Guy Norris/LONG BEACH, CALIFORNIA
McDONNELL DOUGLAS (MDC) hopes to build a lot of future business on its newly launched MD-95. Not only will it lead the attack on the yet-to-be-realised 100-seat market, but the small airliner is expected to form the basis of an entirely new family of twinjets in the 80- to 130-seat range.
Like Boeing, with its phenomenally successful three generations of the 737, MDC hopes to capitalise both on its own hard-won twinjet experience, and the large market it has served with the T-tail family for the last 30 years.
Yet, at the same time, MDC knows that it must move fast to take advantage of its lead over the many amorphous international 100-seat-airliner projects. One of its hardest jobs may be to convince the market that the MD-95 is really new at all, and not just a "warmed-over" DC-9. When major assembly of the first MD-95 begins in May, 1997, it will be almost exactly 30 years to the month since Douglas Aircraft began building the near-identically proportioned DC-9-40.
Naturally, the biggest and most extremely apparent difference between the old and the new is the high-bypass BMW Rolls-Royce BR715 turbofans used on the MD-95. Chosen over Pratt & Whitney's conceptual Mid Thrust Family of Engines in a last-minute competitive struggle, the BR715 holds the key to the MD-95's promised performance.
In terms of reduced environmental impact - one of the fundamental requirements for any 21st-century jet - the engine/airframe combination should score highly. Emissions, particularly those of nitrous oxides (NOx), are forecast to be 40% better than those recommended by the International Civil Aviation Organisation in 1993. Emissions will be cut by a further 33% with an improved low-NOx dual-stage combustor now being developed as a future option. In terms of noise, the aeroplane should slip quietly to almost 4dB below the anticipated levels of any Stage 4 rule - should one materialise.
To achieve the higher thrust requirements of the MD-95, BMW R-R has adopted a larger, 1.42m-diameter fan on the BR715 in place of the 1.22m fan on the BR710 version selected to power the Bombardier Global Express and the Gulfstream V. The larger engine also required a new low-pressure (LP) system consisting of an additional LP turbine stage (to make a total of three), and a two-stage LP compressor.
The 82kN (18,500lb)-thrust variant of the BR715 will power the initial -30 version of the MD-95. Later and larger MD-95 derivatives will be powered by uprated versions of the engine, which is thermodynamically capable of more than 106kN thrust. The first engine shipped is expected to be delivered to MDC's Long Beach assembly line in California in December 1997, a month ahead of the final aircraft-completion deadline. Engines for the longer-range MD-95-50, uprated to almost 100kN thrust, are likely to be delivered around the third quarter of 1999, if MDC goes ahead with this version.
Higher installed weight
The penalty for high bypass and high power is higher installed weight. As a result, the initial MD-95 design incorporated some nose ballast to offset the engine weight. In talks with Scandinavian Airline Systems, and later with launch customer ValuJet, however, MDC decided to stretch the basic fuselage by a total of 1.45m.
The extra length not only eliminates the need for ballast altogether, but increases the seating from 99 to a baseline configuration of 106, 98 of which are economy seats and eight first class. In a single-class, all-economy, layout, the aircraft takes 117 seats at 780-800mm pitch. ValuJet is "looking at 129", which "...is a bit of tight fit", admits MDC.
The final configuration results in an overall length of 38m, which is just one fuselage frame short of the length of DC-9-40. To cope with the aerodynamic changes associated with the stretch, MDC intends to extend the MD-87-based vertical "top cap" by 50mm above the horizontal stabilisers. There will also be a 300mm non-moveable extension added to the trailing edge of each engine pylon "...to help deep stall characteristics", says MDC.
Other physical changes from the basicDC-9-30 include a low-drag fillet for the wing/body join, and an increase in the wing incidence angle to 1.5 degrees, to help cope with the higher take-off weights of the newer aircraft.
The basic -30 will have an operating empty weight (OEW) of around 30,800kg. The -30ER (extended-range) version, fitted with two 2,140litre (565USgal) auxiliary fuel tanks, will have an increased OEW of 31,500kg.
The design OEW has been chosen carefully to meet the optimum range/payload requirements of a 100-seater. According to MDC's calculations, 99.9% of the sectors flown by 100-seaters worldwide cover less than 3,300km (1,800nm). The maximum take-off weights for the basic -30 (52,000kg) and the heavier -30ER (55,000kg) therefore straddle the range/payload line optimised for a 3,300km flight with 100 passengers and baggage.
