Austrian manufacturer Diamond Aircraft has a reputation for creating aeroplanes packed with innovation and technology. Steve Hitchen traveled to Wiener Neustadt to see what this design philosophy would do for the new DA62 twin.
Diamond's latest inspiration, the DA62 twin, is an attempt to combine style, quality and class with capacity; sort of like making a stretch limousine from a Mercedes SLS AMG. But, whereas such a car would have the handling of a barge of bricks, the DA62 is one of the sweetest aeroplanes you could ever hope to fly ... and that includes when one engine stops pulling.
Yes, that statement is coming from someone with very little twin time who fits neatly into the category of neophyte when it comes to asymmetric flight, but that in itself reveals the inherent nature of the DA62: it eliminates many of the stress-inducing features of twin flying to the point that its behaviour is closer to a large single than the traditional twins it was born to replace.
This machine seats up to seven, has two 180-hp Austro AE300 diesels, cavernous entry hatches and enough room inside to hold a small party. The max. take-off weight of 2300 kg says it all; a good half-tonne more than a Piper Seminole for the same power output.
From the tables in the spec sheets, it looks like the DA62 is set to slay everything else in its class, but there are very few in existence and none in Australia to verify the manufacturer's claims. There was no way out of this; I was going to have to go to the Diamond factory in Austria and see for myself.
Lucky for me, Diamond Aircraft was up for the challenge and embraced me with a hearty welcome that showed obvious confidence in their machine.
It was confidence not misplaced.
Come to Papa!
The first impression I got of the 62 as I walked out across the apron at Wiener Neustadt toward the low-slung, two-tone grey twin, was that it was likely just another DA42, but with 180-hp engines on either side. My mentor for the day, demo pilot Robert Mayer quickly dispelled that when he opened the huge gull-wing doors to reveal a beautifully appointed leather interior clearly not intended for the muddy boots of flying schools.
With a fuselage 630 cm longer and than the 42 and an extra 1 m on the wingspan, the 62 is a bigger aeroplane physically, and the longer cabin is evidenced by the third window for row three. Nope, not a beefed-up DA42, but a completely new twin obviously aimed at a different market.
For those people who know Diamond's visionary CEO Christian Dries, the DA62 won't come as a surprise; it epitomises his ideal of a GA aeroplane: it's fast, comfortable, highly automated, runs on diesel and is incredibly pilot-friendly. However, so is the DA42, so what was the imperative to design a larger, higher-powered twin?
"Particularly from North America, we've had complaints about the size," Dries explains. "The DA42 is a little more sporty, you or I might fit in perfectly, but if someone comes up who's 260 lb, and very tall, they have a problem. But, the DA62 seats giants! That doesn't mean that seven giants will fit in, but at least four. Plus, with 360 hp, it performs very well."
But there are twins around that out-power the DA62: Piper's Seneca V boasts 440 hp total and the Beech Baron tops the scales with 600 total. Yet, the DA62 manages to out-perform both of them with less power and a much lower fuel burn.
But it has one other attribute: the 62 is one of the sexiest looking aeroplanes on the market. With slender spreading wings and a low, elliptical nose profile, the 62 looks part Cessna Dragonfly and part Wedge-tailed Eagle. Throw in a touch of Mercedes Benz, and you get an immediate impression that there is no way this aeroplane could not be a super performer.
Tucked in close on each wing is an Austro AE300 180 hp diesel engine that runs on most grades of jet fuel. The AE300 is a 2.0-litre, turbo-charged, common rail motor, which is a Mercedes unit modified heavily for aviation use. By the time Austro (a Diamond subsidiary) is finished with the Benz product, the motor will maintain take-off power all the way to 9000 feet, by which time the Lycoming IO-360 is usually wheezing.
Thanks to the turbo, the Austro engine tips the scales at 186 kg dry, which is much more than the normally-aspirated Lycoming's 136 kg. However, the extra 100 kg in the engines of the DA62 is not apparent; the aeroplane's overall performance masks the weight penalty to the point that you'll never think about it again.
