Airtest – Aero Designs Pulsar

The Pulsar kit does not require the messy, wet, large area lay ups of many other composite airframes, so allergic reactions sometimes caused by even the ‘safe’ epoxies are minimised. Arriving as a recognisable airframe, with only paint and upholstery not included, its preformed left and right fuselage halves glue together like a big Airfix model made from a thin sandwich of oven cured, vacuum moulded pre-impregnated epoxy and glassfibre skin around a PVC foam core. This is more uniform and much lighter than the more common foam, glass cloth and applied resin construction which needs to be heavier, with more soaked in resin and a lot of filler, to guarantee adequate strength and surface finish. Since its epoxy is already cured at high temperature, the Pulsar is not limited to a sunlight reflecting white finish like most other composite homebuilts.

The integral fuel tank, foam sandwich bulkheads and anodized aluminium hardpoints and wing attach plates are built into the fuselage structure with glassfibre fillets. Although the spars are composite and the 2.5cm thick ribs blue styrofoam, the wing skins are thin 1.5mm birch ply. Wrapped around the precut, numbered, 20cm spaced ribs and glued in place, this forms an MS(1)-0313 aerofoil with inbuilt taper and washout, dispensing with complex jigging (although it does require a 3.5m long flat bench which can be made from its packing case). Preformed composite wing skins are now an extra cost option for impatient builders.

The tubular aluminium tailplane spar halves slide into an internal fuselage cross tube, and can be removed for transportation, but the unidirectional composite undercarriage legs are bolted into place. The engine is bedded into a lightweight mounting of the lower cowling and bonded internal crossbeams.

There has recently been some public criticism of the reliability of Rotax engines. Yes, all Rotax engines come with the warning ‘This engine is liable to sudden stoppage’ but this has to be viewed with an understanding of the crippling effect of misguided US product liability legislation (and frankly, for their own safety, pilots should assume that all aero engines come with such a warning). Having read the joint PFA and BMAA publication Rotax Engines, Defects Reported 1983-1993 (which provides interesting information for anybody contemplating flying behind a Rotax) I see that the majority of malfunctions were caused by ignition problems on single ignition engines (mostly by owners disregarding Rotax’s spark plug recommendations) or by poor installation arrangements. Many failures would have been prevented by using a dual ignition alternative like the 582, or by following the manufacturer’s advice. With over 20,000 units now flying worldwide, the muted whine of the Rotax is here to stay.

It took the owner of this Pulsar about 1400 hours of fairly concentrated spare time work over fourteen months to complete his aircraft whereas the factory estimate was 1000 hours. Before starting, he admits to absolutely no prior experience “I had never even built a model aircraft”, and feels he could now complete one in well under 800 hours.

The owner and his wife did a great deal of homework over five years before parting with their money. Having absorbed the contents of many kitplane companies’ brochures and catalogues, they followed this up by reading magazine air tests and visiting dozens of airshows to view the finished products. Finally they actually went to a number of British, Canadian and US manufacturers to assess their operations. Aero Designs won on all counts, not only having a highly competitive product, but being an attentive ‘family concern’. With an obvious pride in their aeroplane, although clearly conservative about not overstating their aircraft’s performance, they took time to explain things and answer the couple’s questions.

The pair towed their aircraft to the airfield and proceeded to roll it off and rig the wings in a remarkably swift sixteen minutes, posing for photographs and answering questions as they did so. Assembly is quick and easy. The main spars’ stub ends slide into fuselage slots just under the front of the seats, extending from side to side and held in place sailplane style by beefy 5/8 inch pippins. The rear spars are secured by safety pinned bolts, while small bolts through the flap torque tubes slot into grooves in the ends of the cross cockpit linkage. The ends of the aileron operating rods bolt through a rocker arm behind the seat back, and are again safety pinned. The tail controls normally remain connected throughout.

