Liberty XL2

Liberty XL2British, Scottish, and American accents blend in the hallways of the frenetic Liberty Aerospace company in Melbourne, Florida, where a sporty two-seater will be assembled from British, Romanian, and American parts. While the Liberty XL2 is based on 10 years of experience with the Europa, an award-winning British kitplane with more than 1,000 copies sold in 34 countries, Liberty is a U.S.-based company that is independent of Europa Aircraft. The two aircraft appear similar in the cowling and cockpit, but are vastly different under the skin. Liberty Aerospace founder Anthony Tiarks also founded Europa but sold that company to its management to launch his new Florida venture.

Thanks in part to its kitbuilt history, the Liberty XL2 requires little assembly time and is thus economical for the company to build. Considerable thought has gone into keeping operating costs low. Liberty Aerospace estimates that for the pilot who flies 100 hours a year, the total operating cost is $57 per hour for insurance, fuel, annual inspection, oil changes, an engine-replacement fund, and miscellaneous service and parts (such as tires, spark plugs, brake pads, starter replacement, batteries, and bearings and rod ends). The operating cost also includes propeller retorquing. Unlike a metal propeller, the wood-composite design requires frequent retorquing because of changes in temperature and humidity. You'll notice that hangar or tiedown fees are not included in the estimate. Hold that thought.

Even the demonstrator was a sprightly performer, reminding me of past aerobatic aircraft I have flown, although the Liberty is not intended to be certified for aerobatics. Flight controls are nearly as responsive as those of an aerobatic aircraft, partly because of the use of pushrods instead of cables. The aircraft is particularly responsive in pitch. Thanks to the use of a stick rather than a yoke, the aircraft can be rapidly flicked into turns to support any pilot's jet-fighter fantasies.

Another very smart trick was to design a large removable carbon-fiber panel covering the bottom of the fuselage below the cabin area. In its simplicity, the aircraft utilizes a steel-tube chassis that contains the landing gear and serves as a mount for the fuselage and wings. This panel exposes the chassis, gear, brakes, welded-aluminum gas tank, and other key systems, reducing maintenance time. The gas tank is mounted inside the chassis and fits under that portion of the molded carbon-fiber fuselage that is shaped for pilot and passenger seats. While the 29.5-gallon tank is near the passengers — reaching half-way up the seat backs — it is protected both by the steel-tube chassis and the carbon-fiber fuselage.

Finally, the fittings are already in place for a system expected to be approved in a year or so to allow the wings to fold backward: That means you can take the airplane home on a trailer to avoid hangar costs. Airplanes bought today will be easily retrofittable with folding wings.

The nosewheel is free-castering, as it is on several competing aircraft models. I found it creates little difficulty and allows the aircraft to pivot sharply when necessary, such as when facing the aircraft into the wind during an engine runup. It did take a nudge of the fingertip brakes occasionally to keep the aircraft on the taxiway centerline. Once full power is applied for takeoff, however, the rudder is fully effective for steering without the use of brakes.

Entering the aircraft proved the more difficult preflight task. The wing is directly beneath the entry door. Some have suggested a step behind the trailing edge of the wing, and one prototype even has one, but the best approach is a two-scoot procedure. Scoot backward onto the leading edge by the cockpit, swing the legs in, and scoot aboard. My first attempt nearly resulted in toppling backward, but by day two I could enter without shame.

Company specifications show the cockpit is four feet wide and high enough that there was no concern about banging my head on the canopy while wearing a headset. The width is just one inch less than a Lancair Columbia or Cirrus SR22 cabin. As far as length is concerned, I am six feet one inch tall and my left knee still had about one inch of clearance from the instrument panel after I used a hand-crank to put the rudder pedals as far forward as possible. I was comfortable, though. Since the seats are molded into the fuselage they are not adjustable.

The items on the panel new to me were two FADEC battery switches — a switch that serves as a gateway from the aircraft's main battery to prevent accidental engine starts and another that arms a backup battery dedicated solely to FADEC — and an Aerosance Health Status Annunciator. The annunciator lets you know which cylinders are working, when you are operating with WOT (wide-open throttle), whether the fuel pump is operating, and the health of the two batteries that keep the FADEC system powered. Both battery switches, labeled FADEC PWR A and FADEC PWR B, must be on for flight. If the aircraft's main battery fails, the FADEC computer switches to battery B in a millisecond to prevent engine stoppage. A drawback of the Continental FADEC system is that the extra battery means extra weight.