Based on this criteria, MDC argues that current competing aircraft for this role are either under-designed, in the case of the Fokker 100 (25,500kg OEW), or over-designed, in the case of the Boeing 737-600 (36,400kg OEW) and Airbus A319 (40,400kg OEW). Both the A319 and 737-600 offer much greater range and payload, but MDC argues that these are not required for the typical 100-seater mission.
Based on the trip cash costs associated with a typical 950km-range flight, MDC claims that the MD-95 will be 4.3% cheaper to operate than the Fokker 100, 6.3% less than the 737-600 and up to 11.6% cheaper than the A319. These were compelling figures to ValuJet, which weighed the MDC jet against both Boeing and Airbus products before finally placing firm orders on 19 October for 50.
Compared to the DC-9-30, the MD-95 will have a 13% lower direct operating cost (DOC) on a per-trip basis. "The DOC is up to 22% lower on a per-seat basis," claims Douglas Aircraft MD-95 deputy programme manager, Jerry Callaghan.
As part of its attack on costs, MDC has designed the MD-95 for a 20-25min turnaround time. The average 23min target time could be reduced by a further 4min if operators select the optional ventral stair located in the tail, says MDC. This compares with the current best turnaround time for the MD-80 of around 28min.
A crucial aspect of the drive for lower operating and maintenance costs was the decision to go from buyer-furnished equipment (BFE) avionics to seller furnished (SFE). "Apart from VHF communications radios and audio control panels [which are still BFE], the move to SFE allowed us to go to ARINC 700 digital systems, which basically doubles the reliability," says MDC. The company cites the mean time between-failures of a typical ARINC 700-standard digital radio as between 1,800h and 2,200h, compared with 800h-1,000h for an ARINC 500-type system.
The baseline MD-95 cockpit will be the same as that of the current MD-90, with an optional full "glass cockpit" based around six 200 x 200mm Honeywell liquid-crystal flat-panel displays. The aircraft will be equipped for Category IIIa automatic landing and will be qualified for Cat IIIb as an option, with a head-up-display. MDC says that the avionics architecture gives growth capability "...for both FANS [Future Air Navigation System] and Euronav".
Other new features
Other new features include an integrated-drive-generator-based electrical system and a low-noise APS 2000 auxiliary power-unit from San Diego-based Auxiliary Power International. The aircraft will also have a restyled interior by Austrian-based Fisher, with a new passenger-service unit and 0.7m3 (2.2ft3) of baggage space per passenger.
In common with the other MDC twinjets, the MD-95 will have five-abreast seating and the option of an MD-90-like 600mm-wide aisle, compared with the standard 480mm-wide aisle planned for the baseline.
MDC intends the MD-95 family to cover up to four more derivatives of the basic airframe. The most easily achievable is the extended range -30ER, which will have a maximum range of 3,700km with 106 passengers and bags. Fuel capacity will be 14,600kg, some 3,250kg more than that of the basic -30. The two optional fuel tanks needed to increase the -30ER's range take up cargo volume, which is consequently reduced from 33m3 to just over 24m3. The ER can also be configured with just one tank, which will be simply connected and driven with the existing power from the cabin-pressurisation system.
"Although the focus is on the -30 right now, we think the -50 will probably follow 18 months afterwards. It will wind up being longer than the -30, probably by the same incremental difference as between the DC-9-30 and -40," says Callaghan. The basic MD-95-50 will have a 3,150km range and seating for around 126 in a two-class configuration, or 145 in all-economy.
An MD-95-50ER, which will take the series range beyond 4,000km, is also envisioned. MDC says that it "...might have to get a new wing to get the range", but that decision lies further down the road. Similarly, plans for a 2,600km-range MD-95-20, with two-class seating for around 85, are in the earliest stages.
Work is accelerating on the static prototype, an ex-Eastern Airlines DC-9-30 rescued from the Mojave Desert and fitted with the additional fuselage plug to represent the MD-95.
Using the static model as a design-verification tool for airframe and system changes, MDC is confident of making a relatively trouble-free start to assembly in May 1997.
Source: Flight International
