When de Havilland Canada began design work on the "King Beaver" (the Otter's original name) in January 1951, it was trying to extend the company's line of rugged STOL utility transports that had begun with the Beaver. The single-engined, high-wing, propeller-driven DHC-3 Otter was conceived to be capable of performing the same roles as the Beaver, but was considerably larger, the veritable "one-ton truck" (in company parlance, the Beaver was the "half-ton truck").

Using the same overall configuration of the earlier and highly successful DHC2 Beaver, the new design incorporated a longer fuselage, greater-span wings, a cruciform tail, and was much heavier. Seating in the main cabin is for 10 or 11, whereas the Beaver could seat six. Power is supplied by a 450-kW (600 hp) Pratt & Whitney Wasp radial. Like the Beaver, the Otter can be fitted with skis or floats. The Otter served as the basis for the very successful Twin Otter, which featured two wing-mounted Pratt & Whitney Canada PT6 turboprops.

The Otter received Canadian certification in November 1952 and entered production shortly thereafter.

Modifications

Stolairus Aviation of Kelowna, BC has developed several modifications for the DHC-3 including a STOL Kit, which modifies the wing with a contoured leading edge and drooped wingtips for increased performance. Stolairus has also developed a 400 lb "upgross" kit which increases the gross weight of the DHC-3 to 8,367 lbs on floats.

Some aircraft were converted to turbine power using a PT6A, Walter 601 (manufactured in the Czech Republic), or Garrett/Honeywell TPE331-10, by Texas Turbine Conversions. The Walter M601E-11 Turbine Engine conversion is manufactured and installed by Stolairus Aviation.

A Polish Pezetel radial engine has also been fitted. Re-engined aircraft have been offered since the 1980s by Airtech Canada as the DHC-3/1000 using current-production 1,000 hp (745 kW) PZL ASz-62 IR radials.

Variants

• DHC-3 Otter : Single-engined STOL utility transport aircraft.
  • CSR-123 Otter : STOL utility transport aircraft for the Royal Canadian Air Force.
  • YU-1 Otter : Six test and evaluation aircraft for the U.S. Army.
  • U-1A Otter : STOL utility transport aircraft for the US Army.
  • UC-1 Otter : STOL utility transport aircraft for the United States Navy. Later redesignated U-1B Otter in 1962.
• DHC-3-T Turbo-Otter : Otter fitted with either a PT6A-27 or PT6A-34 turboprop engine.