Due to the different cooling requirements of the air-cooled engine, the cowling was completely redesigned to incorporate more conventional air inlets, while the extra 70lb of the Continental required a new, steel tube engine mount.

Obviously, having another 70lb so far forward had a profound effect on the CG, so Diamond's engineers set about addressing this in a number of different ways. A relatively easy method of relocating the CG is to move something fairly heavy, such as the battery. On the C1 the battery now lives behind the baggage bay, and concurrent with shifting the empty CG aft, Diamond also moved the Centre of Pressure forward by reducing the sweep angle of the wing from 1 degree aft to 0.5. Other aerodynamic changes caused by the installation of the heavier engine also necessitated increasing the area of the tailplane and elevator by 10% and reducing the tailplane's angle of incidence.

In an effort to claw back some of the extra weight added by the heavier Continental engine, Diamond also used thinner skins on the wings, while another 20lb was saved by replacing the original sprung-steel undercarriage with a lighter aluminium arrangement. The wing uses the same Wortman FX63-137/20 aerofoil as the Katana's big brother, the four-seat DA40 Diamond Star (see Today's Pilot December 2000) but, unlike the simple hinged flaps fitted to Rotax-powered Katanas, the C1 flaps are of the more sophisticated single-slotted variety.

The basic airframe is, in common with other Diamond products, constructed of glass and carbon fibre/epoxy composites, which help to make an aircraft that is relatively light, durable and corrosion resistant. The all-composite construction also allows for the economical manufacture of complex curves, as well as a very accurate aerofoil section. There is no doubt that the hundreds of rivet heads and overlapping metal skins of aluminium aircraft all contribute to creating drag, and the very smooth finish that can be produced by the use of composites obviously goes a long way to reducing total drag.

The canopy of the C1 has also been redesigned but as far as I'm concerned not necessarily improved. More on this later. Getting into the C1 is easy. The large canopy opens good and wide and is well supported, while a conveniently-sited step is complemented by a thoughtfully-placed grab handle. Upon settling myself onto the comfortable leather seat, I immediately noticed that the re-engining process had also produced some significant changes in the cockpit.

The throttle quadrant has been substantially redesigned, with a mixture lever where you would find the prop control on the Rotax-powered version, while an alternate air lever for the fuel-injected engine has replaced the carb heat control of the carburetted Rotax. The instrument panel has lost the redundant coolant temperature gauge and gained a cylinder head temperature gauge. It was also interesting to note that the Continental engine's rpm is indicated by a much larger tachometer than the Rotax-powered aircraft, and that it was been relocated nearer the flight instruments.

I was pleased to see that the C1 has retained the control sticks fitted to earlier Katanas. I know that this observation is entirely subjective but, speaking personally, I prefer a control stick to a control yoke any time. I was also pleased to see that the switch for the electric pitch trim has been moved from behind the throttle quadrant to its rightful place on the stick top, which also incorporates a PTT. Unusually for an aircraft in this class, there is no manual trim wheel, while trim position is indicated by a small stack of green LEDs above the primary flight instruments.

Although the seat is fixed, the rudder pedals adjust over a good range, so having set and locked the pedals to my satisfaction, I strapped myself down. In common with many modern aircraft, the C1 uses a four-point harness with adjustable waist straps and inertia-reel shoulder straps. I have to say that this really is the best system for light aircraft, although I would prefer to see a means of also locking the inertia reel for take-off and landing.

Upon closing the canopy, I instantly became aware that the visibility was somewhat compromised when compared with older Katanas. This is because a large sunshade has been built into the canopy that is not translucent or even opaque. I really didn't think much of this not only did it seem like a retrograde design step but I was concerned that it might compromise flight safety. However, to be fair, the visibility is still superior to many other GA two-seaters, just not as good as it used to be. Bob pointed out that the Eclipse model can be delivered finished to individual customer's specifications, and I imagine that many buyers will opt for either a tinted panel or even an all-clear canopy that incorporates a retractable sunscreen.

Starting the Continental was easy using traditional fuel-injected engine procedures, although it is worth pointing out that as the IO-240 has a different induction system from the Rotax, it does require a slightly different technique. This should be kept in mind if you are flying at a school that operates both Rotax- and Continental-powered versions.
I used a hint of power to nudge us out of our parking space and then set off on the relatively short taxi to runway 21. Taxying the Katana is easy, for although the nosewheel does not steer, the powerful toe-actuated hydraulic disc brakes have a smooth, progressive feel to them. In fact, I got the distinct impression that the brakes on the C1 were better than on earlier versions. It transpired that the brake units are exactly the same as those used on earlier models, but the angle of the brake pedal has been changed slightly to give the user a little more leverage, which makes them more effective.

Coincidentally, the ambient atmospheric conditions were pretty close to an ISA standard day, with a QFE of 1014mb and an outside air temperature of 15°C. The surface wind was 300° at 12 knots, which was producing an honest 90° crosswind. The Katana handled all this with ease: the rudder came alive almost immediately and only small dabs of differential braking were required to track the centreline. As the needle of the ASI swept through 44kts, a suggestion of back-pressure on the stick raised the nosewheel smoothly off the ground and the Katana quickly settled into a brisk climb after a ground roll of around 900 feet.

The guarded flap switch is logically positioned forward of the throttle quadrant at the base of the instrument panel, and as soon as the flaps were retracted, I trimmed for the best climb speed (Vy) of 75kts and noted that the needle of the VSI was hovering around the 1,100ft/min mark. I'd expected that the extra 44 horses would provide a substantial increase over the rather leisurely climb rate of the Rotax-powered aircraft, but I was still most favourably impressed by the scale of the improvement.
We'd arranged to rendezvous with the C172 camera ship over the now-deserted RAF Finningley, and as we approached the area, Bob and I both began scanning for the Cessna, which we'd briefed to orbit the field at 5,500ft, while we approached at 6,000ft in order to ensure separation. As soon as we'd spotted it, I curved around into the camera ship's 'six' and began to slide smoothly into position.

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