Diamond DA52: A Six-Place Diesel Minivan

It’s bigger and faster than the DA42, but don’t call it inexpensive. Diamond’s probing a global luxury and business market niche.

When Piper morphed the Apache into the Aztec in 1960, it was a precursor of sorts for an idea yet to be invented: the minivan. You could say the same of the Seneca, but whichever analogy appeals, Diamond Aircraft’s new DA52 VII goes to the same place. It’s meant to be a people or thing hauler capable of high cruise speeds, but with a fuel economy and speed Piper could only dream about.

But the minivan comparison goes just so far, for the DA52, when certified sometime next year, will be an expensive ride. A price a bit north of a million dollars puts it in the rarefied league of Beechcraft’s still-viable Baron, albeit the DA52 is an airplane with seven seats. Powered by the latest version of the Austro AE300 Jet-A burning engine at 180 HP per side, the DA52 represents Diamond’s most ambitious piston-engine aircraft yet and one pitched at what may be a smaller niche market than the DA42 found.

When we visited Diamond’s Wiener Neustadt, Austria, headquarters in late April, the DA52 was in full-blown testing and we were given a demo ride in the single test article.

When Diamond introduced the DA42 twin concept at the Berlin Airshow in 2002, we thought they were a little nuts. Although it used the same basic fuselage as the successful DA40 single, the DA42 was a new airframe. But the radical part was the airplane’s twin Thielert TAE 1.7 Centurion diesel engines at 135 HP each. The engines were based on the same powerplant used in the massively numerous Mercedes A-Class supermini. Thielert cut a deal with Mercedes to re-engineer the 1.7 using an aluminum rather than a cast-iron block and it designed its own clutch and gearbox to isolate the diesel’s torque pulses from the prop.

The joke turned out to be on us. Between the diesel’s economy and a reviving training market, Diamond hit a sales sweet spot and was selling the DA42 at three a week by 2005, despite what we thought was a high asking price. (The come-on intro price was $360,000, but by 2005, real invoices were around $452,000.)

There turned out to be a brisk demand for new twin trainers and customers liked the Thielert’s ease of operation and impressive fuel economy.

The project ran off the rails in late 2007, when significant maintenance issues with the Thielert engines surfaced and owners complained that neither Diamond nor Thielert were stepping up to address these. By early 2008, what appeared to be flawed economics caught up with Thielert and it declared bankruptcy. It remains in insolvency five years later, but is still supplying parts and engines.

But even before Thielert’s crisis, Diamond had had its fill of outside engine vendors. Investing what would eventually be $100 million, the company formed a separate unit called Austro Engine GmbH and fast tracked its own certified diesel based on the same OM640 Mercedes engine Thielert used as a base.

However, for durability and the option of overhauling rather than replacing the engine at the end of its service life, Austro stuck with the Mercedes’ original cast-iron block and it engineered heavier gearbox and clutch mechanisms that don’t require the recurrent maintenance that so irritated owners of Thielert engines. Years later, Thielert still hasn’t improved maintenance intervals much, while the Austro AE300 variant used in the DA52 is rated at 180 HP and current AE300s have a 1500-hour TBO that Diamond’s Christian Dries says may increase to 1800 by year’s end. All told, about 750 Austro engines are flying in Diamond twins and singles.

Resurrected DA50
Seven years ago, Diamond proposed a follow-on to its successful DA40 single in what was then called the DA50. It was larger than the DA40 and was originally to have a Rotax-designed V-6 engine. But Rotax bailed on the project and because Diamond didn’t want to commit to major development using avgas-burning Continental or Lycoming engines, it shelved the idea.

But now, the basic fuselage is coming back as the DA52. The immediate distinguishing factor—besides its larger size—are the generous gullwing doors that replace the DA42’s forward-hinged bubble canopy. The rear hatch for access to the rear seats is there, but it’s much larger, affording step through into both the center seats and the two rear-most seats.

For the test airplane we flew, dimensions may not be final, so what we’re presenting here should serve only as a general idea of the airplane’s size. The same caveat applies to the performance numbers.

As with its previous aircraft, Diamond will build the DA52 fuselage in two molded halves joined at the center. But it essentially inserted a widening plug between the two halves, so the cabin is about 14 cm wider (5.5 inches), with the added width tapering slightly to the rear. This is noticeable in the front seats, almost giving a large-aircraft flight deck feel to the pilot seats.

The test aircraft had no interior or rear seats, but the photos show

Diamond’s mock-up interior displayed at Aero Friedrichshafen. The rear-most seats, by the way, will accommodate small adults or children, albeit with limited leg and shoulder room.

The DA52’s Overall Dimens
ions are larger than the DA42. The fuselage length is 9.2 meters (30.1 feet) versus 8.6 meters (28.1 feet) for the DA42. Span is 14.6 meters (47.9 feet) for the DA52 versus 13.4 meters (43.9 feet) for the DA42. The wings have gracefully upswept tips and a couple of degrees of washout to improve stall characteristics to accommodate the airplane’s larger CG envelope.

While we’re on the subject of weight, Diamond had only test-article weight-and-balance data, but engineers told us the envelope is wide enough to allow filling all the seats, but with a 120 kg limit (264 pounds) for the rear-most seats. The center seats fold forward to allow carrying long or bulky cargo. Gross weight and payload will depend on the country where the airplane is intended to be used. The fundamental structure is engineered for 2500 kg or 5511 pounds, Dries told us.

For Europe, says Dries, the limit will be 2000 kg (4409 pounds), mainly because EASA cert rules require vastly more budget to certify above that weight, not to mention operational user fees for aircraft above 2000 kg.

