Engine power question???

I own a Cessna 150 with a 150 HP engine installed (0-320- E2D)

The STC states the static RPM is not to be over 2250 RPM.

My airplane meets the Static RPM Requirement.

My question is am I getting the full 150 HP on takeoff??? turning
2250 RPM

When rolling down the Runway the Tach reads about 2250 RPM

During stable Cruise the engine spins up to 2600 RPM ++ full
throttle : no problem

It seem's to me that the engine should turn much faster like 2700
RPM or so for 150 HP??? on takeoff Just like a Cessna 172!

Turning 2250 RPM seems like I am not getting the full rated engine
HP??? perhaps 125 HP or so???????

What sets the engine RPM?? is it the diameter of the prop?? or is
the Throttle travel
limited???

Why would the STC limit the Static Engine RPM to 2250 RPM???

is it because the Tip of the props may exceed speed of
sound ????

The STC states the Prop is a Mccauley 1C172/TM not over 74 inches
not under 72.5 inches.


Thanks for input

On Oct 8, 11:27 pm, wrote:
I own a Cessna 150 with a 150 HP engine installed (0-320- E2D)

The STC states the static RPM is not to be over 2250 RPM.

My airplane meets the Static RPM Requirement.

My question is am I getting the full 150 HP on takeoff??? turning
2250 RPM

A variable pitch prop (expensive) can keep constant RPM near the max
power output at takoff. But your fixed pitch prop is designed for
overall average operation. If it was pitched for near full power 2700
rpm at takeoff it would go beyond the max RPM at cruise and ruin the
engine.

In article om,
wrote:

On Oct 8, 11:27 pm, wrote:
I own a Cessna 150 with a 150 HP engine installed (0-320- E2D)

The STC states the static RPM is not to be over 2250 RPM.

My airplane meets the Static RPM Requirement.

My question is am I getting the full 150 HP on takeoff??? turning
2250 RPM

A variable pitch prop (expensive) can keep constant RPM near the max
power output at takoff. But your fixed pitch prop is designed for
overall average operation. If it was pitched for near full power 2700
rpm at takeoff it would go beyond the max RPM at cruise and ruin the
engine.

The placarding probably relates to the STC, which "limits you to 100
hp", for certification purposes.

It is easier to get an STC for a higher power engine if you "limit, via
placards, the max power" to that called out in the original type
certificate.

So why would a guy "upgrade" to an O-320 and limit it to 100 HP? What's
the "gain" ???

Scott

Orval Fairbairn wrote:



The placarding probably relates to the STC, which "limits you to 100
hp", for certification purposes.

It is easier to get an STC for a higher power engine if you "limit, via
placards, the max power" to that called out in the original type
certificate.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

"Scott" wrote in message
.. .
So why would a guy "upgrade" to an O-320 and limit it to 100 HP? What's the
"gain" ???

For much the same reason that one would spend a lot of money to install a
turbo-normalizer? Same max horsepower, but more horsepower available under a
wider set of conditions?

Just guessing...
Vaughn

Scott: It is simple. An 0320 is said to be a 150hp engine at 59 degrees,
sea level, short exhaust stacks and a certain humidity. At Rioduoso (sp?)
NM on a hot day the density altitude will make you wish that you had put an
0540 on there even if you have to limit it to 100 hp cause you ain't going
to get 100hp out of the 0320 with a Cessna Exhaust and intake system at a
high density altitude.

Stu Fields
Experimental Helo magazine
"Scott" wrote in message
.. .
So why would a guy "upgrade" to an O-320 and limit it to 100 HP? What's
the "gain" ???

Scott

Orval Fairbairn wrote:



The placarding probably relates to the STC, which "limits you to 100 hp",
for certification purposes.

It is easier to get an STC for a higher power engine if you "limit, via
placards, the max power" to that called out in the original type
certificate.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

It IS simple. You are not getting 100% horsepower at takeoff. You
are inventing the need for the constant speed prop. Great example
is the 180hp Tiger with a cruise prop!

Now, I want to learn something from this...

Why is it that maximum static RPM is independent of altitude?

Horsepower drops with altitude. But static RPM does not. Horsepower
is related to the cube of RPM for a fixed pitch prop IIRC. Why is it
that static RPM stays constant?

Good thing, actually, or a fixed pitch prop would be practically
useless.

Bill Hale


On Oct 9, 4:51 pm, "Stuart & Kathryn Fields" wrote:
Scott: It is simple. An 0320 is said to be a 150hp engine at 59 degrees,
sea level, short exhaust stacks and a certain humidity. At Rioduoso (sp?)
NM on a hot day the density altitude will make you wish that you had put an
0540 on there even if you have to limit it to 100 hp cause you ain't going
to get 100hp out of the 0320 with a Cessna Exhaust and intake system at a
high density altitude.

Stu Fields
Experimental Helo magazine"Scott" wrote in message

.. .



