Ed Heinemann, recognized worldwide as an exceptional aircraft designer, had other exceptional qualities: curiosity and courage. In 1937, to learn why the prototype Northrop-designed BT torpedo bomber experienced severe tail buffeting when the speed-brakes were deployed in steep dives, he strapped in behind test pilot Vance Breese to experience the problem firsthand.
They climbed to altitude and Breese put the aircraft into a near-vertical dive. The Southern California landscape appeared distant and deceptively still and there was little sense of speed as the flier and the engineer hurtled toward the ground.
The speed brakes were actuated at the trailing edge of the wings by hydraulic cylinders in a mechanism designed by Heinemann, who was responsible for much of the BT’s design, and he was determined to correct the buffeting, which, he later said, “Damn near shook the tail off.”1 Breese later declared the dives too dangerous for Heinemann’s continued on-board observations because the Pratt & Whitney engine’s carburetor released sufficient unburned gasoline into the hot exhaust during the dive to ignite in a spectacular plume of fire that threatened to incinerate the BT’s fabric tail surfaces. (The engine’s carburetor initially lagged the rapid barometric changes as the BT dived into the thickening atmosphere closer to sea level.)
Barred from the BT’s gunner’s seat, Heinemann nevertheless found a solution. “The Depression was on and we were all broke, but I managed to buy a Bell and Howell motion picture camera and put it on the wing. You wouldn’t believe how much that tail oscillated,” he said later.2
As Heinemann pondered ways to stop the buffeting, Charlie Helm of the National Advisory Committee for Aeronautics (NACA) offered some advice: The magnitude of the disruptive vortices caused by the extended speed brakes could be reduced if air were allowed to bleed through the brake panels. Despite some initial reluctance, Heinemann followed up on Helm’s suggestion by punching rows of circular holes in the speed brakes to permit some air to filter through the braking panels, instead of requiring all the air to tumble over solid brakes.3 The perforated brakes still slowed the BT as desired, and the bleed-through holes eliminated the source of the tail buffeting. In retrospect it was a simple fix. Simplicity became a hallmark for Ed Heinemann, who later was proud to declare his design philosophy to be conservative by nature.
John K. Northrop, who had created Douglas’s El Segundo, California, operation, had supervised the fundamental BT design before leaving in 1937 to form his own company. “About the time Jack [Northrop] left, we converted the BT’s engine and made a lot of changes and came out with a new airplane. That was in the two years after Jack left,” Heinemann explained.
Heinemann and his associates next took the second BT airframe and performed a host of modifications, including a short-lived fling with a tricycle landing gear. Changes in the fuselage, cowling, engine and its mount, canopy, instrumentation, and bomb-displacement trapeze steadily altered the aircraft into the famous Douglas Dauntless dive bomber—the SBD. The signs of Heinemann’s design rationale were so manifest that the SBD Dauntless patent was taken out in his name.
Navy and Marine Corps aviators flew the rugged Dauntless throughout World War II. In a few short minutes of precision dive-bombing heroics over the Japanese carriers near Midway in June 1942, the aircraft played a pivotal role in the first decisive battle on the long road to ultimate victory in the Pacific. Even so, Navy planners soon were anticipating a Dauntless replacement, with enhanced performance made possible by the new R-3350 radial engine that produced 2,500 horsepower—more than twice that of the Dauntless’ Cyclone powerplant.
Out of the Douglas Aircraft Company came the awkward-looking XSB2D, offered as a Dauntless replacement. The Navy ordered two prototypes in October 1943. It rode on tricycle landing gear and was defended by remote gun turrets reminiscent of Douglas’s A-26 attack bomber. One dorsal and one ventral turret covered rear and beam attack vulnerabilities. A single gunner joined the pilot in crewing the XSB2D. The plane rode on a cranked inverted gull wing, albeit with a break shallower than that of the F4U Corsair fighter. The bombs were carried in an internal bomb bay.
