Douglas DC-7

DC-7

Butler Aircraft Services' DC-7, Tanker 66
Role	Airliner and 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 a transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston engine-powered transport made by Douglas, being developed shortly after the earliest jet airliner - the de Havilland Comet - entered service and only a few years before the jet-powered Douglas DC-8 first flew.

Design and development

In 1945 Pan American World Airways requested a DC-7, a civil version of the Douglas C-74 Globemaster military transport. Pan Am soon canceled their order. That DC-7 was 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 40 inches longer than the DC-6B. Four eighteen-cylinder Wright R-3350 Turbo-Compound engines provided power.^[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. Some blamed this on the need for high power settings to meet the schedules, causing overheating and failure of the engines' power recovery turbines. These recovered power from the exhaust stream and delivered it to the crankshaft; they boosted the R-3350's power by 600 HP.^[4]

The DC-7 was followed by the DC-7B with slightly more power, and on some DC-7Bs (Pan Am and South African Airways), fuel tanks on top behind 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

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 (actually, the insert was presumably meant to control induced drag resulting from the higher weight by modulating wing loading and increasing the effective aspect ratio; the reduced propulsion drag producing interaction with the fuselage and tail would have been minimal. In addition to cruise performance, take off and landing speeds and distances would have be a major consideration. B), 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 40-inch 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 a few 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 on cross-polar flights 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 jets in 1958–60.

Starting in 1959 Douglas began converting DC-7s and DC-7Cs into DC-7F freighters to extend their useful lives. The airframes were fitted with large forward and rear freight doors and some cabin windows were removed.

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. 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. 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 most DC-6s lasted longer and sold more readily on the secondhand market.

Basic price of a new DC-7 was around £570,000 ($823,308).^[6]

Price of a DC-7B was around £680,000 ($982,226) in 1955, rising to £820,000 ($1,184,490) in 1957.^[6]

Similarly, the price of a DC-7C was £800,000 ($1,155,560) in 1956, increasing to £930,000 ($1,343,385) by 1958.^[7]

Cost of the DC-7F "Speedfreighter" conversion was around £115,000 ($166,112) per-aircraft.^[7]

Variants

DC-7: Production variant, 105 built.
DC-7B: First long-range variant with higher gross weight and fuel capacity, with most of the added fuel in saddle tanks in enlarged engine nacelles. (Only Pan Am and South African DC-7Bs had the saddle tanks.) 112 built.
DC-7C Seven Seas: Longer-range variant with 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 turboprops.
DC-7F: Freight conversion of all three variants with two large freight doors.

Operators

Main article: Douglas DC-7 operators

DC-7 in Delta Air Lines livery

Airlines

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.

Military Operators

Orders and production

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

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 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 and the body of pilot Jerry Hill 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 (N4SW) 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 fired by the Polisario Front and crashed in the Western Sahara, killing the five crew. A second T&G DC-7 (N90984) was also hit, losing an engine, but was able to land safely. Polisario soldiers thought the aircraft were Moroccan C-130s.^[27]

October 1, 1992: A TBM Incorporated DC-7B (N848D) crashed near Union Valley Reservoir due to pilot error and poor CRM, i.e. Crew Resource management, killing both pilots.^[28]

Repurposing

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

DC-7 cockpit

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

DC-7

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

Maximum speed: 405 mph (652 km/h)
Cruise speed: 359 mph (578 km/h)
Stall speed: 97 mph (156 km/h)
Range: 5,164 mi w/ max fuel & 3,565 mi w/ max payload (8,311 km w/ max fuel & 5,737 km w/ max payload)
Service ceiling: 28,400 ft (8,656 m)

DC-7C