A Sinus Affection
This unfortunately named kit motorglider combines the
joy of soaring with practical cross-country capability.
BY ED WISCHMEYER
irst thing ﬁrst—why, exactly, is this airplane called the Sinus? And its sibling, proper endorsement to ﬂy one, even if
F the Virus? Can’t wait to hear the marketing scheme behind these gems.
Well, bizarre as they may sound, there is logic behind the names. Sinus
(actually pronounced SEE-noose) is the German word for sine, as in sine wave—OK
you already have an airplane license.
Getting a glider license is not a huge
undertaking for an airplane pilot, but
smarty, it’s actually Latin, but the German language (like English) still uses some there are signiﬁcant and interesting
Latin words, especially in scientiﬁc lingo. When the Pipistrel folks saw the reaction differences in operating styles between
of the English-speaking world to Sinus, there was not much to do but admit defeat the two types. Besides, learning to ﬂy a
and call the next one, the short-wing version, the Virus. new kind of aircraft is always fun.
That being said, the Sinus is nothing to sneeze at. (Ouch!)
There was little thought of mathematics, German, Latin or ninth grade (when The Ride
I had all three) as we circled round and round, constantly working the rudder The Sinus and Virus are products of a
to keep the yaw string centered and the turn coordinated, constantly working Slovenian-based aircraft manufacturer
the ailerons to keep the bank angle steady, and constantly working the rudder to named Pipistrel (which, interestingly
compensate for constantly working the ailerons. In the background, the variom- enough, means bird bat in Latin). Under
eter squealed an electronic commentary on our vertical progress. The propeller, the direction of owner Ivo Boscarol,
stopped and feathered, challenged me to gain altitude. the company began business during
Welcome to the world of soaring—this time, my vessel was a motorglider, and the 1980s in what was then Yugoslavia
one that you can build from a kit. Even with an engine and propeller up front, by producing microlight trikes for the
motorgliders are legally considered gliders, and you need a glider license with the European market. As time progressed
Photos: Ed Wischmeyer KITPLANES October 2005 15
Pipistrel Sinus continued to its sailplane heritage, the Sinus’s wings are removable.
Up front are an 80-hp Rotax 912 engine and a two-blade, 65-inch, carbon-
and Pipistrel trikes started selling well, ﬁber propeller. The feathering prop has no governor—it’s a mechanical system
the company eventually expanded that works through the hollow prop shaft of the Rotax gearbox, and it feathers in
into other markets including propeller a single pull of the prop control knob. The two-stroke Rotax 503 is another option,
manufacturing and serving as a dealer and Mudd says that numerous customers have asked about the 912S. But the 912
for Rotax engines. is more than enough power, he notes: “You simply don’t need more horsepower
In 1994, Boscarol hatched an idea with this aircraft—it’ll just get you into trouble faster.”
for a motorglider design to ﬁt into the If the Sinus is not tied down, it is usually parked with the Schempp-Hirth style
European ultralight category—and airbrakes extending from the upper wing surface. The airbrakes are ﬂat panels that
the Sinus concept was born. The idea extend out of the wing, perpendicular to the surface, and they can be plenty ef-
was to build an aircraft that could be fective on a clean airframe. The motorglider has ﬂaps with four positions: neutral,
used for training glider pilots (soaring two down positions, and a reﬂexed (deﬂected upward) setting for high-speed ﬂight.
clubs are ubiquitous
in Europe) but also
for legitimate cross-
country ﬂight. Engi-
neering and design
were contracted to
a nearby company
called Albastar, and
the result debuted
at the AERO 1995
exhibition in Ger-
many to widespread
in the late ’90s, and
more than 180 Sinus
aircraft are ﬂying
today, with most of
the examples found
in Western European
countries. The Virus
and Pipistrel also The Sinus, you ask? Well...there is an explanation. The name derives from the German/Latin word for sine, as in a sine
developed the Apis wave. The unfortunate reaction from the English-speaking world was unanticipated. Get past the name, though, and you’ll
ﬁnd a sleek, high-performance motorglider with distinctive looks to go with the funny moniker.
motorgliders seen in
Europe and the U.S.
Those ﬂaps are for lift, not for drag, and the normal takeoff setting is with full ﬂaps.
