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
atitude.
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.
GETTING DOWN
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.
CONCLUSION
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