japanese Val Dive Bomber

  Our U.S. dive bombing was not the screaming power dive of some historians. Even the Japanese author Mitsuo Fuchida in his personal account refers to the “screaming Hell-divers”4.  The image of the screaming dive bombers was created by the Stukas, which used sirens activated by air pressure as a terror weapon against troops and civilian refugees. Our pilots retarded the throttle and put the propeller in high pitch, while arming the bomb and deploying the dive brakes. There was no way Fuchida could have heard even the engines over the normal sounds of his ships activity and thundering anti-aircraft fire.

The dive bomber was always under control. With dive flaps deployed it would quickly reach a constant speed (terminal velocity). This could not be achieved with an aerodynamically clean plane that would continue to accelerate while plunging earthward in a vertical dive.

In late 1943 the Douglas Dauntless SBD of Midway fame was replaced by the Curtiss Helldiver SB2C. The Helldiver was a larger aircraft, eight tons when loaded, compared to five tons for the Dauntless. It flew further, higher and faster than the Dauntless and carried a heavier bomb load in an internal bomb bay. It had two twenty millimeter cannon firing forward. However, it was more difficult to land on an aircraft carrier because the long nose obscured the pilot’s forward vision.

Homing Helldivers Curtiss SB2C-3

The high flying dive bombers were less vulnerable than the torpedo bombers to anti-aircraft fire and attacks by the Japanese fighters.

 The near vertical dive was our defensive edge. Japanese ships had few HA (high angle) anti-aircraft guns. A target ship could not elevate most of its anti-aircraft guns to fire straight up. The diving plane also presented a slim head-on target profile to enemy gunners. Screening ships had very difficult deflection shots and only 30 seconds to adjust aim.

On the other hand torpedo planes flew low over the water at slow speed through the entire enemy fleet. Fighters and the screening ships’ anti-aircraft fire picked them up as far as twenty miles out and tracked them all the way in under constant fire to their drop point 800 yards from the target. To launch their torpedoes the pilots maneuvered slowly for beam shots on the Japanese warships and were exposed to the broadside barrage of all the target's AA guns.

Douglas Devastator TBD Torpedo Bomber

In fanning out at sea level to make individual attacks from varied bearings the torpedo bombers lost the massed defensive firepower of their gunners’ machine guns, and were easy prey for Japanese fighters. Each torpedo plane became a one on one target for the Zero fighter’s machine guns and cannon, a terribly uneven match.

Dive bomber squadrons maintained a tight stepped down gaggle of V-formations, enabling them to bring the massed fire power of the gunners’ machine guns to bear on attacking enemy fighters. These dense defensive formations were maintained right up to peeling off into the dive on the target.
The dive bombers did more than sink Japanese warships. They supplemented the submariners’ achievements by sinking many tankers, troopships and merchant ships. Dive bombers supported Marine and Army landing troops with pre-invasion bombing of landing beaches, shore installations and airfields, destroying many Japanese planes on the ground. Some blew up oil refineries and oil storage tanks in such faraway places as Camranh Bay and Saigon in Southeast Asia.

 With extra fuel tanks installed in the bomb bay Helldivers navigated long range searches covering 1000 miles. These eight hour flights, with pilot and gunner strapped into a single engine plane, were an endurance test with nothing to look at but ocean in all directions. Navigation was dead reckoning, using the plotting board which slid out of the instrument panel. Since wind force and direction varied at altitudes most of the search was made at a low 50 feet altitude in order to measure the force and wind direction from the whitecaps of the ocean’s waves.

With a K-56 camera mounted under the fuselage Helldivers served as photo planes for reconnaissance and damage assessment. Crewmen were trained to use K-20 cameras as well as the machine guns.

During the carrier raids on Tokyo dive bombers attacked tactical targets with as much  precision as today’s Tomahawk missiles, bombing airfields, hangars and manufacturing plants to supplement the high altitude strategic blanket fire-bombing of the B-29 Super Fortresses.
One of the reasons that this visually spectacular dive bombing weapon never attracted the attention of the film or TV producers is the fact that it had a short life. It was born early in World War I when German and Allied pilots began throwing grenades at troops on the ground.

 Before they had mechanical bomb releases twenty pound bombs would be wrapped in burlap fastened around the fuselage of the plane. Over the target one end of the burlap would be released spilling out the bombs.

It soon became evident a steep dive was necessary to hit small targets on the ground, or moving ships. There are conflicting claims over who made the first vertical dive bombing attack. It appears to be Lieutenant Harry Brown of the Royal Flying Corps of Great Britain when he sank a munitions barge by dive bombing on the Western Front in 1917 5.

During the 1920’s the U.S. Marine Corp perfected dive bombing for tactical support of ground troops in Haiti and Nicaragua.

Japan’s invasion of China during the 1930’s proved the value of the dive bomber as a weapon and their experience in China enabled Japan to enter WW II with superbly prepared dive bombing squadrons. The Spanish Civil War was a testing ground for the Germans, Italians and Russians. The Stuka JU 87 proved its worth in Spain in action against ground targets and as an anti-ship weapon.

 However, neither Britain’s RAF nor the U.S. Army Air Force adopted the weapon. The Royal Navy’s air arm was part of the RAF. As a result the British Navy was starved for modern aircraft as the RAF concentrated on strategic bombers. Fortunately, far sighted aviators of the U.S. Navy were able to pursue development of dive bombers at a time when aircraft were regarded by many ranking officers as merely scouts and spotters for the Main Battle Line.

In 1931 Hollywood released a film called Helldivers, starring Wallace Beery and Clark Gable. This has been the only film ever produced about our Navy’s dive bombers by Hollywood or the TV producers. That was over 70 years ago.

The First Helldiver Curtiss SBC-4
By the end of World War II the unrecognized contributions of the dive
bombers to the Battle of Midway and to the defeat of Japan were forgotten as the weapon approached obsolescence. Propeller driven dive bombers were replaced by jet aircraft firing rockets and guided missiles Accurate targeting no longer needed to expose pilots and aircraft to point blank enemy fire. With the new threat of guided missile anti-aircraft batteries it became necessary to perfect new attack procedures, just as we now adjust to the new attack tactics using drones.

Nevertheless history should record the accomplishments of our Navy’s WW II dive bombers, in particular the part they played in the Battle of Midway. The YouTube video below addresses this issue:

DVD Available on YouTube. Just click:

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Searching for the Truth about 
The Battle of Midway 
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2 Helldiver Squadron, by Robin Olds, Pages 141, 144, 188
3 Scientific American, April 1961, Pages 161-165
4 Midway, by  Mitsuo Fuchida and Masatake Okumiya.
5 History of Dive Bombing, by Peter C. Smith, 1981, Page 18.

© George J. Walsh 2014
Lt. Cmdr. USNR (ret)