The 43kg Rotax nestles neatly behind twin radiators inside its sleek cowling. Because of the limited space this application uses the earlier B series gearbox with its mandatory hundred hour service and internal spring inspection. Engine life is generally reckoned to be up to 1000 hours, with a comparatively inexpensive annual decoke and a 300 hour overhaul recommended by the manufacturers. Equating to six years’ average use in marked contrast to overhaul expenses on established American engines. Although supplied with an oil injection system, most builders conservatively prefer to remove this and use a premixed 50 to one fuel/oil mixture to be sure of exact proportions. Since the twin Bing carburettors permanently breathe warm air from within the cowlings, carb icing is not a problem.

The big, well fitting, streamlined canopy slides forward on three rails. When closed its front edge slips under two stout lugs on the upper decking and it is held shut by a spring loaded hook behind the occupants’ heads. The aircraft can be taxied with it cracked open for supplementary cooling, and air loads blow it closed if the catch should be forgotten. Entry from aft of the wing roots allows one to slide one’s legs down into the snug foot well. The firm seats recline at 35 degrees and are equipped with comfortable four point harnesses. The cockpit is adequately big (and wider than a Cessna 152 at shoulder level) but there is no seat adjustment (although the rudder pedals can be repositioned by altering their turnbuckles).

A small side stick control column between the seats operates both the light elevators (whose centring springs are adjustable for pitch trim by a small lever ahead of the mid panel support) and the well faired differential ailerons through pushrods. Dual cockpit side throttle levers are interconnected by a Bowden cable, and the flap handle behind the left one has a rather crude external aluminium ratchet. Plungers between the lower rudder pedals operate the unusual external band brakes through cables, and have to be held depressed for parking in the absence of a park brake. Instruments are sensibly basic with a vertical fuel contents tube and rotating fuel on/off knob in the centre of the black painted ply panel and an ICOM AC-20 portable radio recessed into its right beyond the engine gauges.

The Rotax started easily, although at first it needed a little help from the primer to keep running at 3200rpm idle and leaving 3200rpm set, we slowly inched forward along the springy unidirectional composite undercarriage. Having a completely castoring nose wheel, steering is by differential braking, but I found it easy enough to control direction just with the rudder while we headed into wind. The turning circle is amazingly tight if needed.

Unfortunately, like so many American types, the Pulsar was really intended for use on concrete or tarmac surfaces, so increasing rpm and speed across the rather hard and bumpy grass tended to cause a pitching motion on its narrow, short wheelbase undercarriage. Propeller damage has been known to result from this bucking at higher speed on the runway and the problem should soon be solved by a damped nose leg spring strut currently under development. Taxying slowly is the compromise solution. The XP with its heavier 912 engine is less affected and, of course, the problem can be circumvented by opting for the tailwheel model.

The same pitching motion briefly manifested itself during the flaps up takeoff, but otherwise this was simple, with reasonable acceleration, no need for differential brakes in the ten knot headwind and no tendency to veer left or right. The stick was held well back throughout to relieve the nose leg and the aeroplane lifted off at around 45 knots (83kmh) in about 400 metres. Carefully holding her down a few feet above the runway, I allowed the Pulsar to accelerate to a comfortable 70 knots (130kmh) for the climb. Best climb rate is placarded at 48 knots (89kmh), but as this is at the bottom of the drag curve, a higher speed is easier to hold as well as allowing better forward vision and engine cooling.

Speed stability at seventy (130) is definitely positive, and I timed our rate at 600fpm (183mpm) from 1000 to 2000 feet (305 to 610m) in a temperature of 20°C using 5600rpm (max power rpm is 6500). Since, with 41 litres of fuel, we weighed the maximum 408kg, this equates well with the published ISA sea level rate of 1000fpm at 48 knots (89kmh). (Later composite sparred models have a 454kg weight limit). Visibility is excellent, and although the nose is high, being so narrow it does not intrude into the field of vision. Neither does the slim, high aspect ratio (7.8) wing cover much of the ground below.

With no engine smell, a comfortable semi reclining seating position, very little vibration from the high revving engine and such superb vision, this aeroplane reminded me more of a sailplane than any powered aircraft. And with a sailplane’s clean aerodynamics, the Pulsar glides at only 500fpm, has a stated 12 to one glide ratio and accelerates quickly towards its 130 knot (241kmh) Vne if aimed downhill under power.

