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PILOT REPORT
Fuel Efficient Flying
Ogar Motorglider
Combines Best of
Two Conditions
(from PRIVATE PILOT magazine,
March 1980)
by Dennis Shattuck
EVERY SAILPLANE pilot has this secret wish
to have a sailplane that would self launch, motor around to sniff out thermal
activity and then soar with the best. Not so much different is the powered‑plane
pilot's repressed desire to have an airplane that combines an excellent cruise
speed with absolute minimum fuel consumption. In short, the soaring pilot wants
a sailplane that acts like a powered plane and the power pilot wants an
airplane that is as efficient as a sailplane.
Both requirements would seem to indicate
an aircraft with high aspect ratio, glass smooth wings, a relatively low output
but efficient power unit, light wind and power loadings and a well‑streamlined
fuselage of minimum crosssectional area with fully enclosed cockpit. If this
description fits the concept of what's popularly described as a
"motorglider," then the reader has a good point of reference from
which to start.
The motorglider, literally a
glider with a "motor," or reciprocating engine, attached, has been
around for some time, but is just now beginning to experience the same sort of
super sophistication that pervaded sailplane design 20 years ago. While
motorgliders have yet to achieve the 40‑45 to I glide ratios of today's
competitive sailplanes, there are a few in the upper 20s and low 30s that make
recreational soaring extremely interesting as well as much easier to obtain.
The lightweight powered airplane,
on the other hand, has not developed. Instead, production‑oriented design
has led us toward higher wing loadings and thus greater dependence upon the
engine to keep us aloft. How many pilots trained in Cessna 150s know that the
airplane is a pretty good glider, capable of soaring flight when conditions are
right? We know of one C‑150 that soared for four hours with engine off in
a low mountain wave not half‑an‑hour's flight from its home base.
The lightly wing‑ and power‑loaded
aircraft was a development of the 1930s, especially in Europe, where gasoline
costs were high (even then) and engines heavy and expensive. Thus the single‑
and duo‑seat Klemms and Miles airplanes achieved "floater"
status without consideration for soaring flight. These aircraft would take off
and land in short distances, fly fast and efficiently on 25‑40 hp
engines, and generally provide enjoyable recreational flying for their pilots.
In this country, the Taylors, Aeroncas and Piper Cubs achieved somewhat the
same status. Interestingly, those aircraft are still prized today for their low
operational cost and enjoyable flying qualities!
Not surprisingly, the European
aircraft makers again are leading the way into more fuel efficient flying . . .
at least for the recreational flyer. We're seeing the development of the
motorglider concept encouraged by economic conditions, and we're seeing pilots
rediscover the joy of flying (and soaring).
One such motorglider to reach our
shores in the last two years has been the PZL SZD‑45A Ogar (greyhound), a
product of Poland but by no means one of those odious Polish jokes. Of unique
design, for a sailplane, it resembles greatly a Republic Seabee that's been too
long at the exercise/slimming salon. It has that same pod‑and‑boom
look with a pusher engine mounted at the rear of the wing. Seating is side‑by‑side
for two under a snug swing‑up canopy, and a T‑tail at the rear
completes the unusual format. What's even more unusual about the Ogar is the
fact that it's good at both soaring and power‑flying; it's both a
motorglider and an airplane that acts like a sailplane.
On the
power flying side, the Ogar claims a cruise speed of more than 90 knots (104
mph) on only 3.1 gallons per hour (32.26 miles per gallon!), Range is 200 n.m.
(230 statute miles), in the pure power‑cruising mode, but this can be
extended by use of either maximum economy cruise power settings or by utilizing
some free lift along the way.
As a
glider, the Ogar does well enough for all but the devout soaring enthusiasts.
With its 28:1 glide ratio it has soaring performance better than any of the
current two‑place training sailplanes, and equal to or better than most
other two‑placers — and this with a draggy profile, open engine cooling
ducts and a stopped propeller. Its large, 57.4‑foot span wing has
generous wing area, 213.9 square feet, and efficient aspect ratio of 15.5:1.
Minimum sink is 200 feet per minute at about 44 knots (50 mph), a very
respectable figure for a 1540‑pound airplane, giving further clue to the
Ogar's polished efficiency.
Charley Gyenes of Aerosport, Inc.,
is importing the Ogar along with several other European‑made sailplanes
to his Elsinore, California, facility. But Gyenes is not the usual importer . .
. he doesn't practice the "ship 'em, sell 'em and forget 'em" tactics
accompanying some foreign‑made products. Gyenes believes in adapting the
product to suit the market. In this case, the Ogar arrives in the U.S. without
engine or instruments. A U.S.‑built engine is installed, along with U.S.
(mostly) instruments and avionics.
