Douglas DC-7

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DC-7
Butler-dc7-N6353C-071029-fox-tanker66-04-16.jpg
Butler Aircraft Services' DC-7, Tanker 66
Role Airliner/transport aircraft
National origin United States
Manufacturer Douglas Aircraft Company
First flight 18 May 1953
Introduction November 1953
Primary users American Airlines (historical)
United Airlines (historical)
Eastern Air Lines (historical)
Pan Am (historical)
Produced 1953–1958
Number built 343
Developed from Douglas DC-6
BOAC DC-7C G-AOIC taking off from Manchester UK in April 1958 for a non-stop flight to New York (Idlewild) (later JFK)
Swissair DC-7C in 1961
DC-7CF freighter of BOAC in 1961 converted with forward and rear freight doors

The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston-engine powered transport made by Douglas, coming just a few years before the advent of jet aircraft such as the Boeing 707 and Douglas DC-8.

Design and development[edit]

In 1945 Pan American World Airways requested a DC-7, a civilian version of the Douglas C-74 Globemaster military transport. Pan Am soon canceled their order, and that DC-7 is unrelated to the later airliner.

American Airlines revived the designation when they requested an aircraft that could fly the USA coast-to-coast nonstop in about eight hours. (Civil Air Regulations then limited domestic flight crews to 8 hours flight time in any 24-hour period.[1][2]) Douglas was reluctant to build the aircraft until American Airlines president C. R. Smith ordered 25 at a price of $40 million, thus covering Douglas' development costs. The DC-7 wing was based on the DC-4 wing with the same span; the fuselage was 3 feet longer than the DC-6. The engine was the eighteen-cylinder Wright R-3350 Turbo-Compound.[3] The prototype flew in May 1953 and American received their first DC-7 in November, inaugurating the first nonstop east-coast-to-west-coast service in the country (unrealistically scheduled just under the eight-hour limit for one crew) and forcing rival TWA to offer a similar service with its Super Constellations. Both aircraft frequently experienced inflight engine failures, causing many flights to be diverted. This was attributed by some to the need for high power settings to meet the aggressive schedules, which resulted in overheating and failure of the engines' power recovery turbines (PRTs, sometimes called turbocompounds). These recovered power from the exhaust stream and delivered it to the crankshaft; they boosted the R-3350's power by a total of 600 HP. [4]

The DC-7 was followed by the DC-7B with a bit more power and, on some DC-7Bs (Pan Am and South African Airways), fuel tanks in the top of the engine nacelles, each carrying 220 US gallons. South African Airways used this variant to fly Johannesburg to London with one stop. Pan Am's DC-7Bs started flying transatlantic in summer 1955, scheduled 1 hr 45 min faster than the Super Stratocruiser from New York to London or Paris.

Operational history[edit]

Early DC-7s were purchased only by U.S. carriers. European carriers could not take advantage of the small range-increase of the early DC-7, so Douglas released an extended-range variant, the DC-7C (Seven Seas) in 1956. Two 5 ft (1.5 m) wingroot inserts added fuel capacity, reduced interference drag, and made the cabin quieter by moving the engines farther outboard; all DC-7Cs had the nacelle fuel tanks previously seen on Pan American's and South African's DC-7Bs. The fuselage, which had been extended over the DC-6B's with a 40 in (100 cm) plug behind the wing for the DC-7 and −7B, was lengthened with a similar plug ahead of the wing to give the DC-7C a total length of 112 ft 3 in (34.21 m).

Since the late 1940s Pan Am and other airlines had scheduled some nonstop flights from New York to Europe, but westward nonstops against the prevailing wind were rarely possible with an economic payload. The L1049G and DC-7B that appeared in 1955 could occasionally make the westward trip, but in summer 1956 Pan Am's DC-7C finally started doing it fairly reliably. BOAC was forced to respond by purchasing DC-7Cs rather than wait on the delivery of the Bristol Britannia. The DC-7C found its way into several other overseas airlines' fleets, including SAS, which used them for cross-polar service to North America and Asia. The DC-7C sold better than its rival, the Lockheed L-1649A Starliner, which entered service a year later,[5] but sales were cut short by the arrival of Boeing 707 and Douglas DC-8 jet aircraft in 1958–60.

