Airtest – IAI Astra SP

US anti trust (anti monopoly) legislators felt that ownership of both bizjets gave the company an unfairly large segment of the market so the Jet Commander design was sold to Israeli Aircraft Industries who marketed it as the Commodore. IAI subsequently upgraded it with bigger engines, tip tanks and better low speed handling into the 1123 Westwind, later further refining the MkII’s wing with an IAI originated, computer derived Sigma aerofoil and winglets. Nearly 300 Westwinds were made altogether with presently 15 on the Australian register.

This was really remarkable low speed handling for a jet with a thin, swept, high speed wing and contrasts strongly with many other corporate jets which require innumerable artificial devices to restore acceptable qualities.

Although initially seeming similar, the 1985 swept wing Astra derivative is an entirely new aircraft forward of the engines, its advanced Sigma 2 section wing mounted below a taller vertical oval fuselage to allow greater internal space. The new SP model is an all round improvement, an aerodynamic clean up enhancing range, speed and hot and high takeoff performance. It has a longer cabin with radically improved interior and a fully digital cockpit vaunting electronic instruments, a more capable autopilot and dozens of smaller but useful refinements.

This was really remarkable low speed handling for a jet with a thin, swept, high speed wing and contrasts strongly with many other corporate jets which require innumerable artificial devices to restore acceptable qualities.

With its lengthened fuselage and slim wings, the Astra SP looks much sleeker than its forbears. The longer Kevlar composite nose hinges open completely exposing all avionics, including the Collins 350 radar scanner, for maintenance. The quick change laminated polycarbonate/acrylic windscreens have recessed wipers and glass outer layers (unlike some competitors) and are tough enough not to need heating for bird strike protection up to Vmo (although they are warmed for ice protection). Below the right one are pitot head, Teledyne angle of attack probe and oxygen filler valve with integral gauges and metric adaptor. Aft of this are four static ports and, below, the twin outflow valves. Under the centre section is a toilet servicing point and a pair of long, belly protecting gear up skids.

Although not required by FAR 25 to which the Astra is certified, each side of the cabin has an over wing escape hatch. Below the left engine’s intake is a 60cm by 65cm lockable composite door to a lighted and heated (but unpressurised) baggage compartment. With a 500 kilogram load limit, its sill is rather high off the ground to easily load heavy objects, but it does contain a small set of steps. Normally installed in this compartment, a removable 380 litre extension fuel tank plugs straight into the twin fuselage tanks to boost range by up to 225nm (415km) but reducing allowable baggage to 168 kilograms. This enables 4250kg of fuel to be carried for a four passenger max range of 3110nm (5760km) at 0.72 Mach with 45 minutes reserve. No additives are needed and pressure refuelling is through a single point at the right wing trailing edge, with a gravity fill port above it on the fuselage. For some reason these lack the obvious necessities of gauges and shut off valve switches, both of which require access to the cockpit, although there is an auto shut off when the tanks are full. A good feature is the ability to jettison fuel at 45kg/min through trailing edge pipes in extremis, allowing weight reduction from max takeoff to max landing in 15 minutes.

The hydraulic, inward retracting, twin wheel main gear legs have trailing link suspension for smooth touchdowns and a nitrogen bottle for emergency extension. Held in place by mechanical over centre locks, they do not need sequencing valves as all the composite undercarriage doors are directly linked to the legs to avoid hindering their operation. The multi disc Goodyear Lorimal anti skid brake packs will absorb 25 million foot pounds of energy in a maximum effort stop and the chined tyre nose wheels are hydraulically steerable through 58 degrees on a conventional forward retracting oleo.

The slender wings have no main spar, but two carry through spars and three outer wing spars. The upper skins’ integral ribs and stringers being milled from the solid for a light, clean and strong structure. Their remarkably smooth, almost flat, top surfaces are free of rivets or any other protuberances but cross headed inspection panel fasteners. The 34 degrees of sweep on the inner sections reduces to 25 degrees outboard of the small, thick, flat plate vortilons which reduce stall speed by 6kt (11km/h). Although apparently accumulating little ice, the leading edges have thin vacuum formed neoprene boots precisely conforming to the aerofoil’s profile. Duane said he had only needed them once in four years, their operation had no adverse effect on pressurisation and they showed good erosion and scratch resistance. The outer wings are fitted with DC electrically actuated slats which, as well as lowering with the first stage of flaps, automatically extend with reducing airspeed. The four position Fowler flaps are also electrical and, like slats and hydraulic two position spoilers, are deliberately designed to run slowly to make the pilot’s life easy.

