Flight Training - August 2013 - 34

f I’ve ever had to feed more than a quart of oil
reduce vibration, every other cylinder must fire in
to a Cessna 172’s Lycoming, then I’ve blocked
sequence—ergo, in a seven-cylinder engine the firing
out that horrid memory. But there I was in
order is 1, 3, 5, 7, 2, 4, 6, while the Lycoming’s firing
Fort Worth, Texas, standing on top of the B-25
order is 1, 3, 2, 4. If a radial’s single bank held an even
Pacific Prowler’s wing waiting for a ride, watching a
number of pistons, say eight, neighboring cylinders 8
mechanic dump two gallons down the throat of one
and 1 would fire one after the other, and the vibration
of its two huge Wright Cyclone R-2600 radials. It
would rattle the pilot’s dental work. I’d hate to have
had just flown roughly five nautical miles. The B-25
been the test pilot who found that out.
consumes up to 14 gallons of oil per hour at takeIn the days before successful human flight, two
off power and eight in cruise. You can even taste it
camps emerged: With enough power a barn door can
inside the cockpit until the
fly, or control’s the thing. The
bomber gets airborne. Until
first camp was personified by
then, you need to open a
machine-gun inventor Hiram
few windows.
Maxim, who called his barn
Superficially, at least, the
door The Great Kite of War.
172’s typical four-cylinder,
Powered by a pair of two-cyl160-horse Lycoming and
inder steam engines that each
the 14-cylinder, 1,600generated 180 horsepower,
horse R-2600 are the same:
the 7,000-pound, 145-footThey are both four-stroke
long sled had elevators for
engines. Fuel and air flow
pitch and a rudder for yaw,
into the cylinder through
while Maxim planned to use
a valve; the piston rises to
divergent thrust to turn the
HIRAM MAXIM
compress the mixture; the spark plugs
beast. During an 1894 test run on a ninedesigned oil, steam, and
gas engines, along with
(two per cylinder in an airplane engine)
foot-gauge safety track, the Kite lifted off
a variety of other invenignite the compressed gasses; and boom,
and broke through the guardrail placed
tions (above). Maxim's
the piston shoves down and its connectthere to, well, prevent the Kite from
massive flying machine
was designed to ride on
ing rod spins a crankshaft attached to
flying off. It floated briefly, then the rail
rails, much like a roller
a propeller, while the burnt fuel gets
cracked a prop before Maxim could kill
coaster, to test if it
exhaled out a second valve and through
the engines. The Great Kite of War settled
would lift off (below).
the exhaust pipe. Both engines are
back to the ground, never to rise again.
aircooled. But the Lycoming has an even
The other camp included birdmen
number of cylinders, while each bank
like Otto Lilienthal, who, before strapof the Wright R-2600 is odd-numbered
ping on an engine (which would flap the
(and each engine has two banks). One
glider’s wings), first hoped to master
reason: Pioneer aviators learned that to
aerodynamics with his gliders that he

OUR WORLD IS FLAT
RADIAL ENGINES are a historically popular choice for
airplanes, partly for their great power output at low rpm.
The more modern horizontally opposed configuration is
much more popular today. Both engines are four-stroke,
aircooled internal combustion engines. The biggest
difference is in the crankshaft. In a flat engine, the
crankshaft is long and runs the length of the crankcase.
Each piston is connected indirectly through bearings. In a
radial, the crankshaft is a central hub, where most cylinders
are connected indirectly—one cylinder, called the master, is
directly connected to the crankshaft as one solid piece.

34 /

FLIGHTTRAINING.AOPA.ORG

STEVE KARP

Horizontally opposed engine

http://FLIGHTTRAINING.AOPA.ORG

Flight Training - August 2013

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