Everything about Douglas Dc-8 totally explained
The
Douglas DC-8 is a four-engined jet
airliner, manufactured from 1958 to 1972.
Development
Background
When the world's first jet airliner, the
De Havilland Comet, was introduced in 1949, Douglas held a commanding position in the aircraft market. Although
Boeing had pointed the way to the modern all-metal airliner in 1933 with the
247, it was Douglas that, more than any other company, made the promise a reality. Douglas produced a succession of piston-engined commercial aircraft through the 1930s, 1940s and 1950s: 138
DC-2s, 10,928
DC-3s (mostly for military service in
World War II), 1453
DC-4s, 537
DC-6s and 226
DC-7s.
Given the success of their designs, Douglas took the view that there was no reason to rush into anything new, as did their rivals
Lockheed and
Convair. Most air transport manufacturers expected that there would be a gradual switch, from piston engines to turbines and that it would be to the more fuel-efficient
turboprop engines rather than pure jets.
In contrast, Boeing took the bold step of starting to plan a pure jet airliner as early as 1949. Boeing's military arm had gained extensive experience with large, long-range jets through the
B-47 Stratojet (first flight 1947) and the
B-52 Stratofortress (1952). With thousands of their big jet bombers on order or in service, Boeing had developed a close relationship with the
U.S. Air Force Strategic Air Command (SAC), and could count on having preference when the time came to replace SAC's fleet of piston-engined
KC-97 Stratotankers. For Boeing, this was an opportunity to build a jet aircraft for
air-to-air refueling that could be turned into a commercial transport.
De Havilland's pioneering Comet entered airline service in
1952. Initially it was a success, but a series of fatal crashes in
1953 and
1954 resulted in the type being grounded until the cause could be discovered. Airlines cancelled orders for it, public confidence in the idea of jet transport plummeted, and it would take de Havilland four years to find and fix the problem. The cause of the Comet crashes was nothing to do with jet engines: it was rapid
metal fatigue failure brought on by the stress of cycling a pressurized cabin to high altitudes and back. A new understanding of metal fatigue that the Comet investigation produced would play a vital part in the good safety record of later types like the DC-8.
In 1952, Douglas remained the most successful of the commercial aircraft manufacturers. They had almost 300 orders on hand for the piston-engined DC-6 and its successor, the DC-7, which had yet to fly and was still two years away from commercial service. The Comet disasters, and the consequent airline lack of interest in jets, seemed to demonstrate the wisdom of their staying with propeller aircraft. Nevertheless, with one eye on the USAF tanker market, Douglas secretly began jet transport project definition studies in mid-year, and by mid-
1953 had decided on something very like the final form: an 80-seat, low-wing aircraft with four
Pratt & Whitney JT3C turbojet engines, 30-degree wing sweep, and an internal cabin diameter of exactly 11 feet (3.35 m) to allow five abreast seating. Maximum weight was to be 95 tons, and range was estimated at somewhere between 3,000 and 4,000 miles (4,800 to 6,400 km).
Design phase
Douglas was lukewarm about the jet airliner project, but believed that the
USAF tanker contract would go to two companies for two different aircraft (as several USAF transport contracts in the past had done). In May
1954, the USAF circulated its requirement for 800 jet tankers to Boeing, Douglas, Convair, Fairchild, Lockheed, and Martin. Boeing was already just two months away from having a prototype in the air. Before the year was out, the Air Force had ordered the first of an eventual 808 Boeing
KC-135 tankers. Even leaving aside Boeing's ability to supply a jet tanker promptly, the flying-boom air-to-air refueling system — as first fitted to the KC-97 — was also a Boeing product: developing the KC-135 had been a safe bet.
Just four months after issuing the tanker requirement, the USAF ordered 29 KC-135s from Boeing.
Donald Douglas was shocked by the rapidity of the decision which, he said, had been made before the competing companies had had time to complete their bids, and protested to Washington, but without success. The U.S. Air Force would buy more than 800 strategic tankers over the next ten years, and every one of them from Boeing.
