Diamond's DA40 Star offers comfort, speed and efficiency in the crowded entry level
Dave Higdon/PLANT CITY, FLORIDA
After a couple of false starts in the 1980s, composite aircraft finally established a foothold as production machines in the last decade, and no fewer than three new designs have come to market within a two-year period. The aircraft leading this new wave include Cirrus Design's SR20, Lancair's Columbia 300 and Diamond Aircraft's DA40 Star. And there are more to come.
Fortunately for pilots, each member of this trio of tricycle-gear machines occupies a distinct niche in horsepower, price and performance, rather than simply being clones of similar speed, size and comfort.
Diamond's DA40 is the latest into service, befitting its status as the least expensive and lowest horsepower of the group. But far from being a shadow of its composite cousins, the Star delivers distinctively solid performance, comfort and a level of efficiency uncommon for even a composite light aircraft.
The Star's performance easily beats other fixed-gear, 135kW (180hp) singles, such as New Piper's Archer III and Cessna's 172 Sky-hawk SP. Furthermore, the Star offers flying capabilities suitable for every level of general aviation pilot - just like the Cessna and Piper.
Diamond Aircraft has poured all of its13 years' experience of building composite aircraft into the DA40 Star.
It was apparent during my walk to and around the prototype flown for this flight test that the aircraft was a workhorse that had already enjoyed a record of use and abuse few production aircraft ever achieve.
The glossy white, UV-resistant finish on the carbon fibre airframe appeared nearly flawless, save for a few signs of wear and tear from its use in an accelerated testing programme.
Tall t-tail
At the time of my flight, this aircraft had already logged more than 1,100h and over 16,000 landings in under a year. Performing the normal pre-flight inspection walk took no more time than for most aircraft of its class, and required only visual or touch checks of the control surfaces. The elevator on the tall T-tail was the only item out of my reach. This has dual actuators, but since even the lock nuts were visible from my position, touching them was unnecessary.
Confirmation of control-linkage integrity involved nothing more than sitting in a front seat and moving either of the dual floor-mounted control sticks which the Diamond's designers elected to use. Uncommon on most light aircraft today, those "joysticks" cannot interfere with the front seats, since all seats are fixed in position to help the airframe meet the stringent 26G impact tests required for US Federal Aviation Administration certification.
To allow for different pilot heights, Diamond has opted for rudder pedals that are adjustable fore and aft. These provide plenty of range for all but the shortest and tallest of aviators. Further adjustment comes by using seat and thicker or thinner back cushions. At my 1.75m height, the standard cushions worked perfectly, as did the rudder pedals set a bit closer than half of their movement range.
Checking the engine oil is easy through a cowling door, which also allows the pilot to determine whether an errant bird has decided to nest atop the Lycoming IO-360-MIAengine used on the aircraft. With 135kW on tap, the Star is the lowest power of its class of four-seat composite designs.
Seated in the left seat, the belts provide all the security against movement a pilot should ever need, while still allowing easy access to the avionics, power and airframe controls.
Entry and exit are relatively easy, thanks to a full-width forward canopy that tilts forward to give access to the front seats. Diamond has also provided a left-side door, aft of the canopy, for access to the rear seats. The structure between the canopy and the rear-cabin door forms a solid roll bar in the event of an arrival that ends upside down.
Wide cabin
The fit and finish of the cabin interior was excellent overall, and the larger-than-average cabin windows provide unparalleled visibility for crew and passengers. The front seats get the best view, thanks to their placement near the leading edge of the 12m (39.5ft) wing.
Space is not a problem in the DA40: the front cabin measures a whopping 1.14m across. The fuselage taper takes away only an inch of the back-seat width, making the rear seats nearly as spacious as the front ones. All in all, the package came across as comparable to the interior of a new sports car of the Lexus or Infiniti class.
Diamond has afforded its new Star with one of general aviation's most-popular and proven powerplants, Textron Lycoming's 360cc flat four. This is an economical choice, designed to warm the hearts of fixed base operators, flight schools and individual owners.
An injected IO-360 with low compression, this engine produces its 135kW at 2,700RPM - more than enough for a machine with a gross weight of 1,150kg (2,535lb).
Advanced ignition
To further improve the Star's efficiency, Diamond has also opted for Unison Industries' digitally controlled Limited Authority Spark Advance Regulator (LASAR) ignition system. Diamond is the first airframe original equipment manufacturer to equip a factory model with this technology.
The LASAR system produces fuel savings of 8-12% over identical engines equipped with conventional magnetos, which helps the Star deliver uncommon efficiency. LASAR also provides added redundancy through conventional magneto functions that come on line instantly should the electronics hardware fail. Yet LASAR requires no new operating procedures and its operation is transparent to the pilot, from starting to shut down.