Starting in 1959, Douglas began converting DC-7 and DC-7C aircraft into DC-7F freighters. The airframes were fitted with large forward and rear freight doors and some cabin windows were deleted. This modification extended the life of the aircraft past its viability as a passenger transport.

The predecessor DC-6, especially the DC-6B, established a reputation for straightforward engineering and reliability. Pratt & Whitney, manufacturer of the DC-6's Double Wasp engines, did not offer an effective larger engine apart from the Wasp Major, which had a reputation for poor reliability.[citation needed] Douglas turned to Wright Aeronautical for a more powerful engine. The Duplex-Cyclone had reliability issues of its own, and this affected the DC-7's service record and usage. Carriers who had both DC-6s and DC-7s in their fleets usually replaced the newer DC-7s first once jets started to arrive. Some airlines retired their DC-7s after little more than five years of service, whereas the vast majority of DC-6s lasted longer and sold more readily on the secondhand market.

Basic price of a new DC-7 was around £570,000.[6]

Price of a DC-7B was around £680,000 in 1955, rising to £820,000 in 1957.[6]

Similarly, the price of a DC-7C was £800,000 in 1956, increasing to £930,000 by 1958.[7]

Cost of the DC-7F "Speedfreighter" conversion was around £115,000 per-aircraft.[7]

Variants[edit]

DC-7
Production variant, 105 built.
DC-7B
First long range-variant with increased gross weight and increased fuel capacity, with most of the additional fuel in saddle tanks formed by extending the engine nacelles, although not all the aircraft had the additional fuel capacity, 112 built.
DC-7C Seven Seas
Improved long-range variant with a non-stop transatlantic capability, improved 3400hp (2540kW) R-3350 engines and increased fuel capacity mainly in longer wings, 121 built.
DC-7D
Unbuilt variant with Rolls-Royce Tyne turboprop engines.
DC-7F
Freight conversion of all three variants with two large freight doors.

Operators[edit]

DC-7 in Delta Air Lines livery

Airlines[edit]

DC-7s were used by Alitalia, American Airlines, BOAC, Braniff Airways, Caledonian Airways, Delta Air Lines, Eastern Air Lines, Japan Airlines, KLM, Mexicana National Airlines, Northwest Orient, Panair do Brasil, Pan American World Airways, Sabena, SAS, South African Airways, Swissair, Turkish Airlines, Transports_Aériens_Intercontinentaux, and United Airlines.

Seventeen DC-7s remained on the U.S. registry in 2010,[8] used mainly for cargo and as airtankers. Due to its engine problems, the DC-7 has not had the same longevity as the DC-6, which is still used by a number of commercial operators.[citation needed]

Military Operators[edit]

Orders and production[edit]

Airline DC-7 DC-7B DC-7C Notes
Alitalia 6
American Airlines 34 24
British Overseas Airways Corporation 10
Braniff Airways 7
Continental Air Lines 5
Delta Air Lines 10 10
Eastern Air Lines 49
Iran Air 1
Japan Air Lines 4
KLM 15
Mexicana 4
National Airlines 4 4
Northwest Orient Airlines 14
Panagra 6
Pan American World Airways 6 27
Panair do Brasil 2
Persian Air Services 2
Sabena 10 3 were leased
Scandinavian Airlines System 14
South African Airways 4
Swissair 5
Transports Aériens Intercontinentaux 4
United Airlines 57 2 were lost in mid-air collisions
Douglas Aircraft 2 Written off before delivery
1 DC-7B prototype delivered to Delta Air Lines
1 DC-7C prototype delivered to Panair do Brasil
Total 102 111 125 Total built: 343

Accidents and incidents[edit]