Composite secondary structures abound on this airframe, with Kevlar wing root fairings and Kevlar/Nomex composite tips and inboard leading edges. The Kevlar/glassfibre honeycomb ailerons are powered by dual 3000psi hydraulic systems, pressurised by twin engine driven pumps and backed up by an electric one. In case of a jam, a 65lb inwards twist on the control wheels allows them to work separately.

Tailcone fairing, fin tip and tailplane tips are glassfibre with pneumatic boots on the all moving tailplane, and the manual elevators can be substituted by high speed simultaneous operation of the variable incidence tailplane’s triple electric motors in the event of malfunction. The rudder is also manual and its trim, too, is run by double mechanically interconnected electric motors.

Pylon mounted high on the rear fuselage sides in Grumman nacelles, the 3700lb (16.6kN) Garrett TFE731-3A-200G two stage turbofans have geared fans and curved blades which give better high altitude efficiency, but produce a distinctive moan and a slight haze of dark smoke. They have electronic fuel control computers, hot air nacelle anti icing and Grumman hydraulic thrust reversers. An optional Garrett APU fitted under the left pylon is rarely supplied because of the high mass flow Garrett air cycle machine’s effectiveness in fast cabin cooling once the right engine is running.

The easy opening, counterbalanced, drop down door has four integral steps, a rigid handrail and rests on a small roller in the handle’s end to allow for small airframe movements. Latched by 10 roller locks and two dogs, it is double sealed and fitted with internal lights. The interior has had a lot of attention, designed by ‘human engineers’ for Henry Dreyfuss and Associates. Like airframe assembly, all furnishing is completed in Israel with modular equipment so that configuration changes can be made relatively quickly.

The cabin is decorated in restful shades of tan and taupe with maple panelling, Ultrasuede sidewalls and plenty of recessed lighting to supplement that from the 11 blind equipped windows. These are at eye rather than elbow level in the space optimising elliptical fuselage whose ceiling is higher than that of its predecessor to give a useful BAe 125 rivalling 170cm headroom from the sunken aisle. The large radius curved walls improve shoulder space in an otherwise slim 1.5 metre wide fuselage. Changed every two minutes, conditioned air has been carefully routed for maximum comfort, warm air entering the cabin through floor level ducts to rise and exit above the sidewall panels, then flowing back down behind to keep them warm before passing out of the outflow valves. On the ground, chilled air cascades from the flood duct in the ceiling for fast cooling.

Carrying up to nine passengers, the standard arrangement has six seats, but this most popular option holds seven, two facing each other on the right, a rear facing one behind the galley on the left, and four in a club layout at the back. Much thought has been expended, with nice touches like twin cupholders for every occupant’s glass and mixer can or ash tray. Each position has air vent, reading light and drop down oxygen mask and the wide seats track to, fro, sideways, recline and swivel with ‘position remembering’ latches on the adjustable arms which, like the headrests, stow internally when not wanted. Facing pairs have folding tables between them and will lie flat to make three beds.

The rear right armchair, designated the VIP position, has cabin temperature bias, PA volume control and Flightfone handset on a long retractable cord to reach any other passenger. The boss also controls the optional Sony VCR TV which pulls out into the centre of the aisle aft of the flight deck door to display the aircraft’s route on one of several stored maps as well as ordinary video recordings. A CD player in the forward right wardrobe is standard, as is the compact but carefully designed, space optimising, left side floor to ceiling galley. Made with the aircraft’s long range and short field capability operation in mind, its removable, easily emptied water tank can be topped up with bottled water wherever the tap variety is suspect. It also boasts an overboard drain, sealed rubbish bin, beverage maker, ice drawer, cup dispenser and bar. The system revolves around lots of identical trays, for which stowages abound, so catering is independent of local equipment. An extension will replace the aft facing seat behind the galley with a module providing extra stowages, an oven and worktop.

In the rear, sliding doors open on a well shaped toilet with recessed lighting, a large mirror, washbasin with hot and cold taps, and lots of little cupboards with gold plated trim. This is again meticulously designed for maximum utility in minimum space, having air vents, cabin signs, drop down oxygen masks and even a tiny roof window. Opposite the toilet, on the left, a .25cu m, 63.5kg stowage area has enough room for carry on baggage and the over ocean dinghy.

At the business end another sliding wooden door leads into the cockpit. Comfortable crew seats upholstered in tan leather with four point harnesses have the normal height, track, recline and armrest adjustments. The slightly dated matt black instrument panels and centre console are dominated by dual Collins EFIS-86C electronic ADIs and HSIs although the surrounding conventional ASI/machmeters altimeters, RMIs and VSIs rather spoil the all digital effect. Controllers for six Collins Pro Line 2 radios span the glareshield and the centre panel holds two columns of engine instruments, the fuel management indicator GNS-X FMC with Loran and GPS, multi function display, annunciator panel and landing gear lever.