Gull-wing doors could have been invented for low-wing aeroplanes, yet so few have them; Socata's Tobago and Trinidad are first into mind. The magic of this design was apparent to me as I stepped up eagerly on to the wing of the DA62. After opening, the door was up in the air out of the way and left a yawning gap to let me step unhindered into the cockpit.
With pilot Rob Meyer busily strapping himself into the other seat, I reached up to the door and pulled it down without having to stretch myself. It locked down with a quality "thunk" that suggested BMW more so than Toyota Yaris. Once contained, I began to understand what Christian Dries was saying about space ... we could have carried a brass band with us on that test flight.
The seats are arranged front to rear in a two-three-two configuration, with the front seats able to lie almost completely flat; a feature you just don't find in other aeroplanes, yet one that can be considerably comfortable to the Pilot Not Flying on a long leg. The seats aren't adjustable forwards and backwards, but the rudder pedal can be adjusted electronically.
Before my eyes was a twin-screen Garmin 1000, with the MFD and PFD divided by back-up glass AH and speed and altitude tapes, comms panel and autopilot. Between the seats, the leather-appointed centre console contained the rudder trim, park brake, cabin heat controls and the magic levers for the electronic Engine Control Unit (ECU).
No throttle as such, no mixture controls, no prop pitch control – just two levers that command the ECU to set the power load as a percentage. Compared with the bouquet of six levers that grow from the quadrants of traditional twins, the Diamond system is neat, simple and defies confusion when the time comes to go asymmetric.
All the serious buttons like the fuel pumps, masters, start buttons, gear and flap levers are arranged across the lower panel, leaving the far left to the de-ice and ECU test switches and the far right to the circuit breakers.
Having settled into my plush surroundings like a fat Sheik, I was eager to see the DA62 do aeroplane things, so Meyer wasted very little time in getting the Austros fired-up.
The keyless starting sequence was frighteningly simple; perhaps annoyingly so for someone like me who regularly combats reluctant O-360s in Piper Archers. Masters on, wait for the glow plugs to reach operating temperature, press the big silver button and the AE300 swings into action without a even a suggestion of splutter or shudder.
No sooner were we off the blocks at Wiener Neustadt than I knew I was in a new generation of twin. The DA62 was so easy to taxi, characterised by a significant reduction in the turning inertia usually displayed by twins of older design. For all the resistance to a change of track, I could have been pedaling a large single.
At the holding point, I handed the 62 back to Mayer for the run-ups. Now, this was a thing of beauty! In your average twin, the run-up means cranking the pitch levers whilst checking to see if the manifold pressure (MAP), RPM and oil pressure respond. But Diamond's love of automation has eliminated that, delegating the engine checks to the ECU.
Now here's the tricky bit: the DA62 has two ECUs per engine. Only one is active on any flight, but both need to be tested. For this there is a simple switch that tests ECU A and ECU B separately, then, if returned to the AUTO position, enables the system to decide which ECU to make active based on the ECU hours. It's called the VOTER switch, because the computer "votes" on which ECU to use. During this process, the only indication that anything is happening is a slight shake as the ECUs click in and out. In fact, the pilot won't ever know which ECU the system chose to use; it's not something they need to know.
In the second test, Mayer simply pressed the ECU test button for each engine and the ECU ran through a series of test the equivalent of a CSU test in traditional twins. It was all over in seconds rather than minutes. In fact, the speed with which we ran through the checks engendered in me an uncomfortable feeling that we had forgotten a lot of important things.
We lined-up on runway 10, with Wiener Neustadt's customary 20-knot crosswind hitting us from the left. I slid the power levers easily forward and the AE300s wound up, accelerating us smoothly toward rotation speed. The DA62 was remarkably stable in that breeze to the point that I was wondering if the sock had gone limp.
After rotating, I instinctively lowered the nose slightly to gain speed, only to have Mayer check me. "Keep the climb attitude from rotation," he said. "Watch what it does."
