McDONNELL DOUGLAS has revealed new details of the medium-range twin-engined version of the MD-11 now emerging as an early leader in Douglas Aircraft's (DAC) studies of potential developments of the tri-jet.

The twin would be aimed primarily at the McDonnell Douglas DC-10-30 - and Boeing 767 - replacement market, but would also form the basis for a longer-range version to compete with the Airbus A340-200/300 and the 767-300ERY being studied by Boeing.

DAC's studies also include a possible stretched-medium-range-variant of the MD-11 twin which would fill a capacity niche between the proposed 325-seat A340-400X and the 390-plus-seat Boeing 777 stretch. The aircraft would be in competition with the A330-300 and A-market 777 and also fill gaps on some narrower Boeing 747-200 routes, believes the company.

"The Twin MR [medium range] is certainly the most promising at the moment," says David Murphy, DAC widebody advanced-programmes business-unit manager.

"There's a smaller demand for the Twin LR [long range] and a later demand for the stretch."

If DAC goes ahead with any MD-11 Twin version, it faces a choice between two major development strategies. The first would be the concurrent launch of two linked designs, the Twin MR and LR, for two markets, followed by an eventual move to an MD-11 Twin Stretch. The second choice is to develop an "optimised" Twin MR for a single market followed by sequential growth to a Twin LR and then a Twin Stretch.

The main features of the basic MD-11 Twin include a slighter shorter fuselage, reduced by just over 5m to balance out the removal of the engine from the tail. The wing would also be extended by 3.6m at each tip to increase overall span to just less than 60m. This revised wing is being studied for a possible long-range version of the tri-jet (Flight International, 14-20 December, 1994).

The twin's new vertical stabiliser would be made from composite materials, with further weight savings achieved by removing the centre main-undercarriage position.

Other differences are mainly structural to allow the "linked" Twin MR design to be able to form the basis for the heavier-gross-weight Twin LR. The LR would have 400kN (90,000lb)-thrust engines, against 310kN engines used in the MR.

Finally, the Twin Stretch MR would be stretched with a 5.6m plug forward of the wing and a 5.2m plug aft. The tail would be of the same reduced height as that of the Twin MR and skin gauges would be increased in the centre section of the fuselage. Fuel-tank capacity would also be reduced.

DAC says that the MD-11 Twin preliminary schedule could be compressed into 48 months from authority to proceed (ATP) to first delivery. ATP would follow around 10 months after the MDC board gives DAC the go-ahead to offer the aircraft to airlines. Assembly could begin as soon as 25 months after ATP.

Source: Flight International