Ahead of the twin throttles and reverse levers, a neat gust lock securing rudders and elevators was useful in the unseasonably stiff and biting tailwind (ailerons are dampened hydraulically). The central console also holds the park and emergency brake lever, set and forget pressurisation controls, speedbrake switch, flap/slat selector and indicator EFIS and autopilot controls. The wide but shallow curved windscreens with rather thick pillars are some way ahead of the pilots so visibility, while good, is not magnificent. All panes are fitted with moveable tinted visors and excellent retractable perforated blinds and eyebrow windows usefully supplement the panorama. Between these an overhead panel carries audio select boxes, circuit breakers and controls for the dual 28 volt DC electrical systems with automatic load shedding, anti icing lights starters heating and simple fuel controls.

Having selected the fuel system to Auto and turned on the boost pump, the right engine was started by engaging its 300 amp starter/generator and lifting the thrust lever to idle at 10% N2 rpm. The two 36 amp hour NiCad batteries quickly spun the gas generator and after peaking at 620°C (well within the 907°C redline) the ITT settled to 500°C with stable readings after 35 seconds. With the second engine having started equally quickly and faultlessly, we were soon able to taxi (although it is normal to do so on just one engine).

The nicely geared, variable rate steering, controlled by a sidewall wheel, allows small, precise adjustments and the brakes, while needing some pressure, are progressive and very effective with neither play nor snatch. The lovely trailing link undercarriage gives a smoother more rumble free ride than on any other business jet I have flown. This aircraft’s operating weight with crew is 6215kg so with a payload of 180kg and 1905kg of fuel (slightly less than half tanks and enough to go 1250nm/2315km at 0.70 Mach) we weighed 8275kg — well within the 10,660 kilogram max takeoff weight and considerably less than the 9390kg max landing weight. Filling the cabin with seven passengers, their luggage and catering would limit fuel to around 3765kg for a 2500nm (4630km) range at 0.70 IMN, while with just four passengers and the long range tank, the full 3110nm would be possible at 0.72 Mach or 2510nm (4650km) at 0.80 Mach (all figures are with 45 minutes reserve on arrival).

Flap settings of zero, 12 or 20 degrees are available for takeoff. We used 20 degrees with a pre computed power of 94.7% N1 and a rotate speed of 114kt (211km/h). At our light weight we accelerated briskly until, with a fairly hefty pull we lifted off at 120kt (222km/h). Our 28 second roll took close to the manual’s stated 1160m (3800ft), and we climbed 2500ft/min indicated at the 123kt (228km/h) V2 with 14° nose up pitch.

Quickly whisking up the landing gear and retracting flaps in stages, we accelerated to the en route climb speed of 250kt (465km/h) which is also the limit for 12° flap and the slats. The flaps are designed to travel slowly (around one degree per second) to minimise pitch changes but I could discern only a slight difference as they retracted. Because of the high set engines there is also very little trim change if any at all – with thrust variation, an aspect of the Astra’s handling that caught me out throughout the flight since every other type I have flown has a tendency to drop its nose with power reduction. I also found the elevators rather heavy and ‘dead’ in comparison with the light and effective ailerons.

Settled into the climb, our indicated rate was a spectacular 5000ft/min through 8000 feet (quoted max sea level rate at top weight is 3650ft/min) and still 3000ft/min at 275kt (570km/h) at FL 250 with a fuel flow of 560kg (1230lb) per hour a side at 100% N1 and 880°C ITT. Levelling briefly at FL 130 to sample the understandably high aerodynamic noise but otherwise straightforward handling at the 360kt (668km/h) Vmo, we reached FL 370 20 minutes from the start of takeoff.

Leaving max continuous power set, the speed crept up to Mach .792 (461kt/854km/h TAS) in an unfavourably warm OAT of minus 42°C (ISA +15) with a combined fuel flow of 708kg (1560lb) per hour. Absolute ceiling is FL 450 and while Mmo is .855 Mach, cruise Mach numbers vary between .70 and .80 depending on time and fuel available (consumption always increases markedly at higher Mach numbers). The Astra SP holds 33 transcontinental records in its class, comparing very favourably with the other mid size 3000nm 5500km jets.

