Airtest – BAe 1000

The latest mark, the Corporate 1000, is a sleek 500mph eight to twelve seater capable of flying 3500nm at 40,000ft in eight hours in the sort of luxury and with the kind of sophistication that until recently was quite unimaginable.

The first DH 125 flew thirty years ago, on August 13 1962. This early business jet was a dumpy six seat Dove replacement powered by two noisy and thirsty little 31201b thrust Bristol Siddley Viper turbojets. Costing just £150,000, it would take nearly three hours to carry barely a thousand pounds payload all of 1000 miles at . 725 Mach (400kts) with no reserves. In fact the -800 uses about the same fuel at cruise as does the original models at ground idle!

In the intervening years the basic design had been improved and refined (in both senses of the word) almost beyond recognition. Range and endurance have trebled, payload has gone up to 1226kg (2700lbs), speed to 460kts (. 80 Mach) and ceiling to FIA30 (although the price is now $13m).

But the Corporate 1000 is more than the latest mark of 125.

This new aeroplane had to be properly non stop trans-Atlantic and transcontinental while the advent of the new multi national Joint Airworthiness Requirements (JARs) virtually meant completely recertifying the machine, so every system and each structural member has been carefully looked at afresh. Gone are the old 125’s rather dated blunt nosed stubby appearance with bump topped cockpit and bulging belly, to be replaced by a much more graceful 16 metre (54 foot) long sleek fuselage with pointed radome, curved windscreens and seven cabin windows per side. But the combination of big ventral tank capacity and high bypass engines hold the key to the major difference between the Corporate 1000 and the earlier BAe 125 range. And the operative word is range. With proper individual gauges the two underbelly tanks now hold an extra 635kg (1400lbs) over the -800’s single tank. Most importantly, the titchy Vipers, replaced by 37001b Garrett TFE 731s in the -700, have been completely superseded by a pair of new, more economical, 52251b thrust Pratt & Whitney PW305, 4. 5 to 1 bypass ratio, two spool turbofans with Rohr hydraulic thrust reversers and dual channel full authority digital engine control (FADEC) disposing of mechanical links between throttles and engines.

Nevertheless the family’s highly successful basic layout has been retained, with the emphasis on simplicity, its ruggedness exceeding that of much of the smaller opposition. Amongst other things JAR 25 required the incorporation of dual, splittable, separately routed channels in the manual flying controls and the DC (rather than AC) electrical power system normally works as two separate halves, parallelled only in the event of generator failure. The -700’s enlarged fin, improved undercarriage doors and row of fifteen small vortex generators ahead of the ailerons remain, as do the -800’s EF1S equipped ‘glass’ cockpit and span increase from 14. 3m (47ft) to 15. 6m (51. 3ft), while the draggy old style chordwisefences have been replaced by small vortex inducing vortilons under the mid span leading edges.

TKS de-icing is retained for wing and tailplane leading edges and now also the chunky stall wedges which, having been moved inboard to get them out of the way of the vortilons, have ended up ahead of the intakes. The bigger 43 litre tank now holds enough fluid for 137 minutes continuous use and the outboard leading edges are now formed from laser drilled titanium for a cleaner profile.

A more capable Turbomach APU provides ground electrical power and efficient air conditioning as well as boosting the batteries for truly independent starting. With auto shutdown the APU can be left unattended, although it does not have auto fire extinguishing. Strangely for a twin it is only available on the ground when it might have a useful inflight role in the event of engine or generator failure over the Atlantic on a dark and stormy night! A larger emergency oxygen supply has been installed and the bottles are now in the nose, both to get them away from possible engine burst damage and to compensate for the two big eighty pound NiCad batteries (which are hoisted into their undertail stowage by an onboard winch).

JARs also called for the pronounced abradable aluminium honeycomb keel to protect the enlarged ventral tanks which are ‘as strong as the wing’. Underbelly tank size is now 1380kg (3040lbs) to give that long fuel total of 5175kg (ll,440lbs 1425gals). The original simple system remains, ventral fuel being transferred by jet pumps to wings when there is sufficient room (not too soon or the excess will overflow) then electric pumps in the wing tanks supply the engines. The pressure refuelling point is under the tail with its simple controller accessible from ground level just inside the main door.

