Douglas DC-7
| Douglas DC-7 | |
|---|---|
 Douglas DC-7 in action as a fire fighting aircraft |
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| Type: | Passenger and transport aircraft |
| Design country: | |
| Manufacturer: | |
| First flight: |
May 18, 1953 |
| Production time: |
1953 to 1958 |
| Number of pieces: |
338 |
The Douglas DC-7 is a propeller -driven airliner that was manufactured by the US Douglas Aircraft Company from 1953 to 1958 . Along with the Lockheed Starliner, it represented the climax and end of the era of propeller - driven aircraft powered by piston internal combustion engines at the transition to the jet aircraft age .
history
At the beginning of the 1950s, some US airlines were looking for a successor to the tried and tested DC-6 with an extended range in order to be able to fly non-stop in both directions from one US coast to the other, as with the competing model Lockheed Super Constellation . After Douglas' initial hesitation, American Airlines ordered 25 aircraft priced at $ 40 million, which covered development costs. The prototype took off on its maiden flight on May 18, 1953 , and the first machine went into regular service in November. In the beginning, however, the non-stop flights were often only theoretically possible due to technical problems.
Technically, the DC-7 is a further developed DC-6, which in turn is partly based on the DC-4 from 1938. The DC-7 was with 33.24 meters 1.06 meters longer than the DC-6, had a wingspan of 35.81 meters and weighed 30,076 kg empty. Its maximum take-off weight was 55,430 kg and, depending on the seating, it could carry between 60 and 95 passengers. The DC-7 had a relatively high speed for a propeller plane and reached a top speed of 656 km / h. The maximum cruising speed was around 584 km / h, the maximum range was 7,130 kilometers and 6,130 kilometers with a payload of 8,100 kg. The DC-7 was powered by four 18-cylinder turbo-compound twin-radial engines of the Wright R-3350 type , each with a maximum starting power of 3,250 BHP (2,423 kW). These engines - also used in the Lockheed Super Constellation - were technically very prone to failure due to their exhaust gas turbines and very complex and demanding in their operation. On average, a Wright R-3350 in the sophisticated TC versions reached about 1,540 hours of operation before a replacement was necessary. The Pratt & Whitney R-2800 engine of the DC-6, on the other hand, had up to 6,000 operating hours. However, the Wright R-3350TC18 with a specific fuel consumption between 200 and 170 g / PSh was one of the most economical piston engine engines in this performance class that was ever built.
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From April 1955 there was the model DC-7B , which compared to the original model had a reinforced structure, somewhat more powerful engines ( Wright R-3350 -972TC18DA1) and an improved landing flap system. This made it possible to optionally install so-called "saddle tanks", which were then housed in the engine nacelles that were enlarged above the wings. This increased the possible fuel capacity from 17,049 liters (DC-7) to up to 24,143 liters for the DC-7B. Pan American World Airways took up the non-stop connection New York – London on June 13, 1955 with its extended-range DC-7B. However, even this increase did not meet the requirements of the European airlines; the B-model was able to cross the North Atlantic nonstop on the route New York - London in an easterly direction because of the jet stream.
