Though less successful than Messerschmitt’s Bf-110, the A-18 was proof that a six-ton twin-engine attack plane could do the job.
The time-worn formulas of World War I— wood and fabric construction, open cockpits, fixed undercarriage and biplane wings—were generally discarded during the mid-1920s in favor of all-metal construction, enclosed cockpits, retractable landing gear, flaps and other aids to improved speed, range and altitude. The years 1935 and 1936 were particularly fruitful for fighters, with prototypes of four important foreign aircraft making their first flights, including the Messerschmitt Bf-109, Hawker Hurricane, Supermarine Spitfire and Mitsubishi A5M.
The advent of more powerful engines seemed to indicate that versatile twin-engine aircraft could be built to compete with fighters in speed and maneuverability and exceed them in range and load-carrying capability. Germany flew the Messerschmitt Bf-110 on May 12, 1936, expecting it to fulfill the long-range escort fighter role, while France created the Potez 63. Although the Messerschmitt did not do well as an escort fighter, it came into its own as a workhorse night fighter. The elegant Potez, however, turned out to be just a pretty face when it came to combat.
In the United States, Curtiss Aeroplane and Motor Company had realized that it was barking up the wrong tree with its very heavy all-metal attack planes, the A-8 and A-12 Shrikes. Marking a change in direction, Curtiss hired Donavan R. Berlin as its chief engineer to turn the situation around. Berlin, whose motto was “design for producibility,” had previously served as chief engineer at Northrop Corporation.Working closely with Jack Northrop, he had pioneered metal construction on the Alpha, Beta and Gamma models, as well as contributed to the design of nifty-looking if ultimately unsuccessful fighters such as the XFT- 1. A burly, jovial man, Berlin came to Curtiss with a charter to restore the company to first place in both the fighter and the attack business.
By the fall of 1935, Berlin saw the first flights of the prototypes of two entirely new planes, both incorporating lessons he had learned at Northrop: the Model 75,which evolved into the P-36 and later into the P-40; and the Model 76, a twin-engine cantilever-wing monoplane that became the Curtiss A-18. It looked like a winner,but for a variety of reasons was not destined to find the same success as the Model 75.
Both aircraft were all-metal cantilever monoplanes, built with the same strong techniques that Berlin had pioneered at Northrop. Both had enclosed cockpits, retractable landing gear and modern power plants. The Model 75 had a compact design that promised maneuverability if not blinding speed. The twinengine Model 76 was the American counterpart to the Potez 63—undoubtedly the best-looking Curtiss plane since the P-6E. While the 76 proved less successful than either the Bf-110 or Potez 63, it significantly affected the development direction of American twinengine light bombers. The Model 76’s failure can be traced in part to problems within the Curtiss organization.
The Curtiss-Wright Corporation had been formed in 1929 by the combination of the two great rival firms, Curtiss Aeroplane and Motor Company and Wright Aeronautical Corporation.Wright was known primarily for its radial engines, while the Curtiss aircraft line, which went back to 1907, included the Curtiss JN-4 “Jenny”trainer of WWI as well as Pulitzer and Schneider Cup racers. Curtiss tended to meet demands for new aircraft from the U.S. Army and Navy by stretching existing designs. Thus its line of Falcon biplanes extended from the original XO-1 of 1924 all the way through 1932, when 10 O-1Es were built under license in Chile. In similar fashion, good-looking Curtiss biplanes formed the Hawk fighter line that began in 1923 and extended through 1936. Both Hawks and Falcons also served in a host of foreign air forces. They were workhorse aircraft with the mixed construction typical of the period, including fixed landing gear and open cockpits. Curtiss tried to maintain a dominant position in the aviation market with a dynamic, resourceful sales force, but it faced strong competition from Douglas observation planes and Boeing fighters.
The conservatism of the Curtiss design philosophy stemmed from two sources: limited military budgets, which ruled out experimentation with advanced types; and the inherent business philosophy of Curtiss’ management. The firm was headed by Clement Melville Keys, an investment banker who had became president of Curtiss Aeroplane and Motor Company in 1920 and subsequently guided the firm’s policy of expansion by acquisition. By 1929, Keys’ new Curtiss Wright Corporation consisted of the original Curtiss Aeroplane and Motor Company, Curtiss-Caproni Corporation, Curtiss-Robertson Airplane Manufacturing Company, Keystone Aircraft Corporation, Moth Aircraft Corporation, Travel Air Manufacturing Company, Wright Aeronautical Corporation, Curtiss-Wright Flying Service’s Sales Corporation and Curtiss-Wright Export Corporation. It was too much to manage in a coherent manner. Many of the companies competed for the same market, and there was a marked lack of research effort among them. As a result, the stock market crash of 1929 had devastating effects on the company, which was saved from extinction only by an order from Colombia, which bought 26 Hawk fighters and 100 Falcon observation planes in the early 1930s. When Keys departed Curtiss Wright in 1932, he left the firm with a series of plants that needed to be shut down and an ailing product line that cried out for rejuvenation.
