Airtest – BAe Jetstream 31

Whilst the exterior paint-work showed minor signs of wear, the commuter interior was beautifully presented and showed an excellent standard of finish equal to any airliner.

The Jetstream 31 is a large aircraft and those faint-hearted nervous travellers who shun small aircraft and only fly when there is absolutely no other way possible of getting to their destination, should feel quite at ease. To board, one climbs a five-step airstair, to be confronted by an airy, well-lit, spacious airline interior with full headroom (71 inches), that can accommodate up to 19 passenger seats. The comfortable seats have cup holders and tables installed to give that real airliner feel. At the rear is a full stand-up toilet that closes off from the rest of the cabin by a cleverly devised door that swings across the aisle to give one ample room. There is also ample room for a galley allowing light refreshments to be served on the slightly longer sectors.

The baggage compartment, accessible in flight, is located at the rear of the cabin. There is no exterior access, necessitating luggage loading up the airstair before passengers embark or after they have disembarked.

Noise levels both on the ground and in the air are quite acceptable and one can hold a normal conversation with a person at least three seat rows away. I took the trouble to walk around the cabin and found noise levels about equal throughout, although the sound at the rear incorporated more wind noise whilst the front was dominated by propeller noise. The flight deck, as is the case in most aircraft, is the quietest area. The slow-turning (1590 rpm) new technology Dowty Rotol props have a very distinctive humming sound, not only in the Jetstream but in other installations as well, allowing one to recognise them without reading the manufacturer’s label on the blade.

The flight deck was spacious, well thought out and comfortable. Vision was excellent and all major functions, other than ground steering, could be handled by either pilot. Seats and rudder pedals are fully adjustable so that any size crew will fit.

Ground handling was very stable and the Jetstream had a comfortable large aircraft feel about it although the responsive nose wheel steering and rather efficient brakes require a little practice by pilots to ensure smoothness and passenger comfort on the ground.

On our flight the aircraft was well under gross weight and conditions were ISA.

Once lined up on the runway, and throttles pushed to the stops (a new era in turbine operation), the rudder quickly becomes effective as the aircraft accelerates smoothly to VR, and with a climb indicated airspeed of 140 kts, the Jetstream had a very respectable sustained 2000 fpm plus showing on the VSI. General handling in both low-speed and high-speed configurations was extremely responsive. Captain Spud Murphy, a British Aerospace test pilot, made the handling look very easy during the close formation photographic sequences; his obvious intimate knowledge of the aircraft and the responsiveness of the Garretts allowed him to place the aircraft wherever he wished.

I found the Jetstream to be extremely docile in the stall. There was plenty of warning via the stick shaker and then a positive forward push from the stick pusher. There was no tendency to drop a wing, and recovery was normal.

We descended to 10,000 feet to experience the aircraft’s single-engine characteristics. The Jetstream has an NTS (Negative Torque Sensing) System which takes some of the worry from the pilot when he loses an engine. The NTS will take windmilling prop blades into a zero thrust position when it senses that the engine is not driving the propeller. This reduction in drag allows the pilot more time to come to grips with his predicament. With one engine feathered and the other producing 100% the aircraft was still producing a 500 fpm climb rate at 10,000 feet. All this was achieved with the live engine trimmed out by rudder trim. Restarting the engine presented no problems either; this was simply a matter of retarding the throttle to flight idle and selecting air start. The engine simply unfeathers and winds up to power with the single Red Line computer seeing to the rest.

With the Jetstream in level cruise at 16,000 feet, ITT 650C, 80% torque, fuel flow 660 lbs/hr, we were indicating 205 kts giving a true airspeed of 262 kts. A more economical setting of 70% torque reduced the fuel flow to 600 lbs/hr and the TAS to 242 kts.

The sharply racked nose is not visible from the flight deck giving an unrestricted view of the runway on approach. This lack of external reference requires a little practice to judge one’s angle of attack without cross-referencing to the instruments. Full flap gives the aircraft a nose-down attitude which makes the flair appear very flat, however, the solid undercarriage allows a smooth landing. Reverse thrust and maximum braking assure a short landing.

The airframe, as mentioned earlier, has been in service for quite some time. It should be noted that some of these early airframes were inspected recently and found to have no corrosion damage whatsoever. This speaks very highly of the corrosion protection incorporated. All joints are wet assembled and then followed up with a coat of epoxy primer; then in the lower fuselage areas, where corrosion is likely to manifest itself first, the aircraft is given a coat of polyurethane enamel paint which is fast-dried to provide a hard protective finish.

Commuter operators will be pleased to know that a test programme is in progress which will give the aircraft a minimum life of 30,000 flights, without major structural repair. The airframe will actually be tested to 150,000 cycles, whilst the landing gear has already been tested to 180,000 cycles.

