The aircraft used in the Around the World Expedition 2009 is based on our production model The Sling, with a few basic modifications.
Sling 002, the ’round-the-world’ Sling that Mike and James are in, is a standard Airplane Factory Sling with 4 modifications. The modifications are:
- The sealing off of two sections of the each wing to make two additional fuel tanks per wing;
- The addition of 15 layers of glass fibre to the main undercarriage;
- The modification of the seating arrangement to allow the seats to lie flat;
- Allowing the joysticks to be removed during flight.
The standard Sling has a 55 litre integrated fuel tank in the inner leading edge of each wing. (This will now be increased to approximately 75 litres per wing). Using the same method used in sealing in the standard tanks, a second tank has been integrated into the leading edge of each wing outside of the standard tanks. Those tanks each hold 83 litres. Then a further 87 litre tank has been integrated into each wing behind the spar. Those tanks are about 30cm wide and run about half of the length of the wing. They hold 87 litres of fuel each. The total fuel capacity of the aircraft has therefore been increased from 110 litres to 450 litres. No ‘structural’ modifications of any kind have been made to the wings or fuselage. Fuel management is simplified by the inclusion of 6 ‘on-off’ fuel selectors, one for each tank.
In order to prevent the main landing gear from splaying under the weight of the additional fuel, especially if forced to land with full tanks (for example, during testing, or in case of an emergency), an additional 15 layers of glass fibre were added to the wheel struts of the main undercarriage, increasing it’s strength and stiffness.
The adjustments to the seats essentially comprise the repositioning of a cross strut in the fuselage just behind the seats so as to enable the seats to lie flat, so that either pilot can sleep during flight. The aircraft can be flown equally comfortably from either side, so either person is able to take responsibility for the aircraft during flight.
The joystick removal arrangement simply comprises the sliding of the joysticks into an outer tube and locking it with a pin.
The development prototype Sling, serial no. 001, had a 914 Rotax engine installed (115hp). The round-the-world Sling, serial no. 002, has a 912 ULS Rotax motor installed (100hp). This is simply because a 912 ULS motor is slightly lighter and simpler than the 914 motor, has historically proven extremely reliable and is likely to be the motor most commonly used with the Sling (although the 912 UL, which is an 80hp motor, will also work perfectly well). An electronically controlled Neuform constant speed propeller unit with 1.8 meter composite propeller finishes the powerplant arrangements.
The round-the-world Sling is well instrumented. The main instrumentation is incorporated in two multifunction MGL Avionics Voyager ‘glass cockpit’ instruments developed and manufactured in South Africa. In the view of the pilots these instruments represent the highest quality and value for money available. They also enjoy an interesting “open architecture” design philosophy, which means that they can be set up to provide exactly the information sought. The instruments therefore reflect not only the full range of ordinary flight and engine management information, but also the ‘sender determined’ fuel levels in all 6 tanks, total calculated fuel remaining and, most importantly, real time range and endurance, calculated by reference to calculated fuel remaining, instantaneous fuel flow and ground speed. These figures facilitate optimum tuning of the aircraft with ease during flight.
Other instruments include an overhauled Becker transponder, a Garmin SL30 navcom radio, an Insight Strikefinder, a Zaon TCAS, a Trio Avionics Autopilot (two axis), a PS Engineering PM1000 II intercom and a handheld Avmap GeoPilot II GPS. Oh yes, there is also a conventional magnetic compass on board, although it has been removed from the dashboard to improve forward vision and can be instantly replaced with a Velcro attachment.
Save for the above considerations, the round-the-world Sling is entirely standard and her features can be read about on The Airplane Factory’s main website. She was essentially built by three people over two months, although substantial help from friends was obtained over the last four weeks. Like the standard Sling, she has a built in ballistic parachute to provide a back up in situations of grave pilot error.
In her current configuration the round-the-world Sling has an endurance at standard cruise of approximately 24 hours. When full of fuel she cruises at approximately 89 knots indicated air speed, which at 6 000 feet over the Pacific Ocean has proven to be 98 knots true airspeed. When closer to empty she cruises at an indicated airspeed of approximately 96 knots, which equates to a true airspeed of approximately 105 knots. Fuel flow decreases from approximately 20 litres per hour at full to less than 17 litres per hour when closer to empty. At full fuel, with Mike and James and all their luggage aboard, she weighs in at approximately 900 kg. At sea level she climbs comfortably at 350 feet per minute. At 8 000 density altitude she climbs at approximately 150 feet per minute. At ordinary maximum all up weight she seems to climb at approximately 1 000 feet per minute at sea level.
To learn more about the Sling, the people behind her and their thoughts and plans, take a trip around The Airplane Factory’s website.