SA Flyer - February 2010 - Slick 360 - Serious Fun - Story : Guy Leitch, Pictures : Frans Dely

The Slick 360 has been designed with one overriding objective – to give the most aerobatic bang for your buck.

The Slick 360 is to aerobatics in 2010 what the Pitts S1 was in the 60’s and 70’s. The most bang for your buck, able to take a pilot from beginner’s to unlimited class at a fraction of the cost of similarly capable aircraft.

DEVELOPMENT

The Slick 360 is the ultimate refinement of ongoing development of the Laser. The Smithsonian National Air and Space Museum credits the Laser 200 as a key influence in the current generation of aerobatic aircraft. It was the most successful of the early monoplanes and made the then class leader, the Pitts Special, seem squat and ugly by comparison.

With the arrival of the Laser, monoplanes came to dominate aerobatic competition throughout the 1980’s and 90’s. Designs such as the Laser, and then the Zlin 50 and Sukhoi series, provided the key attributes of less drag, full-span ailerons for crisp manoeuvres, and, for the judges, better presentation in the sky than biplanes. The monoplane’s strong unitary design and clean lines made it possible to achieve better vertical penetration and less height loss.

DESIGN AND CONSTRUCTION

The original Laser was constructed from traditional 4130N steel tube, with a wooden main spar and wood/fabric covering. Only plans were available.

German aerobatic pilot, Walter Extra saw the demand for an “off the shelf” version of the Laser which, at the time, was only available to build from plans.

As a factory-built aerobatic specialist aircraft, without the benefit of high volume mass productions, the Extras were somewhat pricey. Extra also had difficulty finding sufficient quantities of the very high quality wood required to build the Extra 230’s one main spar.

This presented an opportunity which South Africa’s Glen Dell recognized. As the then Advanced World Aerobatic Champion, Glen saw the opportunity to further develop the Extra EA-230 by making it both simpler and stronger. Further, by building it in South Africa, it could be produced more affordably and sold as a ready-to-fly aircraft.

As with any competitive aerobatic aircraft, key design philosophies of the Slick are the need to be simple, light and strong. To achieve this, the Slick is of all-composite construction. This makes the fuselage, in particular, remarkably simple as it does not have the complex welded steel tube structure of the Extra nor the fabric and tube designs of the Pitts Specials.

In a further quest to reduce weight for his personal aircraft, c/n 009 as featured in this article in Red Bull colours, slick factory, Global Composite Solutions, used pre-impregnated (pre-preg) material for the wing skins. This uses the exact amount of epoxy for the carbon material and means the wing weighs just 65kg, which is 30kg less than the earlier wing. Most importantly, strength has not been compromised, The Slick remains rated at +/- 10G with an ultimate strength of +/- 20G.

Another advantage of utilizing pre-preg materials is that, since the material is baked in an oven at high temperatures in order to cure, exposure to the hot South African sun has less chance of being damaging. The fuselage and empennage however, still use conventional wet lay-up carbon-fibre construction.

COST EFFECTIVE PERFORMANCE

Affordability and performance is what the Slick is all about. In terms of price, the Slick is targeted at being a little over half the price of the current Unlimited aerobatic aircraft available. The benefits of a lower initial acquisition cost are not only felt upfront, in terms of being able to afford a new aircraft instead of an older and perhaps more tired example, but they continue with lower insurance premiums.

By keeping the weight down, a smaller engine can be used. The slick 360 therefore uses a four-cylinder Lycoming AEIO-360. This is both lighter and more fuel efficient than the six cylinder IO-540’s of similar performance aircraft.

In a further quest for simplicity, the Slick uses the parallel valve 180hp version of the AEIO-360. This engine is lighter, narrower and cheaper than the angle valve. It can also be more easily modified to produce greater power than the angle valve version. Thus, the typical AEIO-360, as supplied by Monty Barrett’s BPA Engines, has an output of 220hp.

The Slick uses a two blade Muhlbauer propeller, again to keep cost and weight down. Another advantage of a two bladed propeller that is often overlooked is that it is cheaply transportable from the MT factory in Germany.

Unlike later model Extras, such as the 300L, the Slick uses a mid-mounted wing. While a low wing makes it easier for the pilot to see forward for the landing, it detracts from rolling manoeuvres as the aircraft rolls asymmetrically around the wing. The Slick’s mid-mounted wing means that the wing is at the centre of the roll axis and this means it presents better for aerobatic judging.

Aerobatic aircraft must not just be good at aerobatics. It is a reality that most of their flying is still straight and level, for the flights to and from aerobatic meetings and practice areas. In this regard the Slick again excels as it has benign straight flight handling. It has a very respectable cruising speed of 178 knots for a fuel burn of just 50 litres per hour. The fuel capacity for aerobatics is 60 litres which permits three fifteen minute aerobatic routines between fill-ups.

To save weight the Slick comes standard with the South African developed MGL Electronic Flight Instrumentation (EFIS).

One of the key under-the-skin-developments Walter Extra incorporated in the production Extras when he developed the design from the laser, was the re-routing of the controls and this has been incorporated into the Slick. However, the Extra’s thicker wing has not been used and the Slick continues with the original Laser wing profile. A key advantage of this is that it has a much better flick performance.

The all-round aerobatic competence of the Slick ahs already been established. Flown by Glen, it won the South African National Championships on its first time out. Since then, eight aircraft have been sold.

GLEN DELL ON FLYING THE SLICK 360

Those of you who have had the pleasure of flying the great Pitts S1 series will know what it is like to “strap an aeroplane on”. You sit deep in the fuselage, your head just sticking out above the coaming, with wings, ailerons and aeroplane stuff all around you. You can almost reach out and touch the engine and prop and the tail is not too far behind either.