What it did was keep accelerating from the moment the nosewheel left the ground, transitioning easily into a 1000 fpm climb. I got another rebuke when I went to pull the power back; the DA62 climbs easily at 100% power without a worry in the world.
A great day for a cruise
Cruising along with one hand on the stick and the other resting behind the power levers, I got a sort of space-age feeling. It was odd to be flying such large aeroplane with only a joystick – the same feeling I suppose Boeing pilots had when they first converted to Airbuses. It lasted only for a short time, after that I realised that this was a very civilised way of flying; nothing obscured the instrument panel at all and the hand movement was very natural.
My first reaction in rolling into a medium-bank turn was that the forces on the stick were greater than I had expected. Traditionally, twins have more roll inertia than singles anyway, so in that respect the DA62 was behaving like any other twin. I'll put the surprising control force down to me simply getting used to the stick.
The travel on the stick from centred to about a 30o turn was not a lot, so even though the stick feels stubborn, you don't have to move it far to get the desired result. The upshot is that this aeroplane handles magnificently and displays no sign of instability at all.
I pushed the power levers forward until the Garmin MFD told us we were at 95% power load. With the diesels at 2200 rpm, each engine was consuming fuel at a rate of 9.6 US gallons per hour. In our language, that's 36 lph or 72 lph total.
Some perspective here: respected US publication Plane&Pilot has estimated that the G58 Baron drinks a total of 121 lph at 75% power. I had to look twice at the MFD, and deliberately handed over to Mayer and took a photo because I knew I would question what I saw later on.
So what happens at a more sedate cruise? I backed the power levers until we reached 78% load. The Austros eased their demand for fuel back to a combined 58 lph. With an indicated airspeed of 159 knots at 7500 feet, the day gave us a KTAS of 178. I doubt there is another standard 360-hp twin out there that would give that speed for such a miserly fuel flow.
Cutting number two
It has been said by people more learned than me, that when both engines are running, a twin flies just like a big single. Ironically, a twin-engined aeroplane is never more like a twin than when one engine is out of action. How it behaves with one engine inoperative (OEI) can make the difference between defining an aeroplane as a good twin or an ordinary twin.
By that measure, the DA62 is a great twin!
After Mayer shut down the right engine, I went through the usual "dead foot, dead engine" routine, expecting to have to give it a boot full to keep tracking on the mountain ahead. Instead, I was a relieved to find that the rudder forces needed were remarkably light, I would estimate about half to one-third of that of an older twin.
Moving onto Phase 2 of the engine failure procedure, it was time to secure the engine, which was completed, literally, with the flick of a switch: the engine master. With no ignition switch or mixture control, simply turning off the master does the job, even to the point of the automatic feathering function cutting in and feathering the prop.
Within few seconds, Mayer and I were cruising along happily with Number 2 now officially a passenger.
But the big asymmetric shock came with the ability of the DA62 to climb and maintain height easily during OEI ops. With the nose pointed above the alpine horizon, Mayer demonstrated that the aircraft would climb nicely at 500 fpm. With a OEI service ceiling of 13,000 feet, you're about 5000 feet over the peak of Mount Kosciuszko, so Australian pilots wouldn't have any need to fear hitting anything hard.
Return to earth
The landing was going to answer one outstanding question: how would the DA62 handle the 20-knot crosswind? Once Mayer pointed out to me that the maximum demonstrated was 25 knots, the question sort of evaporated.
According to the book, the landing roll is 390 m, and although I didn't get out and measure the distance to stop that day, I have no reason to suspect it wasn't in that ballpark.
With the Austros cooling down and the hatch open, Mayer naturally asked me what I thought of Diamond's latest twin.
I told him the company had redefined multi engine aeroplanes by using automation to take away the demons of asymmetric flight: ability to control easily and climb at a respectable rate when OEI. Going through my notes later on, I could have come to that conclusion without even testing the plane; the flying philosophies of Herr Christian Dries would not have allowed the DA62 to be anything but easy and relaxing to fly in all conditions.
It's a twin to warm the heart of the most ardent single-engine pilot.