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Thu, Aug 15, 2002

ANN Exclusive: First Flight Test of the Liberty XL-2 (The Whole Story)

Part One: What IS A Liberty XL-2?

I've been looking forward to this one… the first chance to get a hold of an aircraft that appears poised to take on the legacy left SO-o-o-o-o-o long ago by the Cessna 152, Piper "Trauma"hawk, Beech Skipper, Grumman Yankee/TR-2 and a few rarely remembered has-beens.

While the industry's doldrums have relented sufficiently enough to see a number of new and oft innovative four place designs come to the market, there has been a dearth of two seaters that can serve both the airplane-starved training market as well as a burgeoning entry-level aircraft ownership market that I truly believe is far larger than many think.

While the CH-2000, the Diamond Katana, and the OMF Symphony are, indeed, out and about, the market has needed a solid shot in the arm… a little more modern technology (unlike the ultra-conservative CH-2000) and a serious production chain (unlike the Symphony, which may be stopped in its tracks due to the ever-present specter of a legal shutdown -- at least here in the USA). Only the Diamond Katana, especially the Continental-powered C1 rocketship (a heckuva nice bird), seems competitive under the circumstances.

But: the Liberty XL-2 could be the deal-breaker… THE bird that breaks through to a nearly stagnant part of the GA market and excites a significant number of people enough to depart from their occasional aircraft rentals and become real-live aircraft owners.

It offers some significant inducement: outstanding styling, a serious upgrade in technology, an overt effort to make the bird economical to operate, and more performance than the birds in this genre generally offer. Looking, first, like an offshoot of Ivan Shaw's highly regarded Europa trike-gear, the XL-2 is actually a significant redesign of a planform that kept the best aspects of the Europa's aerodynamics (with some inspired tweaking by Shaw and aerodynamicist Don Dykins) but adapted it to a 21st Century airframe that is designed to be durable, buildable and economical.

A Whole New Approach

The $116,500 (base price) VFR/IFR day/night bird mixes a number of technologies -- each according to what suits itself to the mission at hand. The fuselage is a tough high-tech carbon fibre shell wrapped around a rugged steel-tube substructure; the main landing gear is aluminum; the wing/horizontal tail is simple/conventional metal; the 125 HP Continental engine is FADEC-equipped; and the 48-inch wide cockpit was actually designed to fit real-life-sized adults (rather than the midgets GA has been building planes for, lo these many years).

One of the more laudable features of the XL-2 is the decision to go with a FADEC system for the installed powerplant. This is the first serious implementation of such a system on a mainstream GA serial production aircraft. Teledyne Continental IOF-240-B's Powerlink FADEC (Fully Automated Digital Engine Controls) engine control system offers computer controlled electronic ignition, a sequential direct port fuel injection system, a devilishly simple single lever throttle, computerized cylinder control, a maintenance data port (from which you can download and track engine histories and perform diagnostics), induction air filter and a full flow oil filter.

One keeps track of the health of the powerplant via a Vision Microsystems VM-1000 mounted on the bottom center of the panel on the left side of the cockpit (though it is quite visible and readable from the right), that offers both graphic as well as analog readouts, 'Autotrack' Mode (which lets you know when the engine changes its mind about a certain parameter), 'Diamond Graph,' Tachometer, Percentage/Power Readout, EGT, CHT, Volts, Amps, MP, Fuel Pressure, Oil Pressure, and Oil Temp.

The whole works is fed by a single integrated 28 gallon fuel tank in the fuselage. Supporting fuel systems include a quick drain fuel valve, engine driven fuel pump, an additional electric fuel pump-boost, the obligatory fuel gauge (electric) and a fuel shutoff valve.