First Impressions There is a baggage compartment with a 40-pound capacity, but that allowance is
Robert Mudd, one of a handful of U.S. almost completely taken up by the optional ballistic recovery parachute.
dealers for Pipistrel, volunteered to let The walkaround had few surprises other than those dive brakes. There was
me wring out his Sinus and helped plenty of room inside, and the rudder pedals are adjustable inﬂight on each side.
acquaint me with the motorglider However, the lumbar support (or lack of) gave the impression that an hour’s ﬂight
before ﬂight. From the outside, the might be as much as you can take in a single dose. The bottoms of the side win-
Sinus screams sailplane at you—all dows are very low, which invoked the normal insecurity of seeing the ground
white, composite, smooth, with long, where there should be airframe. (Breezy owners will be much more at home.)
skinny, high-aspect-ratio wings and Shoulder and legroom were excellent. So was the headroom but with a caveat—if
a long, graceful fuselage ending in a you’re tall and if you hit a nasty bump, your noggin’ is sure to do battle with a steel
T-tail. But this is a motorglider, not a tube directly overhead.
sailplane, so the wing is head high, not Forward visibility is limited by a high cowling line and especially by a bump
waist high, and the fuselage perches in the top center of the instrument panel. This wasn’t a major problem by any
on a tricycle landing gear instead of means, but the Sinus is a contender for worst forward visibility in a nosewheel
squatting on the ground with just a aircraft. The wingtips were not visible during taxi, probably due to the upsweep
single wheel for support. Tailwheel of the tips. With a 49-foot wingspan, estimating wingtip clearance will test your
conﬁguration is an option, and thanks depth perception.
16 KITPLANES October 2005 www.kitplanes.com
Soaring and Stalling
The Rotax 912 started right up with a quick beep from the all-
in-one electronic instrumentation helpfully exclaiming that the
oil pressure was momentarily low. Mudd handled the engine
and runup chores and taxied us into position while checking to
make sure the trees at the end of the runway were not hiding any
Full power on the grass runway got us airborne in 15 Mis-
sissippis, and rate of climb varied between 1000 and 1400 fpm,
aided by some rambunctious, rising air. Mudd suggested we climb
above the cumulus, but it seemed to me that if we were going to
put up with all those bumps, we might as well thermal.
The drill for engine shutdown is to retard the throttle, slow to
55 knots, and pull the manual propeller control to feather. Then The Sinus features Schempp-Hirth style airbrakes extending from the
the ignition is shut down, and the starter is blipped to get the upper wing surface—these came in handy as the author negotiated
propeller blades horizontal, both to reduce drag and to improve his ﬁrst landing in the motorglider.
In my limited sailplane experience, I’ve learned that there are a variety of tech- is about 115 knots with the short-wing
niques required to perform coordinated turns at thermaling speeds, mostly due to Virus 10 knots faster—certainly accept-
adverse aileron yaw from the extra drag of the down-going aileron—exacerbated able but hardly stunning performance
by the fact that the aileron is way out there. The standard technique for say, a for the horsepower.
right turn, is to use a ton of right rudder to get the yaw rate going while slowly
adding right aileron. Once established in the turn, it is common to require less Put Me Down!
right rudder, but left aileron is often Landing was fun, in that semi-sar-
necessary to manage the overbank- castic sense of the word. The Sinus
ing tendency. provides no visibility aft of the win-
The Sinus showed a new variation dow on the other side of the fuselage,
on this. Turn entry was as expected and that’s where the runway was, of
and opposite aileron in the turn course. As we glided along with the
was as expected, but I had not an- engine at idle, I estimated a good time
ticipated the need for opposite rud- to turn base and did that, starting the
der during a stabilized turn as well. turn with a good chunk of rudder. All
This tendency to “wrap up” isn’t all was looking good until time to turn
that unusual and, as the late Harold ﬁnal, at which point we encountered a
Barnes (my ﬁrst ﬂight instructor) thermal jealous of our lack of interest
said, “Fly what you ﬁnd.” in it earlier in the ﬂight. The thermal
Most sailplanes have fabulous started to seduce those long wings and
visibility with a bubble canopy and the clean airframe, and we began gain-
nothing up front, but the Sinus’s ing altitude. Lowering the nose took
visibility is restricted by those high care of the altitude gain as we acceler-
wings, the engine up front and that ated briskly.
bump in the panel. When ther- On the ceiling, the airbrake handle
maling, it was different to look up was already halfway down, past the
expecting to see the entire cloud over-center lock but with the airbrakes
above, and to instead see only a por- still retracted. As I started to pull the
tion through the skylight. handle down more, the airbrakes leapt
The cabin is built for two, and the author says it I tried some stalls of the airplane out of the wing (as Schempp-Hirth
was plenty roomy with excellent shoulder and
legroom. sort; it was a challenge enough to airbrakes tend to do), and the Sinus
provoke a stall, and the result was shrugged off the tempting lift of the
extremely benign even when induced, due in part to the IMD 029-b airfoil, which thermal and continued its descent.
kept the airﬂow under control. While thermaling, I never felt close to a stall, per- Coming out of the thermal, there was
haps because my predisposition to a lower nose always had me a few knots too fast, a sinker, and as I retracted the speed-
sometimes more. I was also surprised to ﬁnd that after giving the rudder a hefty brakes and lowered the nose to keep
push in straight-ahead ﬂight, the Sinus straightened itself out and the yaw string the runway in sight, we were too fast,
centered, in a most un-sailplane-like display of good manners. again. Meanwhile, the gusts and cross-
After sampling the sailplane’s characteristics, Mudd started the engine and winds kept the hands and feet busy
allowed it to warm, and we headed back to the airport. Cruise speed in the Sinus herding the attitude and ﬂight path
KITPLANES October 2005 17
Pipistrel Sinus continued
vectors back towards civilization.