Our mount, G-LRBJ (Long Range Business Jet?), the first production machine, was painted in diagonal stripes of (curiously) Volkswagen blue, diluted with 10%, 30% and 700/4 white to get the lighter shades. Parked on Hatfield’s ramp among the other 125s it dwarfed the little Lears and Citations.

A walkround confirmed the high build quality but did reveal an apparent abundance of parasite drag from big flap hinge fairings, airbrake hinges, triple rooftop bumps ahead of the heat exchanger inlet, external aerials, ventral chine, vortilons, vortex generators and other odd lumps and bumps. The tiny vortilons look like the remains of podded engine pylons and seem slightly vulnerable protruding as they do ahead of the leading edges. With a modest 20 degree sweepback and efficient double slottedflaps there is still no need for leading edge slats or flaps. A new feature is the external baggage hatch particularly requested by American operators. Small, just ahead of the left engine intake and right over the trailing edge it seemed awkward to get luggage up into and neatly positioned so that a dropped suitcase would damage the flaps.

The single most important feature of the whole 125 series is its high wide interior, made possible by setting the fuselage on dished triple milled metal from the solid wing spars for an unimpeded aisle. The good 1. 75m headroom is far superior to the cramped space in many other bizjets and you can almost stand upright inside. Entry is up handrail-equipped steps built into the back of the spring balanced door (no interior space is wasted, the treads incorporate stowages and a work surface folds down over it when shut). Immediately inside is a 36kg, three cubic metre wardrobe and wood veneered modular galley with conventional oven, sink, fridge, beverage maker and cupboards for china, cutlery and British Aerospace cut glass crystal ware and decanters. Aft of this, the CD player or optional VCR feed music to the superb inflight passenger address system or each seat’s headphone socket.

Interior layout and furnishing are of course to the customer’s personal taste but G-LRBJ’s roomy 1. 8m wide cabin is decorated with Rover designed light grey sidewalls and white ceiling panels. In the forward cabin are four swiveling, reclining, grey Connolly hide imposing armchairs in opposing pairs with pull out tables between them. A slightly less luxurious three person couch faces a fifth in the rear half. The individual seats are comfortable in the extreme, moving both fore and aft and laterally with headset socket, music selector, cup holder, pull up headrests floor level odds and ends drawers under their lifejacket stowages.

One seat has a flight deck intercom which can be patched to the HF for inflight phone calls. Above each seat is a gold plated air vent and reading light, while the sidewalls, like the galley, wardrobe and aft bulkhead, are decorated with beautiful honey warm wood veneer, all from the same specially grown tree and again trimmed with gold plate. BAe are keen to point out they damage no to rainforests in the interests of the opulence of this superior interior. Gold plated seat belt buckles complete the slightly unreal air of sumptuousness.

At the rear of the stylish 7. 4m cabin is a smaller 18kg wardrobe and a sliding wooden door which encloses a neat, fully appointed proper flushing toilet with what else but gold plated ashtray, taps and plug in a real china sink. When pressed in the right place a full length mirror in the lavatory’s aft wall swings forward to reveal a 10 centimetre thick door into the 14 cubic metre, 227kg baggage compartment complete with spare wheel. This light but strong door is part of the secondary pressure bulkhead required by JAR 25, the main one being in line with the engines and though possibly vulnerable in the event of an uncontained rotor burst.

Going forward, George Ellis, BAe’s 125 project test pilot introduced me to the cockpit which is neat, smart, bright and not unlike a smaller version of an airliner’s although the view through the curved windscreens is no better than from many such and worse than from some. It has those peculiarly British, supposedly ergonomic, ram’s horn yokes and comfortable !PECO crew seats with a rather low plug-in jump seat normally stowed in the wardrobe. A handy underfloor stowage holds six Jeppesen books and there are useful chart clips on the window sills. Again, systems are laid out logically airliner like, mostly on the triangular overhead panel, with autopilot controls on the glareshield, a compact centre console and the majority of circuit breakers behind the first officer’s seat.

