Guy Leitch with Goitseona Diale
Pipistrel is a phenomenon. Despite coming from a country few people could find on a map, and burdening their planes with ridiculous names, Pipistrel have become world leaders in light sport aircraft – and they fly the pants off the competition
Pipistrel’s Explorer is the latest, and undoubtably the most developed, version of the Slovenian plane builders’ incredibly successful Virus range.
The Sinus and the Virus were introduced to South Africa in 2003. Based on the aircraft’s reputation, there has been stiff competition for the Pipistrel agency – which is now in the hands of Absolute Aviation at Lanseria.
The Explorer is at heart a Pipistrel Virus which has been fully updated – and certified. It is the certification that makes what was already a remarkable plane even more useful and attractive.
Pipistrel claims that the Explorer is “the first and the only EASA Type-certified aircraft in the CS-LSA category approved for night VFR operations, intentional spins and glider-towing, the only one with an autopilot, dual redundant ADAHRS units and airbrakes.”… it is the fastest, most capable and the most economic aircraft in the CS-LSA category. Its speed performance allows it to fly at IFR speeds in/near complex airspaces and procedures, so it can be used for private use and training also at busy airports next to airliners, without slowing down the other traffic.”
Pipistrel also says that the Explorer is the first small aircraft in history to be type-certified with 3D printed parts. As a certified plane it is aimed at the training market. Pipistrel says that it can be used as a simple ab-initio trainer and for more advanced systems – such as an MT constant speed prop, negative flaps, airbrakes and autopilot. The instructor can progressively increase complexity by adding the systems and options which the aircraft is certified for.
Pipistrel have wisely declined to use the fuel injected Rotax 912-iS and instead stuck to the two standard altitude compensating carburettors of the original engine. Unusually for this type of installation, Pipistrel mounted the coolant radiator above the engine, which gives a distinctive tall nose profile.
The Explorer is also commercially certified for glider towing which makes it very useful for clubs as an all-in-one aircraft and a great platform for pilots to build experience.
Safety is key and the Explorer incorporates a haptic stall warning system. This is essentially a system that alerts the pilot to an impending stall by vibrating the control stick. A ballistic parachute adds the ultimate fall back when all else fails.
THE DEVELOPMENT OF THE EXPLORER
The wing’s the thing. The Explorer’s genesis can be traced back to the Sinus motor glider, whose wing is an aerodynamic marvel. Not only is it a super-efficient laminar flow wing, but like South Africa’s JS1 sailplanes, it uses different profiles along its span to improve the handling characteristics.
As if the Sinus name wasn’t bad enough, it was renamed the Virus when Pipistrel shortened the wing by 2.5 metres to make a cross-country machine that could still be used to soar. Then they decided to drop the soaring aspirations and cut the wing down to ten metres, calling it simply the SW – for Short Wing.
At first glance there’s no obvious difference between the SW and the longer-winged Virus. Presumably on the basis that, ‘If it works, don’t mess with it,’ this is testimony to the soundness of the design that won the first prize of US$100,000 in the NASA CAFÉ (Comparative Aircraft Flight Efficiency) competition for all-round performance, including climb, speed, economy, controllability and noise levels.
ON THE GROUND
The Explorer has a wingspan almost two metres shorter than the standard Virus, but it is still lengthy at 10.7 metres and glider-like in its high aspect ratio. The tail is surprisingly high at over 2 metres above ground, which makes it tricky to inspect.
Even though the shorter wingspan is the most obvious change to the standard Virus, there are other less evident enhancements. The empennage is smaller and most importantly, under the skin it has been seriously beefed up to cater for higher speeds. This has meant that the Vne (never exceed speed) of the Explorer has been raised to a healthy 163 KTAS or 302 km/h.
The strengthening of the basic structure is so extensive that, despite its almost identical appearance with the standard Virus, the SW and thus Explorer’s fuselage structure was redesigned from the ground up. Much of the skin is now built out of honeycomb material. Another indication of the stronger structure is the two braces behind the windscreen, between the firewall and wing spar box, whereas the Sinus and standard Virus only have one brace.