June 30, 1956
United Airlines Flight 718, a DC-7, collided over the Grand Canyon with TWA Flight 2, an L-1049 Super Constellation, resulting in the deaths of 128 people on both aircraft.
January 31, 1957
A DC-7 (N8210H) crashed into a school yard in the Pacoima area of Los Angeles, California, following a midair collision with Northrop F-89J Scorpion 52-1870, resulting in the deaths of the four crewmembers aboard the DC-7, the pilot of the Scorpion jet, and three students on the ground.[9][10]
March 25, 1958
Braniff Flight 971, a DC-7C (N5904), crashed shortly after takeoff from Miami while attempting to return after an engine caught fire. Nine passengers out of 24 people aboard died in the accident.[11]
April 21, 1958
United Airlines Flight 736, a DC-7 en route from Los Angeles to Denver, collided with USAF North American F-100 Super Sabre 56-3755 near Las Vegas. Both aircraft crashed out of control resulting in the deaths of 49 people.
May 18, 1958
A Sabena DC-7C (OO-SFA) crashed near Casablanca Airport during an emergency landing. All nine crewmembers and 52 of the 56 passengers died.[12]
September 24, 1959
TAI Flight 307, a DC-7C, crashed at Bordeaux airport with the loss of 54 lives. After takeoff, the aircraft failed to gain altitude and collided with trees 3 km (1.9 mi) from the start of the takeoff.
November 16, 1959
National Airlines Flight 967, a DC-7B on a flight from Tampa, Florida to New Orleans, crashed into the Gulf of Mexico. All 42 occupants perished. Although sabotage was suspected, no definite cause of the crash was determined due to a lack of evidence. The aircraft was owned by Delta Air Lines.[13]
February 26, 1960
An Alitalia DC-7C (I-DUVO) crashed at Shannon Airport, Ireland, shortly after takeoff with 34 fatalities out of 52 passengers and crew. No cause was established for this accident.[14]
July 14, 1960
Northwest Orient Airlines Flight 1-11, a DC-7C (N292), ditched off Polillo Island, Philippines due to failure of the number two engine and fire; one person (out of 58 on board) died when the number two propeller separated and penetrated the fuselage.[15]
November 1, 1961
A Panair do Brasil DC-7C (PP-PDO) flying from Sal to Recife crashed into a hill about 2.7 km (1.7 mi) short of the runway at Recife. Forty-five passengers and crew out of the 88 persons aboard lost their lives. The accident was attributed to pilot error.[16][17]
March 6, 1962
Caledonian Airways Flight 153 crashed into a swamp shortly after takeoff from Douala International Airport; all 111 people on board died. It is the worst single-aircraft accident of a DC-7.
October 22, 1962
A Northwest Airlines DC-7C with 7 crew and 95 passengers[18] made a successful water landing in Sitka Sound just before 1 p.m. local time after struggling with propeller problems for 45 minutes [19] while operating as a military charter flight between McChord Air Force Base and Elmendorf Air Force Base. The plane stayed afloat for 24 minutes after coming to rest in the water, giving the occupants ample time to evacuate into life-rafts with only 6 minor injuries reported. All passengers and crew were quickly rescued by U.S. Coast Guard ships.[20]
November 30, 1962
Eastern Airlines Flight 512, a DC-7B on a flight from Charlotte, North Carolina, to New York-Idlewild, crashed after a missed approach due to fog. This accident, which cost 25 lives (out of 51 onboard), was attributed to improper crew procedures.
June 3, 1963
Northwest Orient Airlines Flight 293, a Military Air Transport Service flight from McChord Air Force Base in Washington state to Elmendorf Air Force Base in Alaska crashed into the Pacific Ocean near Annette Island, Alaska, with the loss of all 101 people aboard. Due to the lack of evidence, no cause was established for this accident.
February 8, 1965
Eastern Air Lines Flight 663 crashed a few minutes after takeoff from John F. Kennedy Airport in New York after taking evasive action to avoid a possible collision with another airliner (Pan Am Flight 212, a Boeing 707). All 84 passengers and crew died.
December 31, 1972
Professional Baseball player Roberto Clemente and 4 others in a chartered DC-7 died when the plane crashed shortly after takeoff from San Juan, Puerto Rico. Only parts of the fuselage were recovered. The cause was traced to maintenance and pilot errors.[21]
June 21, 1973
A Skyways International DC-7C (N296) crashed in the Everglades six minutes after takeoff from Miami International Airport, apparently caused by an onboard fire and/or severe turbulence. Three crew members, the sole occupants, died. The aircraft was on lease to Warnaco Incorporated.[22]
March 3, 1974
A Douglas DC-7C/F (EI-AWG) operating an Aer Turas Teo charter flight from Dublin landed at Luton Airport on runway 08 just after midnight but failed to achieve reverse thrust. Normal braking application also was ineffective and the emergency pneumatic brakes were applied. All main wheel tires burst. The aircraft overran the runway and continued over the steep bank at the eastern perimeter finally coming to rest in soft ground 90 metres beyond. The situation had also been made worse by an inadvertent application of forward thrust by the crew in trying to achieve reverse thrust. Three of the six passengers and two of the four crew were injured. The aircraft was badly damaged and deemed a write-off.[23]
October 4, 1976
An Emirates Air Transport DC-7CF (TZ-ARC) struck Mount Kenya due to a premature descent, killing the four crew.[24]
September 12, 1977
A Safe Air Cargo DC-7BF (N6314J) crashed on climbout from Yakutat Airport after an engine lost power and caught fire, killing the four crew. 14 CFR 91 subpart D was revised in the wake of this accident.[25]
September 6, 1978
An Advance Aviation Inc. DC-7CF (N244B) was being used to smuggle marijuana when it crashed near Farmerville, Louisiana due to pilot error, killing one of six on board. Thirty-five bales of marijuana were recovered from the wreckage.[26]
September 14, 1979
A Butler Aircraft Inc. DC-7 transporting company employees to Medford, Oregon crashed on the crest of Surveyor Mountain near Klamath Falls, Oregon. The crash, which claimed the 12 occupants aboard, was attributed to the crew's decision to undertake a night flight at low altitude.
December 8, 1988
A T&G Aviation DC-7CF (N284) was shot down by a SAM-7 missile and crashed in the Western Sahara, killing the five crew.[27]
October 1, 1992
A TBM Incorporated DC-7B (N848D) crashed near Union Valley Reservoir due to pilot error and poor CRM, killing both pilots.[28]

