Update – Jetstream J41

J41’s overall length is 19.25m (63’2″), an increase of 4.88m (16’1″) over the original J31 model with fuselage plugs having been inserted fore and aft of the wing, lengthening the cabin to allow an additional 10 seats. The additional length forward of the wing section contains a 1.42m x .74m (56″ x 29″) passenger door with integral airstairs, a notable improvement from the J31’s rear access arrangement. The section added aft of the wing contains a Type II emergency exit. Extra room in the aft fuselage has created a 4.81m3 (170cu ft) baggage hold with an inward and upward moving cargo hatch, allowing easier ramp handling without conflicts between passenger and baggage loading flows. The 18.29m (60’5″) wingspan incorporates an increased wing area, fuel volume (3306 litres/2638kg usable fuel) and improved flap span and chord. The tail plane area of the J41 has also been enlarged. A wing root fairing provides an additional 1.35m3 (47.5cu ft) of baggage area aft of the wing, with two doors either side, as well as easy access to air conditioning and hydraulic systems for routine servicing and maintenance.

Powerplants

The most recent version of the J41 employs two Garrett TPE331-14 engines, flat rated at 1650shp (1231kW) driving five bladed counter-rotating propellers. The swept tips of the McCauley variable pitch propellers combined with synchronising and synchrophasing systems account for much of the aircraft’s low interior and exterior noise levels. The J41’s certificated noise levels are below industry requirements, with an approach noise level of 87.8 EPNdB and a flyover level of 85.8 EPNdB. The Automatic Power Reserve System (APR) of the J41 extends the flat rated power limit to 36 degrees Celsius at sea level by automatically increasing the power of the live engine by up to 11% after an engine failure at takeoff. When APR has been armed for takeoff, the propeller of a failed engine is feathered automatically. An automatic engine starting system is incorporated to minimise departure times and ease operation. The system is controlled and monitored by an integrated ignition control system which can be manually overridden if required. The Garrett engines feature a high degree of modularity to provide easy on-wing servicing and maintenance, comprising nose cone, gearbox and accessory drive module, compressor, combustor and turbine module.

Cabin

While retaining the three abreast seating layout, the cabin’s appearance is markedly different from earlier Jetstream models, and the manufacturer’s considerable efforts to create a light and roomy atmosphere have succeeded. The skilful application of lighting, wall panel sculpting and environmental systems aboard the aircraft continues to receive applause from passengers. Pressurisation is regulated by an ABG Semca system, maintaining a cabin altitude of 8000ft at a maximum operating altitude of 26,000ft. The wing root aisle step of the J31 series has been removed with the use of the continuous torsion box wing section, allowing an uninterrupted aisle with a clear height of 1.78m (5’10”) and a 0.45m (17.7″) width suitable for cabin service trolleys. Standard configuration for 29 passengers provides a seat pitch of 76cm (30″), with an optional arrangement of 30 seats with similar pitches achieved through the modification of the aft galley. An optional forward galley arrangement is also available. Flight attendant facilities and an externally serviced toilet are located aft adjacent to the baggage area which can also be accessed from the main cabin. Carry on stowage capacity has been increased, with under seat space having been significantly improved through the use of space saving seat supports. Storage compartments are located at the front and rear of the cabin. The overall baggage capability of the J41 is a generous 0.25m3 (9cu ft) per passenger. Under evaluation is a QC version of the J41, allowing an operator to gain maximum utilisation of the aircraft with passenger services during the day and overnight freight services, such as those currently being operated by many third level airlines.

Flight Deck And Avionics

One of the major improvements invested in the J41 is the flightdeck which has been designed for maximum crew comfort and ergonomic efficiency. Incorporating a Honeywell EFIS suite, the instrument panel features four 5×6 inch four tube units within a SPZ-4500 avionics package. The system components include:

EDZ805 Four tube EFIS AHS600 (Dual) Altitude and heading reference systems (AHARS) DC800 Digital air data computers Primus 650 Colour weather radar RT300 Radio altimeter system Primus II Digital audio integrated radio system Yaw damper

The DFZ-450 digital flight control system integrates the flight director, optional autopilot and trim functions. The three axis autopilot is capable of both Category I and Category II landing minima. The avionics suite is supported by multiple redundancy together with a suite of standby instruments comprising dual RMIs, artificial horizon with ILS pointers, ASI, altimeter and compass. The windscreen has been redesigned into a V shape to improve aerodynamic flow, replacing the multi-section screens of the earlier J31s. The control columns of the J41 are floor mounted, replacing the J31 panel mounted units.

Continual Improvements

Much of Jetstream’s work in its constant evaluation of its products is borne from the continual interaction between the manufacturer and its customers worldwide. Information from operator conferences and data collection is applied to fine tuning the Jetstream product on a perpetual basis, and the latest derivative of the J41, a heavier design weight and improved power version, appears just fourteen months after the type’s FAA certification in April 1993. The J41 has recently been made available featuring increased design weights, the uprated Garrett at 1650shp and a zero degree flap setting creating an aircraft ideally suited for hot and high Australian operations. Design weights have been increased, with aircraft delivered from mid 1994 featuring MTOW of 10,896kg (24,000lb) +454kg/1000lb, MLW 10,532kg (23,200lb) +454kg/1000lb and MZFW 9716kg (21,400lb) +318kg/700lb. Together with uprated 1650shp (1231kW) engine flat rating with Continuous Power Augmentation (CPA), these improvements allow for a 3295kg (7258lb) maximum payload over an IFR range of 774nm, and a 636kg (1400lb) typical improvement in hot and high useful load. At 1650shp (1231kW) and 9 degrees flap, the J41’s field performance will uplift a MTOW of 10,896kg (24,000lb) in a little over 1450 metres, and with 15 degree flap within 1310 metres. Despite the performance advantages of the increased design weights, there have been no changes to the structure of the aircraft. Field performances with zero flap settings have been successfully tested in Madrid, ensuring that V2 speeds are optimised for best Weight Altitude Temperature (WAT) performance. Combined with the impact of continuous power augmentation the final takeoff climb segment is no longer critical, and improves the WAT limit by 90 to 160kg (200 to 350lbs). A further modification has been made to the J41 as part of Jetstream’s commitment to continually improving its aircraft, with a revised static plate location providing takeoff speeds with V1 < Vr. Due for certification in the third quarter of 1994, any new aircraft destined for Australia would be delivered with this feature which will further complement the aircraft’s performance.

Competitive Edge

The J41’s fuel burn characteristics compare more than favourably with other regional aircraft in its class. Over a 150nm (278km) sector at high speed cruise (295kt/ 547kmh), the J41’s relative fuel burn (according to Jetstream) compared with the Embraer Brasilia represents a 6.7% reduction, the Dornier 328 a substantial 27%, the Dash 8-100 23%, while the Saab 340B, Jetstream 41’s closest competitor in fuel burn, has a 1.6% higher fuel burn. The J41, as a 29 seat aircraft, requires only three passengers more than a 19 seater to break even, comparing favourably with the (admittedly larger) Dash 8-100 which demands 7.3 additional passengers as breakeven, and the Saab 340B +6.1. For many local operators, Jetstream’s proposal that the J41 is a natural growth successor to 18/19 seat aircraft providing ‘least risk’ and low breakeven load, would appear to be an indicator of the aircraft’s ability to move into growing markets such as the regional industry in Australia.