The Explorer comes with just the 100 hp 912 Rotax, as any more power would be overkill for such a slippery airframe. The Rotax drives a hydraulic constant speed MTV-33-1A 2-blade prop.
PRE-FLIGHT
The engine is easily inspected through a hatch on the side of the cowl. For a more detailed look the entire cowl comes off in a minute with Dzus fasteners.
Many consider it sound practice for the first flight of the day to ‘burp’ the dry sump oil system by turning the prop through a couple of revolutions.
There is a good-sized baggage space behind the two seats rated for a useful 25 kgs of bags. This can be accessed through a small baggage bay door on the side of the fuselage. Another of the many changes from the Virus is that there is now a solid bulkhead between the cockpit and baggage bay so the headrests are more firmly mounted on the bulkhead, which also holds the headset jacks. The seatbacks can be removed to access the baggage bay from the cockpit. Our test aircraft ZS-FSC (note the ZS registration!) has a ballistic parachute fitted and this intrudes significantly on the available space in the baggage bay behind the right seat.
Each wing has a 50 litre fuel tank which can be reached from the ground by people of at least average height. So you don’t need to carry steps around as many Cessna pilots do. The 100 litre fuel capacity typically gives a 5 hour endurance, so is more than sufficient for most missions – and it happily drinks mogas, which is more readily available than avgas.
As an LSA the max all up weight is limited to 600 kg. ZS-FSC has an empty weight of 370 kg, giving a 230 kg useful load. A 90 kg pilot and 80 kg pax leaves just 60 kg for fuel and bags. Assuming 50 kg for fuel, that is 67 litres. Two standard South African males with 10 kg of baggage will compromise the fuel load but can still fly for three hours. An increase in the 600 kg MAUW for the South African market, and the pending implementation of MOSAIC in the USA, will give a much-needed boost to the Explorer’s utility. But it is more than capable of carrying a load for training.
The fully faired wheels feature quality Beringer brakes which are easily inspected. Regular operation from rough strips would make the removal of the wheel fairings worthwhile.
Once seated, when the Battery Master Switch is turned on, an unusual feature is that the haptic stall warning buzzes the stick three times in a self-test.
FLYING THE EXPLORER
The two transparent doors fold up against the lower surface of the wing and are held in place by a simple clamp.
It is not necessary to stand on a wheel spat to get in, you simply slide your butt onto the seat and then lift your legs into the cabin, hoisting one over the short control stick.
I found the seats very comfortable as they have excellent lumbar support. As the seats are fixed the rudder pedals are adjustable. Both pilot and passenger have toe brakes and a look under the instrument panel shows a reassuring quality of the fittings.
A big thing about the Explorer is that it has a high wing, but this is not particularly evident in the narrow but tall cabin. Once seated you may notice the wing main spar, which looms across your forehead. But as with the two vertical braces across the windscreen, the spar soon ceases to intrude.
A high wing allows a good view of the ground, which is great for pleasure flying but it still suffers from poor view into turns, although Pipistrel go some way to alleviating this with a large transverse roof window. The view down is greatly enhanced by the transparent doors. An efficient fresh air system and cabin heater is standard.
The Explorer uses dual sticks with a single throttle and pitch control between the two pilots. This layout is ideal for training and it’s good to see that Pipistrel have not gone the cost-cutting route of installing a single centre-mounted stick. Behing the power controls is a large trim switch and ladder indicator and behind that the direct acting and simple ‘Armstrong’ handbrake style flap lever so familiar to Cherokee pilots.
The Explorer has plenty of space in its high and wide panel for the very comprehensive avionics fit, more befitting a bizjet than an LSA. The panel layout is straightforward, with pride of place top centre of the avionics stack being the very capable Garmin GMC-507 autopilot. On either side of the stack there are two portrait oriented certified Garmin GDU-470 7-inch multi-function displays (MFDs), which can operate in split-screen modes and thus function as primary or secondary flight displays. Nav input comes from a Garmin GNC 355A which is WAAS enabled. Further nav input comes from GNC 255 navcom. A Garmin GTX 345 Transponder is standard so the aircraft is ADS-B compliant.
The auto trim system is connected to an angle of attack sensor on the pitot tube and automatically adjusts the trim. For flying schools, the trim system can be switched to manual and operated by a conventional conical hat on the stick.
