Of all the aircraft that passed through the hands of the United States Army Air Corps during the lean interwar years, few were as technically intriguing — or as operationally star-crossed — as the Curtiss A-18 Shrike II. Only thirteen were ever built. Eight of them collapsed their landing gear on rollout. Yet the A-18 remains one of the most sophisticated ground-attack aircraft the United States produced before the Second World War, and a machine that shaped the thinking of an entire generation of tactical airpower planners.
Origins: From XA-14 to A-18
The Curtiss A-18 grew directly from the XA-14 Shrike, an experimental twin-engine attack aircraft that Curtiss-Wright began developing in the early 1930s. The Army Air Corps had been watching with interest as European powers — France, Germany, the Soviet Union — invested heavily in twin-engine light bombers and attack aircraft capable of operating at low level against ground forces. The XA-14 was America's answer to that challenge.
When the XA-14 proved promising enough to warrant a limited production run, Curtiss engineers refined the design considerably. The result was the Curtiss Model 76A, designated Y1A-18 in Army parlance. The "Y1" prefix denoted service-test status — the aircraft would be evaluated in operational conditions before any full production commitment was made. In practice, the thirteen Y1A-18s produced between 1936 and 1937 constituted the entire run. There would be no follow-on order.
The contract price was $1,259,235.00 for all thirteen airframes — an extraordinary investment for a Depression-era Air Corps operating on skeletal budgets. The first example made its maiden flight on 3 July 1935, and the remaining aircraft followed through 1937, bearing serial numbers 37-52 through 37-64.
Design: "Three Beads on a String"
The A-18 was a genuinely modern machine for its era — an all-metal, low-wing cantilever monoplane with an enclosed two-man cockpit, retractable undercarriage, and twin radial engines. Curtiss's promotional literature boasted of the aircraft's elegant frontal profile, likening it to "three beads on a string" — the two engine nacelles and the central fuselage forming a clean, purposeful line when viewed head-on.
"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 twin-engine Model 76 was the American counterpart to the Potez 63 — undoubtedly the best-looking Curtiss plane since the P-6E."
Power came from two Wright R-1820-47 Cyclone nine-cylinder air-cooled radial engines, each developing 850 horsepower. The Y1A-18 variant replaced the original two-blade propellers of the prototype with three-blade, two-position variable-pitch units. Curtiss faired in the landing gear doors to reduce drag, yet deliberately left the wheels partially exposed as a hedge against a wheels-up landing — a practical compromise between aerodynamic cleanliness and operational insurance.
Fully loaded, the A-18 tipped the scales at over 13,000 pounds and could sustain a cruise speed of 185 mph on a single engine. At sea level the aircraft pushed 247 mph, and it could operate up to 25,000 feet.
Armament: Teeth for Ground Attack
The A-18's weapons fit was well-suited to its intended role of low-level interdiction and close air support:
- 4 × forward-firing .30-caliber M1919 Browning machine guns in the wings
- 1 × rear-facing .30-caliber machine gun operated by the observer/gunner
- 400 lb of bombs carried internally in two wing bays
- 200 lb of bombs or chemical smoke tanks on underwing hardpoints
The internal wing bays were a particular point of pride for Curtiss engineers — they reduced drag and protected the ordnance from slipstream turbulence during low-level attack runs.
Service: Barksdale Field and the Harmon Trophy
After completing service testing at Wright Field, the Y1A-18s were re-designated simply A-18 and assigned to the 8th Attack Squadron, 3rd Attack Group at Barksdale Army Air Field, Louisiana, in 1937. The assignment would prove both triumphant and troubled in equal measure.
The 8th Attack Squadron took the coveted Harmon Trophy for gunnery and bombing accuracy during the A-18's first full year of operational service. It was a remarkable achievement — proof that the aircraft, handled by skilled crews, was fully capable of delivering on its design promise.
On the troubled side: eight of the thirteen A-18s suffered landing gear collapse on landing or rollout. The retractable undercarriage harbored a fundamental structural weakness that no amount of revision seemed able to fully correct. The A-18's time with the 8th ended when early-model Douglas A-20 Havocs arrived in 1941. All surviving examples were scrapped by 1943.
Legacy: The Road Not Taken
The A-18 occupies a curious position in the history of American airpower. It demonstrated that American industry could produce a sophisticated twin-engine attack aircraft competitive with anything Europe had to offer — yet without a clear operational requirement and sustained funding, even promising aircraft wither on the vine. Its aerodynamic lessons and engine installation techniques fed directly into the design lineage that ultimately produced the Douglas A-20 Havoc and the North American B-25 Mitchell. The Shrike II may have been a rare bird, but its feathers found their way into American aviation for years to come.
Specifications: Curtiss Y1A-18 Shrike II
| Characteristic | Specification |
|---|---|
| Manufacturer | Curtiss Aeroplane and Motor Company |
| Type | Twin-engine ground-attack aircraft |
| First Flight | 3 July 1935 |
| Retired | 1943 |
| Number Built | 13 (service test) |
| Crew | 2 (pilot + observer/gunner) |
| Length | 41 ft 0 in (12.50 m) |
| Wingspan | 59 ft 6 in (18.14 m) |
| Height | 11 ft 6 in (3.51 m) |
| Wing Area | 526 sq ft (48.87 m²) |
| Empty Weight | 9,410 lb (4,268 kg) |
| Max Takeoff Weight | 13,170 lb (5,974 kg) |
| Engines | 2 × Wright R-1820-47 Cyclone, 850 hp (634 kW) each |
| Propellers | 3-blade two-position variable-pitch |
| Maximum Speed | 247 mph (398 km/h) at 2,500 ft |
| Cruise Speed | 217 mph (349 km/h) |
| Range | 651 miles (1,048 km) |
| Service Ceiling | 25,650 ft (7,820 m) |
| Fixed Armament | 4 × .30-cal M1919 Browning (forward-firing) |
| Flexible Armament | 1 × .30-cal M1919 Browning (rear-facing) |
| Bomb Load | 400 lb internal (wing bays) + 200 lb underwing |
| Unit Assigned | 8th Attack Sqn, 3rd Attack Group, Barksdale Field, LA |
| Notable Award | Harmon Trophy — Gunnery & Bombing Accuracy, 1937 |