Douglas decided to modernise the DC-3, with more power and capable of carrying a greater load. This led to the Super DC-3, or DC-3S, and was issued Approved Type Certificate on 24Jul50. Douglas put Wright 1820-C9HE engines on the prototype and initial production models. Maximum speed increased from 230 mph to 270 mph, cruising speed increased from 207 mph to 251 mph.
It looks like a DC-3 (or C-47), but it was much improved. The Super DC-3 had newly designed wings, an enlarged tail and landing gear doors were added. Also the nose was changed and the wings had square cut tips. It seated up to 37 passengers and it was for 60 percent a completely new airplane.
This post-war development of the famous Douglas twin-engined transport was meant to replace the DC-3 in both military as well as the commercial marktes, but failed commercially due to the many military surplus C-47s flooding the market and the competition on the Convair Liner series with pressurised cabins. The conversion price was between usd 250.000 and 300.000 (excluding the original price of the DC-3 airframe), while a Convair CV340 would seat 44 passengers, flew faster and would cost about usd 570.000 brandnew.
The only 3 Douglas DC-3S aircraft to experience airline service had c/ns 43191, 43192 and 43193 and flew with Capital Airlines for less than 2 years; all three had been converted from early DC-3-178 models: c/ns 1557, 1554 and 1548 (with right-hand side cabindoor).
The US Navy had 100 R4D-5s and R4D-6s converted to "Super Three" (R4D-8) standards. Other engines were used: Wright R-1820-80s. The name "Skytrain II" did not stick much, "Super DC-3" or "Super Three" did. Initially designated R4D-8, the designation was changed to C-117 after 1962.
|C-117A-DK||24-seat transport version|
|VC-117A||Modification of C-117A|
|SC-117A||Air-sea rescue version|
|C-117D||Redesignation of R4D-8; The 101 Super DC-3's or DC-3Ss consisted of (1) the USAF's YC-47F transferred to the USN in 1951 and (2) 100 R4D-5's, -6's and -7's converted to the DC-3S standard. These aircraft were powered by two 1,475 hp (1,100 kW) Wright R-1820-80 nine-cylinder, single-row, air-cooled radial engines|
|LC-117D||Redesignation of R4D-8L, converted with skis and other cold weather equipment for operations in the Arctic and Antarctic. The aircraft had additional fuel tanks and a higher gross weight.|
|TC-117D||Redesignation of R4D-8T, navigational trainers|
|VC-117D||Redesignation of R4D-8Z, 16-seat VIP transport|
|Cruising speed||238 mph / 380 kmh|
|Range||1.600 miles / 2560 kms|
I came across a C-117 Super DC-3 in Alaska (2003), still making a living and looking great !
The "C"-Planes, U.S. Cargo Aircraft 1925- to the Present, by Bill Holder & Scott Vadnais (1996). ISBN 0-88740-912-1.
Douglas Propliners DC-1 - DC-7, by Arthur Pearcy, by Airlife (1995). ISBN 185310261X.