| Journal: Flight International | Section: Features |
| Title: FEA-DA40 TEST | Issue Date: 27/02/01 |
| Author: DeeDee Doke | Page Number: 4 |
| Copyright: No re-use |
Shooting Uncommon comfort, speed and efficiency in a crowded class of entry-level aircraft
Dave Higdon/PLANT CITY, Florida
After enduring a couple of stutter-step starts in the 1980s, composite airplanes finally established a foothold as production machines in the last decade, with no less than three new designs coming to market within a two-year period.
The planes leading this new wave include Cirrus Design's unique SR20, Lancair's brawny Columbia 300, and Diamond Aircraft's sleek, slick DA40 Star. And with more to come.
Fortunately for the pilot population, each member of this trio to tricycle-gear machines occupies a distinct niche in horsepower, price and performance, rather than simply being clones with common speed, size and comfort.
And it falls to Diamond's stellar DA40 to be the last into service, befitting its status as the least expensive and lowest horsepower of this group.
But far from being a shadow of its composite cousins, the Star delivers distinctively solid performance, comfort and efficiency uncommon for even the clean, slippery airframes composites provide.
The Star's performance easily beats other fixed-gear, 180-horse singles, such as New Piper's Archer III and Cessna Aircraft's 172 Skyhawk SP.
Furthermore the Star's performance offers flying capabilities suitable for every level of general aviation pilot - just like the Cessna and Piper.
The basic bird: sturdy, roomy, yet svelte
Diamond Aircraft poured all the experience of 13 years building composite planes into the DA40 Star.
It was apparent during my walk to and around the prototype flown for this story - a workhorse of an airplane that already had enjoyed a record of use and abuse few production airplanes ever achieve.
The glossy white, UV-resistant finish on the carbon-fiber airframe appeared nearly flawless, save for a few items showing some wear-and-tear from its use as in an accelerated testing program.
At the time of my flight, the Star already had more than 1,100h and more than 16,000 landings logged in under a year. Performing the normal pre-flight inspection walk took no more time than most aircraft of its class, requiring only visual or touch checks of the control surfaces. The elevator on the tall T-tail, the only item out of my reach, sports dual actuators. But since even the lock nuts were visible from my position, reaching out to touch them was unnecessary.
Confirming control-linkage integrity involved nothing more than sitting in a front seat and moving either of the dual floor-mounted control sticks Diamond's designers elected to use.
Uncommon on most planes today, those "joysticks" can't interfere with the front seats, since all seats in the Diamond are fixed in position to help the airframe meet stringent 26G impact tests required for Federal Aviation Administration certification.
To allow for different pilot heights, Diamond opted for rudder pedals that adjust fore and aft. Those pedals provide plenty of adjustment range for all but the shortest and tallest of aviators.
Further adjustment comes by using seat and back seat cushions of thicker or thinner dimensions. At my 5-foot, 9-inch height, the standard cushions worked perfectly, as did the rudder pedals set a bit closer than half of their movement range.
Checking engine oil is easy through a cowling door, which also allows the pilot to determine whether an errant bird decided to set up housekeeping atop the IO-360-MIA Lycoming engine used on the Star. With 180 horsepower 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 all avionics, power and airframe controls.
Entry and exit come easily enough, thanks to a full-width forward canopy that tilts forward for access to the front seats. Diamond 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.
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, alike. The front seats get the best view, thanks to their placement near the leading edge of the wide, 39.4-foot wing.
And space is not a problem in the DA40, with the front cabin measuring a whopping 45 inches 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 well as the interior of a new sports sedan of the Lexus or Infiniti class.
Common engine uncommonly equipped
Diamond afforded its new Star with one of general aviation's most-popular, most-proven powerplants, Textron Lycoming's 360-cubic-inch flat four, an economical choice designed to warm the hearts of FBOs and flight schools, as well as individual owners.