Having a FADEC system means that both engine start and shutdown procedures are greatly simplified. FADEC adjusts engine operation for the engine start-up. To start the engine, turn on the two FADEC power switches, turn on the master switch (that unleashes power from the aircraft's main battery, just as the master switch does on a non-FADEC-equipped aircraft), place the fuel pump in the Auto position, and turn the key. As the key reaches the Start position the fuel pump whirs to life and the engine starts as easily as a car. Shutdown, since there is no mixture control, involves turning off the key after the electrical switches are off.

FADEC leans the engine automatically, and you can watch it do so on the Vision Microsystems engine display that also displays engine power in percentages. Want 75-percent power? Make the display read 75 percent. (The Continental software did not match up with the Liberty system properly on the day of my flight, so 83 percent equaled 75 percent, but that was to be corrected on the production aircraft.) Once in cruise flight, you'll watch the cylinder temperatures climb as the computer hunts for the lean point, and then drop as the computer enriches the mixture slightly after finding the peak temperature — just the way you'd do it. Also, the system detects from the power setting when you want maximum power and when you would rather have maximum fuel economy. It leans accordingly. It may even know if you've been bad or good.

After advancing the throttle to full power, I confirmed the WOT indication on the Health Status Annunciator and climbed at 80 KIAS from Melbourne International Airport. While the deck angle was steep, the climb rate stayed at 400 to 500 feet per minute since the aircraft was equipped with a fixed-pitch cruise propeller.

At one point during the photo shoot that followed I felt a sudden nose heaviness and discovered that my right wrist, resting on the trim control to operate the throttle, had inadvertently operated the electric trim. The trim motor runs fast, so a short punch of the switch results in a large change in trim. I mentioned that to engineers after the flight, and before my three-day visit ended they were altering the guard around the switch to prevent further occurrences. I was impressed by the responsiveness of the Liberty design crew. They plan to use a slower motor for trim changes. In the future the trim switch will be moved to the control stick, especially if a Chelton Flight Systems digital autopilot now under consideration is tested and approved.

I also mentioned to engineers that I am not a fan of electric flap control switches, such as the one Liberty has, that require the pilot to monitor a gauge until flaps are at the desired degree of deployment. However, Liberty designers were ahead of me, saying a switch that moves flaps automatically to takeoff or landing position is under consideration. The old flap system does not operate in cold temperatures, and represents the only reason why the Liberty's type certificate prohibits takeoffs at temperatures less than 14 degrees Fahrenheit — another reason why the flap motor and switch are to be replaced on the production aircraft. Are such changes possible once the aircraft is certified? Yes, FAA rules allow the company to make numerous "product improvements."

Landings and air work were left for a second flight. Slow flight provided a demonstration of the Liberty's primary stall warning device, actually a computer-generated female voice dubbed Edith. I flew at a speed that kept Edith talkative ("Stall! Stall! Stall!") before finally inducing a full stall and intentionally prolonging it. Generally the aircraft buffeted straight ahead but occasionally snapped a wing down. It was easily raised with opposite rudder.

During a cruise speed check I recorded 122.2 KTAS at 75-percent power with the company pilot on the controls in bouncy Florida afternoon air. Liberty engineers make no secret of their interest in trimming 20 to 30 pounds of weight out of the production aircraft to add speed.

As Liberty pilot Jason Livingston and I returned to Melbourne and started to descend, he suggested I slow the aircraft in level flight. It is so aerodynamically clean that it retains its speed during a descent even at reduced power. The use of takeoff flaps (15 degrees) does little to slow the aircraft to its approach speed of 65 to 70 KIAS. We used 70. On short final, I lowered the flaps to the landing position of 30 degrees and could feel the deceleration forces as the flaps reached their fully extended position. My landing flare tended to be a little high two times out of four, something test pilots claimed they also experienced on their early flights, and until I got used to the sight picture, I held the nose at a slight angle to the centerline. However, there was no problem on touchdown even with the nose slightly off center. Bottom line: It was easy to land.

