But... What About The DA42?

By ANN Editor-In-Chief Jim Campbell

The proof of any plane is in the flying. And in the case of this airplane?

Wow.

Unfortunately; the airplane currently being flown at the factory is a development bird and does NOT have the production cooling system and other accoutrements associated with the final product. As a result, it's underpowered, a mite slower, and less of a champ in the single-engine department -- and not a fair airplane to use as a source for a full evaluation.

Here are the high-points... expect my usual magnum opus (soon to be a major motion picture) when I can do a fair test of a fully readied production airplane.

Let me say this. The airplane boasts EXCELLENT control harmonies, good visibility and very promising single-engine properties. It IS a stick and rudder airplane... as that BIG high-aspect ratio wing promotes the use of LOTS of rudder in certain flight regimes to coordinate turns, power issues, and course corrections. The overall effect is surprisingly agile, fairly elementary in approach, and a true pleasure to fly... especially since the bird boasts excellent static stability margins (pitch is a rock) and very well-defined dynamic properties (nearly dead-beat in some instances).

Engine management, especially Start-Up chores, are a joke since the FADEC controls everything... turn on each engine's engine control unit (ECU), wait for the glow plugs to get toasty, and turn the key... the FADEC meters everything and each lever is nothing more than an electronic control that tells the computer how much power you want... so that the computer can then apply it.

A test button takes the place of a conventional run-up in that once the switch is depressed, the FADEC goes through a self-test program that cycles the power, prop and ignition systems in a very short interval of time. All you have to do is sit back and watch. It's a system simple enough for an aviation journalist to use (the acid test of simplicity, let me assure you).

Nosewheel steering is agile and just the thing for getting around on tight ramps. And thank god for a parking brake that's actually installed in a place where you can get to it. A novel concept, that. The aircraft is a very miserly bird in terms of runway. A groundhog it is not.

Firewalling the TwinStar is fun because you can do it any way you please, including throttle slams... since the FADEC will accomplish what you ask in a manner best suited to the proper operation of the engine. FADEC will spoil you. Gear retraction produces light disturbances to the aircraft's trimmed configuration, but the effect is temporary and mild.

Low-speed behavior is typical Diamond -- as boring as a Sunday school lecture on the evils of sin (especially for those of us with exceptional expertise on the subject at hand... but I digress). Stall onsets are preceded by light high-frequency buffeting that is both symmetrical and grows slightly more prominent with increasing use of flaps. There is very little pitch trim alteration with flap deployment. The actual stall is barely there, overtly symmetrical, easily controlled with rudder and accompanied by minimal loss of overall control effectiveness. I was quite impressed with both yaw and roll in the stall and through a number of sustained, exacerbated and abused stalls that were fairly mild but typified with a fairly notable sink rate. Uncoordinated stalls... half-ball, full and two-ball widths out, show NO tendency for asymmetric departure or sudden/overt inclination toward autorotation. Once again, so simple even an aviation journalist couldn't screw it up... and I assure you, I tried.

One attribute in this airframe is going to be very useful. The TwinStar has a gear extension speed of almost 200 knots! Throw the gear out and the suddenly draggy TwinStar comes out of the sky like a freefalling safe. The descent rate and attitude are breathtaking... similar to some Space Shuttle landing attitudes I've tried in the NASA sims. No kidding... this thing comes out of the sky like a plugged Mallard and the speed accretion is negligible unless you stand it on it's nose. I never did quite get it into the yellow arc and I was doing the better part of 4000 fpm! 

