There’s little question that the C1’s swept, modern design wins friends among aspiring pilots and old pros alike. In keeping with Diamond’s sailplane tradition, the Eclipse offers uncommon glide and efficiency. The airfoil is a European Wortmann FX-63 section, a combination of short chord and long span that results in an aspect ratio of 10.2. In contrast, a Bonanza’s aspect ratio scores only 6.2, and a Warrior’s registers 7.2. (Aspect ratio is the proportion of chord to span; all other things being equal—which they almost never are—the higher the aspect ratio, the more efficient the wing. High-performance sailplanes make excellent use of the high-aspect-ratio wing.)
The C1’s cockpit is housed beneath an overhead hatch that folds up and backward for entrance to both seats. Accommodations are uncommonly roomy, wider than just about any other two-seat trainer. Aft of the front office, the waspish empennage translates to a graceful T-tail, mounted up out of the propwash to minimize pitch excursions during power changes.
Despite what may appear a delicate structure, the composite C1 is actually stronger than its counterparts. Diamond’s airplane is certified in the utility class (capable of withstanding 4.4 positive G’s) and is certified for spins, a valuable but uncommon talent among trainers.
One interesting aspect of the C1: it isn’t certified for IFR. Yes, you can equip the airplane with full IFR instrumentation and avionics. You can even train for the instrument rating under the hood in the airplane operating in VFR weather, but you can’t fly in actual IFR conditions. Diamond hasn’t yet obtained lightning-strike certification from the FAA, so the airplane is limited to VFR operation.
In keeping with its intended role as a primary trainer, the C1 flies very much like a Grumman American Trainer with a stick rather than a yoke. The Diamond trainer manifests similar control characteristics—granted push-pull tubes for roll. No one will mistake a C1 for an aerobatic airplane, but the Diamond’s quick handling and enthusiastic throttle response makes it a fun machine to fly.
Cruise performance and cabin comfort are good enough that Diamond sells many of its C1s to individual owners rather than flight schools. At 135 knots max cruise with 24 gallons in the tanks, the airplane can range out 410 nm in three hours with a reasonable reserve. Private owners love the airplane’s spacious interior and excellent performance.
Perhaps best of all, however, stall characteristics are about as benign as you could hope for. Instructors know there’s a direct correlation between stall speed and good landings, and the C1’s full dirty stall speed is a slow 45 knots. That means a student can make approaches as slow as 60 knots if necessary. Nothing happens too fast, and the airplane flies so slowly, it’s fairly easy to finesse the Diamond trainer onto the runway.
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