Why This Million-Dollar Plane Kept Melting Its Own Engines: Douglas DC-7

Video from the channel Jet Deck about Douglas DC-7, linked on its Above Ten Thousand entry. Duration: 23:47. Language: English. Video type: Documentary.

Narrated documentary about the Douglas DC-7 explaining why it was created and why its engine caused so many problems. The video argues the aircraft was born for a single commercial goal: crossing the United States westbound in under eight hours. It devotes most of its runtime to the Wright R-3350 Turbo-Compound engine, its maintenance, the flight crew's work in the cockpit and the passenger experience, and ends with the DC-7C version and the type's retirement when the jets arrived.

According to the video, the Civil Aeronautics Board required a relief crew on domestic flights longer than eight hours, and westbound flights into headwinds exceeded that limit. When TWA began flying the Lockheed L-1049 Super Constellation, C.R. Smith, president of American Airlines, pressured Donald Douglas to build a faster aircraft, threatening to take the order to Lockheed. Douglas agreed even though he expected jets to arrive soon. For Pan Am and BOAC's transatlantic routes the DC-7C "Seven Seas" was developed, entering service in 1956. The arrival of the Boeing 707 with Pan Am in October 1958, followed by the DC-8, made the type obsolete: many aircraft were converted into DC-7F freighters, and between the late 1960s and early 1970s they ended up stored in scrapyards in the southwestern United States.

The DC-7 started from the DC-6B's fuselage, stretched 40 inches to just under 109 feet, and had a maximum takeoff weight of 122,200 pounds. Each of its four 18-cylinder R-3350 engines recovered energy from exhaust gases using three turbines, spinning at 19,000 rpm and linked to the crankshaft through hydraulic couplings. Those turbines contributed about 550 horsepower and raised takeoff power to 3,400 horsepower, but subjected the engine to extreme temperatures: burnt exhaust valves, oil consumption of two to three gallons per hour per engine, 144 spark plugs per aircraft and visible flames at night. The video gives a cruise speed of about 360 mph, versus 340 for the Constellation. For the DC-7C, it states that a 10-foot wing section was added, fuel capacity rose from 5,512 to 7,824 gallons, and range exceeded 4,600 miles.