DeHavilland Canada (Viking Air) DHC-3 Otter
As a bigger development of the DHC-2 Beaver the DHC-3 Otter is one of the largest single engine propeller aircraft built after World War II. Like the Beaver the Otter has high wings, braced by struts. The fuselage has the engine up front, with the cockpit close behind. Typical are the triangular side windows, in the cockpit door. The cabin windows are nearly square and have rounded corners. Another key feature is the cruciform tail, with a nicely curved shape, from the dorsal fin all the way to the tail cone.
The DHC-3 normally has a wheeled gear, in a tail gear configuration. However, nowadays many are fitted floats. They can also be equipped with skis.
Viking Air purchased the type certificate for the DHC‑3 in 2006 (together with all models from DHC‑1 until DHC‑7). It continues support for the aircraft still in operation.
The versions of the Otter can be distinguished from the outside by
- the shape of the nose
- the number of propeller blades
- the number and location of exhausts
- the number, location and shape of air intake(s)
DHC-3 (CC-123, CSR-123, YU-1, UC-1, U-1A & (N)U-1B)
The original, Pratt & Whitney R-1340 powered Otter was designated just as DHC-3. It has radial piston engine at the front, with a double exhaust with augmenter tubes on both sides. Underneath the cowling is a cooler intake, which is split in the middle. A three blade propeller is standard.
The US Army evaluated the DHC-3 with designation YU-1, and it was soon ordered in large quantities. This production version was designated U-1A. The US Navy also acquired the Otter. This was first known as UC-1, and from 1962 on as U-1B (and NU1-B for test aircraft). CC-123 and CSR-123 were the designation of the DHC-3 in Canadian military service.
Airtech Canada DHC-3/1000
There have been multiple engine conversions of the DHC-3. DHC-3/1000 is the name of an Airtech Canada converted DHC-3 with a PZL radial engine. This powers a four blade prop. It has a cowl flaps behind the engine all around the cowling, and a single exhaust at the bottom. In fact, the engine exhaust is difficult to see.
Cox/Vazar/Viking Air DHC-3T Turbo Otter
Cox Air Resources was the earliest to try to develop and certify a PT6A powered DHC-3, but ultimately failed. Its DHC-3 Turbo Otter has a long nose with air intakes left and right above the prop spinner, and one below. The Cox version has a four blade propeller.
The most popular turbine engine conversion is that of Vazar, also with the Pratt & Whitney PT6A turboprop engine. It has a long, pointed nose with a single air intake below the prop spinner with has a rounded rectangular shape. It has a three blade propeller.
Viking Air, the current type certificate holder, has its own turbine conversion. The nose it less pointed than that of the Vazar DHC-3T, and the propeller spinner is not flush with the cowling like on the Vazar version. This results in a different nose profile. The air intake has a similar shape though.
All DHC-3T Turbo Otters have single exhausts on both sides of the nose.
Texas Turbine Conversions Super Otter
Texas Turbine Conversions uses a different engines for its conversion, namely the TPE331. It has a nose as pointed as the Vazar DHC-3T, but a big single exhaust on the right side. The propeller has four blades. This conversion is marketed as Super Otter.
The Super Otter has a pointed nose like the Vazar DHC-3T, but a single exhaust on the right and a four blade prop. Also, the prop spinner is not fully flush with the cowling. (photo: Alain Rioux/WikiMedia)
The third turboprop on the DHC-3 is the Walter M601. Otters with this engine can be recognised by the intake below the spinner that is separated, i.e. there is more space between the intake and the spinner than on other conversions. It comes with a three of five blade propeller and has exhausts on both sides of the nose.
The only non-radial piston engine on the Otter was the Orenda V8. It has a cowling that is significantly wider than the prop spinner and there is a somewhat resessed cooler intake underneath the nose.
A one-off was a DHC-3 with a Wright R-1820 engine. This had cowl flaps like the DHC-3/1000 above, and a big exhaust on the right side of the nose.
Finally, there was the Soloy dual-pac engine testbed. This particular aircraft has two PT6A engines side-by-side, driving a single five blade propeller. Their intakes were at the side of the nose, with exhausts below. While Soloy tried to interest operators for the conversion, it was not further proceeded with and the single test aircraft was converted to a DHC-3T.
Confusion possible with
The Beaver is smaller than the Otter. Moreover, its tail is conventional, with the vertical stabiliser having a rounded triangular shape. Also the cabin windows are different.
Fairchild F-11 Husky
The Husky is also a Canadian bushplane and of similar size as the Otter. Typical is the rear loading capability, due to the curved up rear fuselage. Hence the tail wheel is placed just before the curve point. The vertical stabiliser is triangular with a rounded top. Finally, the wings have two struts each.
Another Canadian bushplane, from an earlier generation. Its wing struts are composed of multiple bars, unlike the single one of the Otter. The tail is conventional and without a dorsal fin.
The Antonov An-2 is about the Soviet equivalent of the DHC-3. It is bigger though, has multi-facetted cockpit windows and last but not least is a biplane. The latter should be enough to avoid confusion.