Pilot report - Zlin 142C
vs Diamond Katana
[Reprinted from Fliteguide / Imperial Aviation]
Aviation is fraught with tradition. It pervades almost every opinion, bias or judgement we care to venture. It pervades every level of our aviation environment, be it homebuilts, gliding, general aviation or airlines. It is fair to say that most of us harbour such entrenched ideas of flying, new technology is often an anathema to us. Where does it come from? I venture it rears its head when we step into our first training aircraft and solidifies soon after we master the simple art of touch and go's. I guarantee you'll always be a Cessna person after completing a PPL on 152s or 172s. Likewise for Piper. Those hard hours in the circuit with a Piper Tomahawk or Cherokee will often lead us to purchasing Arrows, Cherokee Sixes and placing a Malibu at the top of our wish list.
The 142 is a development of the original 42, spawned from the former communist bloc's old and prolific aircraft manufacturing industry. The Czech Republic has a long history of making aeroplanes - good ones too. In the bad old days their light aircraft shot to international fame in world aerobatics. The Zlin Trener became the machine to be seen with at competitions and it often won trophies in the hands of some of the world's best aerobatic pilots. The single seat Zlin 50 followed. The 142 replaced the 42 in the early eighties. The 142 was designed not only to provide eastern European aero clubs with a basic ab-initio trainer but to fulfill a worldwide military training environment as well. The Zlin's training credentials are impeccable.
The Katana's roots lie in the somewhat less glamorous pursuit of motorgliding. A low profile activity in southern Africa but with a serious following in Europe, specifically Germany. The Katana's elder sister is the Limbach-powered Hoffman H-36 Dimona. Hoffman Flugzeugbau Gmbh began making the glass-fibre motorglider in Austria in 1979. The company suspended production in 1984 after running out of money and it was to be another five years before Wolff Hoffman was able to restart production. After a change of ownership, the company was renamed HOAC and in 1991 they flew a short-wing, tailwheel version of the Dimona, the LF2000. Shortly afterwards a tricycle undercarriage was installed and the little aircraft was renamed Katana.
Whilst the Katana's origins lie in the popular European gliding industry, the company's boss, Christian Dries, did two very clever things. He certified the Katana under American FAR-VLA rules, enabling the aircraft to be used as an FAR-23 type trainer and he then built a production facility for it in London, Ontario, Canada calling it Diamond Aircraft. Dries shrewdly dumped an entire factory in the middle of the single most important market - the American continent. Although the DA-20 Katana concept is by no means unique, Diamond's dual manufacturing facilities and aggressive marketing paid off. One of its early successes was a sale of 50 Katana's to well-known US training establishment Spartan College - this was almost a universal stamp of approval.
DESIGN AND ENGINEERING
Here are two aeroplanes so diametrically different in execution it's difficult to conceive they were built for the same purpose. The Katana, with its glass fibre construction and an engine with a sound we used to make as kids when pushing Corgi cars across the lounge carpet, represents a leap into the future. The other, the Zlin, is all tradition - all (or almost) metal fabrication with an ancient in concept, inverted six cylinder air-cooled 210 horsepower thumper.
Diamond chose to replace the original Limbach motor with something a little more attractive to the Americans (and everyone else for that matter), a four stroke, dual ignition, combination water and air cooled 80hp Rotax 912 engine. Although Rotaxes are more familiar to owners of snowmobiles and microlight pilots the 912 is fast establishing a reputation for reliablity, low fuel consumption and low maintenance demands. The electronic ignition requires 100 rpm before the magnetos cut in so in the unlikely case of ignition failure, the engine would require a mighty swing to start it. With few high time engines around so far, the Americans have cautiously allowed the engine to operate to 1200 hours between overhauls although this figure should soon be increased to 1800 hours. The 912 differs from conventional aero engines in a number of ways. It runs at 5000 rpm and reduces propellor rpm to a maximum of 2500 rpm through a reduction box. The cylinder heads are cooled by a water-glycol coolant and to further deepen a mechanics curiosity, the ignition is electronic with a 'manual' backup in the form of a couple of magnetos.