The XL-2 uses a 14 volt electrical system, with dual Condorde lead-acid batteries (each chain of the FADEC has its own), a dedicated Avionics Master Switch (to augment the standard master switch), a 60 amp alternator (with warning annunciator), and a series of pull-type (trip-free) breakers on the far right hand side of the panel. An external 14v APU plug is standard. The standard cockpit comes with conventional basic instruments and the panel design is one of the few things slightly reminiscent of the Europa… with the prominent protruding radio stack in the center and the diminished reliance on the right side as a nesting place for instrumentation and avionics (instead being the home of the circuit breakers and such-though a glove box or chart-holder might be welcome here, to boot). The overall effect is expansive, well organized, and reasonably accessible from either seat.

Currently, Liberty offers either Garmin or UPS avionics… though the bird I flew had a UPS stack that included the luscious MX-20… one of the nicest MFD systems currently available (and a box that really makes getting around complicated airspace a singular pleasure). There is good visibility over the top of the panel and the side-slope offers adequate peripheral vision for most operations without having to go into "giraffe mode."

I was particularly pleased with the large and well placed adjustable cabin vents (which abut each side of the cockpit just underneath the bottom ledge of the panel)… since the XL-2 boasts lots of gorgeous glass, its sure to heat up when the Sun is doing its thing. Cabin heating is standard, as is a windshield defroster, stereo headset plugs, and some good sized map/storage pockets attached to each seat. 

The center console between the seats hosts some unconventional features… at least one of them destined to be somewhat controversial.  The ground steering is not accomplished via toe brakes (though an option will allow that for those who insist on it). Instead, the free-castering nose wheel is directed via two small finger-operated levers next to the throttle (which actuate Cleveland wheels and brakes). Slight pressure deploys the brakes, either together or differentially. It's going to tick off a few folks, but I found the system (not the first of its kind that I'd seen) to be easy to operate, deft at directing the plane on the ground, and overtly pleasant to work with -- though I just know that a few folks are going to hate it and opt for the normal (and available) state of affairs. A parking brake is part of the two-lever system and I appreciated its lack of complication: A small lever (between the brakes) is pulled up as you pull back to "lock" both brake levers, and the stopping power was sufficient to hold us during an aggressive run-up. Releasing it is a simple push/release on the lock, downwards, and off you go.

The throttle is a single control… there is no mixture -- that's a function of the FADEC. On the bird we flew, the throttle was pretty sticky to operate and one of the casualties of the constant R&D process, but its positioning is awfully convenient and the ergonomics are "right on."

Close by lies the electric pitch trim, augmented by a panel-mounted gauge that measures deployment (a bit sensitive on the prototype and promised to be detuned well before production birds roll off the line). Forward on the center panel, on the inclined section between the console and the instrument panel is the flap lever and a small gauge that mirrors flap position… though I far prefer looking out over the wing and simply checking it directly (where the Liberty gang has put two taped strips to denote the 15 and 40 degree setting-I hope they do that with production birds).

Overall, the airframe presents a pleasant roomy feel with an obvious effort toward workable ergonomics that produces a cockpit that is a pleasure to work and play in… and an obvious departure from the Marquis de Sade school of cabin design that was typical of most GA designs for way too long. I liked it… it didn't feel like an entry-level basic airplane, but one that that should have been typical of a more expensive airplane… and this was a trend that was to continue as the ground inspection gave way to the actual flying.

Getting Ready For the Flight Test

First, some caveats: this is the much loved but nonetheless abused production prototype; it is a bird that has been ridden hard and put up wet… more than once. It is not a pampered and primped bird meant to be presented to the wimpy media as a best-case scenario. It is a battered and slightly bruised workhorse/test-bed that is already showing some wear and tear and has been used to try out a number of modifications (which have not always worked -- which is the way these things are supposed to go). Under normal circumstances, this is the LAST bird you show the media… but regardless of that, Liberty Aerospace gave me carte blanche to go beat the little critter to death… and I did (but knowing me, they probably didn't want to risk a perfectly good airplane with yours truly).

