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.