Profile – McDonnell Douglas DC-10 Part I

American Airlines had strongly supported the use of RollsRoyce engines (adopted by Lockheed) but Douglas decided upon General Electric’s CF6, which was derived from the TF39 as used in the USAF Lockheed C-5A Galaxy, but modified with a new lower bypass ratio single stage fan. Douglas’ decision to use the American engine was fortunate considering the difficulties which later occurred between Lockheed and Rolls-Royce over the latter’s RB211. On February 19, 1968, American Airlines placed an order for 25 DC-10s with an option for 25 more but the company, now McDonnell Douglas after the merger which had taken effect from April 1967, did not feel that this was enough to make a commitment for production. An intensive selling campaign in direct competition with the Lockheed Tristar continued but it seemed that Lockheed had cornered the market when, on March 28, 1968, it announced orders for a total of 144 Tristars with more to follow. McDonnell Douglas now considered cancelling the DC-10 completely but the go ahead was given on April 25 when United Airlines contracted for 30 plus with an option for 30 more. Northwest Airlines followed suit.

First Service

The initial version of the aircraft was designated the DC-10 Series 10 and the very first machine, painted in the Corporation colours and registered N10DC,made its maiden flight on August 29, 1970, from Long Beach, California. It was powered by three 40,000lb st (178kN) General Electric CF6-6 turbofan engines. With a maximum weight of 410,000lbs (185,976kg) fully loaded, the DC-10-10 could carry 255/270 passengers in mixed class accommodation from Boston to Los Angeles.

FAA certification was obtained on July 29, 1971, and the first revenue flight was made by American Airlines on its non stop Los Angeles/Chicago service a week later on August 5. Nine days afterwards, United flew a DC-10 from San Francisco to Washington for the first time. The aircraft had taken three years four months from the decision to begin production to its entry into regular scheduled services.

Structurally, the DC-10 emerged as a cantilever low wing monoplane of all metal fail safe construction with an aluminium alloy semi-monocoque circular cross-section fuselage. The 35 degree swept back wing featured several cross-sectioned aerofoil shapes along its length. At the root the thickness/chord ratio was slightly over 12. 2% altering to less than 8. 4% at the tip. Inboard, the dihedral was 5 degrees and outboard this changed to 3 degrees while incidence ranged from positive at the wing root to negative at the tip. There were full span three position leading edge slats with a gap where the engine pylon was attached and double slotted trailing edge flaps mounted on external hinges with an inboard and outboard flap panel. Forward of the flaps were five spoiler panels at the rear edge of the fixed wing structure. The outboard low speed aileron only operated when the leading edge slats were extended while the inboard high speed aileron was used conventionally. The spoilers operated in unison for lateral control, as speed brakes and ground spoilers. Fuel storage was achieved by using three integral wing tanks holding a total 21,700 US gal (82,1351).

The tail unit was a cantilever all metal structure with power actuated control surfaces. The twin wheel, steerable nose unit of the tricycle undercarriage retracted forward while the main gear, comprising of two 4 wheel bogeys, retracted inward into the fuselage. On the flightdeck there was room for a crew of three -pilot, first officer and flight engineer-with additional seating for two observers. As already stated, the standard mixed class seating arrangement catered for 255/270 passengers but when the economy class only configuration was used an absolute maximum of 380 passengers could be carried. There were also containerised bulk cargo compartments located just forward and aft of the wing with outward opening doors on the starboard side. Another bulk cargo compartment was located in the lower rear section of the fuselage with its door opening on the port side.

Some later DC-10-10s were fitted with 41,000lb st (182. 4kN) CF6-6D1 turbofans. With these engines the DC-10-10 had a maximum cruising speed of 577mph (928km/h) at 30,000ft (9,145m), and a maximum rate of climb at sea level of 2,750ft (838m) per minute and a service ceiling of 35,200ft (10,730m). There were 120 built.

Long-Range Capability

From the outset the Douglas design team ensured that the basic aircraft could be adapted to suit an anticipated variety of roles and it was the capability of the DC-10 to be able to be produced in longer range versions which resulted in it beating Lock heed’s Tristar in terms of incoming sales orders. The first longrange model, the DC-10-20, flew on-February 28, 1972, powered by Pratt and Whitney JT9D-20 turbofans rated at 49,400lb st (220kN).

FAA certification was received on October 20. Twenty two of these aircraft were built for Northwest Orient Airlines but the type’s designation was changed to DC-10-40 when more powerful JT9D-59A turbofan engines were introduced. Each of these was rated at 53,000lb st (236kN). Like the Series 30, the wing span was increased by 10ft (3. 048m) and there was an extra landing gear under the fuselage. The first flight of the Series 40 took place on July 25, 1975.