Like all Rotaxes, the Explorer’s 912 engine bursts into life enthusiastically, but with the 912’s characteristic gearbox clatter.
Taxying is easy. Nosewheel steering is direct and the brakes sufficiently powerful and easy to use. Both seats have brake pedals. The wingtips are however hard to see and looking at the position of the shadows is a good way to check if there is wingtip clearance.
Another factor behind the Explorer’s clean design is that the windscreen is some distance ahead of the occupants. It is steeply raked and, with a high instrument panel sill, restricts forward visibility somewhat.
For takeoff the flaps are set to +1. Unstick speed is 43 KIAS and rotate after an impressively short ground run of around 250 metres at about 50 KIAS, depending on density altitude.
Unlike some T-tails, the elevator is smoothly effective on rotation. At 70-80 knots the flaps are raised to zero.
Climbing one-up through 5500 ft out of Lanseria routing for Durban’s Virginia, in a cruise climb at 70 knots the Garmin showed a climb rate of 1100 fpm. This is impressive, given that there was four hours’ fuel plus assorted stuff in the baggage bay.
For straight and level cruise the flaps can, glider-style, be selected a further notch up – to negative five degrees, which has the effect of reducing the wing’s angle of incidence and thus attack. You can almost imagine the wing and indeed the whole Explorer high tailing it as it slices through the air.
The cabin noise level is pleasantly low, which creates the impression that the Explorer is lacklustre in climb and cruise speed. But a glance at the vertical speed and airspeed indicators quickly dispels this.
In cruise the controls are well harmonised and responsive, especially the elevator. Control break-out forces are reasonably light, despite the full span flaperons. Whilst the Explorer takes its time to accelerate, it does not like to slow down.
As a minor criticism, the rudder lacks positive feel and so it is important to maintain the ball in the middle. But this makes it a good trainer.
Flying at an unusually high FL115, with just 55% power, Goitseona saw 98 IAS for 120 TAS at just 17 l/h. For a more typical cruise at 6500 feet, full throttle and 5400 rpm, the Garmin PFD showed 125 KIAS for 137 KTAS, burning just 20 litres per hour Mogas. Even at that speed it flies impressively smoothly and quietly. With fixed gear and just 100 normally aspirated ponies, this is a great turn of speed.
The downside of a slippery laminar flow wing is usually found in the stall behaviour and the Explorer is no exception. Lowering flaps to Position +2 with the power off and the nose almost level with the horizon, there is an aerodynamic buffet plus the haptic stick feedback at 49 KIAS before the right wing dropped. As the Explorer is certified for intentional spins, this will further enhance its appeal to flight schools.
With the clean airframe, descent planning is important. It’s easy to end up a bit high and fast. Full flap in combination with the airbrake is typically used for landing. With the prop full fine and the power closed (there’s no risk of shock cooling on the Rotax) you use your right hand to reach up and unlatch the airbrake lever. This allows precise glider like hold-off and touch downs.
The approach is flown at a brisk 65 knots with flaperons at position 2. An idiosyncrasy not uncommon to flaperon-equipped aircraft (and Robertson STOL conversions), is that with full flap the ailerons load up at slower speed and require more effort to roll the aircraft. It is only in the approach phase that pilots will encounter this, and it is by no means a disadvantage as this natural resistance will discourage too high an angle of bank when turning onto final.
The Explorer is easy to land, but once the airbrake is applied on final, the sink rate can get high without judicious use of power. Thankfully the Explorer’s clever auto trim system, geared to the pitot’s angle of attack indicator, makes retrimming easy.
Thanks to the airbrake, the float is minimal. With judicious use of the wheel brakes you can easily get stopped after just 60 to 70 metres’ ground roll.
CONCLUSION
The Explorer has taken a well proven design – the Virus SW – and equipped it to the most modern standards.
The avionics fit makes it a most capable aircraft and especially useful as a trainer. However, the EASA light sport aircraft 600 kg max all up weight cap limits its useful load, especially when similar aircraft are permitted to fly at 700 kg in South Africa. It would be great if Pipistrel can persuade the SACAA to approve a 700 kg version.
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