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The Douglas Super DC-3 / RD4-8



Following the end of WWII, the Douglas Company had to find new opportunities for business while greatly downsizing its operations.  The natural market for the company was the airlines.  First priority became the development of large, pressurized four-engine transports for the blue ribbon transcontinental and transatlantic routes.  Lockheed and Boeing had seen this segment and were developing the Constellation and Stratocruiser.  Douglas opted for the DC-6.

Most shorter airline routes were served by DC-3s. The huge supply of military surplus C-47s at bargain prices made competing in this market sector risky. In the late 1940s, questions arose with the CAA (search) about the airworthiness of the DC-3/C-47 performance and it appeared that the airlines might embrace a more capable, modified Gooney Bird. 

With large financial exposure on the books, and the fact that Martin and Convair were building pressurized twins, the Douglas Company looked for a niche in the medium-range market involving low investment.  In 1947 the Super DC-3 project was initiated with Mal Oleson as project engineer.

It was decided to modify existing  airframes which could be acquired at low cost from the ample surplus market instead of building new planes from scratch.  The company bought two second hand aircraft - one C-47, the other an ex-DC-3 - and made them prototypes of the new Super DC-3.  Engines were upgraded to 1,475 hp Wright R-1820, or 1,450 hp P&W R-2000s from typical 1,200 hp power plants in the DC-3/C-47.  The fuselage was lengthened 39 inches forward of the wing and 40 inches aft, allowing thirty seats to be  installed compared to 21 before modification.  To accommodate the new power and balance characteristics, wing geometry was modified to use squared-off tips as span was reduced by 5 ft.  Tail surfaces were enlarged and laid out with square tips as well and a larger dorsal fin was fitted. The DC-3’s slow landing gear retraction time was reduced as a result of a hydraulic system redesign, and doors were added to the wheel wells.  An airstair and retractable tailwheel were adopted . Electrical system improvements were made and new heating unit was installed in the fuselage below the floor to solve a long time problem of passenger-cabin heating. 

With these mutations in place, Douglas claimed that the  DC-3S was a 75% new airplane. In performance,  cruise speed increased 21% from 207 mph to 251 mph, and improvements in engine-out situations let the airplane meet the 1952 CAR standards. (Which were eventually waived for DC-3s)

First flight was made on June 23, 1949 with John Martin as pilot. (This plane, N30000, served as the company transport for many years.) Flight tests demonstrated better-than-predicted performance.

Despite the Douglas Company’s efforts to keep the cost down, the conversion was not cheap. The price was between $250,000 and $300,000 (excluding the original price of the DC-3 airframe). As a comparison, a Convair CV340 would seat 44 passengers, flew faster and would cost about  $570,000 brand new. As a result, after a demonstration/sales tour, only three Super DC-3s were ordered for airline use - all of them went to Capital Airlines and they flew in scheduled service for only two years. 

The Air Force bought one of the  prototypes from the company, designated it the YC-129 (later changed to the YC-47F) for evaluation.  When the type was not selected by the USAF, it was transferred to the Navy and renamed R4D-8. In 1962 the military changed to designation again to C-117.

At last, a customer was found for the Super Three.  The Navy signed a contract to modify 100 R4D-5s, R4D-6s and R4D-7s to the new type, R4D-8.

The airplane served U.S. Navy and Marine Corps in various roles including staff transports and special missions including cold weather operations for more than 20 years.

Many of the R4D-8/C-117s found their way into the surplus market. As late as 1993, there were at least 19 still flying in the United States. Others were in Canada. Philippines, and Latin America.