In 1934, alongside the Model 75 fighter, Curtiss developed a two-seat, twin-engined ground attack design for the Army, which later became the XA-14. Subsequently, a Service-test order was placed for thirteen Y1A-18s. The change in designation was a result of switching to different powerplants. The second-generation Shrikes featured an all-metal construction, with fabric covering limited to the movable control surfaces and the wing aft of the front spar. The three undercarriage units retracted aft, exposing half of each wheel to the airstream. The nose housed four .30-caliber machine guns, tightly packed due to its extremely short length. Additionally, a single flexible 0.30-inch machine gun was located in the rear cockpit, inconveniently far aft from the forward cockpit. The XA-14 carried bombs in a fuselage bomb bay, while the Y1A-18s had bays in each wing capable of holding 200 lb (90 kg) bombs each. Alternatively, chemical smoke tanks or additional bombs could be mounted under the wings. Though the new Shrikes, the Army’s initial twin-engined models in the ill-defined Attack Series, performed well, no production orders followed. However, the Y1A-18 experience showcased the advantages of twin-engined aircraft, leading to the establishment of Air Corps requirements that eventually gave rise to larger and heavier designs like the Douglas A-20 and A-26. The XA-14 (Model 76) initially flew as a company-owned aircraft with civil registration X-15314. It was equipped with new and unproven Wright R-1670-5 twin-row engines under circular cowlings, driving Curtiss two-position propellers. After its first flight in September 1935, the Model 76 underwent Army testing at Wright Field before being returned to Curtiss. Following modifications, including a notable change in engine cowling shape and the introduction of new constant-speed propellers, the aircraft was accepted by the Army in December as the XA-14 with Army serial number 36-146. Despite its short military life, being utilized for testing 37-mm cannon installations, the XA-14 was eventually scrapped in August 1938, having accumulated only 158 flying hours. As for the Y1A-18 (Model 76A), the Army placed an order for thirteen Service test aircraft at $104,640 each, complete. Deliveries commenced in July 1937 and were completed by October. The primary difference from the XA-14 was the use of Wright R-1820-47 engines, driving three-bladed propellers. The Y1A-18s initially served with the 8th Attack Squadron of the 3rd Attack Group but were later transferred to the Third Bombardment Group for operational training as plain A-18s in 1940. The last A-18 was taken out of service in 1943, and their USAAC serial numbers ranged from 37-52 to 37-64.