Duane explained IAI had taken some time and pains to get the autopilot to its present level of sophistication with smooth and well selected roll rates, bank angles and capture rates. As well as standard modes, it has pre programmed vertical profiles and can make fail passive approaches down to Cat II conditions. Manual handling at this rare altitude is surprisingly easy, almost as straightforward as in the straight winged Citations except for needing a good pull on the stick at 60° of bank. Roll stability is absolutely dead beat, the bank angle staying exactly where it is left, no mean trick with only 2° dihedral. Finding the elevators a touch heavy, the Astra’s very positive pitch stability demands frequent trimming with speed change but this does allow it to dispense with a Mach trim. Unlike some of the shorter bodied jets, its yaw damper is not required for flight, although without it directional stability is poor, induced Dutch roll taking some time to decay naturally while the ensuing undamped motion feels rather uncomfortable.

Noise level in the cockpit is a little high at top speed but it was very quiet back in the light and pleasant cabin, thanks to the engines’ position 4.3 metres aft of the rearmost passenger’s head, and near silent ventilation and air conditioning. Looking out of the windows the elegant wing again impressed me by its complete lack of fences, wedges, strips and vortex generators and the smoothness of the blending line between deicing boots and aluminium upper surface. Long and slim, it acts as a giant suspension spring, bending up under high G and flexing and twisting to shed gusts in turbulence, giving a smooth, if slightly bouncy, ride.

Normal descent is flown at 0.82 Mach and 280kt in a near level attitude with around 87% N1 rpm for 2000ft/min. To increase the rate to a spectacular 10,000ft/min the power is reduced to idle, the nose pitched down ten degrees, speed increased to 320kt, and the airbrakes are extended. Taking a few seconds to deploy, these cause a safe and very slight pitch up and have no configuration or speed restrictions because they blow down somewhat at high speeds. Levelling at FL 170 and checking our weight at 7515kg (16,550lb) we bugged the Vref of 119kt (220km/h). Leaving out the airbrakes to slow down, they took three seconds to retract as we prepared to investigate the bottom end of the Astra’s broad speed range.

Decelerating through 156kt (290km/h) the gear warning horn sounded, followed by automatic slat extension (with melodic warning chime) at 132kt (245km/h). Initial buffet occurred at ten degrees nose up and 122kt (226km/h), becoming more insistent as the speed dropped through 115 (213). At 107kt (198km/h) the wings started to rock and finally, after quite unmistakable portents of the pending, the right wing dropped a couple of degrees as she stalled at 102kt (189km/h) and we lost several hundred feet in a power off recovery. With 12° of flap airframe rumble started at 116kt (215km/h), becoming most insistent by 105kt (195km/h). Experiencing quite severe buffet with the nose 15° in the air at 100kt (185km/h), again the right wing dropped in the G break at 95kt (176km/h). The same thing happened at 93kt (172km/h) with 20° of flap and again at below 90kts and 10° pitch attitude with 40° flap and the gear down.

Encouraging me to fly some turns at 100kt (185km/h) (Vref minus 19kt/35km/h!) Duane demonstrated that the Astra still handled well although response was of course a little ponderous, the controls sluggish, and at this remarkably low speed she needed almost as much rudder as a Cub for a balanced turn. Showing me its recovery capabilities, he urged me to do one last stall with everything dangling and hold it on the ragged edge while applying full power and 30° of bank. Doing so, as the nose went down I pushed forward the throttles and heaved it back to 15 degrees up in severe buffeting but could not prevent the speed increasing as Duane retracted gear and flap and we simply climbed away under full control at 110kt (204km/h).

This was really remarkable low speed handling for a jet with a thin, swept, high speed wing and contrasts strongly with many other corporate jets which require innumerable artificial devices to restore acceptable qualities.

Throttling the right engine to idle I sampled a 3000 feet per minute climb with quite reasonable rudder pressures at the clean V2 of 131kt (243km/h) (Vmca at max weight is 98kt/182km/h), 1kt/2km/h) above the stall). Again the Astra has no rudder bias, Automatic Performance Reserve (which means caning more than certified full power out of the surviving engine to get adequate climb) or other artificial aid to single engine control or performance. Accelerating in a continued descent, I discovered that, although the slats extend automatically, they have to be retracted manually, warning us against exceeding their 250kt (463km/h) limit with that charming chime again. At a range of 18nm (34km) we started flap extension, aiming to intercept the ILS at 10nm (19km) with flap 20° at 170kt (10kt/18km/h) below the gear and flap 40 limit speeds).

