No, it is a 19th century design, with five air cooled cylinders that
rotate around a fixed vertical crankshaft. Having the cylinders rotating
does away with the need for a flywheel, giving a good power to weight
ratio, and creates a forced draught over them that improves cooling
Similar designs were used in world war I fighter aircraft. However, the
gyroscopic effect made turning them rather interesting.
Radial is engines arranged with cylinders in a circle.
Rotary is when the 'crankshaft' is fixed and the cylinders go round it.
Not needing a flywheel is the least of issues for aircraft - the
propellor itself is a massive flywheel.
It was all about cooling really.
Rotary engines are pigs to get the fuel into. too.
"Another factor in the demise of the rotary was the fundamentally
inefficient use of fuel and lubricating oil, caused in part by the need
to aspirate the fuel/air mixture through the hollow crankshaft and
crankcase, as in a two-stroke engine."
The Wankel 'rotary' is a completely different animal.
It has a rotating piston, not a rotating cylinder.
Radial engines reached their peak at the end of WWII and were then
overtaken but the jet engine and turboprops.
Rotary engines didnt even make it to the end of WWI..
Post WWI Bristol engines went down the radial route and Rolls Royce down
the inline route.
There were legals reasons for this.
In the US Pratt and Whitney were the big radial engine people.
As far as cars went, the cooling problems meant that water cooled was
practically de rigeur as power levels went up. So inline was easily
The thing about radials being that they offer better air cooling if the
flat face of the cylinders in=s in a prop blast.
But that is draggy - its better to have an inline arrangement and put
the radiators elsewhere where they can be more aerodynamic
(in-ep-toc’-ra-cy) – a system of government where the least capable to
Although described as a rotary engine, the Wankel is an entirely
Radial and rotary engines both have a number of cylinders arrange around
the crankshaft. Visually, they are similar when stationary. However, the
defining difference is whether the crankshaft rotates, which makes it a
radial engine, or the cylinders rotate, which makes it a rotary engine.
On Sat, 22 Mar 2014 12:08:38 +0000, Part Timer wrote:
Nope, that's definitely a rotary. It's not a Wankel, but it's not a
On radials, the cylinders were static and the crankshaft rotated. Just
like a normal V engine but with banks all the way round.
On a rotary, the crank is static, and the cylinders rotate, just like
that one. Think WW1 fighter plane.
A Wankel is the NSU/Mazda-style one that everybody thinks of as "rotary",
with static cylinders, triangular rotor geared to and spinning around the
Air cooled aero engines have major cooling problems when flying.
When descending they over cool and the cylinders can seize onto the pistons.
At best it causes high wear and tear.
If you look at radial engines, there is a circle of flaps round the engine
nacelle which are closed on descent.
One some aircraft it is recommended to side slip in when landing for rapid
descent to the reduce the cooling effect.
So "someone" didn't have a clue.
Err, it was a joke!
FWIW I've flown a wide range of aircraft, mostly with air-cooled
horizontally-opposed (Lycoming and Continental) engines but a few with
radials, in-line, turbine and part-water-cooled engines.
Your assertions are not correct.
Air-cooled engines do not have "major problems". Power vs speed needs
managing but the clearances are such that cooling is not, in practice, a
big problem up to a few hundred HP. Operations such as towing need
special care not to crack the heads, but this just means leaving a
little power and managing the acceleration in the 10 seconds
post-release (water-cooled is easier here).
Multi-row radials have their own cooling issues, as do high power
water-cooled engines such as the Merlin and Griffon.
Not all radials have cowl flaps but quite a few H-opposed engine
installations do; water-cooled aircraft have rad shutters.
I have never flown an aircraft in which side-slipping was recommended
for cooling - what type are you thinking of?
On 22/03/2014 20:16, Biggles@flies_undone.com wrote:
... forgot to say: the problem with cooling (leaving aside the exotic
multi-row radials) of air-cooled engines is because of the dissimilar
metals used for the heads and the valve seats. If, after a period at
high power, the power is rapidly reduced and the airspeed rapidly
increased, the head cools quickly and shrinks onto the valve seat; this
can result in a cracked head.
On Sat, 22 Mar 2014 20:16:47 +0000, Biggles wrote:
<warning: utter amateur conjection beyond this point>
Tailsliders often side-slip on landing - and there'd be a high crossover
with such older/smaller engine techs and tailsliders, right?
But - aiui - that's more to do with seeing wtf you're going than any kind
It's easier to fly a curved or slipping approach in aircraft with a long
nose or high thrust line because otherwise the runway disappears as you
come down the approach, shortly followed by the entire airfield in some
cases! By slipping, or only lining-up in the last few seconds, the
runway can be kept in sight. These aircraft are usually tailwheel
aircraft, often called "taildraggers" (rather than "tailsliders" ;-) )
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