From Newsgroup: sci.physics

Hi, I did some reading up on the basic math for jet aircraft,
thrust-to-weight ratio, and related concepts. I was trying to relate
this understanding to propeller driven aircraft, like a small
single-prop plane. When I see the stats for these small planes in
magazines, the engine horsepower is listed, along with the power loading
and empty weight.

I was wondering if it was possible, without diving too deeply into the
math and details, to roughly figure out the lbf that can be generated by
a propeller with, say, a 100 hp engine. Maybe by making a bunch of
simplifying assumptions, like a typical propeller, standard barometric pressure, and such like?
--
Christopher Howard
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From Newsgroup: sci.physics

Christopher Howard <christopher@librehacker.com> wrote:

Hi, I did some reading up on the basic math for jet aircraft, thrust-to-weight ratio, and related concepts. I was trying to relate
this understanding to propeller driven aircraft, like a small
single-prop plane. When I see the stats for these small planes in
magazines, the engine horsepower is listed, along with the power loading
and empty weight.

I was wondering if it was possible, without diving too deeply into the
math and details, to roughly figure out the lbf that can be generated by
a propeller with, say, a 100 hp engine. Maybe by making a bunch of simplifying assumptions, like a typical propeller, standard barometric pressure, and such like?

There is a rule of thumb that a decent propeller makes about 20 lbs
thrust per 10 HP.

Alternately Google "how to calculate propeller thrust".
--
penninojim@yahoo.com
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From Newsgroup: sci.physics

Christopher Howard wrote:

I was wondering if it was possible, without diving too deeply into the
math and details, to roughly figure out the lbf that can be generated by
a propeller with,

What do you mean by "the lbf that can be generated"?
--
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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From Newsgroup: sci.physics

Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:

Christopher Howard wrote:

I was wondering if it was possible, without diving too deeply into the
math and details, to roughly figure out the lbf that can be generated by
a propeller with,

What do you mean by "the lbf that can be generated"?

With the wikipedia articles on jet aircraft, there is usually listed the pounds-force thrust that is generated by each of the engines, which
along with the empty weight (or whatever additional weight you want to
add) can be used easily to calculate the thrust-to-weight ratio. Some
fighter aircraft achieve 1:1 but most commercial jets are somewhere
around 0.6 to 0.7, from what I can tell.

In the specs I was seeing for propeller aircraft, it seems what is
usually listed is weight-per-horsepower, or power loading. That is
interesting, but I was having trouble seeing how to compare the two.
Thrust is more intuitive to me one can see directly the ratio between
thrust lbf and weight lbs.
--
Christopher Howard
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From Newsgroup: sci.physics

Jim Pennino <jimp@gonzo.specsol.net> writes:

There is a rule of thumb that a decent propeller makes about 20 lbs
thrust per 10 HP.

Okay, thank you, that is helpful to know.

Alternately Google "how to calculate propeller thrust".

I don't use Google search, but DDG gives some results that are a bit
difficult to wade through. The propeller thrust calculator page gives
these equations:

Velocity = Propeller Pitch * RPM * (1/1056)

Thrust = (2 * Efficiency * Power * 746)
/ (Velocity * Propeller Diameter * 0.0254)

with the Power in watts and the pitch and diameter in inches. That
doesn't sound too complicated to calculate.
--
Christopher Howard
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From Newsgroup: sci.physics

Christopher Howard <christopher@librehacker.com> wrote:

Jim Pennino <jimp@gonzo.specsol.net> writes:

There is a rule of thumb that a decent propeller makes about 20 lbs
thrust per 10 HP.

Okay, thank you, that is helpful to know.

Alternately Google "how to calculate propeller thrust".

I don't use Google search, but DDG gives some results that are a bit difficult to wade through. The propeller thrust calculator page gives
these equations:

Velocity = Propeller Pitch * RPM * (1/1056)

Thrust = (2 * Efficiency * Power * 746)
/ (Velocity * Propeller Diameter * 0.0254)

with the Power in watts and the pitch and diameter in inches. That
doesn't sound too complicated to calculate.

Yeah, but this too is more a rule of thumb.
--
penninojim@yahoo.com
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