Why were only 43 Sunderland IIs built?

Short answer

Because production quickly moved on to the Mk III. The Sunderland II, introduced in 1941, was the first version of the aircraft fitted with ASV radar. The added equipment increased its weight and, despite somewhat more powerful engines, overall performance dropped slightly. Only 43 Mk IIs were built.

Published: November 4, 2026 · Updated: November 4, 2026 · Edited by Above Ten Thousand · Editorial policy

Short Sunderland Mk V

Forty-three aircraft across three plants

Only 43 examples of the Sunderland II were produced: 23 at the Shorts plant in Rochester, 15 at Short & Harland in Belfast, and 5 at Blackburn in Dumbarton.

More radar, more weight

The Sunderland II was introduced in 1941 and was the first version of the aircraft to carry ASV radar. The extra equipment increased the variant's weight, and despite somewhat more powerful engines, its overall performance declined slightly.

The handover to the Mark III

In December 1941 production switched quickly to the Sunderland Mark III, which featured a revised hull configuration, tested the previous June on a Mark I. That modification improved seaworthiness, which had deteriorated as the Sunderland's weight grew with new versions and in-service changes. On earlier Sunderlands, the hull "step" that lets a flying boat break free of the sea's surface was abrupt, whereas on the Mk III it became an upward curve from the forward hull line. That faired main step reduced hull-induced drag by ten percent, though it had some effect on the aircraft's behaviour on the water. The Mark III proved to be the definitive Sunderland variant and was built in greater numbers than any other version of the aircraft.