The XSB2D was a mediocre follow-on to the legendary Dauntless, and never saw active service. Instead, the Curtiss SB2C Helldiver went to sea with the carriers in late 1943—although some naval aviators had misgivings about the ponderous, weighty Helldiver. Even Curtiss officials sometimes referred to the Helldiver by one of its nicknames: “the Beast.”4
Ed Heinemann had his own bone to pick. When Curtiss submitted its bid to the Navy, the Helldiver—on paper—weighed substantially less than Douglas’s SB2D. By the time Helldivers were in production, the weight had grown to that projected by Douglas engineers for the SB2D—all of which Ed Heinemann had predicted long before the Curtiss design entered service.
Reflecting a change in Navy operational philosophy, the SB2D evolved into a single-seat variant called the BTD, which the Navy evaluated in June 1944- The slower Dauntless had relied on a back-seater as a defensive gunner, and as an extra pair of eyes for scouting missions. The SB2D continued this earlier philosophy in spades, weighing the plane down with two power turrets for the gunner to operate. Now, in 1944, the single-seat BTD and its successors were to employ speed and frontal firepower to attack or evade enemy aircraft. Designers downplayed the classic scouting role; the BTD (given the alliterative nickname Douglas Destroyer) was to be a dive bomber first, and a torpedo bomber second.5
The single-seat BTD Destroyer outflew the old XSB2D, but still lacked the clear performance margin of an unqualified success. During the summer of 1944, the Navy called representatives from Douglas, Curtiss, Fleetwing, and Martin to brief Bureau of Aeronautics (BuAer) officials in Washington, D.C., on the progress of their dive bomber projects. The oppressive humidity of Washington in summer—no air-conditioning then—surrounded the enclave in BuAer as Ed Heinemann, backed by his design assistant Leo Devlin, BTD project engineer Reid Bogert, and Douglas aerodynamicist Gene Root expressed views on the less- than-spectacular Douglas Destroyer. The talks, like the heavy air outside, stagnated, so Heinemann boldly asked for the floor to make a proposal.
Rear Admiral Lawrence B. Richardson, assistant BuAer chief, chaired the meeting, and evaluated what Heinemann now offered: The BTD Destroyer was an enigma at best. Ed requested cancellation of the BTD contract, to allow its unspent money to be placed on a completely new design built around the R-2800 powerplant. Heinemann pressed Admiral Richardson for 30 days in which to prepare the new design for approval by BuAer. The admiral saw merit in the direction Heinemann was headed, but attached two conditions: The new dive bomber must be powered by the R-3350 engine—and BuAer would take its first look at the proposal at 0900 the following morning!6
Heinemann and his engineering band—now the owners of a glittering, yet daunting opportunity to create a new airplane—headed for the Statler Hotel where Ed, Gene, and Leo set to work putting their promised airplane on paper. Hamburgers were ordered in to feed the designers as they worked unabated.
Driving Heinemann was the conviction that the XSB2D and BTD had failed in part because the Douglas designers had been too eager to cater to the Navy’s every wish. In an attempt to incorporate a complicated list of features the Navy had requested, the two earlier designs had bogged down in compromises that threatened to drain the life out of the aircraft. Heinemann set out to give the Navy an impressive dive bomber, while scrutinizing the service’s design requests in an effort to head off another mediocre design that was laden with too many diverse features. “If the Navy was not right, and we were sure they were not right, we told them,” he said.7
At 3 A.M., they sat back. Leo’s weight computations and Gene’s aerodynamic calculations were given form by Ed’s dimensioned drawings. “With those pieces of paper,” Heinemann said later, “we could pretty well define the airplane.” Called the XBT2D-1 Destroyer II initially, it became the Skyraider. Ed Heinemann said he may have been overconfident at the conclusion of the overnight hotel design session. In a sense, he felt he was creating an interim plane that would soon be overtaken by newer designs. “When we laid out that airplane originally, we thought it would last for five years.”8 That was in the summer of 1944. The final Skyraider left the Douglas factory in February 1957, and South Vietnamese Skyraiders flew in combat as late as 1975.