Repurposing[edit]

A flight school owner at the New Smyrna Beach Airport has restored a DC-7 to serve as a restaurant, the DC-7 Grille.[29][30]

Specifications[edit]

DC-7 cockpit
DC-7 Cockpit – From the display at the National Air and Space Museum in Washington, DC

DC-7[edit]

Data from American Museum of Aviation[31]

General characteristics

  • Crew: 2 Pilots, 1 Flight Engineer, 2 Flight Attendants
  • Capacity: 64 to 95 Passengers
  • Length: 108 ft, 11 in (33.20 m)
  • Wingspan: 117 ft, 6 in (35.81 m)
  • Height: 28 ft, 7 in (8.71 m)
  • Empty weight: 58,150 lbs (26,376 kg)
  • Max. takeoff weight: 114,600 to 122,000 lbs (51,982 to 55,338 kg)
  • Powerplant: 4 × Wright R-3350-30W radial piston engines, 3,250 hp (2,423 kW) each

Performance

DC-7C[edit]

Data from American Museum of Aviation[31]

General characteristics

  • Crew: 2 Pilots, 1 Flight Engineer, 4 Flight attendants
  • Capacity: 105 Passengers
  • Length: 112 ft, 3 in (34.21 m)
  • Wingspan: 127 ft, 6 in (38.86 m)
  • Height: 31 ft, 10 in (9.70 m)
  • Empty weight: 72,763 lbs (33,005 kg)
  • Max. takeoff weight: 143,000 lbs (64,864 kg)
  • Powerplant: 4 × Wright R-3350-988TC18EA1-2 radial piston engines, 3400 hp (2,536 kW) each

Performance

See also[edit]

Related development
Aircraft of comparable role, configuration and era
Related lists

References[edit]

Notes[edit]