The small capacity engine rewards operators with a miserly maximum fuel consumption of 3.5 gallons per hour which will titillate flight school operators. At overhaul time operators will further look forward to having their Katana laid up for no longer than a day. FTC will remove the engine and install a new one within 12 hours. Another sweetener for training schools is a propellor/gearbox clutch which disengages in the event of a prop strike and thus removes the need for an engine shock test.
The Katana's engine is easily accessible under a lower and upper cowling released by a number of Dzus fasteners. The fuselage bulges at the cockpit section and tapers sharply behind the wing trailing edge and towards the tail where the horizontal stabiliser sits at the top of the fin. The finish is superb as one would expect of a German design. Whilst the aircraft may be mistaken for a homebuilt on the apron, it's clear that the factory has given a great deal of care to surface integrity. The wings too are mirror-smooth with close fitting ailerons and flaps that put a Cessna and a Piper to shame
The wings have only two removable inspection panels. One is to check the wing attach point and the other, underneath, to inspect the control bellcranks. Glass fibre aircraft have always been disadvantaged by Africa's high temperatures and although it won't melt before your very eyes, it is forbidden to fly a Katana when the airframe temperature exceeds 55 degrees Celsius. A small temperature sensitive circle has been placed between the seats.
If the temperature builds up a magical '55' appears in the circle, you then know it is time to seek a cool beer in the bar rather than sweat it out in the circuit. The heat factor also explains why the Katana is only available in a white finish and minimal stripes. Those who want to paint their Katana like the Red Baron would be better off buying a Zlin. The main undercarriage legs are fashioned from a single piece of flat steel that should amply bear the brute strain of years of circuit bashing. The castoring nosewheel is mounted on a thick tubular leg.
The Zlin's six-pot supercharged, hollow crank, 210hp inverted Walther engine is a throwback to the forties and even sooner. The engine breaks no new ground and features such archaic components like the famous 'shower of sparks' starting system - something even Cessna dropped in the sixties. Reluctant starting engines with such an arrangement could always be coaxed into life with a choice of feeler gauge, a sharp tap with a fuel tester or if all else fails a swing of the prop. Lift the cowlings and its reassuring to see theengine mounted on sizeable cast bearers much like the P51 Mustang and later marks of the Spitfire. The Eastern Europeans are not known to pussyfoot around aeroplanes and their aircraft designers usually adhere to strict pick-up truck priorities rather than motor car pretension. Nevertheless, the engine's strength, simplicity and reliability has served many thousands of hours in both civilian and military use. The Walther's TBO is a useful 2000 hours and there are a number of engine shops able to maintain and overhaul them.
Behind the firewall a hefty tubular-steel frame surrounds the cockpit and is bolted to a monocoque rear fuselage. Zlin has used composite panels to cover the frame area. The short, thick-cord and forward swept wings are bolted to a hollow box-section spar which is filled with nitrogen gas. Overstressing the airframe could lead to eventual cracking of the centre spar allowing the gas to escape and providing a warning to the pilot via a gauge on the panel.
The main undercarriage is also a highly resilient steel plate affair. The nosewheel is mounted on a massive shock-absorbing oleo and the Czechs have enough faith in the structure to teach their students to push forward on the stick during the after-landing roll-out to aid braking even on the roughest surfaces.
Why American manufacturers insist on securing inspection panels with screws is a mystery. The Zlin's panels are released by simple single push-button catches and are hinged just like a modern airliner. Whilst this may add a small amount of extra weight, it will bring a smile to any engineer. The Katana is well ahead of the Zlin in ease and cost of maintenance although faced with any kind of airframe damage, the DA-20 may cause more head scratching than the Zlin. However, part of the South African certification process has led to a number of local aircraft engineers learning to repair minor glass fibre damage. This may have caused extra head scratching if they knewtheir task was to be a glorified boat builder when their apprenticeships began!