The Honeywell SPZ-8000 instrument layout is a combination of modern EFIS and old ‘pneumatic/clockwork’ dials with twin Laseref ill laser ring gyro Inertial Reference Units (IRUs), Flight Management Systems (FMSs) and single GPS. The centre panel’s screen will show a north-up map display of present position which is useful for inflight orientation or it can display checklists (although this gimmick seemed no more convenient than the card kind and often more laborious). The usual dual radio fit is supplemented by a single HF set and controlled by a pair of neat digital radio management units above the FMSs.

Secondary controls are logically arrayed and the throttles, although now little more than rheostats, look and work normally but have six detents. Moving them from off to idle for starting or vice versa means first pushing a thumb catch, thereafter progression up the quadrant through CR (cruise), MCT (max continuous thrust, max climb thrust and derate takeoff thrust) to TO (takeoff) is straightforward but for absolute full power (MAX) they have to be forced up a six kilogram ramp. Battery starting power is supplemented by the APU generator and each engine takes about fifty seconds to achieve idle – a little more than some corporate jets but much less than scheduled flights. The operation is simple, select idle and hit the start switch. That’s it!

Putting your head to the window you can see the wingtips for taxying clearance and a slight power increase to 40% Nl is enough to get the show on the road. The hydraulic steering, controlled by a single star wheel on the captain’s left console, turns the nose wheel through 45 degrees to provide excellent manoeuvrability on the crowded ramp. Both steering and brakes need careful handling at first but neither are unduly sensitive, the most noticeable feature taxying along Hatfield’s uneven peritrack being the stiff legged, short travel undercarriage’s ability to transmit every bump to the occupants.

With an APS weight of 8081kg (17,800lbs) and five passengers totalling 397kg (875lbs) we weighed 11,202 kg (24,675lbs) with 2700kg of fuel (enough to reach most of Europe and a useful return fuel figure for many nearby destinations). Maximum takeoff weight of 14,074kg (31,000lbs) would have encompassed all eight passengers and 163kg (360lbs) of baggage plus full (5193kg, ll,4401bs) tanks although we could only have lifted 13,710kg (30,200lbs) from Hatfield’s 1824m runway on this day with the prevailing ten knot headwind.

Either zero or 15 degrees of flap can be set for takeoff and we selected 15, using derate power because full power means turning off the air conditioning pack to reduce bleed air demands. Whilecommon on airliners for twenty years,reduced power takeoffs are new to business jets and this was still in the process of certification. The effective thrust reduction is only about 10% so at our comparatively light weight of 11,202kg (24,675lbs,) feeling for the MCT detent and checking Nl rpm at 92. 2% both engines and aircraft accelerated well and we quietly used just three quarters of Hatfield’s 1823 metre runway. Corporate 1000s will generally use 21% less runway for a given range than a 125-800.

The PW305s have an automatic power reserve (APR) system which, in the event of engine failure, increases the remaining engine’s power by around seven per cent to the flat rated level at temperatures above 19°C. This can also be achieved manually by firewalling the throttles up their ramp. The other handy engine failure assist fitted to the 125 series is the rudder bias system which, taking bleed air tappings off each powerplant to a pair of pistons in the control circuit, applies about half rudder in the required direction to reduce foot loads. This is rather less than the assistance available on earlier marks because the thrust varies in a different way with height and the old enthusiastic autopush would have required opposite rudder at greater altitudes.

At the precomputed speed of 124kts a reasonable pull rotated us to the required twelve degrees and, quickly retracting gear and flaps, a clean climb of 3300fpm was indicated at 200kts. Enroute climb speed is 250kts, changing to . 68 Mach at 31,000ft and with MCT set at 8000ft we were doing over 3000fpm. Throttling back to just CR still gave us 2600fpm. BAe quote a time to 35,000ft at max takeoff weight of 21 minutes which, on the basis of our performance, seems about right.