Ed Heinemann’s willingness to discard the BTD Destroyer in favor of the all-new BT2D Destroyer II paid off. BuAer concurred with his request to stop the BTD and apply the remaining contract funds to the Destroyer II at Douglas’s El Segundo plant. Meanwhile, Fleetwing and Martin had a half-year lead on Douglas with their own competing dive-bomber designs and Ed tried to learn what the competitors were doing so that the Douglas team could capitalize on any flaws in the competing designs.
Heinemann shunned the idea of using a Grumman-style wing folding mechanism that tucked the wings back along the fuselage, minimizing overhead clearance. The Grumman-style wing-fold required a canted wing spar that was more complicated than a traditional one. “It didn’t appeal to me,” Heinemann said. So the conservative Heinemann had the XBT2D’s lower spar disengage to allow the wings to fold overhead. “We’d never built a wing fold before, and we were concerned about it.” The Bureau of Aeronautics required the wing-fold fittings be built for a 5% overstress; Heinemann said his Douglas designers added 10% on top of that just to be sure the structure was strong enough.9
In the summer of 1944, Ed Heinemann was only 36 when he was in charge of the XBT2D design team at El Segundo. In the first few weeks after receiving BuAer approval for the project he borrowed Harold Adams from the Santa Monica plant to augment his engineers and called staff meetings almost daily to hone the design. The sessions ran from 30 minutes to an hour. With copies of a master outline drawing of the XBT2D, Heinemann asked his design team chiefs to suggest—and justify—changes they deemed necessary. These brainstorming sessions helped define what ultimately became the Skyraider.
Initially, Root and Devlin came up with a Dauntless- style wing planform with a constant-chord center section and tapered outer wing panels. Heinemann rejected this, however, as a holdover from the old Dauntless days that was unnecessary. His choice for the new dive bomber was a wing planform with constant taper from root to tip, resulting in a broader wing chord at the root than would have been provided by a constant-chord center section; he said this enhanced structural integrity. He also was able to design the constant-taper wing that was lighter than the Dauntless planform.10
The section chiefs’ specialties of fuselage, wing, tail, weight, stress, aerodynamics, and powerplant all contributed to the formula for the XBT2D Destroyer II. Following the staff meetings, R. G. Smith would redraw the aircraft to reflect the latest validated ideas of the working group. Soon, the changes stopped flowing and the design solidified. Douglas Aircraft Company had sampled this brainstorming design philosophy with the A-26 twin-engine bomber for the Army Air Forces, but the new XBT2D was the first of Ed Heinemann’s efforts that totally embraced this method. Afterward, Heinemann tried to keep the same core of engineers doing the same design tasks on later projects, to build on their earlier experiences.
He reminded his XBT2D engineers to “ . . . use things we know how to use,” instead of leaping into unfamiliar techniques or materials. It was natural for Heinemann to use flush riveting to achieve the XBT2D’s smooth skin; he was too conservative to try anything as exotic as the spot- welding technique Vought had used on its sleek F4U Corsair. His early days on the Northrop team had soured him on castings and magnesium—both of which Jack Northrop had favored. Heinemann recalled that polar explorer Lincoln Ellsworth’s Northrop Gamma had returned from its exploits with weakened castings, and he remembered this as the Skyraider prototype took shape in 1944. He made his engineers prove that alternate materials were superior to aluminum before integrating them into the design.11 Navy counterparts including Captain (later Admiral) John Murphy, head of BuAer’s aircraft section; Captain (later Admiral) John Thomas; and Commander Emerson Fawkes worked with the Douglas designers.