ON THE GROUND
The Katana's preflight ritual is so simple it will be a disappointment to those suspicious and mechanically minded students who enjoy a Sherlock Holmes approach to the walk-around. After lowering the flaps the most uncomfortable part of the preflight is attempting to check the oil and coolant levels without removing a chunk of skin from the edges of the small engine inspection panel. The circular panel should be bigger but fulfills its purpose without allowing the pilot to peer inside and become baffled by the plethora of electrical leads and cooling pipes. Lazy pilots will appreciate the single point refuelling which is easy to get to and requires no crawling beneath the wings to check for water contamination. Hinges are difficult to inspect closely because of the tiny control surface gaps. A simple pressure-activated stall-warning aperture is on the left leading edge and the pitot-cum-static vent blade (like a Cherokee's) is the only item that requires any form of peering under the wing.
The Katana's canopy opens smoothly upwards and backwards after releasing the safety lever with a positive thunk. A step in front of the wing and two hand holds at the front of the glareshield makes climbing in easier than it appears. The Katana sits low on the ground so only those who smoke 60 cigarettes a day and shop at Sweets from Heaven will have difficulty on maneuvering themselves into the seat. The seats form part of the fuselage moulding and spar framework and are fixed in an almost bench-like configuration that cradles the crew in a reclining position. The rudder pedals adjust by either pushing them away or pulling them forwards with a toggle fixed to the end of a Heath Robinson steel wire that is left to dangle untidily on the floor. The partly shrouded rudder cables stretch each side of the cabin and are an un-Cessna reminder of the Katana's glider heritage. Otherwise the cabin is extremely businesslike and well finished. The cabin is deceptively large and provides seven inched greater width than a Cessna 150 at the most important point - the shoulders. Diamond has done a masterful job of fitting the radios, instrument gauges and circuit breakers. With the primary flying instruments and electrical switches filling the left half of the panel and radios in the middle, the engine gauges and circuit breakers occupy the right half. Carburettor heat, choke, parking brake and cabin heat verniers are mounted below the centre panel and throttle, propellor lever and electric trim switch are on the pedestal between the two occupants. Whilst fit and finish are to a high standard only time will tell if the lightweight plastic switchgear and delicate-looking engine controls will stand repeated and (inadvertent) clumsy treatment from students.
After pulling the canopy down and locking it, the engine starts almost immediately with a simple dose of choke. It settles down to an un-aeroplane high-pitched chatter. Having completed the after start check list, the Katana moves forward with little extra power. Steering is via differential braking - a painless process if you do not have big feet. The footwell shrouding is too close to the pedals and my toes caught against something under the panel every time I attempted to apply the brakes - which is often in the Katana. The toe-brakes themselves require considerable ankle movement and whilst they are effective, the pedal movement is a little too much for the available space.
The Zlin's wal-around is more businesslike. The forward-sliding canopy has to be closed to open the engine panels which are secured by three quick-release fasteners each side. The panels open to reveal a separate oil tank mounted against the firewall on the left hand side. The tank remote to supply the engine for four minutes of inverted flight. A dipstick, fixed to the oil tank cap gives a quick indication of the contents and the panels open the entire length of the engine bay so a detailed look at the plugs, leads and engine accessories can be accomplished with ease. The Walter engine is mostly controlled from the cabin with mechanical linkages rather than cables and the wiring harness is fed through the firewall using military style plugs. Whilst all this attention to longevity may add weight, it is a reassuring sight to see such engineering quality. Furthermore, when cold, the propellor has to be turned through six compressions by hand to disperse any collected oil in the inverted cylinders. All hinges are easy to see although students wil have to crawl under the wing to inspect the pitot tube, flap and aileron linkages and fuel drains.
Although climbing into the Zlin appears easier than the Katana, entry into the cockpit is awkward if pilots are to avoid standing on the nicely trimmed seats. Once seated though, the cockpit is truly cavernous. The aircraft has more shoulder room than a Cessna 210. The 142 has individual seats that would not look out of place in an armoured car.