The engine starts typically for Lycoming installations: first set the mixture to the cut-off position, then engage the electric boost pump, but only long enough for the fuel gauge to show flow, and switch it off. Turn the key to start and a lightweight, geared starter aggressively spins the engine to life. LASAR helps the process by firing both magnetos and by sparking the plugs with nearly four times the voltage available from conventional magnetos.
As soon as the engine catches, the pilot should advance the mixture to full rich and set the throttle to idle. The package worked in complete harmony, lighting up the little Lycoming after less than two revolutions. As the engine warmed, I got our taxi clearance and headed to runway 9.
Atypical for a tricycle-gear aircraft and unlike the Archer and Skyhawk, the Star uses differential braking to steer a castoring nose wheel. It operates like the Jim Bede-designed Grumman American, Tiger and Cheetah. The nosegear's geometry puts the pivot point well ahead of the wheel axle, making it easy to start and sustain turns from wide to sharp.
You can easily pirouette the Star around either main gear or reverse a turn with little effort, even coming off a tie-down pad on a tight ramp. Rolling just a foot or so allowed me to start the nosegear toward the opposite direction to negotiate a somewhat tight spot on the busy ramp at Plant City, Florida.
Some may find this arrangement a throwback, but it saves weight and cost compared to mechanically-actuated nosegear steering. The Star also moves easily off a dead stop, and requires only a little extra throttle to start the aircraft rolling.
After a few hours, an adept DA40 driver should need to do little braking unless he is taxiing faster than the brisk walking pace recommended. At taxi speeds of only 10-15kt (20-30km/h), the rudder begins to help lever the nose around, reducing the need for steering by brake.
Aside from the steering, the pre-departure chores are as familiar as ailerons and flaps: engine run-up, magneto checks, cycle the three-blade MT constant-speed propeller, cycle the flight controls and electric flaps - which deploy to 15í or 40í, depending on the setting - and check the convenient fuel selector, which falls easily under your right hand.
Although the procedure remains the same, magneto checks take on a slightly different meaning in the Star, a result of choosing the LASAR ignition system. Instead of turning off each magneto in turn to check the other's function, rotating the ignition key actually shuts off the digital LASAR hardware to both magnetos and switches the system to the redundant mechanical magneto built into each LASAR. The LASAR annunciator light illuminates when the electronics shut down, giving the pilot a visual confirmation that the back-up magnetos have taken over sparking chores.
Twenty seconds after the key is returned to the "both" position, the LASAR electronics come back online and extinguish the annunciator, a sign that all is working properly. Even doubts about the condition of the annunciator can be checked at any time, using a push-to-test lamp fixture.
With the engine checks complete, flight controls free and clear, flaps set and after clearance from the tower, the aircraft is ready to fly.
Eager nature
With nearly full fuel and close to 180kg of people in the spacious cabin, we were still 90kg under gross weight.
With ambient temperature hovering in the high 80°Fs, a stiff quartering cross wind from the south prepared me for a bumpy ride climbing away from runway 9.
Diamond recommends taking off with flaps at 15°, available at the flick of the flap-shaped panel switch, and rotating at 60kt indicated air, fairly typical for an aircraft in this category. But company pilots cautioned me to exercise a light touch on rotation lest an over-eager hand rotate the Star onto a tail skid.
With conditions less than ideal, it seemed prudent to let the Star fly itself off the runway by selecting a few degrees of up elevator trim. As rotation speed arrived, the Star needed nothing more than aft finger pressure to depart.
The trick worked much easier than I expected. The Star lifted smoothly from the runway in under 20s, after a roll of less than 275m. Tracking straight down the runway required ever-gentler nudges of right rudder, which seemed to become effective at about 20kt.
Thanks to a climb rate at 80kt of nearly 900ft/min (4.57m/s), we approached the departure end of runway 9 at more than 600ft above mean sea level (msl), more than high enough to turn south. The Star needed little more than my thinking of a right turn to start a climbing right arc at standard rate, a necessity to avoid very busy airspace, 5nm (9.25km) east at Lakeland Linder regional airport.
Smooth and cool
After flipping the flaps switch to the stowed position and shutting off the boost pump, I dialled the propeller control back to 2,500RPM and flicked the pitch trim forward to lower the nose for a 100kt cruise climb. The pitch change improved my view over the cowling. The Lycoming still delivered a climb rate above 500ft/min, a good level for heading out on a long trip, for instrument work or simply pleasure flying. Throughout the flight, the Lycoming stayed smooth and cool, with all temperatures and pressures solidly in their green bands.
Less than 7min from brake release, the Star lifted us to 5,500 msl as I steered the DA40 south for air work.