Hampered by a traditional design that used eight welded tubes to support the engine in a conventional manner, the Navy agreed with Heinemann’s proposal for a novel engine mount for the XBT2D. Heinemann wanted more space for oil cooler installation and access to the engine accessory section, but strength was the limiting factor. With the orthodox welded steel tube mount, all eight tubes were required, but only “ . . . four legs if we made it out of sheet,” Heinemann explained. Thus was bom a radical motor mount of built-up one-eighth inch aluminum, which provided the necessary strength, while yielding more free space for the oil pumps, oil cooler, carburetor, and other accessories.
Years later, Heinemann acknowledged this apparent deviation from his conservative-by-nature design philosophy by saying : “Well, you have to make some progress.” The requisite R-3350 engine was big. To give proper streamlining in the wake of the engine’s frontal area, the fuselage required a stout cross section. This spacious fuselage was a natural location for fuel tankage, especially since the XBT2D deleted the earlier failed BTD’s internal weapons bay.
Heinemann avoided fuel leaks sometimes present in rigid metal fuselage tank arrangements by selecting the “udder tank,” a self-sealing rubber fuel cell that hung down from the top of the fuselage.12
When the Navy invited manufacturers of naval aircraft to send engineering representatives to the Pacific Theater of Operations to learn firsthand about aircraft in service use, Douglas chose Ed Heinemann. “This was the beginning of one of the most important segments in my life. 1 was on the way to a grand symposium which convened aboard carriers and air stations throughout the South Pacific. I would meet with the men who flew and maintained the planes that my colleagues in the industry and I had designed and built. 1 was about to discover undeniably just how good or bad our products were.”11
Some of the other companies, including the competing Fleetwing, lagged in selecting their design team chiefs for the survey trip. Rather than delay Heinemann, the Navy manifested him aboard a Consolidated PB2Y Coronado flying boat on a mail run into the Pacific on Friday, the 13th of October 1944.
From Hawaii, Heinemann shipped out on the aircraft carrier Ticonderoga (CV-14) on 18 October. Wearing suntan chinos and an overseas cap, Ed listened to aircraft maintenance crews, patiently recording their complaints and their praise. He discerned a thread of continuity from the maintainers, who voiced a universal desire for simplicity. Blending with his Navy hosts, Heinemann wandered among pilots and mechanics, watching launches and recoveries of Helldivers, Avengers, and Hellcats. His voluminous notes yielded recommendations ranging from a preference for 20- millimeter cannons instead of .50-caliber machine guns, to a desire for lighter chart boards, to the wish that all running lights could be controlled by a single rheostat.14
Heinemann had every reason to believe his XBT2D would wade into combat against Japan. In late 1944, the specter of a drawn-out war in the Pacific was very real.
While on Guam in November 1944, Ed noted the detrimental effects of coral dust as it coated planes and created a gummy, abrasive mess with grease and oil. It was there he decided to install canvas boots over the airfoil sections of the XBT2D’s wings when they were folded to keep the elements at bay. Where another manufacturer’s wing folds had incorporated boots that had to be removed before extending the wings, Heinemann gave his XBT2D canvas baffles that could be left in place, to simplify maintenance and protection of the plane. He returned from the Pacific with a heightened sense that the evolving role of dive bombers called for single-seaters that could handle the mission aggressively, sparing fighters wherever possible from compromising their own mission by toting bombs.15
Once back at El Segundo, he pushed his team to keep the project on schedule. By now, the BT2D was known as the Dauntless II—possibly signaling the company’s faith that at last a worthy successor to the Dauntless had been created. Heinemann’s design team worked under strict rules: If a part was overweight, an equal amount of weight must be pared off elsewhere in the design. Some parts failing the weight standards were tested before being accepted, to make certain they were not overbuilt, hence heavier than necessary.