Having started on the DC-8 project, Douglas decided that it was better to press on than give up. Consultations with the airlines resulted in a number of changes: the fuselage was widened by 15 inches (380 mm) to allow six-abreast seating. This led to larger wings and tail surfaces and a longer fuselage. The cost of the program was enormous; it was at that time the most expensive venture of any kind ever taken on by a single company. Donald Douglas provided $450 million towards it out of his own pocket.
The DC-8 was officially announced in July
1955. Four versions were offered to begin with, all based on the same 150 ft 6 in (45.9 m) long airframe with a 141 ft 1 in (43 m) wingspan, but varying in engines and fuel capacity, and with maximum weights between 120 and 130 tons. The maiden flight was planned for December
1957, with entry into revenue service in
1959. Well aware that they were lagging behind Boeing, Douglas began a major push to market the product.
Worldwide, piston-engined airliners still ruled. The French 90-passenger twin jet
Sud Aviation Caravelle prototype had just flown for the first time, the Comet was still grounded and the 707 wasn't expected to be available until late
1958. The transition, when it came, looked likely to be one to turboprops rather than turbojets. The pioneering 40–60-seat
Vickers Viscount was already in service and proving enormously popular with both passengers and airlines: it was much faster, quieter and more comfortable than piston-engined types. Another British aircraft, the 90-seat
Bristol Britannia, was establishing a fine reputation, and Douglas's main rival in the large, piston-engined passenger aircraft market, Lockheed, had committed to the short/medium range 80–100-seat turboprop
Electra, with a launch order from
American Airlines for 35 and other major orders flowing in. The major airlines were reluctant to commit themselves to the huge financial and technical challenge of jet aircraft. On the other hand, no-one could afford
not to buy jets if their competitors did. And there the matter rested until October
1955, when
Pan American placed simultaneous orders with Boeing for 20 707s and Douglas for 25 DC-8s. To buy one expensive and untried jet-powered aircraft type was brave: to buy both was at the time, unheard of.
In the closing months of
1955, other airlines rushed to follow suit:
Air France,
American,
Braniff,
Continental and
Sabena ordered 707s;
United,
National,
KLM,
Eastern,
JAL and
SAS chose the DC-8. In
1956 Air India,
BOAC,
Lufthansa,
Qantas and TWA added over 50 to the 707 order book, while Douglas sold 22 DC-8s to Delta, Swissair, TAI,
Trans-Canada and UAT.
By the start of
1958 Douglas had sold 133 DC-8s as against Boeing's 150 707s. Nevertheless, the pattern from that time on would be for the DC-8 to sell in modest numbers, while Boeing sold roughly twice as many 707s. The first DC-8 was rolled out of the new factory at
Long Beach in April 1958 and flew for the first time in May. Later that year an enlarged version of the Comet finally returned to service — but too late to take a substantial portion of the market: de Havilland had just 25 orders — and in October Boeing began delivering 707s to Pan Am.
Douglas made a massive effort to close the gap, using no less than ten individual aircraft for flight testing to achieve
FAA certification for the first of the many DC-8 variants in August
1959. Much had needed to be done: the original air brakes on the lower rear fuselage were found ineffective and were simply deleted as engine thrust reversers had become available; unique leading-edge slots were added to improve low-speed lift; the prototype was 25 knots (46 km/h) short of its promised cruising speed and a new, slightly larger wingtip had to be developed to reduce drag.
The DC-8 entered revenue service with both
Delta Air Lines and United in September 1959. By March of
1960, Douglas had reached their planned production rate of eight DC-8s a month.
On
August 21 1961 a Douglas DC-8 broke the
sound barrier at Mach 1.012 or 660 mph while in a controlled dive through 41,000 feet. The flight was to collect data on a new leading-edge design for the wing. The DC-8 became the first civilian jet to make a supersonic flight.
(External Link
) The aircraft was a DC-8-43 later delivered to
Canadian Pacific Air Lines as CF-CPG.
