Flying the Liberty XL2
Early in the Liberty XL2’s genesis, the British Europa kitplane designed by Ivan Shaw in the late 1980s was remarkably popular with over 1,000 units sold. But Europa founder Anthony Tiarks saw an even brighter future; he sold Europa to its management, and launched Liberty Aerospace in Melbourne, Florida.
Most modern twin-seat light aeroplane manufacturers were flocking to the new light sport aircraft (LSA) design and certification category, so Liberty Aircraft’s XL2 is a relative rarity. That’s because Tiarks elected to re-work his successful Europa homebuilt with new credentials, and to certify it under the US FAA’s FAR Part 23, which gets harder to embrace with every revision. FAR23 now wants a two-seat trainer that – among other qualifications – can be sandbag-laden up to its maximum takeoff weight (MTOW), dropped upside-down from 12 feet (3.65m,) then dragged along the tarmac (still upside down) for 200 yards (183m) at 35 knots, and still be in a condition that would have allowed its anxious occupant/s to survive.
Although these days few manufacturers care to shape up to such challenges, Liberty has done that and even taken a significant further step.
First with FADEC
For more than 20 years pilots have been wondering when piston-powered aeroplanes would catch up with the off-the-shelf family sedan, in terms of computer-controlled full authority digital engine control (FADEC). TCM (Teledyne Continental Motors) used the Liberty as its guinea-pig for the development and certification of its IOF-240-B4. The IOF designation means injected, opposed and FADEC, and TCM’s philosophy has been to start with the simplest engine and work upwards to certify the rest – which is now happening. TCM expects in the near future to roll out FADEC models across its entire four and six cylinder range
The certification has made Liberty the world’s first production piston aeroplane with FADEC, enjoying all its benefits including improved operating economy, ease of operation and maintenance, and higher reliability. It takes care of all of the engine’s parameters automatically and with a single throttle lever doing a far better job of engine management than any pilot could hope to achieve. It automatically adjusts the ignition timing, the fuel quantity and the fuel/air mixture to each individual cylinder, optimising as never before the energy produced by each litre of fuel while also providing automatic engine protection against exceedance of any critical parameter. It also makes the engine fully self-diagnostic, providing reliable starting when hot or cold, and warning the pilot of any parameter which exceeds limits. As well it provides for a full history of every engine parameter to be downloadable for maintenance purposes, and TCM believes that the condition monitoring capability is likely to flow on to eventual overhaul life extensions.
The FADEC engine was originally designed for Cessna’s Skycatcher LSA which is not yet certificated, and because of SkyCatcher’s high wing configuration does not have provision for an engine driven fuel pump. However Liberty and (later) other low wing manufacturers provide an electric boost pump as backup.
The commonest concern with FADEC is that unlike the blend of magneto and engine-driven fuel injection system which will continue to operate despite electrical failure, FADEC is totally reliant on electrical power. This means that if (for example) battery power is lost, the engine will simply quit, making Liberty a much more electricity-dependent aeroplane.
Liberty therefore provides two separate and independent batteries; the main one powered by the alternator and the backup battery still powered by the main electrical bus.
This means that if the alternator fails you still have two batteries to operate the FADEC. If one battery fails you’re still in good shape with a full battery capability and continuous charging.
And even if the main battery and the generator both fail, the backup can provide an hour of power for engine management with a safety margin. It’s something to keep in mind when you’re planning a long remote-area flight, but pretty much anywhere in Australia you can find somewhere to land in half an hour. And of course magnetos too have been known to fail either electrically or mechanically, so there’s some debate about which option carries the higher risk.
So there go three of GA’s biggest troublemakers in one hit: carbies, mags, and vacuum-driven gyro instruments. And as a bonus your XL2 is capable of full IFR certification.
In the airframe department, although Liberty and Europa have a lot of visual similarities, their design and structures are many years and dollars apart.
Rugged construction
Liberty Aircraft Company’s Nigel Hutchinson-Brooks walks me around the Liberty to explain its design and underlying philosophies. The fuselage is of “hybrid” construction with a welded 4130 chrome-moly steel tubing structure surrounding the entire cockpit area, providing a high-safety roll cage as well as attachment points for the wings, main and nose gear and engine. The fuselage and vertical fin are of carbon fibre, as is the internal structure including wide stitched-leather seats, whose structures complement the rollover frame to provide strong protection for occupants. Their contours, intended to resemble the interior of designer Ivan Shaw’s Range Rover, impart a spacious and refined environment.
A single 106 litre fuel tank is also housed within the protected central structure, but outside the actual cabin, and provides over five hours total endurance. A flush-mounted filler cap is high on the fuselage behind the door on the left side and well placarded. The electric flap actuators are also housed in the protected structure, and the ‘dry’ wings are of conventional spar and rib construction, with aluminium flaps and primary flight control surfaces. The all-moving tailplane has an anti-servo tab, and all primary controls are activated by push-pull rods, reducing inspection costs and complexity and giving fast but fluid control responses as we’re about to discover.
The airframe’s modular construction is designed for simplified manufacture that translates to lower purchase price, and easy and low-cost component repair or replaceability. The wings and tailplane, for example, can be removed or refitted in just half an hour – a legacy from the Europa which was designed to be folded and towed home to beat Europe’s astronomical hangarage costs. Lightning strike resistance is provided by copper-weave material built in to the fin area of the composite fuselage skin, and the same material in the fuselage roof acts as a ground plane for the avionics antennae.