For other countries, Dries said the target weight will be between 2150 and 2200 kg (4738 to 4850 pounds) against a projected empty weight starting at or a little below 1400 kg or 3080 pounds. “But this airplane will have 400 pounds of options,” says Dries, “so it’s not possible to say what a typical empty weight will be.”

Those options include TKS, weather radar, air conditioning, infrared camera and electrically adjustable rudder pedals, to name a few. Pick 200 pounds worth, and the empty weight might be around 1490 kg or 3284 pounds. Best case, then, the useful load would be about 1570 pounds (714 kg), plus or minus.

With the tanks full of 90 gallons of Jet A, that could leave as much as 960 pounds of payload, or five people and bags or four people and 280 pounds of stuff. Loaded with options, the real-world airplanes may be heavier, so subtract a half person from that estimate.

How about six people? Well, yes, but not six adults of typical American girth and gross. “The DA52 is a minivan concept. If you take a minivan, you can put in seven people, but not all of them are adults. This is a little bit the same. It will be a very comfortable four to five seater,” says Dries.

Flight Demo
We took a tour of the Alps in the DA52 with Diamond’s chief test pilot, Ingmar Mayerbuch. The airplane we flew weighed about 1750 kg at takeoff and had just basic seats, with no rear cabin fittings at all. It also had a DA42 panel and glareshield, whose width fell short of spanning the DA52’s cabin, showing how much wider it really is. The extra shoulder room is immediately noticeable.

The Austros start with car-like smoothness and we’ll they should, since they’re engineered by one of the largest carmakers in the world. At the light weight, the airplane practically bolts off the runway—it was difficult to hold a camera against the acceleration. With a 15-degree deck angle on climbout, two-engine climb rate is a healthy 1500 FPM on what was close to a standard day. At 10,000 feet, despite some bumps, we saw as much as 1900 FPM in climb. Fuel flow in climb—or at max output for the Austros—is about 9.3 to 9.5 gallons per side.

Cruise setups offer some interesting options. With everything forward, the DA42 is a 200-knot airplane, and then some. At 10,000 feet, we noted 204 knots on 9.3 gallons per side, which is 97 percent power and is considered maximum continuous. Throttling back to something more sane, the airplane tooled along at 177 knots on 6.1 gallons per side; that’s about 65 percent power. With full fuel, that’s 6.5 hours of endurance—with 45-minute reserve—or 1150 miles of still-air range with five people and bags. Even if the airplane gains some weight, it will probably do that distance with four people and heavy bags.

Just for fun, we reduced to max range cruise of 50 percent and checked the G1000’s range map. With only 34 gallons aboard, we had range sufficient to reach we’ll past Ukraine to the east, into Scandinavia to the north and the eastern UK from Austria, near the Czech border. That setting pegged the speed at 160 knots at 4.5 gallons per side.

One of Diamond’s stated design goals is safety and crashworthiness and beyond question, we think the company has achieved this. Three points are worth considering: As with other Diamond airplanes, the DA52’s fuel system is we’ll protected against crash forces by having aluminum tanks situated between two robust spars and plumbed with armored fuel lines. Second, Diamond airplanes typically have benign stall characteristics and, heavy as it is, so does the DA52. Holding it in an aggravated stall barely provokes bobbling, much less a break. Like the DA40, it has an easy-to-manage parachute mode, with little tendency to fall off on one wing.

With single-lever power, engine-out management is as simple as it gets. Simply switch off the engine master switch, the prop spins down and autofeathers and you’re done. There’s no flurry of fingers and hands over the control pedestal to secure an engine. To bring it back, just reverse the process. Let the engine build some oil pressure and warm up and you’re back in business. At our weight, we saw single-engine climb rates as high as 500 FPM or more. But it was too bumpy to gather reliable data. Suffice to say the DA52 does we’ll on one engine, critical (left) side or not.

The DA52 has good roll and lateral stability. In turns, you can keep your feet on the floor and notice no undue yawing. If released in a turn, it tends to right itself rather than banking into a departure and once trimmed, it stays put on airspeed, even when bouncing around in light turbulence.

Diamond’s Dries is blunt about the DA52. He’s not sure who the buyers will be, given its high price. On the other hand, he doesn’t seem too worried, either. “You know, in a lot of regions, people don’t care how much it costs. They want to fly in a very comfortable way,” Dries told us. One region Diamond is doing we’ll in is Russia. He expects China will go likewise, eventually. Besides, says Dries, the special missions market—airborne sensing—is a major part of Diamond’s business and for that market, the DA52 might be an attractive 2800 kg option. Buyers of airborne sensing aircraft like high payloads.

If Beechcraft finds 30 or 40 buyers a year for a Baron G58 selling for $1.4 million, is there any reason to believe Diamond can’t do as we’ll with a slightly less expensive airplane that’s faster, carries more and is cheaper to operate? When Diamond introduced the original Thielert-powered DA42s, we presumed that people who could afford to buy $460,000 airplanes wouldn’t care about operating costs. We presumed wrong.

Low fuel consumption does something else: it adds range and load flexibility, which is something that avgas engines burning 40 percent or more of fuel don’t do as well. Further, Jet A is the aviation fuel of the future, avgas of the past. As Dries sees it, that‘s an important part of the DA52’s attraction. We’ll see if he’s right once the DA52 is certified and available.

For more on the Diamond DA52, see the company’s European Website at www.diamond-air.at. Obtain further
details on other Diamond aircraft at www.diamondaircraft.com.

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Paul Bertorelli
Paul Bertorelli is Aviation Consumer’s Editor at Large. In addition to his valued contributions to Aviation Consumer, his in-depth video productions on sister publication AVweb cover a wide variety of topics that greatly contribute to safety, operation and aircraft ownership. When Paul isn’t writing or filming, he’s out flying his J3 Cub.