As aerobatic aircraft developed and new materials became available, it was almost inevitable that these craft would go the “monoplane route”. Less drag, faster roll rates, better visibility and better presentation to the aerobatic judges. In order to have the same wing loading, wings became longer and, in order to maintain overall proportions, so did the length of the fuselage. As performance increased, so did engine size. To maintain an ideal C of G, the pilot had to be moved back, ending up sitting behind a long nose that looked quite sexy, but the pilot lost that feeling of being part of the plane.

The Slick has the best combination of new monoplane performance and the old Pitts S1 feeling. It uses the same engine as that used in the S1, the Lycoming AEIO-360 (180hp version). The low weight of the engine allows the pilot to be situated quite close to the lateral axis and this helps with “g” tolerance and reduces the sometimes disconcerting feeling of being thrown around in the cockpit as one often experiences in a Sukhoi or Extra.

Another reason for some modern “super planes” making you feel as if you have spent time in a tumble dryer is the fact that they have wings that are situated off the longitudinal axis. Most super aerobatic aircraft these days are low wing. This means that the majority of the pilot’s body is above the axis of roll. With roll rates of anything from 360 to 500 degrees per second, you can imagine the amount of “tumble drying” that can be experienced. From a spectator’s point of view, the neatness of a roll is also compromised.

A pilot of a biplane executing a roll has the longitudinal axis passing approximately through his tummy. An equal amount of body mass is therefore moving around the rolling axis. Of course this is the same in a mid-winged monoplane and allows for a relatively comfortable ride and pleasing manoeuvre when viewed from the ground.

The Slick is the same size as a Laser or Extra 230 and quite a bit smaller than a Sukhoi, Extra 300 or Edge. Empty weight is 470 kg which gives sufficient power to weight ratio to do all unlimited manoeuvres or sequences.

Pre-flight is the same as any other aerobatic aircraft, bearing in mind that the nature of their flights may be considerably more testing than that of most “straight and level” planes.

Starting is standard but can be a challenge because of the 11 to 1 compression pistons and light-weight battery. The EFIS instrumentation may take a little getting used to, but is a small inconvenience considering its value in being very light weight.

Taxiing is a pleasure compared to most long nosed aerobatic planes and very little wagging of the tail is required, as with a stretch of the neck you can see over the nose.

Take-off is quick and easy and anyone with tail-dragger experience will find it a breeze. There is less tendency to swing as the fuselage is relatively long – especially when compared to that of a Pitts S1.

There is more weight on the tailwheel than you might expect. This is because the main landing gear is attached to the firewall, which is the only place strong enough on an all-composite mid-winged aircraft. Even so, the tail comes up immediately full power is applied and forward visibility becomes excellent.

At 65 mph the nose is raised slowly due to the main gear being far forward. Rotating too fast results in a slight bump of the tailwheel on the runway surface. Angle of climb-out at sea level is impressive, being a little under 45 degrees and giving a rate of climb of 2300 feet per minute.

Once leveled off, max indicated airspeed is 197 mph at sea level. This allows for most manoeuvres to be flown without having to dive for speed, which is a huge advantage for completing a complicated aerobatic sequence without losing height.

Pulling to vertical from straight and level will allow two vertical rolls and a “cap off” or four vertical rolls and a stall turn. Pulling to vertical from 230 mph (Vne is 260) gives a vertical penetration of 2300 feet. Loops and rolls off the top can all be comfortably flown from straight and level and cruise power.

Roll rate at 360 degrees per second is slower than that of an Extra or Edge but perfect for competition, where no points are given for roll rate but rather for precision of the manoeuvre. The Slick still suffers from a difficulty to stop precisely on a point when rolling, but this is being addressed by Greg Cole from the USA, a noted expert in this field.

Flick rolls are a joy and there is no monoplane that can execute this manoeuvre as well, or biplane that can fly it better (considering the wonderful flicking characteristics of the Pitts S1S).

The 360 stalls at 58 mph and the characteristics of the stall are very predictable, as one would expect from a competition aerobatic aircraft.

Precision spins may require practice as the powerful elevator tends to cause an oscillation in pitch if held fully back during rotation. Most modern aerobatic monoplanes do this and all that is required is a lightly forward of full up elevator position, the amount of which depends upon C of G position during that flight.

Stall turns are really fun to fly and certainly, from a spectator’s point of view, the Slick appears to rotate perfectly around the vertical axis.

Another very good attribute of the Slick is the minimal attitude change from flying upright to flying inverted. Although a normal amount of forward stick pressure is required to maintain inverted flight, the attitude remains quite flat. This can be seen from the photos and assists in making the appearance of straight rolls very clean.

Circuits can be flown normally as forward visibility (which can sometimes be a problem in a long nosed aircraft, especially on final approach) remains good throughout. Touch down and rollout are simple from a taildragger perspective because of the relatively long fuselage and distance between the main gear and tail wheel.

All in all, a great aerobatic plane. Visually pleasing to the judges, simple to manhandle on the ground, performance to compete at the higher levels of aerobatics. As an added bonus, it has the legs and speed to go places (Johannesburg to Durban with 45 minutes fuel reserve) and a lower cost than the unlimited aircraft now available. Sukhois, Caps and Edges are no longer manufactured and the Extra 330 SC will cost around R3 million.

What improvements would I like to see on the aircraft? Twenty kilograms lighter would be nice and a little more power (as always!). A slightly higher roll rate and a lower cost (albeit that the Slick costs just over half of what is currently out there). Most of these wishes are achievable – watch this space!