Levelling at FL350 the OAT was -53°C (ISA+l) and with MCT set, our speed slowly built to . 79 Mach for a TAS of 456kts at 96. 5% Nl and 690°C I’IT (interturbine temp) with an indicated fuel flow of 950lbs per hour per engine and some airflow noise. Reducing to CR showed a slight drop in speed to M. 78 and 451 knots with a usefully reduced combined consumption of 1800lb/hr. A long range cruise of M. 70 is more normal, giving a book TAS of 403kts and fuel flow of 1250lb/ hr. At this speed I was truly surprised by the lack of vibration or movement and the silence of both cockpit and cabin at altitude. With neither wind nor airconditioning noise it was quieter than I have experienced in any aircraft and the passengers remarked that it had been possible to converse in normal voices even during the takeoff Although the pressurisation is controlled by pneumatics, both it and the extremely capable air conditioning worked faultlessly, the only noticeable odour being experienced on starting the APU when taxying downwind after landing. The generous windows and light interior trim combine to make this ultra-civilised cabin eminently comfortable for the eight hour leg lengths of which it is capable. High altitude flight would normally be managed by tli. e comprehensive autopilot which usually climbs the aircraft following an FMS generated vertical navigation profile and cruises it along a predefined track derived through the FMS from the twin DME updated inertial platforms and GPS. Llke its predecessors, for simplicity the BAe 1000 has all manual unboosted controls and it is quite feasible to fly it by hand at high speed although both elevator and, in particular, the ailerons are much heavier than at low speeds. Pitch stability is good and laterally the bank angle stays exactly where it is left. Yaw stability is fine even with the Yaw-damper out although a slight directional uncertainty reminds of its disengagement. Development of the 1000 was slightly delayed by the need to prove faultless handling to Mach . 87, allowing a Mmo of . 80 for cruise. The trouble was an insistent buffeting – cured by resetting the tailplane at a slightly reduced angle. Opening the throttles to MCT and lowering the nose slightly allowed the speed to build gradually through the ASI’s warning red line past . 815 Th1N when the horn abetted the onset of slight buffet up to . 84. Out of the comer of my eye I saw the trim wheel rolling forward as the speed increased to fulfil its new Mach trim function and counteract any tendency towards tuck, otherwise the excursion was uneventful.

Descent is normally flown with idle at . 76 Mach and 280kts giving a rate of 2600ft per minute for the usual three miles per thousand feet angle. The hydraulic airbrakes (on both top and under-surface of the wing) cause no noticeable pitch change while increasing the descent to 5500fpm. At 15,000ft we levelled off to investigate the stall but, with a clean airframe and high residual thrust, the speed took some time to bleed off. The controls are much lighter and nicer below 200kts and remarkably little trim is needed with reducing IAS. The gear warning horn sounds at 162kts and, leaving the trim as set at 145kts, a firm but not heavy pull was needed to induce the clean stall. At our reduced weight of 9761kg (21,500lbs) this was presaged by the stick shaker at 115kts and, preceded by slight real airframe buffet at 15 degrees nose-up, was defined by the over enthusiastic stick pusher, wrenching the controls from my hands at 107kts. George says the 125 series does not suffer from deep stalls, the aeroplane exhibiting normal stick force characteristics and proper pitch down and the pusher is there only to enforce absolutely unmistakable symptoms but this over violent, irresistible, ten degree lurch seems rather extreme and causes much greater than necessary height loss. The results are not too bad in the cockpit but passengers would be thrown around the cabin. Fifteen degrees of flap delayed the shake to 107kts and stall to 101. Control is still fine and the ailerons work normally right to the push. Flap 25 and undercarriage get stall speed below lO0kts and with gear and full flap it becomes 94 with a battle against the pusher to keep the nose up anywhere near the horizon. Although the engines’ rpm subsided to 41% during these manoeuvres, they always responded promptly for recovery. Thanks to the vortilons, stall speeds are said to be a few knots lower than on previous models at comparable weights.