An injected IO-360 with low compression, this engine makes its 180 horsepower at 2,700 rpm, more than enough for a machine with a gross weight of 2,535 pounds.
To further improve the Star's efficiency, Diamond also opted for Unison Industries' digitally controlled Limited Authority Spark Advance Regulator (LASAR) ignition system. In picking LASAR, Diamond became the first airframe original equiment manufacturer (OEM) to equip a factory model with this advanced technology.
The LASAR system allows an engine to make its power on 8 to 12% less fuel than identical engines equipped with conventional magnetos, which helps the Star deliver uncommon efficiency. LASAR also provides added redundancy through conventional mag functions that come on line instantly should the electronics hardware fail.
Yet LASAR requires no new operating procedures and is invisible to the pilot, from starting to shut down.
And this engine starts typically for Lycoming installations: First set the mixture to the cut-off position, engage the electric boost pump 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 mags and by sparking the plugs with nearly four times the voltage available from conventional magnetos.
As soon as the engine catches, 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 tricycle-gear aircraft like the Archer and Skyhawk, the Star uses differential breaking to steer a castoring nose wheel - like the Jim Bede-designed Grumman American, Tiger and Cheetah.
The nose gear'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 nose gear toward the opposite direction to negotiate a somewhat tight spot on the busy ramp at Plant City.
Some may find this arrangement a throwback. But it saves weight and costs compared to mechanically actuated nose-gear steering.
Some may worry that about excessive brake wear. But the Star moves easily off a dead stop, requiring only a little extra throttle to start the plane rolling.
After a few hours, an adept DA40 driver should need little braking unless taxiing faster than the brisk walking pace recommended. At taxi speeds of only 10 to 15 knots, however, 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, mag checks, cycle the three-blade MT constant-speed prop, cycle the flight controls and electric flaps - they deploy to 15 or 40 degrees, 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 Diamond's choice of the advanced LASAR ignition system.
Instead of turning off each mag in turn to check the other's function, rotating the ignition key actually shuts off the digital LASAR hardware to both mags and switches the system to the redundant mechanical magneto built into each LASAR mag. The LASAR annunciator light illuminates when the electronics shut down, providing the pilot with a visual confirmation that the back-up mags have taken over sparking chores.
Twenty seconds after the key returns to the "BOTH" position, the LASAR electronics come back on-line and extinguish the annunciator, your sign that all is working properly. Even doubts about the condition of the annunciator can be checked with the push-to-test lamp fixture at any time.
With the engine checks complete, flight controls free-and-clear, flaps set and our clearance from the tower, we're ready to fly.
With nearly full fuel and close to 400 pounds of people in the spacious cabin, we were a couple hundred pounds under gross weight.
A temperature hovering somewhere in the high 80s and a stiff quartering cross wind from the south prepared me for a bumpy ride climbing away from Runway 9.
Diamond recommends launching with flaps at 15, available at the flick of the flap-shaped panel switch, and rotating at 60 knots indicated, 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 right onto its 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 aft finger pressure to depart.
The trick worked much easier than expected, as the Star lifted smoothly from the runway in under 20 seconds after a roll under 900 feet; tracking straight down the runway required nothing more than ever-gentler nudges of right rudder, which seemed to become effective at about 20 knots.
Thanks to a 80-knot climb rate of nearly 900 feet-per-minute, we approached the departure end of Runway 9 at more than 600 feet msl, plenty high 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 the very busy airspace five miles east at Lakeland Linder Regional Airport.
After flipping the flaps switch to the stowed position and shutting off the boost pump off, I dialed the prop control back to 2,500 rpm and flicked the pitch trim forward to lower the nose for a 100-knot cruise climb. The pitch change improved my view over the cowling and the Lycoming still delivered a climb rate above 500 fpm, a good number for heading out on a long trip, for instrument work or simply boring holes in the sky.
And throughout, the Lycoming stayed smooth and cool, with all temperatures and pressures solidly in their green bands.