It was definitely an acid test: the temp was above 90 degrees, the DA was a little higher than we normally get at near sea-level Winter Haven, the load was right at the max gross (especially on my side of the aircraft--and this was BEFORE lunch, thank God), and the prop's paint had been chewed up in a recent rainstorm so badly it had to be cavitating like a Waring blender. I wasn't expecting a whole lot from it under the circumstances and expected to have to give the airplane the "benefit of the doubt" during the flight test. I was wrong.

Space, The Final Frontier…

The current prototype is not yet equipped with a step, so the preferred entry method is to walk to the leading edge of the wing, turn around, sit back and slide back on the wing and up onto the door ledge and into the cockpit. Not as cumbersome as it sounds, this is a temporary move that will serve until steps are installed. Once inside, one notices something really unusual in a two seater: space. Lots of it. There is shoulder room, leg room (especially with the adjustable rudder pedals), head room, you name it… and just behind the two seats is a BIG baggage compartment (4ft x 3ft x 2ft) that will easily take more baggage than one should reasonably load (please note… space is one thing, payload is another… be sure you know what your baggage weighs before throwing it aboard -- and the limit in the XL-2 is 100 pounds).

Adjustable pedals and comfy seats, four point belts and the roomy confines making settling in for the flight a pretty secure and easy affair -- especially for those of us who are "dietetically enhanced." The clamshell doors swing way up and out of the way so that they are of little consequence until time comes to shut them.  The XL-2 offers dual controls… that are actually not quite dual. Each stick is one half of a U-shaped affair that connects in the center of the fuselage, underneath the center tunnel that separates the seats. The effect is agile and not nearly as disruptive as similar implementations I have seen on other designs trying for the same simplicity of control circuitry.

This one works.

Startup is no big deal… turn on the master, ready the appropriate support systems (lights, pumps, avionics, your favorite boogy-woogy music, etc), flip on the dual FADEC systems, and turn the key to get the little IOF-240 rumbling to life.

With the housekeeping out of the way, it was time to make our way to Winter Haven's Runway 4 for the good part of this job. A little throttle got us rolling and some tweaking on the brake levers kept us on the straight and narrow… while I am generally one for "creative" taxiing (i.e., wallowing around like a drunken sailor), I played with some adherence to the centerline and found the system to be easy to precisely direct. Braking action is good, taxi visibility is very good and the ride is fairly comfy… even with some of Winter Haven's well-known pavement irregularities to make things interesting.

Run-up is conventional: lock the brakes, set the revs and simply add a check of either FADEC chain to the list before you head for the wild blue. The Vision Micro System gauge's placement makes for easy diagnostics and offers little guess-work when it comes time to make the decision to aviate.

I elected a no-flap takeoff for the first go. We had a light quartering crosswind of less than 6 knots, and after centering the nosewheel, I advanced power swiftly, pleased with the IOF-240's excellent linear response to throttle input right from the get-go. The rudder on the XL-2 is no wimp… even as we barely got rolling, it was obvious that we were done with the brakes. A tap on the pedal centered things very obediently and the Liberty tracked the center line like a slot car heading for the finish line.

With excellent coaching from Liberty's Jason "Ace" Livingston, the new Liberty demo pilot, (who is going to learn the true definition of fear over the next few weeks--nothing I have ever done is as weird and potentially hazardous as shepherding pilots of all kinds through the rudiments of a demo ride…), I lightened the nose wheel with a half pound or so of aft stick pressure (the aircraft pre-trimmed for conventional take-off norms), at about 40, increased the pressure slightly about 55-60 knots and started flying just a hair short of 1000 feet down the runway. The no-flap takeoff attitude is fairly flat… only a few degrees pitch positive but the bird accelerated well to 70-75, gave me a solid 550-700 feet per minute and immediately showed its John Wayne nature with aggressive corrective response to the building thermals as we proceeded over the wilds of Winter Haven for the dreaded Captain Zoom Torture Test (i.e., which happens every time I fly… It ain't pretty, I admit it. KIDS, don't try this at home).

