Alan Baldry, an affable and generous individual, kindly asked if I would like to fly his Zlin, G-BPNO. Of course I would. It transpired that this aircraft had originally been constructed as a Z.326 and was later upgraded to Z.526 standards by the factory. The fixed pitch propeller was replaced with an Avia V503 constant speed unit and this heavy addition altered the centre of gravity, requiring the solo pilot to sit in the rear cockpit. This position in turn was re-wired so that the pilot is able to operate the facilities the front seat, therefore, lost its switches. Alan and his partner Terry acquired the aircraft in 1988, specifically to accommodate their love of aerobatics and annually they average around 40 hours each. A typical detail consists of 15 minutes of aerobatics while the other critiques (sounds so less harsh than criticises) the performance before the roles are reversed. A PFL and then a couple of circuits conclude the flight. Fuel burn for such practical fun is an almost frugal seven Imperial gallons per hour.

WALK-ROUND
During the walk-round, the impression created by the two-seat Zlin Z.526 sitting on its narrow track mainwheels and tail, is that of clean lines purposefully reflecting the advanced design philosophy of the day, from the vanes of the propeller spinner right back to the angular rudder. The wings are of all-metal construction with Duralumin sheet surfaces, including the ailerons. The fuselage is a welded tube space frame and is fabric covered, the tailplane and fin are Duralumin sheet clad but the rudder and elevators are fabric covered. The fin appears quite small in relation to the large rudder, while the forward upper section of the fin is unpainted and houses the VHF aerial.

The non-retractable tail wheel is fitted with an anti-shimming tyre and a break clutch that unlocks for short radius turns while taxying, rather like the Yak-50. The 5ft 7in main gear is relatively narrow tracked and retracts rearwards into the under surfaces of the mainplanes. In the POH the undercarriage is described as "partly tiltable", which really means it semi-retracts with about one-third of the wheel and tyre protruding into the airflow in the up position. There are no undercarriage doors but the undercarriage legs are fitted with fairings. The half-span ailerons are differential, with the aileron down throw by 3.8in and up by 4.2in. Incidentally, with the single-seat version, the Z.526A, the ailerons have a slightly greater throw of 4.4in up and 4.2in down, providing a greater response and roll rate. The ailerons sport spades under the mainplanes, aiding rapid application while providing a lighter feel. The inverted six-cylinder Walter Minor 6-III of 160hp is closely cowled with six short exhaust stubs exiting on the right. It is fitted with an electric starter, two-stage fuel and oil pumps and two impulse magnetos. For inverted flight there are fixed chokes in the two carburettors and special fuel and oil piping arrangements ensuring that supply pressures are maintained. During the model upgrade of November Oscar from Z.326 to Z.526, the oil cooler was re-sited from inboard the left wing leading edge to a more 'natural' installation within the left engine cowl. The highly-polished propeller blades are of a higher aspect ratio than normally seen on the front of our regular US training aircraft and are really quite elegant. The small blades on the spinner turn it relative to the propeller hub and these drive a hydraulic pump in the hub. The spinner also moves axially by around a third of an inch relative to the propeller hub, under dynamic air pressure. This axial movement actuates the pitch control mechanism of the blades.

From the pilot's viewpoint, there is only one 'power lever'. All that has to be done when setting rpm is to move the throttle and then, when in a dive or climb, when the rpm would normally change, the blade pitch alters to maintain the set rpm. The stable rpm also increases the efficiency of operation, both in terms of a light work load and improving aircraft performance.There are two internal wing tanks, each holding 9.9 Imp gal. Within the fuselage are two smaller tanks, a 0.65 Imp gal collector and 1.5 Imp gal header (under and above the front pilot's feet respectively), the first gives up to four minutes of inverted flight and the other, ten minutes flight should the fuel pump fail. Ferry tanks may be fitted onto the wing tips. Mechanical fuel gauges are fitted in the upper surfaces of the wings, similar to those on the Chipmunk.

The undercarriage position is indicated by annunciators in both P1 and P2 positions and has wing-mounted mechanical indicators, which project above the wings when the undercarriage is down. These retract, becoming flush with the wing top surfaces when the undercarriage is raised. The undercarriage is operated by an electric strut (under the P1 seat) and has an independent mechanical unlock in case of strut or battery failure. It also has a 'dead-man' switch on the right leg.

COCKPIT
Access to the cockpit is via either wing, avoiding the flaps as you step up. The solo cockpit (for P1) is the rear of the tandem seats and places the pilot squarely in the fuselage with a good all-round view, in line with the wing trailing edges. The front cockpit is similar to the rear but lacks the electric service switches, artificial horizon, rudder trim, primers and fire extinguisher lever. All levers and trims (elevator and rudder) fall easily to hand (and foot) and the five-point harness makes you feel secure, as if part of the machine.
In the rear cockpit a large red plastic warning light is centrally placed and illuminates should more than 6g be pulled. There is also a canny main spar pressure gauge fitted in the front cockpit and this illuminates should the sealed, gas tight, metal spar crack from being over stressed.

The front (P2) cockpit view is marred only by the position of the compass, located on top of the instrument panel and directly in line with the nose.
Logically, the cockpit is easy to interpret. I particularly liked the flap lever marked with aircraft symbols with the flaps showing up, intermediate and down positions; the near friction-less controls with no play; the Eastern European fuel and oil coding (yellow and brown) on the instrument panel; and the feel of the throttle. All appear familiar with no real oddities. In fact, it is well conceived and constructed.

Oddities are saved for the Pilots Operating Handbook, The retractable undercarriage is "tiltable", graphs are termed "tablets" and when opening the throttles to full power the pilot is actually "admitting fully fuel to the engine". When discussing the 'g' overload indicator, it warns that during "acrobatics, overpass of limited permissible values is signalled"! Mixture control is referred to as "altitude balance", idle cut-off is "gas arrestment" and the electric bus bar is "sectional switches", close enough when you know the answer, but slightly removed from our idiom. Values of weight, speed and pressures are, of course, in metric with a simple and easy-to-use 'Weights and Loads' chapter.

START UP AND TAXI
For engine starting, the fuel cock is selected to main tanks (or the header) prime the hand pumps and after checking that the magnetos are off in both cockpits, have the prop' pulled through at the same time. Switch on the dynamo, instruments, undercarriage indicators, magnetos and starter with the hand brake applied. Engage the starter and once the engine is running, set 800 rpm and ensure that the stick is held back. The oil pressure shows within a few seconds of starting. As the oil temperature rises to 35°C or 45° in winter, the revs should be increased to 1,400 rpm. The magneto and spark plug check uses 1,750 rpm and idle check 600 rpm.

Taxying is straightforward for a taildragger weave and clear the area ahead. It has a good turning circle when the tailwheel castoring lock disengages; and solid brakes. The tail doesn't even think of unsticking, unlike a Piston Provost I flew but in its defence they were pneumatically operated and I was doing more than 2mph! Wing walkers are recommended for the Zlin with winds above 13 knots. The book figure for take-off, to clear a 50ft obstacle, separates a grassy surface from concrete by only 33ft 1,350ft versus 1,319ft. The still air, flat ground roll quoted is a short 755ft from a hard surface.

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