Throttle? No thanks, no hands free for the throttle, but the
clean airframe, a little extra energy and the airbrakes made the
throttle a “don’t care,” as the software engineers call it.
As the ground approached, still with some airbrakes out, the
extra energy was gone and we were in a reasonable position
to ﬂare and touch down. As the nose came up, the forward
visibility temporarily disappeared. Mudd advises that when
you’re ready to touch down, a good pull on the airbrakes will
ensure that you touch down and stay down. He was right,
of course, and a fortuitously timed tug on the airbrakes gave
us a smooth and irrevocable touchdown on the grass. With
the seating position and the low window bottoms on the side,
there was a tremendous illusion of speed, but even with only
light use of the toe brakes, the ground roll was conventional.
The crosswind component was 5 knots or so, easily handled
with the tricycle gear despite the long wings.
A second trip around the pattern was nearly identical to the
ﬁrst in all regards except pilot workload, seemingly half that
of the ﬁrst approach as I adapted to the control setup. Overall,
the Sinus is not hard to ﬂy, but the cues conveyed and controls
called for are different from power planes. Mudd says that a
Standard on the motorglider is a feathering propeller, which stops during
soaring. In ﬂight, you’d use the starter to line the prop blades horizontally,
both to reduce drag and improve visibility.
18 KITPLANES October 2005 www.kitplanes.com
5-hour checkout is standard, and that seems reasonable.
According to Mudd, one tailwheel Sinus owner with low time in tailwheel air-
craft has had no problems, even on pavement. Looking at the geometry of the Price (excluding quickbuild options) . . . . . . . . . . . .$66,347
Estimated completed price . . . . . . . . . . . . . . . . . . . .$75,000
aircraft with the track of the maingear narrow in relation to the long wheelbase,
Estimated build time . . . . . . . . . . . . . . . . . . . . . . . 400 hours
that report seems unlikely; but if accurate, it’s a good testament to the handling Number flying (at press time). . . . . . . . . . 180 (worldwide)
qualities of the Sinus. Powerplant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rotax 912
80 hp @ 5500 rpm
Mudd owns several sailplanes and says that there are really two kinds of
Propeller . . . . . . . . . . . . Pipistrel two-blade full-feathering
motorgliders: the touring-type motorglider (like the Sinus), and the folding-motor Powerplant options . . . . . . . . . . . . . . . . . . . . . . . .Rotax 503
motorgliders, which are really self-launching sailplanes and are limited in their
powered ﬂight capabilities. Checking out in one makes you legal for the other, but
Wingspan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 ft
Mudd says that alone won’t prepare you for the other type. The lesson? Make sure Wing loading. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.0 lb/sq. ft
you get the appropriate training for whichever type of motorglider you decide to ﬂy. Fuel capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 gal
Maximum gross weight. . . . . . . . . . . . . . . . . . . . . . . 1200 lb
Typical empty weight. . . . . . . . . . . . . . . . . . . . . . . . . . 626 lb
Want One? Typical useful load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574 lb
According to Mudd, the Sinus is currently available in the U.S. as a kit aircraft or Full-fuel payload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 lb
Seating capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
in ready-to-ﬂy format. You can order a 200-hour kit or a 400-hour kit, the major
Cabin width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43.5 in
difference being that on the 200-hour kit, the seam where the two fuselage halves Baggage capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 lb
join has been ﬁlled, ﬁnished and gel coated by the factory. On both versions, most
of the bonding work is complete and nearly all the work that remains has to do
Cruise speed. . . . . . . . . . . . . . . . . . . . . . . .137 mph (119 kt)
with assembly. sea level @ 70% power, 3.4 gph
The big question we had: With such low build times, do the kits meet the FAA’s Maximum rate of climb . . . . . . . . 1280 fpm (at max. gross)
Stall speed (landing configuration) . . . .39 mph (34 knots)
major-portion rule? The answer: Hopefully! So far, none of the four U.S. customers
Stall speed (clean) . . . . . . . . . . . . . . . . . .41 mph (36 knots)
has opted for the kit version—all chose the ready-to-ﬂy version (see below). Mudd Takeoff distance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 ft
is optimistic, however, and says he foresees no problem earning 51% approval. He Landing distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 ft
built an Apis motorglider from Pipistrel, which shares a number of similarities in
Specifications are manufacturer’s estimates and are
construction, and that aircraft met the rule with no problem. based on the configuration of the demonstrator air-
Mudd is currently selling his demonstrator airplane, and the plan is to replace craft. As they say, your mileage may vary.