Like the Katana, a shelf behind the seats provides for baggage space and the area below it is masked off from the aeroplane's innards with a heavy plasticised canvas. The wide instrument panel is shrouded by a deep glareshield.As in most aircraft, primary instruments are on the left and engine gauges to the right. The centre pedestal contains the mixture, supercharger, propellor and throttle controls.The Zlin 142 has dual throttle levers for student and instructor and each one is fashioned from indestructible, heavy gauge steel.
This is a common feature in military basic trainers as single-seat or tandem seat military aircraft always have their power levers on the left hand side of the cockpit. Eastern European light aircraft manufacturers prefer to replace pop-out circuit breakers with switches. Before starting, the pilot has to ensure the separate battery and starter switches are engaged before the master and magnetos are activated. The switches are positioned at the front of the panel between the two occupants and each one is shrouded and operates with a pleasant positive movement. The flaps are deployed with a hefty two-position 'handbrake' lever between the seats. Manual rudder and elevator trim controls are where they should be, on the floor and immediately available without having to look down.
The engine supercharger has to be engaged for starting and after securing the five point harness, pumping the primer three times, the engine comes to life after thumbing a separate starter button. With the Walter started, the radio, beacon, gyros and engine gauges are switched on individually. The supercharger is disengaged and the engine allowed to warm up until the oil temperature and CHT needles enter their operating range. This takes some time and can add a point to the hobbs on cold days but the Czechs insist on it.
The Zlin has heavy but effective nosewheel steering and the powerful brakes need little application unless swivelling into a tight spot. The pre-takeoff checklist calls for a full power run up whilst checking magnetos, exercising the constant speed propellor and then engaging the supercharger. There is no vernier-controlled mixture cutoff. Instead a measure of adjustment is achieved by setting a rotary knob on the panel according to pressure altitude.
IN THE AIR.
With the application of full power, it's hardly surprising the Katana accelerates slowly with only 80 horsepower. With two up, the DA-20 eased off Grand Central's runway at about the halfway point. The aeroplane requires only slight back pressure to rotate and liftoff almost immediately. The occupants contribute considerably to the Katana's mass, therefore its takeoff distance is is more sensitive to weight than heavier aircraft. On short strips, close attention to the handbook would be very important. The aeroplane settled into a 450 fpm climb at 60 knots.
The Katana has individual control sticks and a rocker switch to activate the electric trim. The trim position is indicated by a series of lights on the panel and provides for little fine adjustment. It is not a comfortable arrangement but largely ignored due to the minimal tril changes required for cruise, takeoff and landing. Furthermore, the trim switch shares space with the map and instrument light switches and to be sure you've got the right one requires a concerted look at the pedestal. The flaps are three-position electric with a shrouded switch to guard against inadvertent operation. Again, a light is used to indicate position.
The throttle movement has too much friction even with the friction knob at its loosest. However, this may be due to poor adjustment although HOAC should do something to improve smoothness.The little glassfibre Katana is otherwise pleasant if uninspiring to fly and is stable in all axis.
Despite brochure claims of 'light' controls, the ailerons and rudder are fairly stiff at higher speeds for such a small aircraft, discouraging the pilot from indulging in enthusiastic banking maneuvers. We did not explore the spin environment. The Katana is an easy plane to fly and displays little tendency to deviate from the straight and level when hand and feet are removed from the controls.
Due to the high seating position in relation to the short nose, instructors will have to ignore the 'finger' exercise in establishing level flight. This is something the student will have to get used to. The Katana's slippery aerodynamics and low power mean that cruise speed takes a little while to build up but once there the aircraft will happily bound along at a remarkable 120 knots.
The Katana benefits - or suffers, depending on individual instructors tastes, from an entirely undramatic stall. The aeroplane gives plenty of warning, at 55 knots the airframe begins a gentle buffet followed quickly afterwards by a Donald Duck squawk from the stall warner. Some 14 knots later at just over 40 knots, the Katana begins a downwards mush with only a tiny nose drop and little tendency to drop a wing. The ailerons are effective after the break and the aircraft shows no inclination to drop into a spiral dive let alone a spin.