The initial climb to 2000 AGL took about three minutes and I noted a pretty significant bit of low amplitude vibration from the much-abused prop, which was obviously not up to doing its thing too well -- though it didn't seem to hurting the aircraft's overall performance one whit. Climb visibility was fairly good in all but steep/best angle configs where the panel finally got in the way, and cruise visibility is just plain panoramic…all that glass is put to good use… especially peripherally…it's like flying in a goldfish bowl and is a thoroughly enjoyable pursuit, at that.

Set up for cruise, (about 100-110 kts IAS), I noted a modest amount of aerodynamic feedback inherent in a control system that had already distinguished itself with a lack of mechanical friction and little in the way of mechanical breakaway inhibition. The stick offers a slightly wider than normal range of movement in both pitch and roll as well as an appreciable mechanical advantage for the pilot… which translates to a system that is slightly to moderately-pressured, even at high speed, and promotes an unwillingness to act overtly sensitive or over-control the critter.

Steady as She Goes!

Stability and control investigations were immediately impressive. Overall, the XL-2 is highly responsive, as required, but the control system boasts a high degree of linearity on cruise control responses and equally linear force requirements. Since there is a wide range of control in the stick, light inputs are not radically responsive… but if you get persuasive, this thing can rock and uh, well, ROLL. Yeah, baby!

Pitch stability is tightly defined. Properly configured, a cruising XL-2's static stability also takes on slot-car like adherence to the trimmed attitude. Numerous excitations from the trimmed configuration of some 10-20 degrees (3 degree per second onset and stick-free), produced one, occasionally two, excursions before getting back to business. In most cases, the oscillation (a poor term for what really occurs) is practically deadbeat with but a single wimpy "girly-man" cycle. The cycle was highly convergent and of low frequency. A few quick attempts to excite some aero-uglies in the short-period pitch profile produced a highly convergent response that was also about as deadbeat as it gets -- especially in a light piston bird.

Roll/yaw harmonize really nicely… especially for those of us who feel the need to play "12 O'Clock High" every now and then (OK… all the time). Yanking and banking with the XL-2 can be a lot of fun… but is also a most obedient pursuit. The rudder is modestly separated (just about right, I think, for this genre of light aircraft) and also banks the aircraft well with anything more than a modest tap on the pedal. The roll axis offers light to modest adverse yaw and coordinates well with the rudder to produce an excellent roll rate… especially with significant input. With steady-heading side-slip investigations and such, the XL-2 proved itself fairly positive and directionally persuasive in both roll and yaw. Control pressures vary from light to moderate, are nearly as linear as pitch, and blend to produce a pretty nice combo of obedience and stability.

Slowed down, control pressures lighten up perceptibly but modestly. I noted some 20-25% diminution of control force feedback over the cruise to slow-flight transition and less diminution in overall control response. Stability investigations were somewhat less positively defined (in terms of dynamic response... but the static margins still were still impressively accurate), but still far more positive than other birds this light and in this performance profile. All in all, a pretty nice mix.

I Feel the Need… The Need for Speed

OK… I can hear you all now… "Screw all the funky stuff, Zoomer, just how fast is this critter?"

Well, OK, I'll tell ya.

Even with the paint still peeling off the prop (a horrible thing to do to what was obviously a nicely matched Sensenich), a few runs were made at 2000-2500 MSL with GPS coordination on a few reciprocal runs. With the FADEC popping along at 65-70%, the Liberty bird offered a solid 114-116 knots… far better than I had a reason to expect. Full tilt boogy, with everything mashed to the firewall, and all 125 ponies beat into a furious FADEC frenzy, the XL-2 offered up well over 120 knots… with 121-123 being the mean. Mind you, that's with the prop doing the strip tease, a full gross load, and playing down in the weeds, instead of up high where this thing is really meant to shine. Liberty says it will do 132 knots at max cruise, and at a more efficient altitude (I think they're using 8000 feet for that…) and I feel quite strongly that they'll meet or exceed those numbers… especially with the way that Continental is reportedly starting to dial in that FADEC…

Whoa! Liberty!