Returning to Hatfield for a tailwind ILS on 24 I found the aeroplane easy to establish and fly down the slope although it is understandably more lively in the bumps than a large jet and the pink ‘speed trend vector’ line tends to constantly shoot half an inch up and down from the ASI datum in gusts. Selecting flap 15 at 200kts causes an easily countered pitchup, subsequent settings induce the normal nose down pitch and the undercarriage causes no apparent trim change at all. Breaking off at 1000ft to circle for 06, using the very useful instantaneous wind vector arrow on the electronic HSI, I positioned for a visual final at lOkts above the Vref of 118. A tight base leg left me high but prompt thrust reduction and a positive dive quickly got us back into red/white on the VASis. Power can be reduced to idle approaching the threshold

without any trim change and a very slight flare breaks the descent.

George tells me that with the l000’s improved super critical outboard wing section and lengthened fuselage there is plenty of both elevator and lift to flare even if the speed gets way too low – unlike on earlier marks. The stiff, short travel undercarriage is rather unflattering but with all that elevator control fairly smooth landings should be possible with practice, given sufficient runway length.

For a touch and go you simply advance the throttles two detents, retract flap to 15 and reset the trim, the last two of which George did for me. Then it was rotate, hold the speed back, pull off the power quickly before we rocket through. 1000ft and turn right onto downwind again. This is flown with gear down and 15 flap at 180kts, reducing to 160 with flap 25 on base leg. Being in parallel with the rudder pedals the yaw damper can be felt working all the time though it must be disengaged before touchdown. If you forget to re-engage it the aeroplane develops an easily identified wandering motion in the circuit. Dropping 45 degrees of flap on final allows the speed to be brought back to 128 with a power of around 64% NI.

Engine failure at lift-off is easily controlled since the fan takes a second or so to run down. Although full rudder is needed, the force is not high but old 125 drivers might get a surprise. Climb rate is more controllable with sufficient time to wind on lots of rudder trim before levelling out.

The single engine approach is flown at Vref +20 (138kts) with flap 25 to 200ft when either speed can be reduced to Vref +5 or 45 flap is lowered and it drops to Vref. We simulated a go around at 200ft, applying only CR power and retracting flap to 15 with the gear up to find that, even with full rudder, if you don’t bank into the dead engine the aeroplane will slide slightly sideways across the sky. We went up at a good 800fpm and in even the worst sea level engine-out case of MTOW and ISA plus 35 (+50°C) the BAe 1000 will still climb at a sedate 375ft per minute if you get it right. At our weight the only sweat was keeping the speed under control.

Our final full stop landing was made with both engines so, after a reasonable touchdown, I struggled the airbrake lever into its stiff, awkward lift dump position where it commands the flaps to a draggy 75 degrees and fully deploys the spoilers for maximum aerodynamic retardation. This quickly reduced our speed to 60kts when nose-wheel steering was used with light braking (400psi of an available 2000) to slow us for a gentle taxi back.

For thirty years the 125 series has been one of the world’s most popular business jets and a rare British aviation success story holding as it does nearly half the world market for mid sized executive jets. So far, 820 of all marks have been sold for an average production rate of nearly two aircraft per month throughout that time. Corporate Jets who market the new. aeroplane, are a newly formed subsidiary of British Aerospace and intend to attract external investment for development of more advanced types. For the first time, the earlier cheaper and smaller Corporate 800 airframes will still be produced in parallel with the new 1000s. The company anticipates delivering twenty -800s and 24 of the new 1000s before the end of the year.

Built to the near airliner standards of JAR 25, the Corporate 1000 is now the first really long range mid sized business jet, with proven construction, basic systems and big jet handling. It is no great secret that bigger aircraft with more mass are slower to deviate and therefore easier to fly accurately than small ones and it is this stability and lack of skittishness that makes the 1000 such a pilot’s delight.

In his autobiography, Sky Fever Sir Geoffrey de Havilland said “The reasons that make ‘good’ aeroplanes. . . are simplicity, right size, cleanness in design, and of course, a very reliable engine” How right he was, and it is those features, combined with the PW305’s improved thrust and economy. that will ensure the 1000, the latest mark of his company’s 125th type, goes on to be at least as successful as its predecessors.