Visibility is panoramic and Diamond has 'painted' a cabin roof on the canopy to protect occupants from the sun. Ventilation, through two man-sized eyeball vents each side of the panel will keep frustrated instructors temperatures and pressures well down. Engine noise from the busy Rotax is well muted and only slightly raised voices are needed to communicate in the cockpit without headsets. The voice-activated intercom is of the highest quality.
The Zlin 142C is an altogether different kettle of fish in the handling department. On takeoff the aeroplane leaps forward as it should with so much horsepower. Over 45 knots it gets skittish, especially in gusty conditions. As soon as the aeroplane reaches flying speed, control input sensitivity becomes immediately apparent. Slight movement on the stick brings an instant reaction. The control response will surprise a Cessna or Piper pilot (as well as revealing just how mushy are traditional light planes are). The 142 lifts off at just under 55 knots and after lowering the nose to establish its best climb speed of 65 knots, the aircraft manages a respectable 600 fpm climb with one occupant. Flaps are best tucked away slowly to avoid a sharp pitch change and the propellor is then brought back to 2500 rpm as the aircraft passes 300 feet. The trim wheel falls naturally to hand and matches the quick-handling with an equally low-geared adjustment.
The Zlin is a dynamically superior aircraft to the Katana. The controls are light, powerful and extremely well harmonised. The aircraft feels 'alive'. The Zlin's fuselage is fairly short, hence a big vertical and horizontal flying surface. Both the rudder and elevator occupy almost half the available tail surface areas and during turns in either direction, rudder input is needed to keep the ball centred. Once established in cruise, the supercharger is disengaged and the draggy airframe settles to about 110 knots.
The supercharger, for a penalty of 2 gallons an hour fuel consumption can be engaged to push the cruise speed to 120 Kts. Although stable, the Zlin can be demanding to fly smoothly in turbulent air. Czech pilots are taught to input rudder movement just as much as stick movement during straight and level flying and it's rare to find an Eastern European pilot with his feet on the floor during any phase of flight.
Cockpit noise level is far higher than the Katana and headsets are a necessity for crew communication. Zlin provide a push-button intercom activated by a button on the top of each stick. A voice activated unit would be far more satisfactory. Ventilation is provided by two small eyeball vents positioned at the top of the panel and on hot days, struggle to keep the cabin cool. To reduce glare, the Czechs have added a curtain that unfolds concertina fashion over the luggage area and pilot's heads. The canopy can be opened a couple of inches in flight but the increased noise and draught makes this impractical.
The Zlin has an arguable advantage over the Katana. It is almost fully aerobatic. Almost, because snap maneuvers are prohibited due to the hollow engine crankshaft. The 142 begs to be thrown around and it's an extremely good platform to demonstrate basic aerobatics. Sadly, few instructors are aerobatic rated in South Africa. A situation the Czechs find unbelievable. Furthermore, whilst there's an argumant for basic aerobatic training in the PPL course, it is not a compulsory requirement and never likely will be.
Spinning is. The Zlin breaks
into a spin from an entry speed of 55 knots with the application of full rudder
and full aft stick. It takes three turns to stabilise into a good nose down
Recovery froma standard spin in either direction takes one and a half turns after full opposite rudder and a positive forward movement of the stick. The 142 demonstrates a clean stall in any configuration. The stall-warner sounds off 6 knots before the nose drops sharply into a positive nose down attitude at 40 knots. If any aileron displacement id carried, a wing will drop too but comes smartly back with rudder application.
