Update – BAe Jetstream 41

Supply and Demand

Despite its relatively short production life, the Jetstream found itself in great demand by US operators during the 1970s, although the Astazou with its marginal hot and high performance and low TBO was a problem and a number of aircraft were re-engined with either TPE331s or Pratt & Whitney PT6s. Sensing an opportunity to take advantage of the burgeoning, deregulated US commuter market, the newly formed British Aerospace in 1978 decided to re-launch the Jetstream with 900shp (later 940shp) TPE331-10 engines, increased weights and other refinements as the Jetstream 31 with production based at Scottish Aviation’s Prestwick facility. Scottish Aviation became BAe’s Scottish Division, a prototype Jetstream 31 (converted from a Handley Page built aircraft) was flown in March 1980, the first true J31 followed in March 1982 and deliveries began later in the same year.

Since then, more than 300 Jetstream 31s have been sold, most of them to US commuter operators and the aircraft has captured the lion’s share of that country’s 19 seat pressurised commuter market. The basic J31 was joined in 1988 by the Super 31 with 1,020shp TPE331-12 engines, increased weights, improved performance and modified interior design. The original Jetstream 31 went out of production in the second half of 1989; the Super 31 will remain available in conjunction with the stretched J41, at least for the time being.

The Matched Pair

In launching the J41, British Aerospace is placing great emphasis on its commonality with the short fuselage Jetstreams, its profitability and its placement in the market so as to provide an easy ‘step up’ from the 16 seaters, particularly for those many operators already using the J31. BAe claims the J41 will offer a significant reduction in aircraft/mile costs compared to other 30 seaters whilst retaining similar seat/mile costs to them. The J41 is also cheaper to purchase than its main competitor, the well-established Embraer Brasilia at (in 1989 dollars) $US5. 5m compared to the Brazilian aircraft’s $US6. 0m.

Even though it shares many features with its predecessors, there are nevertheless substantial differences. The cabin cross section of the J31 is retained with its nearly six feet tall ‘walk around’ cabin height and adequate width for three abreast seating in commuter configuration. The extra cabin length is achieved by stretching the fuselage 16 feet (4. 88 metres), 87 inches (2. 21m) aft of the wing and 105 inches (2. 67m) forward of it. An extra emergency exit is incorporated in the port side of the fuselage.

A major change is the passing of the wing completely under the fuselage rather than through its lower parts as in earlier Jetstreams with the resultant intrusion of the main spar into the cabin. Although costing a few knots in speed, the new arrangement does allow an extra 35 cubic feet of baggage to be stowed in the fairings which surround the lowered wing. Rear fuselage baggage capacity is also substantially increased in the J41, to 170 cubic feet, while other external changes associated with the fuselage include a redesigned windscreen, an increased chord rudder and the fitting of a larger fin/fuselage fillet. Inside, the J31’s maximum cabin pressure differential of 5. 5psi is retained, giving an 8,000ft cabin when the aircraft is cruising at its maximum certified altitude of 25,000 feet. Changes m the cockpit include the introduction of floor rather than panel mounted control columns, a function of the incorporation of duplicated control runs.

In the Jetstream 31 both passengers and baggage were loaded though a door on the port side rear fuselage. In the J41 the baggage hold has its own door in that area and passengers will enter the aircraft by an airstair door in the port side forward fuselage. This latter feature will make the type more suitable for freight operations as it provides a forward crew door when the aircraft is used in that role.

The J41’s larger wing houses more fuel (up from 406imp gals/1,846 litres in the Super 31 to 660imp gal/3,000 litres) and incorporates flaps of increased chord. The main undercarriage is also changed from the single wheel units used on the J31 to a dual wheel design which retracts forwards into the powerplants’ redesigned nacelles instead of inwards into the wing roots as before. The undercarriage must withstand substantially higher weights than before, in the case of the J41 a maximum takeoff weight of 22,377Ib (10,150kg), a figure some 38% greater than the Super 31.

It was not until the Jetstream 41 was formally announced that the choice of powerplant was made known. Speculation as to whether it would be a more powerful version of the J31’s Garrett TPE331 or a Pratt & Whitney PT6 variant continued while the aircraft was being developed. The final choice is the Garrett TPE331-14 flat rated at 1,500shp up to 35°C and incorporating automatic power reserve. The engines are ‘handed’ (counter-rotating) and will drive advanced technology five or six bladed propellers of a type yet to be decided. In interesting point is the way the engines are mounted. In the J31 the Garretts were installed inverted (with the intakes visible above the propeller spinners) while in the new model they are ‘right way up’ with the intakes below the spinners.

The powerful Garretts give the J41 field performance equal to or better than the Super 31, substantially higher cruising speeds and useful payload/range characteristics. With 29 passengers on board it is capable of two one hour sectors without refuelling out of a 2,000ft elevation ISA+26 airfield or a single one hour sector from a 5,000ft elevation ISA+20 field.

Maximum cruise speed will be 290-295 knots (537-546km/h), some 35 knots faster than before, and at that power setting the J41 will be capable of flying 50 nautical miles (1,093km) with 29 passengers and their baggage with full lFR reserves. With maximum fuel and a reduced payload of 17 passengers and baggage, the aircraft will be able to fly 1,400 nautical miles (2,600km), again at maximum cruise and with IFR reserves.

The J41 ‘s launch cost of approximately $A270m will be split between BAe and several risk sharing partners. These include Gulfstream Aerospace (wings, as they are already building for the J31), Pilatus (fins, tailplanes, rudders, elevators, ailerons and flaps) and Field Aircraft at East Midlands Airpor t who will be responsible for installation of flight deck instrumentation, avionics, wiring looms, cabin furnishings and external painting of the aircraft. Field has performed similar work on most of the Jetstream 31s but in the case of the J41 will have complete design and manufacturing authority for the cabin and flight deck as well.

The first Jetstream 41 is scheduled to fly in the early northern hemisphere summer of 1990 with deliveries scheduled to commence in the second half of 1991. The J31 and J41 will be built side by side at Prestwick, the smaller variant accounting for 25 to 30 units per annum and the 29 seater around 35 per year initially. With some 100 options already placed, the Jetstream 41 looks set to continue the successes achieved by its smaller predecessors