Gyenes has worked with, and tested
extensively, the engine manufacturer, Revmaster, Inc., to obtain a package best
suited to Ogar operation. Equipped with a turbo‑supercharger the engine
delivers outstanding performance at both low and high levels, something no
other motorglider powerplant can claim. It can be equipped with either a
controllable pitch metal propeller or a fixed pitch wooden prop (obviously, the
wood prop is less expensive, less weight and less complex).
The first Ogars, delivered to the
U.S. with a German version of the same engine, but without turbocharging,
performed rather anemically, thus prompting Gyenes' continuing program of
improvement. The modifications do not alter the gliding performance of the
aircraft (in fact, they may improve it slightly) which was its strong point in
the beginning. However, with the stronger engine and the Ogar's better
performance as a powered aircraft, Gyenes now feels he has a package that will
be appreciated by Western Hemisphere flying enthusiasts.
Now, a bit of detail on the
vehicle itself:
Airframe—the Ogar is officially the Zaklady
Szybowcowe Doswiadczalny model 45A, design from the Polish national aircraft
industry's experimental glider works. It emerged in the early 1970s, the
prototype making its first flight in 1973. The fuselage pod is molded
fiberglass, the boom extension that supports the tail is an aluminum tube. Two
major internal bulkheads of wood carry the loads of wings, engine, tailboom and
landing gear.
The
sailplane is wood and fiberglass and separated into conventional horizontal
stabilizer and elevator segments. The vertical fin is blended into the tailboom
with fiberglass and the rudder also is fiberglass covered. Controls are pushrod‑actuated.
Cockpit—The Ogar has dual stick controls and seats are side‑by‑side.
The seats are semi‑reclining and very comfortable, while vision out of
the bubble canopy is extremely good. A single pushpull throttle is in the
center of the conventional instrument panel, but the fuel shut‑off is on
the left side. However, there's a spoiler handle on each side of the cockpit.
The landing gear retraction handle is in the center between the two seats; a
removable pin is used to safety lock the control in the down position. Rudder
pedals for both sides may be adjusted fore and aft in flight. The canopy hinges
up and back for entry/exit.
The instrument panel features the
usual flight reference gauges, plus variometers for soaring use, on the left
side, the engine condition gauges on the right. There's limited space for radio
equipment on the right side and beneath the panel.
Baggage, oxygen tanks and take‑along
equipment can be accommodated in a generous area behind the seats. The area is
placarded for up to 110 pounds.
Fuel Tank—A 30‑liter (7.926 gallons) fuel tank is built
into the upper fuselage area behind the cockpit. The back cockpit wall has a
vertical stripe left unpainted, through which the gasoline
quantity
may be seen. Tick marks for the various quantities are painted across the
stripe, making an effective, never failing fuel gauge. A single filler point is
atop the fuselage.
Landing Gear—A single main wheel under the fuselage, a steerable
tailwheel and two outrigger wheels comprise the Ogar's ground support system.
The main wheel is retractable in flight by mechanical means. A spring‑assisted
cockpit lever moves the wheel up or down. (No wheel‑up warning system,
other than handle position, is fitted, however.) Tail and outrigger wheels are
fixed in place. The outriggers, sprouting down off each wingtip, are fiberglass
rods which flex easily to absorb shocks as the Ogar is taxied over lumpy terrain.
Outriggers that retract to a trailing position are under development, Gyenes
says, and these might add a point or so to the glide ratio, once installed. The
tailwheel steers with the rudder to provide directional control on the ground.
Wing—While the wings are basically
wooden structures, they are glass‑fiber covered for smoothness and
protection against the elements. They utilize a Wortmann FX‑61‑1261
airfoil at the tips, blending into a Wortmann FX‑61‑168 airfoil at
the roots. These are excellent high lift/low drag ratio airfoils akin to those
used in many high performance sailplanes. They are characterized by rather
sharp leading edges and downward cusps at the trailing edges.
The wing is
assembled from two separate components and these can be removed/installed like
those of any sailplane for transportation ground. As they are heavy panels, it
takes at least two men to lift each 29‑foot section, and another to
position and fasten it on the fuselage. A folding wing option, such as used on
the Fornier RF‑5B Sperber motorgliders to reduce the span to 36.8 feet,
would allow it to be stored in a normal width hangar.
AiIerons are internally hinged, no‑slot
panels of narrow chord but generous length. They are effective enough at low
speed, probably because of the long span, to pick up and balance a wing at
around 8‑9 mph airspeed. The Ogar has no flaps, but does have vertically
actuating spoilers on both the top and bottom sides of the wing. These spoilers
are extremely effective for glide path control. Both ailerons and spoilers are
pushrod‑operated.