The Katana excels in the circuit environment. The fantastic view and good frontal visibility helps to spot others in a busy circuit. From takeoff the Katana reaches Grand Central's circuit height early on the downwind leg with two on board. With downwind checks complete, flap limiting speed is 100 knots and full flap can be applied on the base leg. The aircraft requires little trim input with the drop to approach speed and the stiff controls add a feeling of solidity on final. The clean design and short undercarriage will make students pay careful attention to the 60 knot final approach speed. Over the fence, the Katana's speed should be left to bleed off to 50-knots - anything higher will result in a float. The flare is easy to control with the well balanced elevator and the aircraft sinks into ground effect with no danger of suddenly dropping out of the sky. A slight back pressure is all that is needed to place the wheels gently onto the ground. This ease of handling will lead to a shorter time to first solo - it is an absolute honey to place on the ground.
The Zlin also benefits from great visibility and landing behavior is also predictable although less benign. The Zlin's flap operating speed is 100 knots and the lever requires a hefty pull for the first stage and an even heftier one for full flaps, particularly if the speed is still on the high side. The controls remain sharp and responsive all the way to touch down. Final approach speed is pegged at 70 knots. The Zlin's speed is less easier to nail as the higher drag airframe is a lot more susceptible to airspeed fluctuations. The student will be working harder with throttle adjustments when flying the 142. Flap deployment is accompanied by a sharp nosedown pitch change which will have the pilot reaching quickly for the trim wheel.
It is best therefore to establish the correct speed and height early during the approach.The Zlin's speed is best reduced to 60 knots over the fence and the flare needs to be accurately judged as the speed bleeds off quickly. Too high and the aircraft drops suddenly and sharply onto the runway leaving little time for a burst of power - too low and the lengthy nosewheel oleo extension will touch first and set in motion an uncomfortable see-saw bounce. The touchdown position is best achieved with the stick almost fully back.
Landing the Zlin smoothly is a rewarding exercise but you need to have your out to do it consistently. It would take longer to solo the 142 but then once mastered, pilots will have little trouble converting to less sensitive aeroplanes.
There is little doubt a pilot with his PPL earned on Zlin 142C will be more skilled in aircraft handling and to a lesser extent, aircraft systems. If only it were as simple as that the decision would be easy. However, as flight schools are only too aware, producing a safe pilot as a competitive cost requires a number of other factors, amongst them being instructor experience and the students natural flying ability or lack of - and his attitude. All things being equal, the pilot trained on a Katana will be solo at an earlier stage than one flying a Zlin. Indeed, it will be easier for students to complete their course within the prescribed 40 hours in the DA-20, even though their transition onto more sophisticated aeroplanes will take longer.
In deciding to buy a new trainer, flying clubs and flight schools will be better seduced by operating costs and reduced down time. It's here the Diamond is forever as the manufacturer has paid special attention to this area. Bearing in mind the relative cheapness of running glassfibre aeroplanes and the obvious cost benefits of a Rotax engine, the diminutive Katana sips fuel. In practice the Katana population available to ab-initio students has slipped since the first aircraft were imported into South Africa.
There is now only one available at Grand Central's Flight Training College. The others have been sold to private users which was in line with FTC's dealership arrangement with Diamond Aircraft. The disastrous exchange rate fluctuations have pretty much put paid to widespread usage throughout the flying training community. Moreover, the single Katana retails for about the same as a second hand Cessna 172 on an hourly basis, so any cost advantage has not been ultimately passed to the students.
Since this article was first published in 1996, the troubled Otrokowice factory just outside of Zlin which makes the 142 has suspended production of the Walter engined version. The company is now making a Lycoming-powered model, the 242. Whilst this may help the type's salebility in the USA and Europe, it has made the aircraft more susceptible to exchange rate fluctuations and perhaps less attractive to Africa. The factory has not been well advised on choosing dealers in the region and thus the type has had little dealer consistency. However, many more Zlins have been sold in South Africa than Katana's and the aircraft has been especially well received by those wanting something to practice aerobatics in. It's relative obscurity has also made it a bargain second hand purchase - and the few that are on the market represent incredible opportunities to operate a low-houred fune aircraft.
[END OF REPORT]
Note: PlaneCheck often has some nice Zlin 142's for sale