IN FOCUS: Flight Design CTLS in the air

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During a demonstration flight with pilot Tom Gutmann on 28 March, a tower controller at the bustling Lakeland Linder Regional airport in central Florida, home of the annual Sun 'n Fun general aviation gathering, repeatedly called us "the Remos". It is an easy mistake to make - both are similar in shape, composed primarily of composites and are German-engineered.

However, Flight Design is officially the top player in the factory-built light sport aircraft (LSA) market in the USA, with a 15% market share - with 1,800 aircraft delivered to date - compared with Remos' 5% share as of the end of 2011.

flight design ctls, jogn croft/flightglobal

 © John Croft/Flightglobal

The CTLS's small size belies a tough pedigree proven by multiple round-the-world journeys

Our demonstration CTLS was built in 2009, but with no signs of wear or tear on paint or in the relatively spacious cabin. Powered by a four-cylinder normally aspirated Rotax 912ULS - fitted with a three-bladed, ground-adjustable composite propeller - N635CT carries a Dynon Avionics EFIS 100 glass cockpit 18cm (7in) primary flight display, a portable Garmin GPSmap 496 navigation unit in the middle, and 18cm Dynon EMS 120 engine-monitoring system display on the right side.

Along with a BRS parachute, activated by a pull-pin and lever in the aft portion of the centre console, the CTLS carried a TruTrak FD-Pilot two-axis coupled autopilot on the left side of the panel.

COCKPIT CHOICE

The glass cockpit was relatively dated for a light sport, with recent customers tending to equip the Dynon SkyView 25cm displays, including synthetic vision, with a Garmin 696 navigation unit in the centre. Starting this summer, the Flight Design will also offer the new fuel-injected, electronically controlled Rotax 912iS engines as part of the CTLSi package, priced at $13,000 more than a legacy CTLS.

The CTLS's diminutive size belies its tough pedigree, proven by multiple round-the-world journeys with the CT family. Gutmann, who hails from Tulsa, Oklahoma, where winds can howl, says he has flown the CTLS in 40kt (74km/h) winds without issues. The aircraft's maximum crosswind capability is 16kt, similar to much heavier normally certificated single-engined aircraft such as the four-seat Piper Archer.

Wind was not a factor during our mid-morning flight. Gutmann, co-owner of Airtime Aviation in Tulsa, which in 2001 became the first Flight Design dealer in the USA, performed the pre-flight, which was standard fare for a small aircraft.

Getting into the CTLS is fairly easy compared with some LSAs, the procedure being to back into the seat - in my case, the left seat - then swing your right leg over the floor-mounted control stick.

Seats are adjustable in horizontal position and pitch before entering the aircraft. I had enough legroom for my 160cm height, but could have pulled back another 15cm or so for more leg room had I been launching on a cross-country flight.

The two sides of a four-point seat belt can be a challenge to grab from behind your back without help, but is comfortable and gives a sense of security once strapped on. Spartan metal tube rudder pedals on both sides of the cockpit provide nosewheel steering on the ground, with a single brake lever on the centre console, similar to the design in older Piper aircraft such as the Colt and Cherokee 140. I found both steering and braking to be smooth and predictable.

Also on the centre console are an electric flaps lever and manual controls for elevator, rudder and aileron trim. Flap deflection ranges from minus 6˚ for cruise flight - Gutmann says the upward deflection adds 6kt of cruise speed - to 35˚ down for short-field landings.

ENGINE EFFICIENCY

Engine start is standard Rotax-style: a turn of the key and a jolt as the propeller comes to life through the 2.43:1 gear ratio. The gearing allows the engine to run at an efficient 5,000rpm, while the propeller turns at optimum and quiet 2,050rpm in cruise.

The liquid-cooled Rotax burns 6.7gals/h (25 litres/h) at full throttle (5,050rpm) on take-off and about 5gals/h in cruise, making the CTLS relatively easy on the wallet compared with light aircraft which burn 7-9gals/h at similar cruise speeds.

Flight Design says the new 912iS engine will cut cruise fuel flow to about 4gals/h compared with the 912ULS. The CTLS holds 17 gallons of avgas or auto gas in two wing tanks, all of which is usable.