Japan Air Lines (JAL) was a major customer for the DC-10-40. A total of 41 were built. Early in 1983, FAA certification allowed a Delco Electronics’ Performance Management System (PMS) to be installed which could provide fuel savings from 1-3%. This was connected through the autopilot and autothrottle systems to control automatically the plane’s pitch and thrust for maximum fuel efficiency during climb, cruise and descent. The first machine equipped with this was a JAL Series 40 and a PMS was also installed in a KC-1DA Extender for USAF evaluation.

By far and away the most prolific long-range model was the DC-10-30, a total of 174 (including DC-10-30ERs) being built. This version first flew on June 21, 1972, and was initially powered by three 49,000lb st (218kN) General Electric CF6-50A turbofans; then 51,000lb st (226. 9kN) General Electric CF6-50Cs; and later 52,500lb st (233. 6kN) General Electric CF6-50C1s or C2s; or 53,000lb st (235. 8kN) General Electric CF6-50C2B turbofan engines. To obtain the increased range, the wing span was increased by 10ft (3. 048m) and fuel capacity was increased by introducing four, instead of three, integral wing fuel tanks plus an auxiliary fuel tank in the centre section of the wing with a connected compartment fitted with a bladder cell. This layout and method of storage was used on the Series 40 as well. Total fuel storage of the DC-10-30 was 36,500 US gal (138,1651) and maximum range without a payload was 7,490 miles (12,055km). Range carrying a maximum payload was 4,606 miles (7,413km). An extra twin wheel main landing gear was mounted on the fuselage centreline between the four-wheel bogie units to spread the heavier load. FAA certification for the DC-10-30 was granted on November 21, 1972, at the same time as first deliveries of the type were being made to KLM and Swissair.

A derivative of the Series 30 was the DC-10-30ER two of which were ordered by Swissair in 1980. These machines had their range extended even further by the installation of a 1,530 US gal (5,792 I) auxiliary fuel tank in the rear of the cargo compartment giving a total fuel load of 38,100 US gal (144,2221) which increased their range by 230 miles (370km) over a standard DC-10-30. They were powered by 54,000lb st (240. 3kN) General Electric CF6-50C2B turbofan engines. Swissair also ordered two conversion kits to alter two machines already in service. Another extended range aircraft was ordered by Finnair.

Meanwhile, the Series 10CF and Series 30CFs were convertible freighter versions similar to the basic DC-10-1O and -30 aircraft but designed for an easy change to either passenger or cargo configuration. They featured provision for containers and pallets, conveyors and a loading system, a strengthened heavy cargo floor and a large cargo door in port side.

A DC-10-10CF delivered to United Airlines on September 15, 1982, was the 2,000th Douglas jet transport to be built. The first DC-10-30CF was powered by General Electric CF6-50A turbofans and it flew for the first time on February 28, 1973. It could carry 380 passengers and baggage or 143,000lb (64,860kg) of cargo over an ‘intercontinental’ distance. A total of 23 were built. Later Series 30CFs were powered by 52,500Ib st (233. 6kN) General Electric CF6-50C1 engines.

A variant of the earlier Series 10 was ordered by Aeromexico and Mexicana in mid 1979. This was the DC-10-15 specially designed for hot, high conditions and short takeoffs. It was powered by upgraded 52,000lb st (23,587kg) General Electric CFC-50C2F engines but apart from this it varied little from the standard Series 1O. Altogether 7 were produced, 5 of them going to Aeromexico.

On December 19, 1977, following evaluation trials of the Boeing 747 and the McDonnell Douglas DC-10, the USAF announced its acceptance of the latter to meet its requirements for an advanced tanker/cargo aircraft. The basic airframe chosen for conversion into this role was that of the DC-10-30CF and the first KC-10A Extender, No. 79-0433, made its maiden flight on July 12, 1980.

Changes to the avionics were concerned mainly with omitting equipment required for commercial flying and adding the necessary military equipment such as UHF and secure com systems, IFF, Tacan, beacon transponder and a radar beacon mode. There was an inflight refuelling boom, hose and drogue and 7 bladder fuel cells were housed in the fuselage lower-cargo compartments. The provision of a refuelling receptacle above the flight deck greatly extended the aircraft’s nominal range of 6,000 miles (11,112km) with a 100,000lb (45,400kg) payload. The first aircraft of this type to enter service, No. 79-0434, was delivered to the USAF at Barksdale, Louisiana, for the Strategic Air Command (SAC) on March 17, 1981.

In Part II, the DC-10 goes from boom to bust as the stigma of the early eighties’ crashes take their toll. Don’t miss it!