The Star's long, thin wing gave the aircraft both its aggressive take-off performance and its strong climb. Spanning 39.4ft, no aircraft in its class matches it. That wing, with an aspect ratio exceeding 10:1, also helps the Star achieve its 147kt cruise speed, and strong performance on only 75% of its full 135hp. If there is a downside to the wing, it shows solely at lower speeds when starting co-ordinated turns: adverse yaw is mild but noticeable.
No correction needed
Turns at high speed require no noticeable correction because the adverse yaw seems to give way to good roll-yaw coupling, thanks to the power of the Star's long, thin ailerons. Rolling the DA40 from 45í to 45í took just a few seconds and needed only wind-induced rudder inputs to keep the skid ball centered.
Diamond's engineers gave the Star wingtips that angle upward and back, to reduce drag at cruise and improve airflow over the ailerons at all speeds. These are most effective at low speeds, such as slowing through the pattern for landing or when approaching stalls, where they remain fully engaged. But stalls may be too harsh a word to describe what happens to the Star at its lower speed limit.
Full-flap stalls at idle power occurred at about 49kt indicated airspeed at our altitude, or about 55kt true airspeed, and it needed little corrective rudder as it approached what passes for stall break. There is a nose-high mush with an accelerated sink rate, without a clean break or hard pitch-over. Power-on stalls arrived even slower, at 45kt indicated, or about 50kt true.
These high-altitude checks seemed to confirm Diamond's book stall speed of 45kt at gross weight and sea level ISA conditions. Set up for as close to 75% power as the conditions would allow actually delivered a bit more than 65%, a product of a density altitude of nearly 8,000ft. Yet the Star still achieved 142kt true airspeed - again, better than anything flying on comparable power.
Best of all, fuel flow at this setting came in at less than 32 litres per hour, with the LASAR system saving about a 4 litres an hour. At the book settings, the Star is good for 600nm, with reserves, on the standard 150litre tanks. An optional 200 litre fuel system ups the range to 800nm. At either capacity, these distances are as efficient at they get, comparable to the efficiency of Mooney's 150kW 201 model of the 1980s.
Altitude to lose
If some pilots find it easy to drag the DA40's replaceable tail skid, they also find the Star less draggy than expected when the time comes to slow down and come down.
As the Star took me back north in a tailwind-enhanced haste, I applied my standard IFR-arrival habits - habits a bit late for the slippery Star. Instead of the usual calculations delivering an easy 500 ft/min descent at an ever-slowing airspeed, the DA40 surprised me with its resistance to slowing down. It's not what one expects from an aircraft with three fixed wheels.
As it dawned on me that we had excess altitude to bleed off, I decided to work with what I had and avoid leaving the pattern and re-entering the growing queue of aircraft heading towards Plant City. Instead, a sideslip seemed in order. With the nose pointed south, and the north wing angled down, the Star fairly fell out of the sky at a brisk 700ft/min without any airspeed acceleration.
I then pulled the power back to let the descent grow to the 1,000ft/min mark with no hint of instability, even as it seemed we were dropping from the sky like a piece of iron at a stable 65 kt.
As the big white "9" on the runway grew larger in the windshield, I simply relaxed my cross-control input as I added the full 40° of flaps.
The Star quickly realigned with the runway centerline as the vertical speed indicator on the runway passed through the 500ft/min mark and continued toward zero.
With the Star's shadow in full view, my left hand rolled the pitch trim full aft and held the stick steady at about 15í up pitch while my right eased back the throttle to idle.
My reward was an easy touchdown, upwind wheel first, downwind wheel next, nosewheel last. This was too much fun, so with full power reapplied, the flaps raised back to 15° and the pitch trim racing back to a few degrees of up, the Star sailed off the runway again in seconds and back around the patch we went.
My speed and descent co-ordination worked much better on my second and third trips around the pattern, rewarding me with an easier, cleaner landing each time. My second landing used a short-field approach profile, while my third employed a standard arrival technique. Each time, the Star touched down deftly indicating well under 50kt; each time, the first taxiway turnoff was within coasting distance. Getting into serious trouble landing the DA40 will involve major effort on the part of the average pilot.
A new Star in the sky
Diamond has a winning aircraft on its hands, suitable for every level of pilot, from raw primary student to seasoned veteran.
The harmony between the centre sticks and rudder pedals makes for an easy adaptation for a pilot in transition to a larger aircraft. The easy access to controls, avionics and arc breakers will hearten the veteran flyer as much as it should flatten the learning curve for primary and instrument students alike.
Compared to the two most-popular 135kW airplanes available, New Piper's Archer and Cessna's Skyhawk, the Star flies faster, farther, on less fuel, carrying more payload with more cabin room. Diamond offers an aircraft distinctly better than anything in its class and distinctively different than almost anything you'll find parked next to it on a ramp.
Source: Flight International