The most significant change in the Jetstream is the engine – the Garrett TPE 331 has now been in service for over 25 million hours, and whilst in the early days Garrett was a little tardy in supporting its products, they now stand right behind it with service centres and representation worldwide. This is particularly so in Australia where Ron Gartenschlaeger masterminds the situation for all Garrett engines.

The TPE 331-10UF-501M is similar to other Garrett engines in being a two-stage centrifugal compressor and a three-stage axial turbine based on a single shaft driving a propeller through a reduction gearbox. The engine is flat rated to 900 shp to 26. 7°C, although British Aerospace are offering a water-methanol injection system for delivery this year, making the Jetstream 31 an ideal aircraft to carry full payloads in high summer temperatures.

One significant change incorporated in the – 10 is that it is of modular construction, breaking down to five main modules, those being the output shaft housing module, the diaphragm module, the compressor module, the turbine module and the exhaust module. The obvious advantages are ease of maintenance and the ability to keep spare modules in place of spare engines; both areas will save the operator money.

Another very significant improvement is the single Red Line Computer which constantly monitors the Exhaust Gas Temperature which in the – 1O’s case is a max 690°C, making the operation of a turbine far simpler than it has ever been before. The engine is so flexible that one can go from flight idle to maximum power in about one second or on the ground, in the event of an aborted take-off, from full power to full reverse. Gone is the ‘kid glove’ treatment normally associated with turboprop engines. This very significant step forward in turbine technology will certainly reduce the sleepless nights an aircraft operator tends to suffer. The problem of ingestion has also been minimised by having the air intake on top.

The powerplant story would not be complete without mentioning the Dowty Rotol four-bladed propeller. These new propellers are of lighter weight and incorporate the advanced ARA-D aerofoil design improving pressure distribution around the aerofoil, in turn reducing noise. As the efficiency of the propellers is increased they permit lower rotational speeds (1591 rpm compared to 2000 in earlier units). This in turn further reduces noise and vibration. All these powerplant features combined with a 6000 hr TBO and 1500 hr Hot Section Inspection programme will make the -10 engine and Dowty Rotol propeller a significant step forward in reducing DOCs for operators.

Three basic civil versions are on offer: Commuter Airliner with an 18/19 passenger convertible interior, able to haul freight or stretchers; Executive Shuttle, a twelve-seat executive transport intended for either the executive charter market or to provide a comfortable Interbase company transport; Corporate Aircraft – in this guise the Jetstream offers a truly opulent interior for its 8-10 pampered passengers in a Falcon 200 size cabin at turboprop economy.

One might wonder how they managed to alter a three-abreast seating arrangement separated by an aisle to a two-abreast seating arrangement. The engineers have in fact cleverly devised a movable air-conditioning duct that runs along the floor. This duct can be moved from the left to the right of the aisle in 90 minutes, thus offering total flexibility. One could, in fact, take up the option of all three interiors, ensuring a true multi-role capability.

AUSTRALIAN AVIATION has computed its own figures based on an annual utilisation figure of 1800 hours. Our figures include DOCs (i. e. fuel, oil, inspection, maintenance and parts and engine overhaul reserves), fixed costs of ANC’s Insurance, two complete crews and total lease recovery. On this basis, the Jetstream would cost $684. 89 per hour to operate.

The present airline fare between Sydney and Melbourne is $372. 40 return for first class and $248. 20 return for economy class. For a corporation that regularly moves executives between these centres this translates to 12 first-class seats with all airline comforts including a stewardess at a cost of $205. 47 per seat return. A significant saving. Or said in another way, if a company moves seven first-class passengers on a Jetstream return journey, they are saving money on transportation.

The freight forwarder will find the Jetstream 31 to be an aircraft with excellent cubic capacity able to haul 1775 kg between Sydney and Melbourne at a competitive 69¢ per kilo.

Obviously, these figures will vary slightly from one operator to another, however, they should provide a sound guide.

In conclusion, British Aerospace are offering an Australian-equipped Jetstream at a competitive $2. 6 million. This is backed by the vast resources of one of the largest aircraft corporations in the world. Marketing and support will be handled ex-factory, dispensing with dealerships. This will give one the benefit of instant contact with factory expertise and lower costs. General spare back-up is also ex-factory with local storage of normal consumables.

British Aerospace has invested $60 million into the Jetstream programme, showing its confidence in the product. This is further underlined by a two-year structural warranty with no limitation on the number of landings or hours flown during that period. The company will produce 18 aircraft in 1983, 25 in 1984, and 36 for 1985 and beyond; although this last figure will be governed by future market demands.

The Jetstream appears to have a good future in Australia.