Despite the large number of DC-8 early models available, all used the same basic airframe, differing only in engines, weights and details. In contrast, Boeing's rival 707 range offered several fuselage lengths: the original 44 m 707-120, a 41 m version that sacrificed space to gain longer range, and the stretched 707-320, which at 46.5 m overall had 3 m more cabin space than the DC-8. Douglas steadfastly refused to create stretched or shortened versions of the DC-8, and gradually lost market share to Boeing. After an excellent start, 1962 DC-8 sales dropped to just 26, followed by 21 in
1963 and 14 in '64, and most of these were for the Jet Trader rather than the more prestigious passenger versions. Despite fair sales for the DC-8 and excellent results from the twin-jet DC-9 program, in 1967 Douglas was forced to merge with
McDonnell Aircraft Corporation to become
McDonnell Douglas (MDC).
Further developments
In April 1965, Douglas announced belated fuselage stretches for the DC-8, with not just one but three new models, known as the
Super Sixties. The DC-8 program had been in danger of closing with fewer than 300 aircraft sold, but the Super Sixties brought fresh life to it. By the time production ceased in
1972, 262 of the stretched DC-8s had been made. With the ability to seat 269 passengers, the DC-8 was easily the largest airliner available, and remained so until the
Boeing 747 arrived in 1970.
All the earlier jetliners were noisy by modern standards. Increasing traffic densities and changing public attitudes led to complaints about aircraft noise and moves to introduce restrictions. As early as
1966 the
New York Port Authority expressed concern about the noise to be expected from the then still unbuilt DC-8-61, and operators had to agree to operate it from New York at lower weights to reduce noise. By the early
1970s, legislation for aircraft noise standards was being introduced in many countries, and the 60 Series DC-8s were particularly at risk of being banned from major airports.
In the early
1970s several airlines approached McDonnell Douglas for noise reduction modifications to the DC-8 but nothing was done. Third parties had developed aftermarket
hushkits but there was no real move to keep the DC-8 in service. Finally, in
1975,
General Electric began discussions with major airlines with a view to fitting the new and vastly quieter Franco-American
CFM56 engine to both DC-8s and 707s. MDC remained reluctant but eventually came on board in the late 1970s and helped develop the 70 Series DC-8s.
The Super Seventies were a great success: roughly 70% quieter than the 60-Series and, at the time of their introduction, the world's quietest four-engined airliner. As well as being quieter and more powerful, the CFM56 was roughly 20% more fuel efficient than the JT3D, which reduced operating costs and extended the range.
Legacy
Throughout its production life the DC-8 was often regarded, unfairly, as little more than a copy of the 707, which outsold it by roughly two to one. But in the longer term the DC-8 proved its value. By 2002, of the 1032 707s and
720s manufactured for commercial use, just 80 remained in service — though many of those 707s wound up converted for
USAF use, either in service or for spare parts. Of the 556 DC-8s made, around 200 were still in commercial service in 2002, including about 25 50-Series, 82 of the stretched 60-Series, and 96 out of the 110 re-engined 70-Series. Most of the surviving DC-8s are now used as freighters.
Variants
Early models
- DC-8 Series 10 For U.S. domestic use and powered by 60.5 kN Pratt & Whitney JT3C-6 turbojets. The initial DC-8-11 model had the original, high-drag wingtips and all examples were subsequently converted to DC-8-12 standard. The DC-8-12 had the new wingtips and leading-edge slots inboard of each pylon. These unique devices were actuated by doors on the upper and lower surfaces that opened for low speed flight and closed for cruise. The maximum weight increased from 120 tonnes to 123 tonnes. 28 DC-8-10s were manufactured. This model was originally named "DC-8A" until the series 30 was introduced.
DC-8 Series 20 Higher-powered 70.8 kN Pratt & Whitney JT4A-3 turbojets allowed a weight increase to 125 tonnes. 34 DC-8-20s were manufactured. This model was originally named "DC-8B" but was renamed when the series 30 was introduced.