Its controls are delightful, slightly heavier than in some twitchier homebuilts, but much lighter than any production aircraft, and may come as a surprise to those more used to “spam cans”. They are very effective and reasonably well harmonised (the elevators are slightly lighter than the ailerons) with a very good roll rate, and little need for rudder to coordinate turns except at low speed. Yaw stability is very powerful, pitch stability is positive at all normal speeds and configurations, and the aeroplane is neutrally stable in roll, with good roll damping, meaning that it can be flown without input for long periods, the bank stays where you leave it and the rolling stops as soon as you let go of the stick. Although incredibly light, the aircraft is not upset by gusts and bumps, riding the low level convective turbulence very well.

Leaving full throttle set, at 2500 feet the ASI wound up to 118 knots (219kmh) at 6400rpm (red line is 6800) which is pretty darned good on 66 horsepower and trues out at 123 knots (230kmh). At the lower setting of 5800rpm we still zipped along at 105 knots (195kmh) while sipping fuel at under 18 litres per hour for a safe full tanks endurance of over three hours and a range exceeding 350nm (649km) from the standard fuselage tank (larger twin wing tanks are optional). Although noticeably high pitched, the engine note is neither intrusive nor too loud. While the sun nicely warmed us through the canopy, the panel end air vents maintained a pleasant internal temperature.

The side stick was easy to apply sufficient leverage in any direction and, having noted the control when I started the flight, its use did not once cause conscious thought thereafter. Big advantages of the system are the useful ability to brace your forearm against the armrest to damp out unwanted inputs, and the way your lap is left completely clear for a map or clipboard.

Its plain flaps have a low 65 knot (120kmh) limit and four positions down to a maximum deflection of forty degrees each setting inducing a slight further pitch down. They usefully increase drag, while lowering the stall speed from 38 knots (70kmh) to off the clock at a ridiculously low speed below thirty (55). This suggests an excellent low speed to high speed ratio of nearly four, a tremendous achievement.

In all configurations the stall itself is quite sharp, often with a wing drop, but the height loss is small. Care must be taken not to exceed the flap limit in the recovery. Adequate buffet, the high nose attitude, aft stick position and reduced control response give fair warning. This behaviour may not be representative of all Pulsars because, being homebuilt, each wing inevitably has a slightly different shape. Handling at fifty knots (93kmh) is adequate, but degraded.

Below fifty knots (93kmh) there is a noticeable increase in drag, which in a low powered, low mass aeroplane with light stick forces can spell trouble unless there is sufficient height available to dive and regain speed. Witness the number of low level stalls suffered by Turbulents, Kitfoxes and similar low power, lightweight aircraft. With familiarity, a competent pilot can soon sense decaying speed, but this problem usually occurs to folks with low hours on type. The remedy in the Pulsar is to stay well on the positive side of the drag curve by approaching at sixty (111) and to keep an ever watchful eye on the speed. In such a clean airframe, this can be easier said than done, and some forward planning is needed to slow down for the circuit. Downwind at seventy knots (130) and 4000rpm seemed about right, slowing to sixty to extend the flaps, and using this with 3500rpm for a fairly flat attitude on final.

After my brief acquaintance with the Pulsar I was very impressed. It is nothing like the flimsy compromise I had expected. It flies well, like a much more substantial aeroplane, but with better controls than any production machine.

Its efficiency is remarkable, and a real testimony to the importance of light weight over all other construction parameters.

Yet its structure is stressed to operating limits of +4 and -2g (+6/-4 ultimate). Hearsay testimony to the structure’s strength is the tale that one Pulsar’s G meter recorded an instantaneous +8g after a forced landing and is still flying. With a reasonable purchase price, easier construction than many other kits, decent short field performance and a fair turn of speed the type is bound to increase in popularity.

The Pulsar’s unbeatable operating costs are the clincher. By removing its wings (saving the cost of hangarage) and performing one’s own maintenance one could recoup the price of the whole aeroplane in six or seven years! The final acid question has to be would I like one? The answer? – Yes I would.