When last we left ANN Editor-In-Chief Jim Campbell, he was just finishing up the weapons systems testing of the Liberty XL-2 by pickling off a few "Saddam Surprises" during a short run over downtown Baghdad… or not.

OK, he was really over Central Florida and the bomb racks were empty… but he was going pretty fast and getting ready to see what happened when the XL-2 finally slowed down…

As previously noted, the XL-2 is equipped with electric flaps. However; before I deployed them a few runs at 55-60 knots and then to the onset of a stall buffet showed off good response, a lightening in overall control pressure that was accompanied by a milder diminishment in overall control authority. Particularly positive was the rudder response up to and through the initial buffets and recoveries… with a surprising amount of roll authority still at my beck and call.

making sure things were down to about 80 knots (which requires retardation of the throttle and a pretty pitch positive attitude), I offered up 15 degrees of flaps (associated with the preferred take-off setting) and noted a significant negative pitch trim excursion that required a few pounds of aft stick pressure to correct until I could re-trim the bird. Immediately; I noted a significant change in personality. While the no-flap XL-2 is a speedy (even slightly "slippery") little devil with some speed-demons at its heart, the "first notch" of flaps on this thing produces an even milder mannered personality that still boasts excellent authority and stability (especially in pitch) but the enhanced drag profile makes it far easier to keep things in the 70-80 knot range… which the slipperier no-flap bird zooms through with abandon. Maneuvering in this configuration is docile, a bit more rudder-dominated (and attended by more significant adverse yaw in the roll axis) and very pleasant. Speed degradation in this draggier configuration is not that big a deal since the bird offers excellent physical and aural clues when it approaches the critical angle of attack. A stall is not going to catch you by surprise unless you're doing a Helen Keller impersonation.

Initial attempts at a full stall were met with little success in that the bird offers a prominent high frequency, low amplitude buffet that increases with severity (with increasing alpha) but we simply ran out of pitch authority before we ran out of lift… even with a 2-3 degree per second pitching onset. Flat out, we simply couldn't coax a real-live break out of it with only 15 degrees of flaps.

Hanging It ALL Out…

Full flaps (about 40 degrees) presented an interesting configuration. It didn't feel like a lot more drag, the trim change was milder than with the first 15, and the overall effect on the bird, outside of a more negatively trimmed attitude, was pretty much a non-event. Proceeding to a stall was just as "shaky" an affair with a slightly more pronounced buffet of modestly higher frequency and slightly more adverse yaw. We got some mild buffets out of it with mild pitching onsets but a more aggressive pitching sequence (in excess of 5 degrees per second and with a slightly accelerated "load"), finally got the Liberty XL-2 to do something that wasn't boring us silly. With significant inducement, we got a good solid break that favored the increased weight on the left side of the aircraft and a pitch down of some 40-50 degrees. The aircraft rolled off to the left quickly for some 20-30 degrees and then just quit as the aircraft immediately reasserted itself into a flying configuration. No corrective rudder was needed (and indeed the roll-off was just that) and no yawing through the break was noted. Each axis was immediately response and a few quick boots (either way) on the rudder showed that it was VERY much alive and well throughout the process but not willing to do anything obnoxious, either. I kinda surprised Jay Livingston a mite since I had a feeling no one had abused the XL-2 like that but the recovery was swift, thoroughly controllable, and utterly conventional. Altitude loss was in the range of 150 feet. Hmm… if that's as bad as it gets, that's gonna be just fine with me (you should see what kind of nasties you can get out of a ho-hum Cessna 152 with similar inducement…).