Less than seven minutes from brake release, the Star lifted us to 5,500 msl as I steered the DA40 south for air work.
Credit the Star's long, thin wing for both its aggressive take-off performance and its strong climb. Spanning 39.4 feet, no aircraft in its class matches it.
That wing, with an aspect ratio exceeding 10:1, also helps the Star achieve its 147-knot cruise speed, strong performance on only 75% percent of its full 180 horsepower.
If there's a downside to the wing, it shows solely at lower speeds when starting coordinated turns: Adverse yaw, mild but noticeable.
Turns at high speed require no noticeable correction because the adverse yaw seems to give way to great roll-yaw coupling thanks to the power of the Star's long, thin ailerons. Rolling the DA40 from 45-degrees to 45 degrees took just a few seconds and needed only wind-induced rudder inputs to keep the skid ball centered.
Diamond's engineers gave the Star tips that angle upward and back, reducing drag at cruise and improving airflow over the ailerons at all speeds. They most show their effectiveness at low speeds, such as slowing through the pattern for landing and approaching stalls, where they remain fully engaged.
And 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 arrived at about 49 knots indicated at our altitude, or about 55 knots true and it needed little corrective rudder as it approached what passes for stall break: A nose-high mush with an accelerated sink rate, absent a clean break or hard pitch-over. Power-on stalls arrived even slower, at 45 knots indicated or about 50 knots true.
These high-altitude checks seemed to confirm Diamond's book stall speed of 45 knots at gross weight and sea-level ISA conditions.
Set up for as close to 75 percent as the conditions would allow actually delivered a bit more than 65 percent, a product of a density altitude of nearly 8,000 feet. Nonetheless, the Star still achieved 142 knots true - again, better than anything flying on comparable power.
Best of all, fuel flow at this setting came in at less than 8.5 gallons an hour. Thank the LASAR system for saving about a gallon an hour compared to 180-horse Lycoming engines with conventional mags. Swap in conventional mags and these numbers increase by between 8 percent to 12 percent
At the book settings, the Star is good for 600 nautical miles, with reserves, on the standard 41-gallon tanks. An optional 52-gallon fuel system ups the range to 800 nautical.
At either capacity, these distances are as efficient at they get, comparable to the efficiency of Mooney Aircraft's 200-horse 201 model of the 1980s.
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 Star.
Instead of the usual calculations delivering an easy 500-fpm descent at an ever-slowing airspeed, the DA40 surprised me with its resistance to slowing down. All in all, it's not what one expects from a plane with three fixed wheels.
As it dawned on me that we had excess altitude to bleed off, I made a conscious decision to work with what I had and avoid leaving the pattern and re-entering the growing cue of Sun 'n Fun plans headed toward Plant City.
Instead, a slip seemed in order.
With the nose pointed south, the north wing angled down, the Star fairly fell out of the sky at a brisk 700 fpm with not a hint of airspeed acceleration.
I then pulled the power back to let the descent grow to the 1,000 fpm 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 knots.
As the big white "9" grew larger in the windshield I simply relaxed my cross-control input as I added the full 40 degrees of flaps.
The Star quickly realigned with the runway centerline as the VSI passed through the 500 fpm 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 15 degrees up pitch while my right eased back the throttle to idle.
My reward was an easy touchdown, upwind wheel first, downwind wheel next, nose wheel last. This was too much fun, so with full power reapplied, the flaps raised back to 15 degrees 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 coordination 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 50 knots; each time, the first taxiiway turnoff was within coasting distance.
Getting into serious trouble landing the DA40 will involve serious effort on the part of the average pilot.
A new Star in the sky
Diamond has a winning airplane on its hands, suitable for every level of pilot, from raw primary student to seasoned veteran.
The harmony between the center sticks and rudder pedals makes for easy adaptation for a pilot in transition to a family airplane. The easy access to controls, avionics and 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 180-horse 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 airplane 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