Engine — The Volkswagen‑based, four‑cylinder opposed,
air‑cooled engine is built up from new components by Revmaster, Inc., of
Chino, California. Revmaster utilizes so many of its owndesign modifications
that it is more accurately a Revmaster engine than a VW conversion. The R‑2100‑D
version used in the Ogar has dual ignition, 125 cubic inches (2170 cc)
displacement, turbosupercharging and develops 78 horsepower at 3200 rpm and 34
inches of mercury manifold pressure.
It features a built‑in
electrical system with 20‑amp alternator and geared starter. A large oil
cooler fits horizontally beneath the oil sump. A Revmaster/Posa fuel injection
carburetor meters fuel to the engine and is fitted with a mixture control. Dual
Bendix D2000 magnetos are fitted to a special accessory drive at the rear of
the engine.
Fitted with turbocharger and the
Maloof/Revmaster two‑position controllable propeller, the engine has an
installed weight of 215 pounds. As installed in the Ogar with the above
equipment and accessories, the R‑2100‑D would cost nearly $5000
retail. A noncertified engine, it is designed and sold for the use of sport
aviation builders who need a strong, lightweight powerplant.
Propeller — The Ogar is equipped with a fixed‑pitch,
wooden prop but a Maloof controllable pitch metal propeller can be ordered as
an extra‑cost option. The wood prop works well, especially when pitched
more for climb than for cruise (this would be ideal for the pilot who intended
to use his Ogar for mostly soaring). The Maloof propeller, developed in
conjunction with Revmaster especially for use with the Volkswagen‑based
engine, is a real gem. While the Maloof prop is basically a two‑position
propeller (high for cruise, low for takeoff and climb), it will hold a selected
engine rpm. However, it does not feather for gliding flight.
PZL Ogar Motorglider
New, FAF, Elsinore, California .................................................................. $38,000
Equipped as flown ....................................................................................... 41,500
External
Dimensions:
Wingspan ..................................................................................................... 57.4
ft.
Wing area ............................................................................................... 213.9sq.
ft.
Wing aspect ratio .............................................................................................. 15.5
Length overall .............................................................................................. 26.0
ft.
Height overall ................................................................................................ 6.6
ft.
Weights and
Loadings:
Gross
weight 1540
lb.
Empty weight (standard aircraft) 1054
lb
Useful load 486
Ibs.
Payload, full fuel 438
lb.
Fuel capacity 30
Itr (7.93 gal.)
Oil capacity 1
gal.
Baggage area capacity 110
lb.
Seats 2,
SBS
Wing loading 7.2
Ib./sq. ft.
Power loading 19.74
Ib./hp
Power Unit:
Revmaster‑VW
R‑2100‑D, four‑cylinder opposed, air‑cooled, turbo‑super
charged; injector‑type carburetion; 78 hp at 3200 rpm and 34 in. Hg.
manifold pressure.
Propeller:
Maloof/Revmaster
controllable pitch, hydraulic, metal hub and blades,
52‑inch
diameter.
Performance:
Maximum allowable speed 118 kt. (135 mph)
Cruise speed, 75% power, optimum altitude 90 kt. (104 mph)
Range* at cruise, 75% power 200 n.m. (230
s.m.)
Fuel consumption at 75% power 3. I
gph
Economy cruise, 50% power, optimum altitude 76 kt. (87 mph)
Range* at economy cruise 300 n.m.
(345 s.m.)
Fuels consumption at 50% power 2.0 gph
Stalling speed 37
kt. (42 mph)
Rate of climb 600
fpm
Service ceiling 20,000
ft.
Takeoff over 50‑ft. obstacle 1000
ft.
Landing over 50‑ft. obstacle 1150
ft.
*No
allowance for climb, descent or reserve.
Importer/Dealer:
Aerosport,
Inc.
32301
Corydon St.
Elsinore,
CA 92330
Phone (714)
674‑1584
Ray Maloof
is a Southern Californian who wanted a better propeller for sportbuilt
aircraft. Hartzell and McCauley constant speed props being too heavy, he set
about designing his own controllable pitch prop. He uses very high quality
materials, builds the props to air craft standards, and is on the verge of
becoming a full‑fledged manufacture At this point, they are classed
"experimental," like the Revmaster engine but conceivably they could
be certified at a future time.
The Maloof
prop's blades are move by engine oil pressure working again springs in the hub.
An electrically operated solenoid varies the oil pressure to establish rpm.
Engine speed, measured at the flywheel, either from the alternator or, if not
so equipped, by a sensor mounted on the crankshaft flange. The electronic controller
sort out the information engine speed and energizes the oil pressure solenoid
accordingly. A side benefit of this electronic controller is its ability to
flash; red panel light when the engine reaches restricted rpm readings (1800 to
2400 and above 3600 rpm).
