Mooney 201 prop

[Nathan Young]

Walking out to my plane yesterday, I had the opportunity to walk
through a number of A/C to get to mine. I passed a Mooney (looked
like a 201) and realized that the width of the prop blades was
significant... It was much wider than my fixed pitch Sensenich,
wider than the blades on the Bonanza sitting next to it. In fact, it
had about the widest blades on the ramp (besides maybe a Navajo and
the turbines). So my question - why?

Blade width should create additional frontal drag. I would think you
would want to minimize that. A 201 has 200hp, so it isn't like it
needs to get several hundred HP transferred to the air.

Since Mooney's sit low, does this mean prop clearance is an issue?
Hence a short prop, hence a fat blade?

Inquiring minds want to know.

Thanks,
Nathan

[Frankie]

> Since Mooney's sit low, does this mean prop clearance is an issue?
> Hence a short prop, hence a fat blade?

You probably have it right.

From my observations, prop design seems to be more of an art than a science.
This topic is very confusing.

An interesting aspect of prop design is not only the chord shape but also
the number of blades. People generally think that more horsepower requires
more blades. But witness the Piper Malibu's two-blader (350 hp) and the
Piper Turbo Seminole's three-blader (180 hp).

Mooney's Ovation was initially sold with a three blade prop but later
changed to a two blade (Ovation 2) and it picked up 8 knots of airspeed.
Evidently this was due to the efficiency gains of the two blade, the same
reason it was chosen for the Malibu.

I believe three bladers are preferred for their reduced vibration, quiter
operation, greater low speed thrust, and appearance. Chord design probably
is the main factor in determining the efficiency of the prop regardless of
the number of blades.

Frankie

[john smith]

Look at the early P-47 Thunderbolt props and their performance.
Then look at the replacement prop and its performance.

[Frankie]

> Look at the early P-47 Thunderbolt props and their performance.
> Then look at the replacement prop and its performance.

....not familiar with this example. Perhaps you could fill us in.

Frankie

[George Patterson]

Frankie wrote:
>
> ...not familiar with this example. Perhaps you could fill us in.

Early P-47s had a fairly typical military prop when they first came out. The
planes were heavy for a single (over 7 tons). They had pretty good high altitude
performance, unbeatable dive characteristics, could take immense amounts of
punishment, but they didn't maneuver well (compared to planes like the Spitfire)
and they guzzled gas. 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. Fuel consumption
also improved a bit. The prop simply made better use of the engine's power.

Not sure this is applicable to the Mooney. I suspect that the short legs on the
Mooney make a short prop necessary, so a paddle blade gets the best results.

Don't forget that a prop is essentially a rotating wing. Increase the width of a
wing and you will increase lift (at the expense of increased drag). When the
wing is your prop, that increased "lift" translates to increased thrust. With
the P-47, the plane had the power to make the increased drag unimportant.

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

[Seth Masia]

Specifically, here's the first XP-47 prototype with its conventional
four-blade prop: http://www.warbirdsresourcegroup.org/URG/images/xp47j-1.jpg

And here's the late-war P-47D with the paddle blade prop. Note the cuffs
around the prop roots. http://home.att.net/~historyzone/p-47d-27-re.JPG

"George Patterson" > wrote in message
news:qWaOe.2407$SW1.1776@trndny09...
> Frankie wrote:
>>
>> ...not familiar with this example. Perhaps you could fill us in.
>
> Early P-47s had a fairly typical military prop when they first came out.
> The planes were heavy for a single (over 7 tons). They had pretty good
> high altitude performance, unbeatable dive characteristics, could take
> immense amounts of punishment, but they didn't maneuver well (compared to
> planes like the Spitfire) and they guzzled gas. 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. Fuel consumption also improved a bit. The
> prop simply made better use of the engine's power.
>
> Not sure this is applicable to the Mooney. I suspect that the short legs
> on the Mooney make a short prop necessary, so a paddle blade gets the best
> results.
>
> Don't forget that a prop is essentially a rotating wing. Increase the
> width of a wing and you will increase lift (at the expense of increased
> drag). When the wing is your prop, that increased "lift" translates to
> increased thrust. With the P-47, the plane had the power to make the
> increased drag unimportant.
>
> George Patterson
> Give a person a fish and you feed him for a day; teach a person to
> use the Internet and he won't bother you for weeks.

[Seth Masia]

My mistake. The "XP-47" I found in the previous post is really an 1943
XP-47J speed-record prototype and it probably has a fat prop. I can't find
an online pic of the original prop -- I have plenty of books around here
that show it. The paddle blade prop increased high-altitude climb
performance by about 400 feet per minute.

"Seth Masia" > wrote in message
...
> Specifically, here's the first XP-47 prototype with its conventional
> four-blade prop:
> http://www.warbirdsresourcegroup.org/URG/images/xp47j-1.jpg
>
> And here's the late-war P-47D with the paddle blade prop. Note the cuffs
> around the prop roots. http://home.att.net/~historyzone/p-47d-27-re.JPG
>
> "George Patterson" > wrote in message
> news:qWaOe.2407$SW1.1776@trndny09...
>> Frankie wrote:
>>>
>>> ...not familiar with this example. Perhaps you could fill us in.
>>
>> Early P-47s had a fairly typical military prop when they first came out.
>> The planes were heavy for a single (over 7 tons). They had pretty good
>> high altitude performance, unbeatable dive characteristics, could take
>> immense amounts of punishment, but they didn't maneuver well (compared to
>> planes like the Spitfire) and they guzzled gas. 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. Fuel consumption also improved a bit. The
>> prop simply made better use of the engine's power.
>>
>> Not sure this is applicable to the Mooney. I suspect that the short legs
>> on the Mooney make a short prop necessary, so a paddle blade gets the
>> best results.
>>
>> Don't forget that a prop is essentially a rotating wing. Increase the
>> width of a wing and you will increase lift (at the expense of increased
>> drag). When the wing is your prop, that increased "lift" translates to
>> increased thrust. With the P-47, the plane had the power to make the
>> increased drag unimportant.
>>
>> George Patterson
>> Give a person a fish and you feed him for a day; teach a person to
>> use the Internet and he won't bother you for weeks.
>
>

[Newps]

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?

[Matt Barrow]

"Newps" > wrote in message
...
>
>
> 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?

Better thrust, acceleration...

[Seth Masia]

Steep bank=higher wing loading=more drag. More thrust means you overcome
the added drag. Think of it as having the thrust to pull through a tight
turn -- especially a climbing turn.

"Newps" > wrote in message
...
>
>
> 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?

[[email protected]]

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

[Robert M. Gary]

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

[Seth Masia]

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/newsletters/03v12i2_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
>