Take-off was brief, appearing to be less than the 250m (820ft) gross-weight take-off distance in the book for this 80˚F (27˚C) morning. Gutmann used 15˚ flaps for take-off, the same increment he and most other owners use for landings, and began pulling in back-pressure when passing through 40kt. Off the ground at 50kt, he lowered the nose and accelerated to a 75kt climb speed that offered good visibility over the nose and 500ft/min (2.54m/s) climb rate.

Once away from the airport we climbed above 3,000ft, where Gutmann demonstrated the CTLS ginger control characteristics - new pilots tend to over-control - and benign, perhaps boring, power-off and power-on stall characteristics. With no flaps, the aircraft stalls straight ahead at 52kt, descending at 1,000ft/min if held in the stall, and recovering quickly into a climb with application of power. A full-flap stall at 38kt produced similar results, but with a 1,500ft/min descent until power-on recovery.

As for the Remos comment, Gutmann let the controller's honest mistake stand, putting the CTLS down at 50kt with 15˚ of flaps on the requested orange marker halfway down the runway.

SEARCHING FOR A NEW COMFORT ZONE

German airframer Flight Design, the world leader in light sport aircraft sales with its two-seat CT family, is about to try its well-engineered luck in a new and larger market space - the four-place general aviation sector.

The move highlights a coming of age for Flight Design, a company which started out in the 1980s building ultralights and hang-gliders, but has now found much success in the steadily growing, seven-year-old factory-built light sport aircraft (S-LSA) market in the USA. Worldwide, the company has more than 1,800 aircraft in service, 400 of which are in the USA. Of the 400, about 200 are the all-composite CTLS model, first introduced in 2008.

flight design ctls, jogn croft/flightglobal

 © Flight Design

The CTLS's maximum cruise speed is 120kts

Overall, the company has almost doubled its market share (15%) compared with its nearest S-LSA competitors, Cessna and Cub Crafters, both with 8%. Like all USA-bound Flight Design aircraft, the CTLS is manufactured in Ukraine and reassembled and test flown at the company's office in Connecticut.

ADDED EXTRAS

A nicely equipped CTLS with synthetic-vision glass panel and 100hp (75kW) Rotax 912ULS engine costs about $160,000. Add another $13,000 and you can get the latest Flight Design innovation - a fuel-injected, electronically controlled Rotax 912iS engine, available later this year (see sidebar).

The four-place composite-built C4, scheduled for first flight in the second half of this year and entry into service in 2013, will offer a new class of customers a leap in performance and price, setting Flight Design against mainstream airframers of similarly performing aircraft such as Cessna's 182 Skylane and Diamond's DA40, but at a projected buy-in cost about $100,000 lower.

When certificated in 2013, the $250,000 C4 will have a 160kt (300km/h) maximum cruise speed or 1,200nm (2,200km) maximum range with 70-gallon fuel supply, while burning 7-10gals/h (27-38 litres/h) with a Continental IO-360-AF six-cylinder fuel-injected engine. A diesel-powered version will follow, says the company, although it has yet to reveal an engine provider.

By comparison, the CTLS can cruise at a maximum speed of 120kt (the limit set by ASTM standards) or fly as far as 850nm on 34 gallons of avgas or auto gas, with typical fuel burn rates of 5gals/h.

The C4 cabin has left and right front-seat automobile-style doors, with a "Pullman" configuration on the left side, with a rear door that opens aft to create a large entry area on the left side. Flight Design says the back seat will accommodate two large adults.

Avionics remain a mystery but promise to be enticing. Product information sheets say the aircraft will have a glass cockpit with optional autopilot and dual 25cm (10in) displays, offering traffic, terrain and synthetic, but an integrated avionics vendor has not been identified.

"We have had some delays on avionics," says John Doman, US-based director of business development for Flight Design. "We need a proper combination of new technology features, price and path to certification." He says the company is "in negotiations with various avionics suppliers" and is targeting year-end for an announcement.

NEW AVIONICS

Matthias Betsch, chief executive of Flight Design, says the avionics package must have synthetic vision to protect against controlled-flight-into-terrain crashes, but will also have a means for envelope protection. "We should not take the avionics of the last generation for an aircraft of the next generation," he says.

