Mooney 201 prop

On Mon, 22 Aug 2005 07:52:01 -0600, Newps wrote:

George Patterson wrote:
Later in the war, the
Thunderbolt was re-equipped with a prop which had comparatively wide
blades -- the pilots called it a "paddle-blade" prop. Rate-of-climb and
maneuverability immediately improved to the point that a good Jug pilot
could out-maneuver a Spitfire.

How does a prop change make the plane more manuverable?

That depends on the pilot. This story likely came from Robert Johnson
who was the pilot who "wrote" the book "Thunderbolt" with Martin
Caidin. Johnson was apparently a natural at flying fighters and
intuitively understood how to get the most from his mount and how to
best maneuver it for a successful attack. He was one of the first to
use the vertical for combat maneuvering rather than just banking and
yanking and holding your breath.

While Caidin has often been accused of not letting the facts get in
the way of a good yarn, Johnson's prowess in the vertical was also
described in the fighters bible on Air Combat Maneuvering. That may
not be the exact title, but it was a book written by a fighter pilot,
for fighter pilots, and described various methods for getting your
target aircraft in front of you by maneuvering.

Johnson did not have the benefit of that kind of training or insight,
he just learned how to do it by experience. He naturally used the
Thunderbolt's best assets which he thought was it's rapid rate of
roll, it's incredible dive and it's ability to zoom climb.

When he encountered an enemy fighter that normally could out turn him
in a normal horizontal turn and attempted to do so, he'd pull back the
stick and go vertical, rotating around so that he had the enemy
fighter in his vision as he went up. Now the enemy fighter was
basically trapped. No matter what it did, turn right, turn left or
attempt to dive away, Johnson would roll so that his canopy was
towards it and pull the stick back and pull the nose down on it. The
dive then took over and within seconds the enemy aircraft was in his
sights. Only climbing vertically with him would have offered some
protection, but few German fighter pilots knew to do that.

Johnson also described some mock dogfights he had with two Spitfires,
both before he got the paddle blade prop installed, and after. He
claimed that after the prop was installed, he was able to climb away
from the Spitfire, whereas prior to it's installation the Spitfire
readily outclimbed him, although he did not describe what type he was
flying against. That would have made a difference.

With the paddle blade prop, he basically started out with a drag race,
which the P-47 won by pulling ahead, then used the rapid roll rate,
which the Spitfire could not match to roll rapidly in one direction,
then roll rapidly in the other, while the Spitfire got further and
further behind as he tried to follow. A quick dive gave Johnson a lot
of momentum and then he went vertical and pulled back down on the
Spitfire. The hapless Spitfire pilot was then faced with a canopy
full of snarling engine and 8 machine guns.

Johnson doesn't state this, but the paddle blade prop was accompanied
by water injection, which added quite a boost in engine performance.
without that added power, it isn't clear that the P-47 would have been
able to make use of the wider cord blades. Johnson apparently also
had no problem using water injection when he wanted it. It was war,
and engines were swapped out regularly for shipment back to the states
for overhauling.

Corky Scott

I don't know about that, I always thought there was a lot of science
behind props. I also drive a Mooney but never noticed my prop having
longer cord than others. However, other than ground clearance (my
Mooney has 13 inches but looks like 2" ) I would imagine that the
cord of the prop would be just like different cord's on wings. Don't
most props include an efficiency index? Perhaps I'm over thinking it
though...

-Robert

One of the reasons that we don't often talk about or compare propeller
efficiency is that almost all modern props score around 82 to 85%
efficiency -- it's very very tough to improve on that. In fact the Wright
brothers did most of the essential design work on props, and one of the
reasons they beat Langley and the Euro experimenters so soundly is that they
built props with 70% efficiency (according to modern testing -- they
themselves thought they had 66%). So the past century has produced only
about a 25% improvement in prop efficiency, and I suspect very little of
that bump has happened since WWII.

See http://www.fluent.com/about/news/new...i2_fall/a2.htm
for a very cool summary of this issue.

Seth
Comanche N8100R

"Robert M. Gary" wrote in message
ups.com...
I don't know about that, I always thought there was a lot of science
behind props. I also drive a Mooney but never noticed my prop having
longer cord than others. However, other than ground clearance (my
Mooney has 13 inches but looks like 2" ) I would imagine that the
cord of the prop would be just like different cord's on wings. Don't
most props include an efficiency index? Perhaps I'm over thinking it
though...

-Robert