A case can be made that the twin-diesel DA62 from Austria’s Diamond Aircraft represents a new pinnacle in piston aircraft design. Its long list of positive attributes includes superb efficiency, quality construction, technological sophistication and aesthetic appeal from every angle. With so much going for it, there’s little question this is an airplane that belongs on the shortlist of the greatest light twins ever. In a word, it’s a winner.
It's a pity, however, that so few people are expected to buy it. Don't blame Diamond for that. Light-piston twin sales have been so slow for so long that most aircraft buyers — and aviation writers — have written off the segment as all but dead. And no wonder. There aren't nearly as many pilots hanging around airports today who will tell you they need a twin. That's mainly a byproduct of the rise of high-performance piston singles like the Cirrus SR22 and Cessna TTx, which can do pretty much everything a twin can but with substantially reduced operating costs and essentially no safety penalty.
With a single, obviously, there's only one engine to care for, and the chances of it quitting are low — and if it does quit in the Cirrus, there's a full-airframe parachute to save the day.
That's what makes the emergence of an all-new light-piston twin in this class something of a surprise. With the elegantly sculpted DA62's arrival amid a field of brawny gasoline-powered singles, suddenly we have to ask ourselves if the market for twins isn't quite as dead as we thought. Perhaps it has merely been in a state of prolonged hibernation, slumbering peacefully through a long winter, awaiting the arrival of a new kind of light twin, one that can do more with less.
Still, it's not quite time to announce a comeback for the piston twin segment. The DA62 is an anomaly, an outlier. After all, most pilots coming up through the ranks today who aren't dreaming of an airline career feel no pressing urge to “move up” to a twin. Those who used to — the pilots who flew twin-engine bombers in World War II and trusted two engines more than one — have all but stopped flying and, for the most part, offering advice to younger pilots.
The resulting shift in attitudes and buying habits in favor of single-engine airplanes is clear. In the late 1970s, for example, there were 33 different piston twins on the market. Today, there are only five serious contenders — and apart from the seven-place DA62, only two of these, the Beech Baron G58 and Piper Seneca V, offer more than four seats.
Seven seats in a twin in this class, by the way, is quite an engineering feat. I'm not a fan of describing any airplane as an “aerial SUV” — even if, yes, it's roomy inside and has a decent payload — because the label is almost always an exaggeration dreamed up by someone in the marketing department. But in the case of the DA62 it would be ignoring a glaringly obvious design characteristic not to mention it. With its third-row seating option, oversize doors and seats that fold flat to accommodate bulky items, there's no other way to say it — the DA62 is a sport utility vehicle with wings.
That's no accident. In developing this airplane as an evolutionary step up from the four-seat DA42, Diamond Aircraft founder and CEO Christian Dries challenged his engineering team to create a safe, simple-to-operate, fuel-efficient twin and wrap it around a passenger compartment mimicking the latest luxury SUVs. Unlike gas-guzzling sport utility vehicles, though, the DA62 boasts outstanding fuel economy. Its twin 180-horsepower Austro AE330 diesel engines burn less than 10 gallons per hour per side at maximum continuous power, propelling the airplane to a top speed of right around 200 knots. Pull the throttles back to 75 percent power and the speed is still a respectable 187 ktas, but fuel burn drops to just 7.4 gph per side — an impressive 14.8 gph total that's lower than a number of light-piston singles can manage on one engine.
I had the chance to spend a couple of days flying the DA62 recently on a visit to the Diamond Aircraft factory at the company-owned Wiener Neustadt East Airport south of Vienna. I came away from the experience persuaded that, for the right buyer, this is very nearly the ideal airplane. If, for example, you need seven seats versus the five or six offered in competing airplanes, the DA62 makes perfect sense. If you also don't have access to a ready supply of 100LL avgas, the DA62 is a great alternative to gasoline-powered models. And if you simply feel more comfortable flying over inhospitable terrain or water, sometimes at night, and desire the power and systems redundancy that come with a second engine, the DA62 should absolutely be on your shopping list.
There are other reasons to like the DA62 as well. One of the characteristics that left an impression on me is how dirt simple this airplane is to operate. Take the engine start procedure, for example. It involves the easy-as-pie steps of hitting the master switch, flipping the engine master on, waiting a moment to ensure the glow plug annunciation is out and then pushing the engine start button. That's it. The Austro diesels come to life in an instant as the dual-channel full authority digital engine controls (fadec) manage rpm and continuously check for faults while your only other job is to glance at the oil pressure indication. As long as the gauges are in the green, you're good to go.