A memorandum to BT2D project members made their efforts seem real by explaining that 100 pounds equaled:
►22 more miles of combat radius
►8 feet less roll on carrier takeoffs
►18 feet-a-minute more on sea-level climb outs
When they successfully challenged the Navy’s original request for an internal bomb bay, Heinemann and his team lopped 200 pounds from the weight of the earlier BTD. Another 100 pounds was cut from the old BTD weight by making the BT2D’s wing center-section one piece instead of two. Fuselage- mounted dive brakes on the new Dauntless II saved an additional 70 pounds over wing-mounted brakes. The team found another 20-pound savings by making the BT2D’s horizontal stabilizer a one-piece unit that passed through the aft fuselage/vertical-fin section. When all the savings were tallied, the new BT2D was 1,000 pounds lighter than Douglas had promised the Navy, affording growth capability. After early Korean War losses prompted the addition of bolt-on armor plate to Skyraiders, the planes were able to accept the new bulk without exceeding acceptable weights.16
The BT2D Dauntless II had a gross weight of 16,500 pounds. In so many ways, the Dauntless II bested the BTD. Fuel servicing time per man was two minutes on the Dauntless II, compared with 13 minutes on the BTD. It took two man-hours to remove the Dauntless II’s new udder fuel tank; taking out the BTD’s tank took 72 manhours; the original SBD Dauntless had taken 144 manhours.
The ill-fated SB2D and BTD designs had poorer performance in their lower speed ranges than in the high end, because they used an air foil designed for high-speed performance. The BT2D Dauntless II returned to a more standard NACA air foil that gave better low-speed handling, although possibly at the expense of performance at the top end of the new plane’s speed range. This NACA air foil additionally gave the Dauntless II more lift than the BTD.17
In any attempt to achieve a 90° dive, a wing’s aerodynamic lift—acting increasingly parallel to the earth’s surface—tends to move the aircraft to the target’s 12 o’clock position along the run-in heading, making it difficult for the pilot to keep his aim on the target. Dive brakes, which slow the aircraft, can counter-act this force, especially if they are wing-mounted—where they act as spoilers to kill the lift component.
Such was the case with the classic SBD Dauntless. When the XBT2D was being designed, the Navy still valued zero- lift vertical dives, in which a true vertical descent was attained, probably with the aid of lift-killing wing brakes. But the XBT2D was heavier than the older Dauntless, and Heinemann forecast problems if the Navy insisted on true vertical zero-lift dives for the new bomber. Ed considered wing-mounted brakes for his new plane, but rejected them because they would complicate the wing-folding problem, and could possibly contribute to buffeting. Drag parachutes were considered and rejected and the team even looked at a reversible-pitch propeller, but could find none with adequate characteristics for the job.
When it was evident to Heinemann that he could slow the XBT2D with more stable fuselage brakes if the Navy would abandon the quest for zero-lift dives, he kept his promise to challenge the Navy’s design specifications if they appeared unrealistic.18 Pointing out that, in combat, the SBD Dauntless often attacked in a 70° dive, Heinemann went to the Navy with his proposal—and the Navy agreed that the XBT2D would be designed for 70° dives.19 The XBT2D’s fuselage-mounted brakes of the XBT2D slowed the dive to 300 miles an hour.
The fuselage-mounted dive brakes had other advantages. While the wing-mounted brakes on the Dauntless killed lift effectively in a dive, they were impractical to use in other phases of flight. Fuselage-mounted brakes, on the other hand, caused drag without affecting lift, and this meant they could be deployed to slow speed during normal descents; to assist maneuvering in formation flight; and to gain an advantage in air-to-air combat. They have since become standard on fighter-attack aircraft.
The cockpit of the XBT2D underwent five mock-up iterations at considerable cost to Douglas, as Heinemann’s team improved pilot safety, comfort, and ease of operation. Special instruments using quarter-inch numbering were devised for the XBT2D after the team concluded this to be the optimum size for legibility at the average cockpit distance of 24 inches from the pilot’s eyes.20 Ed Heinemann made good on lessons he learned during his Pacific cruise with the Navy. Douglas workers estimated the XBT2D Dauntless II would need only half as much time to service as had been required by the BTD.
