The A-28 and A-28A were American military designations for specific variants of the Lockheed Hudson procured under the Lend-Lease Act. These designations distinguished aircraft initially ordered by the British but taken over by the United States Army Air Forces (USAAF) for administrative and delivery purposes.

A-28 (Hudson Mark IVA)

• Production and Engines: The A-28 designation applied to 52 aircraft. These were powered by Pratt & Whitney R-1830-45 "Twin Wasp" engines, each producing 1,050 horsepower at takeoff.
• Operational History: All 52 of these aircraft were diverted to the Royal Australian Air Force (RAAF). In Australian service, they were known as the Hudson Mark IVA and assigned serial numbers A16-101 through A16-152.
• Serial Numbers: Their USAAF serial numbers were 41-23171 through 41-23222.

A-28A (Hudson Mark VI)

• Production and Engines: The A-28A designation was used for 450 aircraft, which corresponded to the Hudson Mark VI. This variant featured more powerful Pratt & Whitney R-1830-67 engines, producing 1,200 horsepower.
• Technical Details: These aircraft had a gross weight of approximately 22,360 lb. While many were delivered to the RAF (receiving serials in the EW837–EW972 and FK381–FK730 ranges), some were diverted to other allies.
• Service in Brazil: A total of 28 Lockheed A-28As were sent to the Brazilian Air Force under Lend-Lease, where they were used for anti-submarine patrols. In 1945, three of these aircraft were converted into transports and redesignated by the Brazilians as C-28s.
• Training Variant: The USAAF's AT-18, an advanced gunnery and navigation trainer, was a specialized development based on the A-28A airframe.

Distinguishing Features

The A-28 series utilized the 14-cylinder Pratt & Whitney engines, which required longer, broader-chord cowlings with cooling gills compared to the 9-cylinder Wright Cyclone engines used on earlier Hudson marks. The A-28As intended for transport roles often had their dorsal turrets removed and the area faired over.