As John Glenn once said on reaching space, "That view is tremendous." You might want to buy a slap-on sun screen from a nearby auto store for your XL2 in case you are heading into the sun for an extended period of time. Most manufacturers of bubble-canopy aircraft end up painting the top as a sun screen. This aircraft uses gull-wing doors, and between them the cabin ceiling liner blocks the sun in just the area needed. The view is why most of us fly in the first place, but this aircraft adds cross-country speed and responsive controls.

Given all the thought that has gone into keeping the aircraft's operating costs low, the Liberty XL2 is a good value, but more important, it is fun to fly. If you think it is just a trainer, better take another look.

See the original article

Liberty XL2: Give Me Liberty
Alton K. Marsh, AOPA Pilot, July 2004

The aircraft is a 2-place, low wing, single engine airplane equipped with fixed tricycle landing gear.
This airplane is certificated in the normal category. See the airplane’s P.O.H. for approved maneuvers. The airplane is approved for day and night VFR operations when equipped in accordance with F.A.R. 91 or F.A.R 135.

The airplane is powered by a Continental IOF-240-B, Full Authority Digital Engine Control (FADEC) equipped, four cylinder, horizontally-opposed, air-cooled, naturally-aspirated, fuel-injected engine rated at 125 hp at 2800 rpm. The microprocessor-based FADEC system monitors engine operating conditions and then automatically sets the fuel mixture and ignition timing accordingly for any given power setting. Consequently, the FADEC equipped engine does not require magnetos and eliminates the need for a manual fuel/air mixture control.

The Liberty XL-2 airframe fuel system incorporates a fuselage-mounted fuel tank, fuel strainer assembly (“gascolator”), electric fuel boost pump, cockpit fuel shutoff valve, and associated plumbing. There are no fuel tanks installed in the wings. Additional fuel system components installed on the engine include an engine-driven fuel pump, fuel distribution manifold, inline fuel filter, and fuel injection nozzles. The fuel indicating system includes a capacitance-type probe in the fuel tank and an indicator in the left instrument panel.

The primary source of power for the airplane electrical system is a 60-ampere alternator installed on the right forward side of the engine and driven by a V-belt installed around a pulley on the main engine shaft. The primary battery is of the recombinant-gas type and has a nominal capacity of 25-ampere-hours. It provides power for engine starting and as a backup source of power in case of alternator failure, as well as serving to help damp electrical system fluctuations. The secondary battery, also of the maintenance-free recombinant-gas type, has a nominal capacity of 7 ampere hours and is secured to the battery and electrical equipment shelf in the aft fuselage. Its purpose is to provide emergency backup power to the engine FADEC system, attitude indicator, and turn coordinator in the event of loss of primary power.

  1977 Grumman American
AA-1C T-Cat (with climb prop)
1977 Grumman American
AA-1C Lynx (with cruise prop)
Engine:    
Model Lyc.  O-235-L2C Lyc.  O-235-L2C
No. Cylinders 4 4
Displacement 233.3 cu. in. 233.3 cu. in.
HP 115 115
Carbureted Or Fuel Injected Carbureted Carbureted
Fixed Pitch/ Constant Speed Propeller Fixed Pitch Fixed Pitch
     
Fuel:    
Fuel Capacity 24 gallons 24 gallons
Min. Octane Fuel 100 100
Avg. Fuel Burn at 75% power in standard conditions per hour 6.8 gallons 7.8 gallons
     
Weights and Capacities:    
Takeoff/Landing Weight Normal Category N/A N/A
Takeoff/Landing Weight Utility Category 1,600 lbs. 1,600 lbs.
Standard Empty Weight 1,002 lbs. 1066 lbs.
Max. Useful Load Normal Category N/A N/A
Max. Useful Load Utility Category 598 lbs. 534 lbs.
Baggage Capacity 100 lbs. 100 lbs.
Oil Capacity 6 quarts 6 quarts
     
Performance:    
Do Not Exceed Speed 169 KCAS 169 KCAS
Max. Structural Cruising Speed 125 KCAS 125 KCAS
Stall Speed Clean 57 Knots 57 Knots
Stall Speed Landing Configuration 53 Knots 53 Knots
Climb Best Rate 750 FPM 700 FPM
Wing Loading 15.9 lbs./sq. ft. 15.9 lbs./sq. ft.
Power Loading 13.9 lbs./hp 13.9 lbs./hp
Service Ceiling 11,900 ft. 11,500 ft.