When Diamond Aircrafts snazzy little Katana emerged into the flight training scene three years ago, it seemed an easy set-up for a bloody nose or two.
Way too small, some said.
A plastic airplane? Are you kiddin? That thing wont last a month on the training line.
No way Im instructing in any airplane with a chainsaw engine.
While that carping may have some merit, the Katana has nonetheless established itself as the leading-edge trainer for the 1990s, with some 300 airframes toiling away at flight schools across the country. That Diamond has the new trainer market virtually to itself doesnt hurt. But the fact remains, the Katana seems to be delivering on its promise of being a new-age trainer thats both fun and cheap to fly.
Still, those wisecracks about the engine have scored some hits. Its easy to get past the Rotax 912s braaapy exhaust note but not so easy to ignore its 81 HP, which delivers respectable cruise speed but anemic climbs at high density altitudes and high weights.
Diamonds response to this shortcoming rolled off the companys London, Ontario assembly line last fall in the form of the Katana C1, an improved airframe sporting a 125 HP Continental IO-240. Frankly, warts and all, we liked the Rotax-powered version we’ll enough to recommend it without noteworthy reservations. The C1 represents significant enough improvements over the original to nearly qualify as a different airplane.
Diamond plans to sell both Continental and Rotax-powered Katanas but both engines will be installed in an improved, lighter airframe. The TCM version is the Katana C1, the Rotax version will be called the Katana A2. (The original Rotax model is now the Katana A1.)
Hard to say how the market will respond but we predict that if Diamond sticks with the realistic marketing plans it has thus far pursued, the C1 will eventually displace the Rotax version and likely earn a reputation in the training arena similar to venerable Cessna 150/152 series. Assuming, of course, that the IO-240 develops no nasty maintenance traits and that its higher fuel burn isn’t a significant issue.
Rotax vs. Continental
When Diamond morphed the Katana from the Austrian-designed Super Dimona motorglider design, it took a sizeable gamble on the Rotax powerplant. Rotax is we’ll known in Europe and in the U.S. for two-cycle ultralight engines, which have also found their way into homebuilts.
But the four-cylinder 912F3 represented its first foray into FAR 33-certified aircraft engines and Diamond openly admits to an uphill battle convincing buyers that this was no snowmobile engine. Indeed, with electronic ignition, autoleaning carburetors and water-cooled cylinder heads, the Rotax has more in common with a Honda Accord than a Cessna 152. Moreover, it has a controllable pitch prop, which some flight schools were bound to shy away from due to worries about training and maintenance complexities.
Although relatively cheap to replace-$6000 initially for both an exchange engine and prop-the Rotaxs out-of-the-box TBO was only 1000 hours. TBO has since been raised to 1200 hours but the exchange cost has ballooned to $10,100, meaning the hourly engine cost is about $8, versus about $6 for the Cessna 152s O-235 Lycoming. However, since the Katana burns half the fuel, its direct hourly operating costs-on paper, at least-edge out the 152 by a couple of bucks or more.
In nearly 200,000 hours of total fleet time worldwide, says Diamond, the Rotax has turned in a respectable if not stellar service history. Some operators have easily exceeded the recommended 1200-hour TBO and, of course, a few have come up short. The Rotax has had its share of cylinder problems and inevitable operator-induced glitches, plus a handful of premature failures, none of which involved the engines bottom end. Maintenance wise, mechanics havent exactly taken to the Rotax like ducks to water.
We find that sophisticated operators-the UNDs [University of North Dakota] and the larger schools love it. Some of the smaller operators don’t, says Diamond CEO Michael Slingluff. If its in Petes Aircraft Maintenance, Pete is trying to find the mags so he can tap on them to get it going, just like he does with a Lycoming. Thats not going to work on this engine.
More to the point, the Rotax is an adequate performer in moderate weather and light weights but a bit of a dog when the weather turns hot and humid or at high density altitudes. Operators have complained about 300 FPM climb rates in the pattern than can make a few touch and goes an all-day affair. Even a ratted out 152 can do as we’ll or better.
Further, Diamond is learning what other airframe makers have: Putting all your eggs into one vendors basket is risky. Although Slingluff and Diamonds sales manager, Jeff Owen, say theyre still sold on the Rotax, they also note that the company has not raised its profile in the U.S. with the kind of national advertising and behind-the-scenes technical support that Lycoming and Continental have routinely provided.
Although Rotax has technical developments in the works-including a 100 HP 912 variant-Diamond has had to shift for itself on many technical problems that engine vendors traditionally tended to in the past. Further, Diamond needed to address the Katanas anemic climb performance forthwith, preferably with an off-the-shelf engine.
