54 AUGUST 2018 ÇPlane&Pilot

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Rotax 915

TEXT & PHOTOS BY DAVE UNWIN

It

would be fair to say that,

since the Rotax 912 arrived

onto the general aviation

scene 29 years ago (in 1989), the Nine-

series of Rotax engines have trans-

formed GA. At irst, it was an engine

used solely in homebuilt aviation, as

the LSA category was still 15 years

in the future. In Europe and amidst a

busy U.S. light sport scene, the engine

was a godsend.

It speaks highly of the vision of the

company that Rotax had the foresight

to predict the need for a relatively light-

weight yet powerful engine. With its

innovative design of air-cooled cyl-

inders but liquid-cooled heads, rela-

tively small capacity and a mechanical

reduction gearbox, the Rotax was a

whole diferent animal from the reliable

air-cooled Lycoming and Continental

engines that most of us grew up with.

hanks to its good power-to-weight

ratio and low fuel consumption, the

912 rapidly gained acceptance, even if

the way it started and stopped—all at

once with a shudder—made most of us

wince. However, it was the emergence

of the Light Sport Aircraft class in the

USA and its strict 1320 lb max takeof

weight that really secured the 912’s

place as the engine of choice for most

light aircraft designers.

he original 80-hp 912 was soon

joined by the 100-hp 912S and then

the turbocharged 115-hp 914, while the

100-hp model was subsequently mar-

keted in both carbureted and injected

versions, and either certiied or Light

Sport-compliant.

he 912 and its variants produced

between 80-hp and 115-hp, which

was perfect for a fairly wide range of

applications in sport lying, and its

light weight made it highly competi-

tive against airplanes that have tra-

ditionally been powered by opposed

four-cylinder air-cooled engines, as

mentioned from American manu-

facturers Continental and Lycoming.

A lot of folks have been asking for a

more powerful Rotax to compete with

popular air-cooled models putting out

between 125-hp and 160-hp.

his is the year that Rotax made

those wishes come true. And after this

year’s AERO at Friedrichshafen, I—

along with several other aviation jour-

nalists—was invited to visit the Rotax

factory at Gunskirchen in Austria to

hear more about the latest engine, the

141-hp 915, learn how it’s made and

sample it in light.

Before going lying, I enjoyed a visit

to Rotax’s ultra-modern factory. It’s

quite an easy place to ind as it’s based

on Rotaxstraße. If you’re lying into the

lovely local airport of Wels, you can’t

miss it as “Rotax” is written in big red

letters on the factory’s roof.

Wandering around the factory was

very interesting. he production line

is modern, slick and eicient, and on

the occasions when there is some sort

of issue on the line, it is immediately

apparent to everyone as the theme

from “Mission Impossible” plays over

the PA. A humorous moment occurred

when, having been told that the techni-

cians working on the production line

all use dedicated “smart tools,” with the

torque settings pre-programmed, for

example, one of the workers put down

a device that wouldn’t have looked

out of place in an operating theater

and administered a couple of hearty

whacks with a medium-sized hammer.

I laughed and couldn’t help but ask if

it was a “smart hammer?”

One facet of the factory that I

found particularly interesting was

the nitriding process, which hardens

some components. he temperature

of the plasma within the machine is

an incredible 1,500°C, and the light

produced by this process is so power-

ful you cannot look directly at it but

must view the process via a special

mirror. Visits to the areas where the

aero-engines are built and tested were

particularly interesting.

While watching the motors being

run on the dyno, I asked if there were

any big diferences between the way the

certiied and ASTM-compliant engines

are built and tested—and there isn’t.

Each engine is built using exactly the

same materials and to the same speci-

ications, and then tested in exactly

the same way. Most of the diferences

seemed to be in the paperwork, and

here’s an interesting fact—you can

tell if an engine is certiied or ASTM-

compliant at a glance, as the data

plates are color-coded. Many people

know you can tell the power produced

by any given nine series Rotax from 50

meters away, as the heads are color-

coded. Black for 80-hp, green for 100,

red for 115 and blue for 141. However,

The Austrian engine company's newest model

could be downright revolutionary.