It was on this day in aviation history that a British European Airways DC-3 carrier freight on a commercial flight for the first time. What made this special was the fact that the aircraft was powered with Rolls Royce Dart engines. Only 3 years earlier in 1948 has this engine powered an aircraft in flight This modification was performed in order to get crews turboprop experience prior to them flying the Vickers Viscount.
Another version of the turboprop-powered DC-3 then the one mentioned above was the Conroy Turbo Three. A DC-3 aircraft received turboprop engines in early 1969, they were Rolls Royce Dart MK.510 engines previously used on a Vickers Viscount that had had an unfortunate landing some time previous.
The first Turbo Three fitted with two Rolls Royce Dart turboprops, displayed at the 1969 Paris Air Show
As the RR Dart engines are considerably less heavy than the original P&W Radial engines they were installed on extensions far more forward than the original radial engines, as is clearly visible in the picture above. With the turboprop engines installed the cruise speed increased from 147 knots (170 mph) to ~185 knots (215 mph). In 1977.
This aircraft would be modified to the Conroy Tri Turbo Three. Three PT6A engines were fitted to the aircraft, with the third being placed on the nose. (Click on the picture adjacent to this text for more information on this aircraft.)
Another conversion was called the Super Turbo Three, as it was a Super DC-3. With this modification, the engines were mounted on the bulkhead of the original nacelle. As the (original) Viscount propellors had a smaller diameter than the DC-3 props, a large part of the airflow from the propellor airflow was obstructed by nacelles and (landing gear) fairings. This rather inefficient configuration gave the aircraft a take-off distance of 6000 ft, way too much for the intended (commuter) flights of the aircraft.
The Super Turbo Three (Note the small propellers!)
Some specifications for the Super Turbo Three as stated in the Supplemental Type Certificate:
Power Plants: Rolls Royce Dart RDa6 1600 hp shaft jet thrust 370 lbs – 170 hp @ takeoff.
Wing Span: 90 feet
Length:67 ft. 8 in.Height: 18 ft. 3 in
Horizontal Stabilizer span: 38 ft
Max take-off gross weight: 35,500 lbs
Empty operating weight: 22,500 lbs
Maximum payload: 7,500 lbs
Maximum fuel: 1,626 pounds
Fuel consumption: 1,100 to 1,500 pounds per hour
Cargo floor load capacity: (sta. 97 to 450) 250 lbs/sq.ft.
Cargo floor load capacity: (sta. 450 to 583) 125 lbs/sq.ft.
Maximum load: 2,330 lbs
Stall speeds Power off: - full flaps:(25,000 lbs)70 mph - 35,500 lbs84 mph