The before-takeoff run-up procedure is equally as stress free. It involves setting the parking brake, manually selecting the A and B channels of the electronic engine control units (EECU) to ensure both are online, and then pushing and holding the engine run-up buttons. Here's where the magic starts as the AE330's fadec computers automatically increase power to 1,950 rpm and perform a number of health checks, including cycling the props. The throttles never physically move and there aren't any prop levers to move in the first place. If no fault messages appear on the Garmin G1000 primary flight display when the test sequence is completed, you're ready for departure.
In this case, that meant swinging the airplane onto Wiener Neustadt's Runway 10 with a 25-knot direct crosswind blowing from the left. I added a fistful of that smooth diesel power and, per the book, rotated at 80 knots. Acceleration to 95 knots for the climb-out was brisk as I began the bizarre sequence of noise-abatement twists and turns designed to keep air traffic away from residential areas as well as a military airfield right next door to the airport.
Climbing to 5,000 feet at 110 kias, the DA62 maintained a 1,450 fpm rate of climb at our midweight with two on board and half fuel. Accelerating to a cruise climb speed of 128 kias produced a 1,200 fpm rate through 8,000 feet. That's when I asked my host in the right seat, Diamond Aircraft director of flight operations Martin Scherrer, for a demonstration of the DA62's single-engine performance. Still climbing, at his direction I flicked off the left engine master switch (the left is the critical engine in the DA62). The propeller immediately stopped, automatically feathering as it did so.
The airplane lurched left as a result of loss of thrust on that side, and I instinctively raised the left wing, stepped on the rudder, and then dialed in rudder trim to compensate. After that, the airplane was as easy to fly on one engine as on two. Earning a multiengine rating in a DA62 with its two power levers (opposed to the usual six levers found in most piston twins) would almost be cheating, I decided. I let the speed come back to the 87-knot blue line (single-engine best rate-of-climb airspeed) and was impressed to see us still climbing at 450 fpm.
Next I wanted to evaluate the DA62's cruise performance to see if this really is a 200-knot airplane as Dries originally envisioned. I leveled off at 14,000 feet with the throttles pushed full forward to max continuous power of 95 percent and let the speed build. On this day, slightly warmer than standard and a little lower than optimal, I managed to coax 195 ktas from those twin AE330s while burning 18.6 gph. Hitting 200 knots in a Beech Baron in similar conditions would result in a fuel consumption of around 30 gph, so I wasn't terribly disappointed with the results I was seeing.
I tried out a variety of power settings and found what I considered a sweet spot at 60 percent power showing 170 ktas and 11.8 gph fuel consumption. After heading lower and trying a series of steep turns and power-on and -off stalls (which were, predictably, nonevents with nothing more dramatic than a slight wing drop in the stalls), I shut down the right engine for some engine-out maneuvering. Here's where the economy really improved. Loafing along at 100 knots in level flight we were showing a fuel burn of an eye-popping 3.6 gph. I did a quick mental calculation and realized that, even with less than half fuel on board, at this rate our flight endurance would still be more than 11 hours.
There would be virtually no way to stave off boredom on such a long flight, in part because the pilot doesn't have much to do in the DA62 in cruise. By design, pilot workload is low in all flight regimes, something I think nonprofessionals will come to greatly appreciate. Even performing aerial engine restarts is an almost total no-brainer for the pilot. The single-lever power controls don't require any special adjustments, meaning all the pilot has to worry about is maintaining the proper airspeed so the prop will windmill back to life when the engine master is switched back on.
In fact, fitted as it is with the latest generation of Garmin G1000 avionics with synthetic-vision technology (SVT) and electronic stability and protection (ESP), plus a three-axis Garmin GFC 700 autopilot and GWX 70 weather radar, there's an argument to be made that the DA62 is the among the most capable and easiest-to-fly piston airplanes ever produced. It's a 21st century technological marvel wrapped in a slippery and sensual carbon-fiber package.
After a sightseeing detour through some breathtakingly gorgeous valleys in the Alps southwest of Vienna (where handling in the bumps was rock solid), we headed back to Wiener Neustadt so I could try my hand at landings in the DA62. The wind was still blowing at 20 knots for my first arrival, which involved flying the strangest pattern I've ever performed as I was compelled to wheel around small towns at odd altitudes to accommodate for departing traffic and the bordering military airspace.
The landing culminated with a tight descending turn at the edge of the adjacent military airfield as I targeted 90 knots on final with full flaps selected. Max demonstrated crosswind component with full flaps in the DA62 is 25 knots, slightly better than in the DA42, and I found that the DA62 handled the wind with no problem, even with its slender wing spanning nearly 48 feet.