To Keys’ credit, however, the company had started experimenting with all-metal construction in 1930, with the delivery of the Curtiss XF9C-1 Sparrowhawk to the Navy. Intended to be carried by the huge Akron and Macon dirigibles, the Sparrowhawk performed well enough in a role that was destined to die in crashes of the two airships.
The next Curtiss all-metal effort was the Stukalike Model 59 that was developed into the A-8, A-10 and A-12 Shrikes. All-metal, with trailing edge flaps and full-span leading edge slats, the awkward-looking Shrikes also featured enclosed cockpits and a faired though bulky undercarriage. Modernity did not extend to a fully cantilever wing; the Shrikes were festooned with struts and wires. They were also heavy, with an empty weight for the production A-12 of 3,898 pounds, compared to 2,902 pounds for the A-3 Falcon. With a maximum speed of 176 mph, they were 40 miles an hour faster than the Falcon and carried 100 pounds more bombs, but had 150 miles less range.
The Model 76 made its first flight in September 1935 at Wright Field, Ohio. It was returned to Curtiss for modifications before being accepted as the XA-14. Powered by two Wright R-1670 engines of 775 hp, the XA-14 had a top speed of 243 mph—considerably faster than Boeing’s P-26 fighter and about 30 mph slower than the Model 75 single-seater.
The XA-14 packed four .30-caliber machine guns in the nose, with a similar flexible gun in the rather distant rear cockpit. Later in its 178-hour flying career, the XA-14 conducted secret tests with a 37mm cannon installed. The aircraft could carry 20 30-pound bombs in the internal bomb bay and proved fairly maneuverable. The Army was sufficiently impressed to buy 13 service test Y1A-18s at the staggering cost of $104,640 each, a price that made procurement officers wince, as the last batch of A-12 Shrikes had been purchased for $19,483 apiece. It raised a question: Were A-18s five times as good as A-12s?
The A-18s were much improved over the prototype, equipped with 850-hp Pratt & Whitney R-1820 engines and three-blade Curtiss electric constant speed full-feathering propellers—a great advance for the time. Fully loaded, the A-18 could sustain a 185-mph cruise speed with one engine shut down. Curtiss faired in the landing gear doors in an effort to reduce drag, but still allowed the wheels to peek through in anticipation of a possible wheels-up landing. The aircraft was stiletto clean; in company brochures its frontal appearance was likened to “three beads on a string.”Yet to the modern eye, the A-18 has a disproportionate look. The wings are too thick, the aft fuselage too fat, the nose too short.
Full military equipment brought the empty weight up almost 1,000 pounds, and the maximum speed fell off to 239 mph. After a short testing period, the A-18s were sent to the 8th Attack Squadron, 3rd Attack Group, at Barksdale Army Air Field, La. The 8th quickly proved the A-18’s effectiveness in exercises, and was awarded the Harmon Trophy for gunnery and bombing accuracy during the A-18’s first year of operation. But the retractable landing gear was weak: Eight of the 13 A-18s were damaged when their gear collapsed on landing or rollout.
It’s interesting to speculate what could have happened if Berlin had been allowed to substitute Alison engines on the A-18 as he had done on the P-36. The resulting aircraft might have allowed Curtiss to compete with the Douglas A-20 for orders. Instead, the true value of the A-18 was in proving to the Army that a 6-ton twin-engine aircraft could be effective in an attack role. It effectively cleared the way for the Army to specify requirements that led to the A-20 and A-26.
World War II brought huge production orders for the P-40, SB2C, C-46 and other planes. But it did not cure the basic management problem that Don Berlin had inherited and which he left behind when, frustrated with Curtiss, he moved to General Motors in 1942 to design the unforgettable (unforgivable?) Fisher XP-75. Curtiss simply no longer had the research and development capability to come up with competitive aircraft. Thus a long string of prototypes—the XBTC-2, XP-55, XF-14C-1, XP-60, XP-62, XF-15C-1, XP-87 and finally the unlamented X-19—all became milestones on a once-great company’s path to oblivion.
Originally published in the March 2007 issue of Aviation History. To subscribe, click here.