Heading for the Home-Drome

With the slow stuff out of the way it was time to reacquaint ourselves with Terra Firma.  Heading back to Winter Haven, we slowed up in the pattern to 90 knots, and then 80 knots, as we turned base, with 15 degrees of flaps adding nicely to the speed management chores. The day was getting kinda bumpy, but the XL-2 rode the uglies nicely with a minimum of Dutch roll and other displacements.  Jason did a great job of briefing me on what was required from there on, so I used a slight slip to get rid of some extra altitude, and still keeping us on the high side of the slope; I dropped the rest of the flaps and was rewarded with 65-70 knots and a great descent attitude that offered equally great viz. No additional power was necessary to make the field as the efficient little XL-2 kept flying and held onto altitude pretty tightly. A light crosswind was child's play with a slight bank to counter the drift), and a roundout about 2 feet in the air (with a modest tendency toward floating) turned out to be just a tad late as I touched down a smidgeon over 60 kts (a little too fast). The resulting skip damped out quickly, the rudder remained very active and kept us pointed exactly down the centerline (a sight I'm not all that used to, I admit). Light braking produced good deceleration, but I missed the first turn-off and turned in a 1500 foot landing that could have been a heck of a lot shorter.

Click to Enlarge Heading back for another try, I elected to use 15 degrees of flaps for this departure and was rewarded with a really nice change in that the aircraft rotated a lot more readily at 50 knots, lifted off about 55 kts (and well under 700 feet down the way) and climbed rather well at 65 kts for a bit, until I elected a 70 kt attitude and settled into a 700 fpm climb. The whole personality is a good bit more "uplifting" with a little flap, and I heartily recommend this procedure for all but the longest runways. A quicker trip around the patch resulted in an already familiar and comfortable profile that I kept on the high side in order to play with the slip a bit more… an area in which the XL-2 excels nicely.

A slightly higher and more positive roundout (still holding a slight slip in order to kill off the float and the growing cross) offered up a more draggy touchdown, as we decelerated through 55 kts, that produced the proverbial greaser... which, with light to moderate braking, gave me an easy 900-1000 foot landing and a turnoff at the first exit off the runway. It was a very pretty landing (a genuine novelty for yours truly) and I so wanted to get out and take a bow, but the Winter Haven airport manager tends to frown on such things. Still; it was a piece of cake!

Test Pilot's Summary

Wow… not bad at all. But then again, as the god-child of guys like Ivan Shaw, Don Dykins and the team at Liberty (who has impressed us all the more, with time), I shouldn't be surprised. This is a very competitive aircraft and with only one other truly modern and available bird (the Diamond Katana series) out of the four or so in this genre (Liberty, Diamond, OMF and AMD) that deserve any real consideration for your aero-bucks; it's going to be fun to see how the XL-2 sells over the next year or two… I have feeling its going to do well… especially once owners get out and do some braggin'.

The $116,500 XL-2 seems modestly priced, though one should note that this is for the bare-bones airplane. A number of packages will bring that price up a bit to suit the needs of the owner. The basic gyro package (Artificial Horizon, Direction Indicator, Turn Coordinator and the appropriate plumbing) is $4450, wheel pants and flap hinge fairings are $1425, a leather interior is $1200, an extra-snazzy paint job (instead of the plain white version) will set you back another $2k and a series of VFR and IFR avionics packages from Garmin or UPS start at $6651 and top out at $27,369. Count on $130K for a well-equipped VFR bird and $145-150K for an IFR scooter with lots of capability (including an MFD).

Overall; the XL-2 is living up to the hype that is building over this new entry in the two seat GA sweepstakes. The bird emphasizes a playful but overtly obedient personality with excellent stability, great performance and truly outstanding economics. While a good bit of my background is filled with flying various rocketships willy-nilly through the ether, I have to admit that I both appreciated and enjoyed the feel of this simple little side-by-sider. It, simply put, was a lot of fun to fly. Liberty has a hell of a good little airplane on its hands, and I really look forward to flying a production bird later this year. Highly recommended.



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