Inside, the DA62 has the same center control stick, throttle placement and cockpit display layout that are familiar to pilots of the Diamond DA40 and DA42. Round-dial backup instruments have been replaced with an electronic standby instrument with emergency battery. The seats are leather with seatback adjustments, but they don't move fore and aft. Instead, the rudder pedals can be adjusted forward and back to accommodate a variety of pilots. I found that I had plenty of headroom and adequate forward visibility from my vantage point in the left seat. My companion in the right seat, at 6 feet, 8 inches tall, fit the space surprisingly well. A welcome touch is an armrest in the center of the cockpit between the pilots that is just the right width and height.
The DA62's three large gull-wing doors and the forward-folding seats, plus smart placement of handholds, make entry and exit from the DA62 extremely easy. There are cup holders for the front-seat occupants and a variety of LED interior lighting options throughout the cabin. Options include air conditioning, a 36-gallon aux fuel tank, Garmin weather radar and satellite data receiver, and Avidyne TAS600 traffic advisory system. New for the DA62 is an upgraded metallic paint option that lets buyers choose colors other than the standard white found on many carbon-composite aircraft.
Although it isn't offered with a parachute, the DA62 benefits from a variety of standard and optional safety features. Its benign, big-airplane handling makes it easy to hand-fly. It also features aluminum fuel tanks sandwiched between the carbon-fiber main wing spars for exceptional crashworthiness, and incorporates Diamond's trademark high-impact fixed seats that are attached to strategically located crush points in the floor. The composite monocoque cabin design was borrowed from the Formula 1 racing world. Like all Diamond products, the airplane has undergone crashworthiness testing similar to what is performed in the auto industry. The DA62 also offers full icing protection with its TKS weeping wing option.
The U.S. spec version that goes on sale this month offers a 5,071-pound gross weight (versus 4,400 pounds for the European version to avoid the ATC fees levied on heavier airplanes) and a 1,300-nautical-mile range with a full-fuel payload of over 1,000 pounds. Its 2.0-liter Austro compression ignition engines, meanwhile, sip jet-A fuel while offering the peace of mind that comes with a 13,000-foot single-engine service ceiling (at max gross weight) and the turbocharged power to propel it to respectable top speed. The cabin is the roomiest in its class, plus there are two spacious baggage compartments in the nose that can accommodate full-size suitcases, golf bags and more.
One of the big questions I had about the DA62, obviously, is whether this really is a bona fide seven-person airplane with those two extra seats way in the back. There's ample room in the front seats and in the middle row as well with its three seats, but the rear seats would be cramped for two adults. I hopped in back and felt there was plenty of room for me alone, but I wouldn't want a seatmate. It would be ideal, though, for two children.
The DA62's useful load in the international spec version is 1,609 pounds — about 100 pounds more than a Baron G58 — meaning that with half fuel the average weight of each passenger could top out at around 190 pounds. I ran through a number of weight and balance scenarios and came away convinced that with those fuel-efficient Austro diesels, this truly is a seven-person airplane that still offers decent range and speed. A real-world scenario I plugged in involved loading five full-size adults, two children, bags and 60 gallons of fuel for a 644 nm range at standard cruise power at 14,000 feet.
At $1.08 million for the U.S. model before typical options, the DA62 compares well with the competition, slotting in above the price of a new Piper Seneca V and below the Baron G58. What could give some buyers pause is the short engine overhaul interval, which at the moment is a mere 1,000 hours for the new Austro AE330s. Based on the Mercedes-Benz diesels in B-class automobiles, the engine is a proven design, and the 1,000-hour limitation is projected to be short-lived as Diamond gains experience with the aero engine. The company hopes to increase TBO to as high as 2,400 hours eventually. Other required engine maintenance, meanwhile, includes inspection of the generators at 300 hours, and replacement of the high-pressure fuel pump and inspection of the two-mass flywheel at 600 hours.
The DA62 earned its type certification in Europe last April and should have received its Part 23 approval papers from the FAA by the time you read this. Sales are slated to begin in North America before the end of the year, meaning it won't be long before you start seeing the DA62 appear on airport ramps.
With its long, tapered high-aspect ratio wing featuring slightly upswept tips, unusual engine cowl shape and silky-smooth composite fuselage, it'll be hard to miss. Once you see it in person, it will probably take all of about five seconds before you decide you want to fly it. It's an experience I highly recommend, but don't be surprised if you suffer from a serious case of twin envy afterward.
The Diamond DA62 flown for this report was an international spec model with optional third-row seating accommodating seven people, increased 5,071-pound maximum takeoff weight, built-in oxygen, air conditioning, TKS icing protection, Garmin GWX 70 weather radar and GSR 56 satellite data receiver, Avidyne TAS600 traffic advisory system, 36-gallon auxiliary fuel tank, metallic paint and more.