  1. ^ Aviation Week, February 1, 1954, p. 16.
  2. ^ Aviation Week, June 21, 1954 p. 16.
  3. ^ "Douglas Airlines". Sport Aviation, April 2012, p. 19.
  4. ^ Aviation Week, April 21, 1958, p. 38: "In one three-month period, CAA records indicate that operators of the Douglas DC-7B ... reported 334 feathered propellors, or one feathered propellor for every 1,472 engine hours."
  5. ^ Breffort, Dominique. Lockheed Constellation: From Excalibur to Starliner, Civilian and Military Variants. Paris: Histoire and Collecions, 2006. ISBN 2-915239-62-2
  6. ^ a b "Max take-off, Hamilton Standard, price today." Flight Archive, 1960.
  7. ^ a b "Douglas." Flight Archive, 1960.
  8. ^ "FAA registration database." FAA. Retrieved: November 26, 2010.
  9. ^ Hill, Gladwyn. "7 Die as Planes Collide and One Falls in Schoolyard: Planes Collide, School Yard hit; Roar Alerts Students 'Everything on Fire' Witness Describes Crash." The New York Times, February 1, 1957, p. 1. Retrieved: February 3, 2010.
  10. ^ "Douglas DC-7B N8210H." Aviation Safety Network. Retrieved: February 3, 2010.
  11. ^ "Douglas DC-7C N5904". Aviation Safety Network. Retrieved: September 6, 2013.
  12. ^ "Douglas DC-7C OO-SFA." Aviation Safety Network. Retrieved: September 6, 2013.
  13. ^ "Aircraft Accident Report." specialcollection.net. Retrieved: December 22, 2011.
  14. ^ "Douglas DC-7C I-DUVO." Aviation Safety Network. Retrieved: September 6, 2013.
  15. ^ "Douglas DC-7C N292." Aviation Safety Network. Retrieved: September 6, 2013.
  16. ^ "Accident description PP-PDO." Aviation Safety Network. Retrieved: May 20, 2011.
  17. ^ Germano da Silva 2008, pp. 197–203.
  18. ^ Aircraft Accident Report: Douglas DC-7C, N285 Northwest Airlines, Inc. Ditching in Sitka Sound, Alaska October 22, 1962. Washington, DC: Civil Aeronautics Board. 19 September 1963. p. 1. 
  19. ^ "DC-7 Ditches In Sea Near Sitka; All Safe". The Seattle Daily Times. 22 October 1962. 
  20. ^ Sims, Ward T. (23 October 1962). "102 Saved As Plane Ditches". Seattle Post Intelligencer. 
  21. ^ "Roberto Clemente While Flying A Relief Mission To Earthquake Torn Nicaragua Dies In Plane Crash." avstop.com. Retrieved: November 26, 2010.
  22. ^ Accident description for N296 at the Aviation Safety Network. Retrieved on 29 November 2013.
  23. ^ "Accident description: Douglas DC-7CF EI-AWG". Aviation Safety Network, 2013. Retrieved: October 10, 2013.
  24. ^ Accident description for TZ-ARC at the Aviation Safety Network. Retrieved on 29 November 2013.
  25. ^ Accident description for N6314J at the Aviation Safety Network. Retrieved on 29 November 2013.
  26. ^ Accident description for N244B at the Aviation Safety Network. Retrieved on 29 November 2013.
  27. ^ Accident description for N284 at the Aviation Safety Network. Retrieved on 29 November 2013.
  28. ^ Accident description for N848D at the Aviation Safety Network. Retrieved on 29 November 2013.
  29. ^ "DC-7 plane to be converted into restaurant." Retrieved: April 12, 2013.
  30. ^ "DC-7 Grille." dc7grille.com. Retrieved: April 12, 2013.
  31. ^ a b "Douglas DC-7." American Museum of Aviation. Retrieved: December 22, 2011.

Bibliography[edit]

  • Germano da Silva, Carlos Ari César. "Buraco negro." O rastro da bruxa: história da aviação comercial brasileira no século XX através dos seus acidentes 1928–1996 (in Portuguese). Porto Alegre: Edipucrs, Second edition, 2008. ISBN 978-85-7430-760-2.
  • Pearcy, Arthur. Douglas Propliners: DC-1–DC-7. Shrewsbury, UK: Airlife Publishing, 1995. ISBN 1-85310-261-X.
  • United States Air Force Museum Guidebook. Wright-Patterson AFB, Ohio; Air Force Museum Foundation, 1975.
  • Whittle, John A. The Douglas DC-6 and DC-7 Series. Tonbridge, Kent, UK: Air Britain (Historians) Ltd., 1971. No ISBN.
  • Wilson, Stewart. Airliners of the World. Fyshwick, ACT, Australia: Aerospace Publications Pty Ltd, 1999. ISBN 1-875671-44-7
  • Yenne, Bill. McDonnell Douglas: A Tale of Two Giants. Greenwich, Connecticut: Bison Books, 1985. ISBN 0-517-44287-6.

External links[edit]