Clean Sheet
Continentals IO-240 is a clean-sheet powerplant introduced four years ago, primarily for the homebuilt market. The initial version, the IO-240 A1, had fuel injection but with TCMs traditional log-and-runner induction system. But Diamond wanted a more state-of-the art powerplant.
The IO-240B is just such. It has a balanced topside induction system similar to that used on the larger displacement IO-550G found in the Mooney Ovation. Otherwise, its systems and components are identical to those found on any other trainer and will thus be familiar to any maintenance shop.
In comparing the two installations, we noted a striking contrast: The Rotax, with its watercooling and electronic ignition, is festooned with hoses, wires and sensors, while the Continental has but a few umbilicals. The IO-240s accessory case-including the oil filter and mags-are readily accessible for maintenance, although its a tight squeeze for the mags. The alternator-a belt-driven 40-amp Denso-is mounted frontside, automotive style. Production C1s will have a TCM lightweight starter. Outwardly, the C1s snout is less pug nosed and the overall length is 1.6 inches greater. Natch, since the Continental is air cooled, the Rotax versions sealed cowl has given way to a couple of small cooling inlets. There are more changes beneath the skin; the emergence of the C1 model is coincident with a number of minor but significant airframe improvements which will be incorporated into both the TCM C1 and Rotax A2 airframe.
To account for the Continentals higher weight-246 pounds versus 160 pounds for the Rotax-Diamond squeezed 60 pounds of excess weight from the airplane, chiefly by retooling to produce composite parts more precisely and with better repeatability and by switching from steel to aluminum gear struts.
To account for the more forward CG, the spar was moved forward 1 inches, the wing sweep was reduced slightly, the distance between the main and nosegear wheels was decreased and the battery was moved from the firewall to a bulkhead behind the baggage compartment shelf. Further, the C1s gross weight rises to 1650 pounds, from 1609 on the Rotax-powered version.
Other changes include:
A redesigned horizontal stab and elevator thats larger and reduces parts count by eliminating an anti-servo tab
Replacement of simple hinged flaps with Fowler-type flaps
Improved two-stage canopy latch
Improved brake master cylinders
Instrument panel moved higher and more forward, creating more knee room
Higher recline angle on seatbacks
Improved heating and defrosting system
Additional instrumentation, including EGT, fuel flow and large tachometer
Price, Payload
The C1 sells for $114,260 versus $106,785 for the A2. The numbers cover a basic airplane, certified for night and day VFR but not IFR. Diamond has no plans to certify either model for IFR, which has been a source of some irritation to buyers. The DA 40 four-place version, under development in Austria, will be IFR-certified. It will also be Continental powered, using a 170 HP version of the same IO-360-ES Cirrus picked for the SR 20.
A line-by-line performance comparison between the C1 and the existing Katana reveals that the higher horsepower doesnt yield improvements across all categories. The C1 cruises and climbs faster, but its payload with full fuel is 364 pounds versus 394 pounds for the Rotax-powered variant. However, the C1 carries 4 more gallons of fuel than the A1, so with equivalent fuel, theyre about equal in payload.
In the real world of flight training, this means that in the C1, a student and instructor each weighing 200 pounds can launch on a cross country with 18 gallons of gas. Theyll have to watch fuel consumption carefully; learning leaning will be a must.
According to Diamonds preliminary specs, at 65 percent power and 123 knots, that 18 gallons will last a bare two hours or, with careful leaning, about 2:20. Reducing to the max range cruise of 50 percent power drops the fuel flow to 4.8 gallons leaned at a speed of 109 knots, stretching the endurance to 3:45.
In the Rotax version, student and CFI taking off with the same 18 gallons could cruise at 110 knots, burning 4.5 gallons for an endurance of 4 hours.
The A1 Katana has a service ceiling of 14,000 feet, versus 13,000 feet for the C1. Landing and takeoff distances are comparable, although the C1 enjoys a slight edge in landing performance.
Flight Impressions
Right from start-up, the C1 clearly has a noticeably different personality than the Rotax-powered Katana. Rather than the car-like start procedure used to fire up the Rotax, the IO-240 starts like a real airplane motor: mixture rich, pump on and crank. You can feel the loppy idle through the airframe, rather than sensing it as a distant vibration somewhere beyond the instrument panel, as with the Rotax.
The downside of fuel injection is usually cantankerous hot starting. After our flights, we did try a couple of hot starts. With throttle open and mixture at idle cutoff, the engine seemed to catch and fire within a half dozen blades.