PRIVATE PILOT – January 1992 – WILEY WILGA
FLYING THE UTILITY WILGA – by Peter Obst
Have you ever wished for an airplane that could take off
from a short runway, carry four people, be reliable and fun to fly? Who
hasn’t. Airmen everywhere have their particular favorites, but here’s a
newly available contender that will soon have its group of fans. The airplane is
the Wilga Model 80 made in Poland by Polish Aviation Enterprise (PZL) and now
sold in the USA by Melex USA.
The Wilga design originated in 1962 when the Polish aero clubs found a need for a utility airplane, one that could be used to tow gliders, carry parachute jumpers, as a basic trainer and for just flying around. The design that PXL delivered did all thas and more. It could tow as many as three gliders into the air at one time. It had excellent dhort-fild performance and room for four people. The exceptional handling characteristics became apparent as Polish pilots started to bring back trophies from various precision flying competitions held in Europe. Thes world class competitions found that the Wilga gave them the extra edge to lead the field again and again. Maneuverability and stability were not the only features that contributed to these successes – its excellent visibility afforded by generously sized windows front, sides and rear helped a great deal, too.
No doubt the greatest compliment paid to this aircraft was that, after witnessing its performance, the German and Swedish aero clubs placed orders with PZL. To date, more than 900 have been built and are doing service in places as remote as Venezuela and Egypt.
Just one look will tell the casual observer and the true aviation enthusiast that this aiplane is different. It is a high-wing, all-aluminum short-takeoff-and-landing (STOL) aircraft of semimonocoque construction. Yet this is where the mundane description ends.
The airplane, contrary to prevailing fashion, is equipped with a radial engine, an AI14RA mime-cylinder, 260-hp (at 2350 rpm) radial, to be exact. The engine is paired with 8.7-foot diameter, constant-speed, two-blade prop. The paddle-shaped blades are made of fiberglass overlaid on a wood core, with a stainless-steel leading edge.
In examining the cowl, one will quickly notice the interesting way the problem of regulating the airflow used to cool the engine has been solved. The louvers are anchored to a ring around the prop shaft, which is the center mounting point. In effect, the inlet can be opened and closed using something that resembles a circular venetian blind. This is very helpful when warming up the engine on a cold morning or preventing stressful engine cooling during a fast descent. Underneath the cowl, convetional louvers regulate airflow through the oil cooler.
It is the engine that sets the style for the airplane, which was designed to the strictures of form follows function. Everything was thought out carefully to make the job of the pilot and the mechanic easy. The airframe is durable and well built, able to take abuse and still keep going.
A good example of the design philosophy is the landing gear. It is probably the toughest set of legs ever put on a light airplane. Sloped forward for stability and widely separated (9.3 feet), they form one unit with the steel-tube engine mount, which is integrated into the forward section of the fuselage. The wheel assemblies, which carry large disk brakes, ride on trailing rocker arms, which are equipped with gas-loaded, oleo strut shock absorbers. These and the large (500x300 mm) tires serve to damp out the ruts in most grass fields and make landing on a paved runway a sheer pleasure.
The steerable tailwheel (255x110 mm tire) is mounted on an assembly that is also equipped with its own small shock absorber. Near this assembly are hard points for jacking up the tail should it need servicing. The tailwheel assembly is equipped with a glider tow hook, now standard equipment on the Wilga.
Throughout the aircraft are many small touches that testify to the great care and thought that went into this design. It may seem that one would need a stepladder to get aboard – the lower door edge is about 4 feet off the ground. Fortunately, the builders added a rung and handholds to be used for climbing aboard. More ingeniously, two rungs on the landing gear legs allow a person of average height to reach the top of the wing for inspection and fueling.
The right side has a jump step for skydivers. To make the fob easier for a skydiving instructor, the front passenger seat can be turned to face the rear. An attach point is provided for static line jumps.