The controllable prop gives the
Ogar its best combination of climb and cruise performance, allowing the pilot
to spool the engine down to 2800 rpm for cruise, yet rev up to 3200 for maximum
power at takeoff. Then, all he has to do is monitor manifold pressure for the
desired power output.
Power Management— For takeoff, the Ogar‑Revmaster pilot dials
up 3200 rpm and runs in 34 inches of manifold pressure. The turbocharger takes
a few seconds to spool up and the pilot has to be careful not to overboost the
engine as the turbo develops more and more pressure. The engine can be run to
3300 rpm and 38 inches (which produces 85 hp) for emergency use, but this is
not recommended as a steady diet.
Once off
the ground, the pilaf retracts the wheel and sets up cruise climb power at 2900
rpm and 30‑31 inches. At gross, and with 50 mph indicated airspeed, the
setting nets 400 to 500 feet per minute. On a test flight, we climbed to 2000
feet AGL in five minutes, and to 4000 feet AGL in 10 1/2 minutes.
At cruise altitude, the throttle
is reduced to whatever fuel consumption/power percentage the pilot wants. A
2850 rpm/31 inches setting at 5000 feet MSL showed us an airspeed of 90 knots,
this approximated 75% power. Gyenes reported that fuel consumption at that
setting, leaned properly, would net about 3.1 gallons per hour. At 2800 rpm/25
inches, or 65% we saw 85 knots, and at 2800/21 inches, we were getting 76
knots. Gyenes reports 2.0 gallons per hour at this 50% power setting—over 43
miles per gallon.
Descents can be made with the prop
in either position, with the throttle backed off only enough to allow the
engine to stay warm. With a redline of 118 knots, plus the availability of
spoilers if faster descents are necessary, the Ogar pilot has no problem with
taking care of his engine and getting the plane down, too.
As a matter of precaution, to
prevent thermal shock, i.e. too rapid cooling, the Revmaster turbo engine
always is allowed to run for a few minutes at low powersettings. This lets it
cool evenly, at a slower rate than if it was suddenly switched off.
"Ogar" means "greyhound" in
Polish.
Photos:
Dennis Shattuck
Soaring Flight—Despite its size and weight (for
a sailplane) the Ogar is an excellent soaring aircraft. The Wortmann airfoil
wing is no doubt the key. It seems to possess good qualities at both ends of
the performance scale. Stalling speed is only 42 mph, and it sinks at only 200
feet per minute when the engine is off. The 28:1 lift/drag ratio is
exceptionally good for this type of airplane.
Along with Gyenes, we sampled both
powered and non‑powered regimes of flight and found them completely
acceptable. The Ogar will thermal at 50 mph, out‑climbing a number of
production pure sailplanes along the way. As a cross‑country cruiser, it
does well, too. The seating position is quite comfortable and the view
fantastic.
Control pressure requirements are
moderate, as would be expected for a big bird, but tend to become more firm as
speed increases. Ailerons require an authoritative hand on the short stick for
rapid deflection movements at speed. Pitch control is lighter and more
sensitive. Rudder also is sensitive, but needs relatively more force. In all
axes, the response to control inputs is quick, but not fast.
Ground Handling— Here is
where the power‑only pilot may have a problem, while the soaring‑oriented
pilot will not. The Ogar balances nicely on its two centerline wheels if it is
taxied at 10 mph or more, and can be taxied along on one or the other wingtip
wheels, too. On takeoff and landing runs, the pilot must remember to level his
wings, however, to keep the outriggers from contact, lest they drag him into a
groundloop. There's plenty of authority in rudder and ailerons to do so, and
the transitioning pilot needs good instruction in this phase of motorglider
operations.
A cable‑operated brake is
fitted to the main wheel, and this will stop the Ogar in reasonably short
order. Aerodynamic braking is not possible as the craft sits in a level
attitude while on the ground. That single wheel retracts flush with the Ogar's
belly but has no covering doors.
In retrospect, the Ogar, while a
more complex machine than the pure sailplane, seems to offer a great deal more
flexibility of operation. The handiness of self‑launching for a day of
chasing thermals is far more interesting than having to wait for the
availability of a towplane and pilot.
As a cross‑country machine,
it seems to have reduced appeal, although its abilities for economical
transportation are certainly attractive. Gyenes' Ogar buyers have flown
themselves home from Elsinore to Connecticut and Alaska, as well as other
points in the U.S., all without complaint or delay.
So, if the idea of an airplane
that can act like a high performance sailplane, too, seems interesting, take a
long look at the Ogar . . . it fills the bill.