KITPLANES October 2005 19
Pipistrel Sinus continued category. Wait—isn’t that
the trick that some dis-
that with a Sinus he’ll build from a kit honest companies have
version. During that build process, his been using to sell ready-
goal is to take the plane through the to-ﬂy airplanes before
FAA’s kit approval process to demon- they’re certiﬁed in the
strate that it can be done and in hopes new Light-Sport Aircraft
that the aircraft will be added to the category? Yes, indeed.
FAA-published list of kits that meet the The difference here, how-
rule. Also, Mudd notes that the 200- ever, is that Pipistrel is not
and 400-hour build times are factory trying to hide that fact.
estimates; by building a kit, he plans Talk to them, and they’ll
to determine whether these numbers tell you up front the
Not a ton of space on the instrument panel, but enough for the
are accurate. restrictions of operating basics of ﬂight instrumentation and engine monitoring espe-
Additionally, the kits are extremely from that category. cially if you use an all-in-one electronic unit like this German-
inclusive compared to U.S.-produced In short, the operat- produced system, which is standard equipment on the Sinus.
airplanes. They include the engine of ing limitations usually
your choice, all accessories, and an constrict owners to a 300-
instrument panel. According to Mudd, n.m. radius unless they’re traveling to an exhibition, ﬂy-in, airshow or air race and
everything you need to ﬂy but gas and have ﬁled a request in advance. Filing such a request is easy, Mudd says, and it can
oil. The panel features a Bräuniger Flug- be done as little as 24 hours in advance. The drawback, however, is that you might
electronic device for instrumentation want to go beyond the 300-n.m. limit for something other than an airshow. Sorry,
and engine management. While not buddy, but you’re out of luck.
So far, the four Sinus owners in the U.S. (other
than the dealer airplanes) have all opted for the
Exhibition/Racing category. But Mudd says others
have been turned off by that option. Our advice—
build from a kit, especially considering the low build
Or, of course, you can wait for the Sinus to earn
its LSA certiﬁcation and buy a factory-built version
with fewer restrictions. The catch, however, is that
who knows when the plane will earn that certiﬁca-
tion. Slovenia does not have a bilateral airworthiness
agreement with the U.S. (a requirement for a poten-
tial LSA to earn a certiﬁcate), so this option does not
appear imminent. Additionally, the factory will have
With a 49-foot wingspan, the author says that estimating wingtip clearance during
to slightly modify the Sinus for it to conform to the
taxi will seriously challenge your depth perception. LSA deﬁnition—currently, it’s slightly fast. For this
option, you may be waiting around a while.
a full EFIS system (there’s no attitude Going The Motorglider Route
indicator), the Germany company’s Sailplane pilots self-certify, medically. The limitations that might keep you from
Alpha MFD includes airspeed, VSI, self-certifying as a Sport Pilot don’t apply to motorgliders, so if you can’t ﬂy as a
rate of climb, altitude, fuel, CHTs and Sport Pilot, you can ﬂy a motorglider as long as your self-certiﬁcation is legitimate
EGTs, tachometer, automatic logbook and you have a glider pilot license. But be careful, here. The story goes of one wan-
and a number of other features. nabe motorglider pilot who was busted. His would-be motorglider? A Van’s RV-6!
Prices vary with the euro/dollar ex- So does a motorglider ﬁt into your plans? It sure could—you’ll do more stick
change rate, but at press time, a 912- and ruddering in an hour of thermaling than you will in 10 hours of elementary
powered Sinus 400-hour kit cost about aerobatics or a week of touch and goes. And instead of going for the usual $100
$66,000 and the 200-hour kit sold for hamburger, a motorglider can let you commit satisfying aviation in your own
$73,000. backyard, anytime there’s lift. And isn’t that a key reward of ﬂying?
Or, for about $78,000, you can buy
the Sinus in ready-to-ﬂy format. How?
Well, the U.S. dealers are currently FOR MORE INFORMATION on the Sinus, visit www.mcp.com.au/pipistrel-usa/ for a list
offering the factory-built plane in the of dealers in the U.S. No access to the web? Try New Mexico-based dealer Robert Mudd at
Experimental/Exhibition and Racing 505/269-8234. He’ll point you in the right direction.
20 KITPLANES October 2005 www.kitplanes.com