Finally; let's talk single engine work. Oh man... I haven't flown a twin with this kind of single-engine manners since I sold my old Aztec (GREAT bird... scary fuel flows...). Since FADEC feathers the dead engine during real trouble, there is little to do once one mill takes a dive -- stomp the rudder, assume the attitude, and fly the d****d airplane. The TwinStar has plenty of rudder to counter asymmetric thrust and lots of rudder trim to ease that chore over the long-term. Shut-downs at 6000-8000 feet (up to approximately 10K DA) showed a good climb at Vyse (200+ fpm), very good control authority, and surprisingly good manners when it wasn't being flown strictly according to the rules in regards to proper single engine procedure. Steep turns into and opposite the dead engine were easily to accomplish so long as one was willing to hold a lot of rudder, as needed, with each turn cycle while the "safe" operating envelope seems fairly wide. And this, I must remind you, is in an airplane without the power boasted by the production engines.

I assayed a number of single-engine landings. The workload is necessarily higher than a standard landing and the rudder workload is likely to be on the high side, but it's nowhere near as heavy as many others in this category (though I will single out the Piper Seminole as being pretty nice to fly in that regime, from a controllability standpoint... and NOTHING beats the Aztec in airplanes with less than 300 HP, as far as I'm concerned... but the TwinStar comes REALLY close).

One exercise was a gas. Sucking the power levers back to 40-42 per cent turned up a total fuel burn of LESS than 6 GPH, in TOTAL... and a cruise speed of some 120 knots. This is the profile that was used to ferry the 2004 Oshkosh display bird (with ferry tank) all the way back to Europe... including a long haul across the pond. Remarkably, the twin diesel engine DA42 was flown from London (Ontario) to Porto (Portugal) with only one stop, in St. John's Newfoundland (Canada). The leg from London to St. John's spanned 1300 NM and took Guillaumaud seven and a half hours. The transatlantic leg from St. John's to Porto, a 1900 NM stretch, was completed in twelve and a half hours. Had it not been for adverse weather conditions in Europe, the remaining five hours of fuel upon landing in Porto would have been sufficient to reach Guillaumaud's planned destination of Toulouse (France), a planned non-stop distance of over 2500 NM. Average combined fuel burn for the crossing, flown at 11,000 ft, was just 5.74 GPH (2.87 GPH per engine).

Just for giggles, compare this to the lowly Cessna 152 we all know and have abused -- which burns more than 6 gph at anywhere over 100 knots and the only way it's gonna see 120 knots is to push it downhill. That's remarkable efficiency, and for people who truly want to venture off into otherwise unattainable locales, this thing may prove to be an amazing transportation system to partake in the most amazing adventures of your life. Damn. Cool.

One final exercise said a lot for this bird. After a number of fairly easy single-engine approaches, I decided to try a real-world scenario that is (too many times) a hapless flyers last act as PIC. I hammered the power to the stops, rotated, stabilized the attitude, retracted the gear, and then killed the right engine (though the left is somewhat more critical in this bird) by retarding it to idle (which DOES closely approximate the effect of a feathered engine based on a fair amount of actual time with a feathered mill).

Of course, the "failure" was no big surprise, so all I did was hug the blue line (plus a few knots for insurance, since my DA was through the roof -- nearly 100 degrees on the deck), stomp the rudder and flew the airplane. Well, it still flew... and a positive rate of climb was, indeed, eked out by the bird on a hot, nasty day while barely staying on the right side of the power curve (Vyse is about 83 knots). I saw about 200 fpm, and had actually seen a slight bit better at altitude where the air was a mite cooler/calmer and the turbo was still able to strut its stuff. It required a modest amount of wrestling to get everything settled into a proper set of attitudes (mostly rudder), but once settled into the proper profile, the plane remained pretty easy to fly. Should something like this happen in the real world, the benign nature of this mount will give a struggling pilot a chance at success. I can't wait to try this on a production diesel, as well as the Lycoming.

OK... it's a first look, not a full flight test, and our test bird had a number of strikes against it... a hot day, a full load of gas, a power handicap, and yours truly in the left seat. That's an acid test in anyone's book. But suffice it to say, for now, that it appears that the DA42 is very much on the right track.

Much more to come... soon.

FMI: www.diamondair.com