Pilots must be able to override the envelope protection system, Betsch says, labelling it the design team's "next goal" in the coming 12-24 months.

"Everything is available at the moment but in a different category of airplane and at a different price. There are directions, however, where this should be possible," he adds.

Given Flight Design's desire to contain cost, the requirements would appear to favour Garmin or Avidyne for the cockpit, as both are present on other light aircraft and both have envelope protection systems that yield to the pilot if so desired. But other avionics providers are likely to develop solutions, including Dynon.

Although the number of C4 orders has stayed at 65 since July 2011, Doman says he expects a "ramp up" after first flight. Last year, Flight Design said it invested in tooling and production systems to build 250 aircraft per year.

Betsch appears to be more reserved in his projections in the near term. "Everything when we sell more than 100 aircraft per year makes us happy," but he added that he thinks "there is a high potential" for this aircraft.

APPLYING A LIGHT TOUCH TO ENVIRONMENTAL IMPACT

Saving fuel becomes a concrete concept when each gallon costs more than $5, yet traditional mechanical leaning methods - "one-point" solutions - rarely result in best fuel economy. That is why Rotax and Rockwell Collins joined forces about three years ago to cut fuel burn and associated costs and emissions. The resulting product, set to hit the market this summer, is the 100hp (75kW) Rotax 912iS fuel-injected, electronically controlled four-cylinder piston engine. Flight Design will offer the engine on its new CTLSi model this year, as will a variety of other light sport and small aircraft manufacturers.

The 912iS at a typical power setting and cruise altitude cuts fuel burn in the 100hp Rotax engine by 21% compared with its dual-carburetted Rotax siblings. For a US-based operator annually flying 300h, that is about $1,500 in fuel not burned per year, resulting in an eight-year return on investment, assuming an extra $12,000 or so to equip with the 912iS rather than the 912ULS.

"Fuel burn is such a dramatic inhibitor to flying," says David Vos, senior director of UAS and control technologies at Rockwell Collins. "Anything that can be done to show improvements there is very exciting."

A FADEC for a commercially available Rotax engine has been a long time coming. Starting in the early 1990s, Aurora Flight Sciences began developing digital controllers for Rotax engines for unmanned aircraft using algorithms developed by Vos.

Vos continued the work at start-up company Athena Technologies, which transferred to Rockwell Collins when it purchased Athena in 2008. Rotax issued a request for proposal for the project about three years ago, attracting several bids.

ENGINE MONITORING

Coupled with an engine control unit (ECU) that can cut fuel burn by 21% at cruise power - 4-5gals/h (15-19 litres/h) for the Rotax 912 compared with the carburetted version of the 912, and 30-70% less compared with some other similar-performance engines - the 912iS features an engine monitoring unit (EMU) to allow pilots to monitor engine performance data hitherto unavailable for small piston engines.

flight design ctls, steve fletcher

 © Steve Fletcher

Flight Design is among the manufacturers planning to use the Rotax 912iS engine

The EMU itself is connected to cockpit displays using a four-wire "CANaerospace" network protocol developed by Germany's Stock Flight Systems. Owner Michael Stock says the EMU records engine data at 10Hz and stores the data on an SD card up to 16Mb, allowing for 500h recording. Owners can download an analysis program from Rotax to evaluate the data, or obtain the information via service centres.

As well as various typical engine performance parameters, the EMU will record latitude, longitude, airspeed and universal time using a built-in GPS/Galileo receiver by Swiss company u-blox. Along with enabling pilots to view flight tracks post-flight, the data could help engine analysis by linking engine operating parameters with phase of flight, which could be particularly useful in accident or incident investigations, says Stock.

Rotax expects to finish the internal documentation required for ASTM compliance (for US light sport aircraft) in June and expects European Aviation Safety Agency certification approval in June or July.

"It's a pretty exciting step for me personally," says Vos of the 912iS, adding that new control system-related projects are also "under way" at Rockwell Collins. However, he notes that "good amounts of time" take place before game-changing new technologies enter the market. His first patents for the ECU design for Rotax date back to 1997.