A third variant followed on December 20, 1955 with the maiden flight of the DC-7C , also known as "Seven Seas" as a play on words. This model was the first commercial aircraft to be able to cross the Atlantic non-stop in both directions and to reach destinations in Europe from the American west coast as planned and without stopping. The wings of the DC-4 used up to the DC-7B were no longer sufficient for the necessary fuel capacity of around 30,000 liters and the higher maximum take-off mass of around 65,000 kg . Between the inner engines and the fuselage, a 1.5-meter-long wing section was inserted. This increased the wingspan to 38.80 meters and the fuel capacity by 5,474 liters to a total of 29,617 liters. The saddle tanks were now installed as standard on all DC-7C. Since the engines were now further outside and the diameter of the propellers could be increased from 3.96 meters (DC-7B) to 4.26 meters, the lower speeds resulted in a positive side effect of noise reduction in the cabin. Furthermore, the DC-7C now received Wright R-3350 -988TC18EA1 or EA2 engines, which increased the maximum take-off power to 3400 BHP (2,535 kW ) per engine. The hull was lengthened by 0.99 meters to 34.23 meters. The cross-section of the fuselage remained unchanged at a width of 3.28 meters and a height of 3.50 meters. The range of the DC-7C with 21,300 kg of fuel was 9,050 km with a payload of 6,945 kg. This version was used on even longer long-haul routes, for example on the San Francisco - London or Amsterdam - Anchorage - Tokyo route . KLM operated a non-stop flight from Long Beach to Paris in May 1957 - the flight time was 21 hours and 35 minutes. Competition from Pan Am and their DC-7C forced BOAC to order this type instead of waiting for a revised Bristol Britannia . Another direct competitor was the Lockheed Starliner; However, this was no longer commercially successful because of its somewhat later market launch. The DC-7C "Seven Seas" was the undisputed "queen" of intercontinental air traffic for a few years until the appearance of the first passenger jets at the end of the 1950s, such as the Boeing 707 or Douglas DC-8 .
Finally planned Douglas nor the DC-7D , for the Rolls-Royce Tyne - Turboprop were provided -Triebwerke each with 4,273 kW (5,800 hp). However, due to the approaching jet age, this no longer went into series production.
After their time as a passenger aircraft , many DC-7s were used as cargo or transport aircraft, here now called DC-7F .
A total of 338 DC-7s were built, of which 105 DC-7 (base price $ 1.8 million), 112 DC-7B (base price $ 1.9 million) and 121 DC-7C (base price $ 2.3 million), with the last DC-7 a DC-7C was delivered to KLM on December 10, 1958. In 2007 around 70 aircraft of this type were still registered in the USA.
Surname
As early as 1944 Douglas Aircraft Company was planning an aircraft called the DC-7 , which was to be developed from the C-74 , but was not realized.
Military users
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Incidents
Between the first flight in 1953 and the end of operations in 2010, a total of 74 DC-7s were destroyed or irreparably damaged. 726 people died in 28 of the total losses.
Technical data (DC-7C)
Information from: Jane's All The World's Aircraft , 1959–1960, pp. 294–295 (see below)
| Parameter | Data |
|---|---|
| crew | 3-5 |
| Flight attendant | 5 |
| Passengers | 62-99 |
| length | 34.23 m |
| span | 38.86 m |
| Wing extension | 9.93 |
| height | 9.65 m |
| Wing area | 152 m² |
| Empty mass | 33,034 kg |
| payload | 9,752 kg |
| Max. Takeoff mass | 64,865 kg |
| Cruising speed | 557 km / h |
| Top speed | 653 km / h |
| Landing speed | 156 km / h |
| Rate of climb | 5.3 m / s |
| Takeoff route | 1,940 m |
| Max. Service ceiling | 9,200 m |
| Max. Range | 9,070 km |
| Engines | 4 × Wright R-3350-988TC18EA1 |
| Max. Starting power each | 3,400 bhp (2,535 kW) |
| Max. Continuous output each | 2800 bhp (2,087 kW) |
| Fuel capacity | 29,575 l (21,300 kg) |
See also
literature
- Arthur Pearcy: Douglas Propliner's DC-1 - DC-7. Airlife Publishing, Shrewsbury 1995, ISBN 1-85310-261-X .
- Harry Gann: Douglas DC-6 and DC-7 . In: Airliner Tech. specialty press, ISBN 978-1-58007-182-6 .
- Holgar Lorenz: Start of the nozzle age . hollipress, ISBN 978-3-931770-75-4 , p. 50.
Web links
- Photos at airliners.net
Individual evidence
- ^ Leonard Bridgman: Jane's All The World's Aircraft, 1959-1960 . Sampson Low, Marston & Company, London 1959, pp. 294-295.
- ^ Pearcy p. 151
- ↑ registry.faa.gov
- ↑ Accident statistics Douglas DC-7 Aviation Safety Network (English), accessed on August 11, 2019.