The wing is a single-spar, all-aluminum, cantilever construction with a single degree of dihedral. A fixed slat, the secret behind the excellent low-speed performance, runs down the length of the leading dege. The ailerons are generously sized and balanced with counterweights that protrude on the underside of the wing. The right aileron is provided with a trim tab. The left wingtip houses a high-inntensity landing light. The wing skins, ailerons and tail control surfaces, as well as the empennage, are beaded for extra strength. Slotted flaps complete the control surfaces. The can be positioned at 0*, 21* and 42*. At 21* of flap extension, the ailerons droop, providing even more lift, but setting the flaps at 42* makes them rise again.
Under the wing are more thoughtful touches. Both wing fuel tanks (22 usable gallons each) are equipped with sight gauges, which can be read through the cockpit window. To make them visible at night, each is provided with a light that illuminates it from the cockpit.
One boards through the side doors – on per side – which swing up and lock under the wing to allow unimpeded loading. A single lever locks them into closed position for flight. But should the day’s assignment – aerial photography or skydiving – require it, then can be easily removed. For serious aerial photographers, a panel in the belly of the airplane covers a camera port that is ideal for the straight-down shots required in aerial map-making.
After boarding and adjusting the seats, locking the clever double safety latches, one can properly contemplate the cockpit. Though Spartan, it has a few niceties. There are net pouches for charts, a rearview mirror (handy for glider towing) and a windshield wiper for those misty mornings.
The vital instruments – altimeter, vertical speed and airspeed indicators – are calibrated in US units but the remainder – the pressure and temperature gauges – are all in international (metric) units. Even if you can’t convert kilopascals to PSI and Celsius to Fahrenheit, it makes no difference. All one needs to know is to keep the needles in the green range, as specified by the operating manual.
The panel layout is not quite standard but not at all unfamiliar to most pilots. The vital instruments, again, are where they should be. As for the rest, one quickly becomes accustomed. Because of their functionality, the controls seem to be in their proper places – where they can be easily reached without unnecessary twisting or turning. Even the left-hand throttles and the hefty curved control sticks seem natural, even desirable.
Unfortunately, there is not much space behind the panel, so American-made avionics tend to protrude. A molded housing masks the opening and there is still plenty of space in the cockpit. The electrical switches and circuit breakers are overhead, above the pilot’s position. All are within ready reach. So is the flap lever, it is to the pilot’s left, descending from the cabin ceiling.
What is it like to fly the Wilga? Just fasten your seat belts, snap the doors closed, prime generously, set the throttle and engage the starter valve. As youdo, compressed air from the dual tanks in the rear of the fuselage rushes into the cylinders and kicks the engine over. This is an unusual method of starting but is very effective, especially on cold days. An engine-mounted compressor keeps the pressure tanks filled. In case of a problem, there is a fitting for hooking up an auxiliary tank or the aircraft can be hand-propped.
One must remember, however, that his is a geared radial (0.787:1) and the propeller revolves clockwise, as viewed when facing the front of the airplane.
As the supercharged radial spins, you throw the mags on and, accompanied by a throaty rumble and a small cloud of oil smoke, the engine comes to life. While many engines of this type have a voracious appetite for oil, the PZL radial uses less that a quart per hour. Still, because oil is so important for cooling and lubricating the engine, a 4.2-gallon supply tank is standard equipment. Surprisingly, while the engine is running, the cockpit is relatively quiet, not something one would expect from a nine—cylinder radial. This one is equipped with two large stainless steel mufflers mounted on the underbelly. This is a feature that makes the Wilga an airport-friendly airplane, as many airports have become targets for noise complaints.
With the propeller in fine pitch and the flaps at the first (21*) notch, the throttle is advanced and the Wilga begins to move. Applying plenty of left rudder and gently tickling the toe brakes as needed, you roll about 400 feet and at a very low speed, somewhere around 50 MPH, the seemingly heavy machine becomes a thing of the air.
It climbs at nearly 1000 fpm – proving that the engine is no slouch. At altitude and in trim, with 75% power, the Wilga cruises at a comfortable 100 mph. It is stable and well balanced but, as evidenced by the man-sized control sticks, it is a large airplane and has that kind of feel about it. This is not a detriment, however; it turns beautifully and the controls are a little heavy but crisp and pleasant to handle. In the slow-speed configuration, it seems to hang in the air, almost hovering in place.