Here the Astra’s excellent handling actually lulled me into an unwise sense of relaxation — not a sensible frame of mind when preparing to do battle in a swept wing jet with a 25kt (46km/h) 45° blustery crosswind! In the slot on the ILS at 2000 feet with gear and 40° flap extended and one to two degrees nose up, we started to lurch and yaw just slightly in the bumps and at first I found it a little difficult to stabilise the speed at the required Vref +10 of 126kt (233km/h). Even with everything dangling the airframe is still quite clean and slippery and Duane warned that, because of this, the maximum wind increment to add to Vref is 10kt (19km/h). (There is also a 10kt/19km/h) increment with damaged or unusable slats). A sensible approach power seemed to be between 60% and 65% N1 but with no pitch effects and few aural clues from the near silent engines I found myself over compensating with one inch movements of the throttles when small quarter inch adjustments would have been enough. That and the gusts caused the speed to vary between 120 and 130kt (222 and 240km/h) while I hauled and pushed to stay with the glideslope. This was where I discovered the disadvantage of a leather covered seat, finding that, however tight my straps, I tended to slip around on it.

Half a mile from the runway we hit a sudden lull. Initially not pulling hard enough and then over correcting for the sink left us slightly high, fast and rather wobbling over the threshold as I fought to compensate for the changing drift. Duane cautioned against too much bank because the low set wings’ tips are only 125cm from the ground and we would not want to scrape one. The Astra’s published max demonstrated crosswind is a generous 27kt (50km/h), but I was assured its capable controls can cope with up to 40kt (75km/h) at 90 degrees if needed.

After a short float, pushing off the drift was easy and the gentle touchdown on those lovely trailing link legs was a non event. Easily holding the centreline, I advanced the thrust levers as Duane reset flaps and trim for a touch and go. Flying a compact six minute visual circuit, with 20 flap and Vref +20 (+37km/h) downwind and turning base at 1500 feet, I saw a wind readout of 300/32 at 900ft on final which helped explain the tussling. The second, rather more stable approach led to a briefer float and an even smoother touchdown as I settled down and anticipated the windshear.

On this roller Duane throttled back the left engine but we still climbed at nearly 2000ft/min and I found control easy with light enough rudder pressure to fly the circuit without trimming. Quoted single engine climb at max weight, ISA and sea level is an admirable 1100ft/min. Duane recommended using Vref +20 (135kt/250km/h), reducing to 120 (222km/h) over threshold with 70-75% a useful power setting on the good engine. Intending a full stop landing we armed the ground airbrakes so that, after touchdown, they would automatically deploy in 1.5 seconds. I found swapping from right to left rudder in the flare no problem and, lowering the nose wheel, I simply selected reverse idle and braked gently. At 7265kg (16,000lb) in this wind the landing distance is quoted as a touch over 310m (2000ft) without reverse and just a little less with it, so light braking alone easily stopped us before the intersection 1000m (3300ft) along the runway. On shutdown we had burned 1016kg of fuel in 1 hour 40 minutes.

Recently IAI revealed the improved Astra SPX, featuring TFE731-40 turbofans, new digital avionics suite, winglets and New York to London non stop range.

Iai 1125 Astra Sp

Powerplants: Two 3700lb (16.6kN) AlliedSignal (Garrett) TFE731-3C-200Gs. Performance: Max cruising speed 463kt (858km/h), long range cruising speed 430kt (795km/h). Range with reserves 1730nm (3200km). Weights: Basic operating empty 6005kg (13,225lb), max takeoff 10,670kg (23,500lb), or optionally 11200kg (24,650lb). Dimensions: Wing span 16.05m (52ft 8in), length 16.94m (55ft 7in), height 5.53m (18ft 2in). Wing area 29.41m2 (316.6sq ft). Accommodation: Flightcrew of two. Typical executive arrangements for six passengers, with max seating for nine.

IAI is also working on the bigger, Challenger rivalling Astra Galaxy, which it is jointly developing with Russia’s Yakovlev for first delivery in early 1997. This ‘truly trans Atlantic’ jet will use a new, wider Gulfstream sized 8-19 seat body on substantially the same advanced wing.

It is this wing that holds the key to the Astra SP’s capabilities. Its aerodynamic sophistication gives it the broad speed range and versatility to fly fast and cover long distances yet operate from small airports. It is ideally suited to operations around the Pacific Rim, holding class records between Perth and Sydney, Auckland and Sydney, Melbourne and Perth, Honolulu and Auckland, Brisbane and Pago Pago and Honolulu and Pago Pago.

As a direct competitor to the Hawker 800, its fuel capacity and range are very nearly as great, its balanced field length better, its cabin only slightly smaller and it carries a little less payload. At $US8.5 million as equipped it is considerably cheaper, usefully faster, and a newer, more sophisticated design. With a 20,000 hour airframe life, it is certified to FAR 25 through to the later amendment 54. IAI is currently planning to increase production and it is no surprise that the Astra is presently taking a good portion of the mid size biz jet market.