Update-Dornier 328

Intensive research and consultation with airlines in the mid 1980s led to the firming up of the design as a high speed 30 seat airliner. After a delay of some six months, the 328 programme was launched in December 1988, when negotiations had been concluded between Daimler Benz (Daimler Benz’ shareholding has since been assumed by DASA) and the Dornier family. Continued development led to the type’s first flight on December 6 1991 and it is now due for European certification in early 1993 and FAA certification by mid 1993.

In a heavily contested market, a new aircraft needs to be a particularly good design to achieve success. Dornier’s design team has used a no expense spared philosophy, oriented towards superior economy. Particular attention has been paid to providing an aerodynamically clean design, using composite materials in some areas of construction to save weight and increase strength, while a completely integrated glass cockpit of the type up until now not seen on a commuter, six bladed propellers and fuel efficient PW119 turboprops all combine to make this a technologically advanced, high speed, efficient and quiet airliner.

The airframe design is the result of extensive wind tunnel testing, yielding an egg shaped cross section with extended wing fairings and tailcone. The airframe was designed to be as close to the optimum shape for high speeds as possible, the streamlined elongatedfairings over the wing and fuselagejoints, extended tail cone and main landing gear fairing giving an enhanced, low drag design. The wing design, based on Dornier’s earlier 228, is an advanced aerofoil and features triangular tip platforms which limit drag without using winglets. An external rivetless construction, made possible by rivetting ribs and spars to integral flanges, give reductions in drag because of a smooth external surface. Further decreases in drag are a result of placing the engine nacelles high on the wing.

The use of composite materials, where appropriate, has lightened the airframe weight and improved strength. The Dornier 328’s entire rear fuselage, with the exception of the tailcone, is constructed from carbonfibre and Kevlar providing a substantial reduction in weight, although at a higher cost. The use of composites was not always practical, the pressure fuselage was going to be constructed with aluminium lithium alloys, giving an estimated saving in weight of 50kg on conventional aluminium, however Dornier felt the risk was commercially and technically too high to take.

The third factor in producing a high speed yet efficient aircraft is the engines. Dornier selected the Pratt and Whitney Canada PW119 turboprops, a member of the proven PWIO0 series. The PW119 features modified hot end hardware and uses a reduction gearbox of higher capacity with three, instead of two, mounting pads. Acompound reduction gearbox delivers maximum power at a low propeller speed. The PW119 is rated at l,815shp.

The 328’s powerplants drive innovative Hartzell six bladed propellers, which make extensive use of composite blade technology. The blades are made of graphite composite and offers a weight reduction in the order of 40% when compared to blades of conventional construction, and also feature a high strength to weight ratio.

An improved performance kit option is also available for the 328 and features uprated PW119s of 2,180shp and roll and ground spoilers, combining to give the aircraft a short field performance, with a runway takeoff distance of only 2,720ft (830m) and a landing distance of 2,450ft (760m) at sea level in ISA conditions.

The use of an exceptionally clean aerodynamic design, composite materials and the PW119 give the 328 impressive performance, with a maximum cruising speed of 345 knots (640km/h) at 25,000 feet (7,620m), and a range with 30 passengers of 700nm (1,300km). The high cruise speed means that on a sector of up to 600km the 328 is only minutes slower than jets, while having substantially lower operating costs. Required takeoff and landing distances are also impressive, as are approach speeds to airports, which are equivalent to those of jet aircraft, thus contributing to reduce airport congestion and aircraft operating costs.

Passenger comfort and interior space was one of the major design criteria of the 328 programme. The cabin is claimed to be the roomiest in its class with a width of 7. 16ft (2. 18m) and a height of 6. 16ft (1. 88m), providing standing room for most people. Depending on the specifications required by the operator, the Dornier 328 can be fitted with a meals galley, toilet and wardrobe, while in the rear of the cabin is a capacious baggage compartment. Various combinations of this equipment allow the 328 a maximum seating capacity of 33. Large overhead bins are fitted throughout the cabin.

Reductions in cabin noise was another important design consideration, and Dornier claims that it has achieved the quietest cabin of any turboprop airliner, with an estimated noise level of 78dba over 75% of the cabin. This has been achieved by using spring mass systems which counter vibrations, noise-absorbent materials, low speed propellers and by locating the propellers further away from the fuselage than is usual.

For pilot ease, the 328 features the advanced Honeywell Primus 2000 integrated avionics system which is comparable to systems found on modern jet airliners such as the MD-11 and A340. The cockpit features five 7 x Sin display screens which electronically present flight instruments and are flexible enough so that information can be transferred from screen to screen, negating the need a sixth screen. As well as being substantially lighter than conventional cockpits it will feature improved flexibility and reliability. The Primus system features advanced options such as global positioning, turbulence detection devices electronic flight instrument system (EFIS), an automatic flight control system and flight management, while in the future it will be able to be expanded to include a Microwave Landing System and a Traffic Collision Avoidance System.

One further option for the 328which is currently available is the Flight Dynamics head up guidance system which will enable the 328 to land in CAT IIIa conditions with 700ft (214m) runway visibility and a 50ft (15m) decision height, without the need for a more costly autoland system. Without the optional head up display, the Dornier will be able to operate under CAT II conditions, which equates to takeoffs and landings with a minimum of 1000ft visibility.

The 328 is a German design, although it is the subject of international collaboration, with forty per cent of the aircraft being constructed by subcontractors. Notably, Daewoo Heavy Industries of South Korea is responsible for construction of the airframe, Aermacchi the nose while Westland is in charge of constructing the engine nacelles. Israeli aircraft industries has recently been awarded a contract to build the wing.

While the basic 328 heads for certification in the new year, Dornier is also studying future variants of the 328 which may well see it becoming the basis of a family of regional airliners. Most study has been devoted to a stretched 328, which Dornier has dubbed the 328S. The proposed 328 Stretch would feature two fuselage plugs, increasing the length of the fuselage by 20ft (6m), with a wing stretch of 8ft (2. 5m) which would give the 328S a passenger capacity of 48 seats.

However, there are two key points that Dornier needs to keep in mind before launching a stretched 328. Firstly the 328S would compete with the ATR42. The ATR consortium and Dornier’s majority shareholder Deutsche Aerospace are currently involved in a joint venture aimed at producing jetliners in the 70-130seat class. Secondly, a stretched 328 would also compete against the Saab 2000, which has a projected cruise speed of 365kt (676kmh), while the 328S would lose the benefits of the standard size 328’s speed advantage, as the 328s would cruise at a slower 345kt (639kmh). However, the 328S would offer a high degree of commonality with existing 328 operators, as well as enabling Dornier to reduce construction costs by having a family of similar airliners in production, taking advantage of economies of scale. A wider 328 featuring four abreast seating has also been proposed. At this stage though, it seems that the fate of a stretched 328 will be secondary to the success of the 328 programme, as it already has achieved significant orders, most notable being that of Alaskan subsidiary Horizon Air’s order for 60 (35 firm). Orders stood at a healthy 78 with 70 options, including one order for an executive version. However, with the collapse of Midway who ordered 33 and 40, orders now stand at a fair 45 firm and 30 options. With the 328, Dornier certainly has an excellent product and as long as airlines do not find it cost prohibitive, it should do well