This is a good time to relax and enjoy the scenery through the panoramic windows. If the sun makes the cabin a little warm, then it’s a simple matter to twist open one of the many fresh air vents. Too cold? Don’t worry, there’s cabin heat as well. A nice touch are the floor vents that pipe warm air to back-seat passengers.
When stalled, the airplane shows no bad habits, dropping its nose after giving the pilot plenty of warning. Recovery is easy – no wonder that this plane has found use as a trainer in various parts of the globe.
Landing the Winga can be an interesting experience for passengers not familiar with the type. To take full advantage of its unique characteristics, one can come in on a high final approach and then make a quick descent toward the runway. With the throttle full back, the propeller acts as a brake; there is no airspeed gain. An experienced pilot can maintain a landing speed of 75 mph and roll to a stop in a little over 500 feet.
Can a plane of this caliber find a place in the US market? Most certainly. Its US$ 80,000 price is competitive and its quality is high. The wilga’s greatest virtue is the fact that it can do many jobs and do them all well. It is a durable airplane that is pleaseant to fly. Aside from the personal flying market, it may be just eh airplane for traffic patrol and pipeline patrol, which require a high degree of durability and good cockpit visibility. Glider tow pilots and skydiving school operators should find it ideal for their applications, as well.
This airplane could also be a lifesaver in remote areas, transporting injred individuals to hospital facilities. With the rear seats removed, it can easily accommodate a stretcher. The baggage area by itself is a generous 17.5 cubic feet. Then there are the hundreds of sport pilots who are looking for a reliable transport or trainer.
This is by no means the end of the Wilga’s flexible and ever-changing personality. Earlier versions have already feen fitted out with Canadian-made CAP floats, creating the Wilga Model 80H floatplane. Currently, it is being tried with Edo 2960 floats. With a set of metal skis, which also allow the wheels to contact the ground, it has become a roamer of the northern territories, with or without snow. Plans are being made to test the Wilga with a belly tank for light crop spray application. There seems to be no end to its possible uses.
More Info: George Lundy – Meles, 1221 Front St., Raleigh, NC 27609. 919 828 7645.
Specifications: PZL-104 Wilga (Oriole) Model 80
|Wing area||166.8 sq ft|
|Wing chord (average)||4.6 ft|
|Overall length||26.3 ft|
|Overall height (3 point attitude)||9.6 ft|
|Wheel track||9.3 ft|
|Landing gear type||conventional, fixed|
|Tire size (mains)||500x200 mm|
|Tire size (tail)||255x110 mm|
|Gross weight||2866 lb|
|Empty weight||2085 lb|
|Useful load||781 lb|
|Wing loading||17.28 lb/sq ft|
|Power loading||11.02 lb/hp|
|Payload (full fuel, full oil)||517 lb|
|Fuel capacity, standard (option)||44 gal usable (67 gal usable)|
|Baggage capacity||17.5 cu ft|
|Engine||PZL AI14RA nine-cylinder, air-cooled radial with reduction gear (ratio 0.787:1), 260 hp at 2350 rpm.|
|Propeller||US 122000 consant-speed, two-blade, 8.7 ft diameter, fiberglass on a wood core.|
|Max speed (sea level)||133 mph|
|Cruise speed (75% power)||101 mph|
|Range (75% power)||353 sm (with 30 min reserve)|
|Rate of climb (sea level)||925 fpm|
|Service ceiling||12,000 ft|
|Stall speed - clean (Vs)||58 mph|
|Stall speed - flaps down (Vso)||43 mph (*note - with power on, the aircraft will not stall, but its downward vertical descent rate will increase)|
|Approach speed (Vref)||57 - 67 mph|
|Takeoff ground roll (grass)||365 ft|
|Takeoff over 50' obstacle (grass)||900 ft|
|Landing ground roll (grass)||650 ft|
|Landing over 50' obstacel (grass)||509 ft|
|Manufacturer||PZL (Polish Aviation Enterprise), Warszawa-Okecie (also known as Pezetel), Al. Krakowska 110/114, 02-256 Warszawa-Okecie, Poland|