The XBT2D’s main landing gear twisted 90° and folded aft to lie flat in the wings. While more complex than inward- or outward-folding gear, the rearward-retracting gear consumed much less span-wise space, freeing underwing and fuselage area for stores hard points—vital on the XBT2D in the absence of the bomb bay of the shortlived BTD.
LaVerne Browne took the controls of the unpainted aluminum XBT2D-1 for its first takeoff on 18 March 1945. He was enthusiastic about the aircraft’s performance after the flight; after only 32 more test hops, Douglas certified the XBT2D-1 for delivery to the Navy’s Patuxent River test center in Maryland on 7 April 1945.21 The competing Kaiser Fleetwing XBTK was still untested, and the Martin XBTM returned to the company for alterations following problems at Patuxent River. The Douglas XBT2D Dauntless II roared through its Navy tests in only five weeks, receiving accolades from the Navy pilots who flew the new dive bomber. On 5 May 1945, the Navy signed a letter of intent to purchase 548 BT2Ds. The otherwise placid XBT2D story involved a few hiccups—propeller vibrations, engine exhaust system cracks, and engine detonation problems—but these were corrected.22
Ed Heinemann’s decision to confront Navy requirements he considered inappropriate paid off with a simple BT2D dive bomber with great promise. By February 1946, as post- World War II contract reductions affected procurement of both the Douglas and Martin bombers, the name of the Douglas BT2D was changed from Dauntless II to Skyraider. This fit the Douglas family tree that already included Sky- master, Skytrain, and Skytrooper transports. Douglas Navy combat planes following the Skyraider were christened Sky- hawk, Skyshark, Skyray, and Skywarrior. By April 1946, revised Navy aircraft nomenclature simplified the Skyraider’s designation to AD; the BT2D-1 became the AD-1, which signified Attack, Douglas-Model 1.
In May of 1953, an AD-4 Skyraider carried a useful load of 14,941 pounds total, which included 10,500 pounds of bombs.
The Douglas Skyraider, with its eloquent simplicity, was chosen for fleet standardization, resulting in an end to Martin Mauler production by October 1949. The bulk of the AM-ls went to Reserve units in 1950, and some of the former first-line Mauler squadrons converted to the Skyraider, giving Ed Heinemann’s simple design the highest accolade.
1. Interview, author and Edward H. Heinemann, 20 July 1982.
2. Ibid.
3. Edward H. Heinemann and Rosario Rausa, Ed Heinemann—Combat Aircraft Designer (Annapolis: Naval Institute Press, 1980), p. 36.
4. Service Department, Curtiss-Wright Corporation, Airplane Division, Columbus, Ohio, "Pilot and Beast: What Every Young Pilot Should Know About the Helldiver.”
5. B.R. Jackson, Douglas Skyraider (Fallbrook, California: Aero Publishers, 1969), p. 11.
6. Heinemann and Rausa, op. cit., pp. 100-105.
7. Interview, Frederick A. Johnsen and Edward H. Heinemann, 20 July 1982.
8. Ibid.
9. Ibid.
10. Ibid.
11. Ibid.
12. Ibid.
13. Heinemann and Rausa, op. cit., p. 111.
14. Ibid.
15. Heinemann’s trip was written in report form for the Bureau of Aeronautics as Report On Trip To Pacific Combat Area, 27 November 1944, Report Number ES 6712, El Segundo Division, Douglas Aircraft.
16. Heinemann and Rausa, op. cit., pp. 125-140.
17. Ibid.
18. Ibid.
19. Barrett Tillman, The Dauntless Dive Bomber of World War Two (Annapolis: Naval Institute Press, 1976), p. 14.
20. Heinemann and Rausa, op. cit., pp. 125-140.
21. Jackson, op. cit., pp. 18-19.
22. Ibid.