Rotary aircraft engines were first developed in the early part
of the 20th Century, and bear no relation to the pistonless
'rotary' engines developed by Wankel and later used in
some Mazda automobiles.

Rotaries have the cylinders arranged radially around the
central crankshaft, like a radial engine, but instead of having
a fixed cylinder block with rotating crankshaft, the crankshaft
in the rotary remains stationary and the entire cylinder block
rotates around it.

The early adoption of rotary engines for aircraft was due to
the fact that they delivered power very smoothly; when the
engine was running, the rotating cylinder assembly created
its own fastmoving cooling airflow, even on the ground; and
they had a significant powertoweight ratio advantage by
having no need for an added flywheel.

It's often stated that all rotaries had no throttle and thus
power could only be reduced by intermittently cutting the
ignition using a "blip" switch. This was almost true of the
"Monosoupape" (single valve) type engines as seen here in
the Sopwith Camel, but other rotaries such as those by Le
Rhône & Oberursel had more conventional throttle systems.

Rotary engines had a totalloss oiling system. To reach the
whole engine, the lubricant (usually castor oil) needed to
enter the crankcase through the hollow crankshaft; but the
centrifugal force of the revolving crankcase was opposed to
any recirculation so the oil was ejected hence the strong
smell of castor oil when these aircraft fly.

These three aircraft belong to The Vintage Aviator Ltd in New Zealand, and are regularly flown at the Wings Over Waiararap Air festival events held in Masterton.

For more info see: www.wings.org.nz



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