Plane & Pilot
Tuesday, January 25, 2011

World's Best Trainer

Diamond Aircraft’s entry-level trainer hopes to lure new pilots to the company’s innovative line of aircraft

Demo pilot Rob Johnson flies for Diamond Aircraft, and he’s also a DA20 owner, and uses his personal aircraft to instruct in Ontario, Canada, near the Diamond factory.
TBO on the Rotax 912 was initially 1,200 hours, fairly low by aircraft standards, but the recommended overhaul interval has since been increased to 1,500-2,000 hours, depending on serial number. A few advantages of the Rotax included slightly better specific fuel consumption and lower installed engine weight than most alternative powerplants. The Rotax 912 was 70 pounds lighter than the Continental that replaced it. This translated directly to better payload. Another benefit was the Rotax cooling system, water cooling for the cylinder heads and conventional air cooling for the cylinders themselves. Hot weather usually wasn’t a problem for the Rotax.

Conversely, the Continental IO-240 offered 55% more power, and that allowed Diamond to increase the airplane’s gross weight by 150 pounds, to 1,764 pounds. The result was a gain in payload, especially significant for a two-seater and a major advantage for the C1.

To further accommodate the heavier weight and maintain a reasonable CG, Diamond moved the battery off the firewall to behind the baggage compartment. The wing sweep also was modified, from one degree aft to about .5 degrees to help shift the center of lift farther forward. The Rotax-powered airplanes included simple, hinged flaps, but the heavier model demanded more sophisticated slotted flaps to reduce stall speed to the JAR/VLA-specified maximum of 45 knots. As a result, the current C1 Eclipse offers a dirty stall of 42 knots.

Like all other Diamond products, the Eclipse is a composite design, intended to help minimize drag, reduce weight and curtail maintenance. The carbon-fiber-reinforced plastic offers an otter-sleek, uninterrupted surface with no rivets or section lines. This presents less drag to the relative wind and helps maximize the airplane’s drag coefficient. In combination with the 125 hp Continental engine, the Eclipse sports an alleged 138-knot cruise speed. More on that later.

Fuel goes aboard the Eclipse through a single filler at aft left fuselage into a 24-gallon tank mounted behind the cabin. There’s only one tank, so there are only two positions, on or off.

The overhead canopy is hinged at the rear and folds up and back to provide ultimate access to the cockpit. You merely step over the sidewall and settle into the seat. As you might imagine, visibility is exceptional with nearly a 360-degree view, but the price of the semi-bubble canopy is a greenhouse effect in hot weather. There are small vent windows on each side that may be opened in flight. Once you’ve buckled up the four-point harness, you definitely feel as if you’re a part of the airplane.

Diamond has a slightly different philosophy about seating comfort in that the seats are fixed and the rudder pedals are adjustable. This has the benefit of providing good crash protection, as the 26G seat is hard mounted to the airframe. There’s no provision for changing the geometry of the stick to accommodate an individual pilot’s arm length, however.

The C1 employs a nonsteerable nosewheel, and to my mind, that’s the best possible compromise between a tailwheel and a steerable nosewheel. The free-wheeling forward gear allows unusually responsive directional control. You can reverse direction in the C1’s wingspan, though locked-wheel turns aren’t recommended. Pretty obviously, directional control is by differential braking until the rudder takes effect, and that means more wear and tear on the brakes, a reasonable price in exchange for such positive ground maneuvering.

Labels: Piston Singles


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