So why would a guy "upgrade" to an O-320 and limit it to 100 HP? What's
the "gain" ???

Scott

Orval Fairbairn wrote:

The placarding probably relates to the STC, which "limits you to 100 hp",
for certification purposes.

It is easier to get an STC for a higher power engine if you "limit, via
placards, the max power" to that called out in the original type
certificate.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)- Hide quoted text -

- Show quoted text -

wrote:
I own a Cessna 150 with a 150 HP engine installed (0-320- E2D)

The STC states the static RPM is not to be over 2250 RPM.

My airplane meets the Static RPM Requirement.

My question is am I getting the full 150 HP on takeoff??? turning
2250 RPM

When rolling down the Runway the Tach reads about 2250 RPM

During stable Cruise the engine spins up to 2600 RPM ++ full
throttle : no problem

It seem's to me that the engine should turn much faster like 2700
RPM or so for 150 HP??? on takeoff Just like a Cessna 172!

Turning 2250 RPM seems like I am not getting the full rated engine
HP??? perhaps 125 HP or so???????

What sets the engine RPM?? is it the diameter of the prop?? or is
the Throttle travel
limited???

Why would the STC limit the Static Engine RPM to 2250 RPM???

is it because the Tip of the props may exceed speed of
sound ????

The STC states the Prop is a Mccauley 1C172/TM not over 74 inches
not under 72.5 inches.


Thanks for input

It forces you to use a certain minimum prop pitch to avoid overspeeding
it in flight.

An O-320 makes 120 hp at 2300 rpm and 26". At wide open throttle at SL
and 2250 it is probably around 130 hp. Add a couple thousand feet and
125 hp at the start of the roll sounds about right.

Any fixed pitch airplane is the same. A 150 with a stock O200 doesn't
have 100 hp available while static either, probably more like 80-85. So
all things being equal you still have 50% more power available than stock.

With all the old wives' tales about running constant speed engines
"oversquare" (rpm below mp) it's amusing to note that fixed pitch
aircraft are way oversquare all through their takeoff and climb phase
until they're going fast enough.

John

On Oct 9, 8:27 am, Orval Fairbairn wrote:
In article om,



wrote:
On Oct 8, 11:27 pm, wrote:
I own a Cessna 150 with a 150 HP engine installed (0-320- E2D)

The STC states the static RPM is not to be over 2250 RPM.

My airplane meets the Static RPM Requirement.

My question is am I getting the full 150 HP on takeoff??? turning
2250 RPM

A variable pitch prop (expensive) can keep constant RPM near the max
power output at takoff. But your fixed pitch prop is designed for
overall average operation. If it was pitched for near full power 2700
rpm at takeoff it would go beyond the max RPM at cruise and ruin the
engine.

The placarding probably relates to the STC, which "limits you to 100
hp", for certification purposes.

It is easier to get an STC for a higher power engine if you "limit, via
placards, the max power" to that called out in the original type
certificate.

Baloney. The STC, and any TCDS, will specify a static RPM range.
Yours probably says "Not under 2150 RPM, not over 2250 RPM." The
O-320E2D in a 172M will spec not under 2270, not over 2370 RPM. The
figure relates to brakes locked, full throttle, zero wind RPM and
won't change much with density altitude. The static RPM is used for
engine and prop health purposes. A fixed-pitch prop will never give
you full engine hp until you are in flight at standard conditions (sea
level, 59°F) so you'd have to be at or near full throttle with the
wheels just above the waves.
Your O-320 in the 152 is NOT derated any more than the O-320s
in our 172s are. We don't get 2700 RPM unless we're in flight and the
throttle is wide open. Many aircraft with fixed-pitch props use
exactly that criteria for propeller pitch: max throttle in level
flight gives redline RPM. Too much pitch would prevent reaching full
hp, too little would leave unusable throttle travel in level flight.
Since the O-320 is certified to produce full power with no time
limitation, you could, with the correct prop, cruise at 2700 and go
places fast. Your range would be a lot shorter since the fuel burn
would be pretty bad. We have to break in new engines over a 3-hour
flight, with the last half-hour being at full throttle, which gives us
2700 RPM. The old 172 goes nearly 140 mph at that setting. Without
wheel pants, too.

Dan

Baloney. The STC, and any TCDS, will specify a static RPM range.
Yours probably says "Not under 2150 RPM, not over 2250 RPM." The
O-320E2D in a 172M will spec not under 2270, not over 2370 RPM. The
figure relates to brakes locked, full throttle, zero wind RPM and
won't change much with density altitude. The static RPM is used for
engine and prop health purposes. A fixed-pitch prop will never give
you full engine hp until you are in flight at standard conditions (sea
level, 59°F) so you'd have to be at or near full throttle with the
wheels just above the waves.


Just one that I know of...
you da man, Leon!
http://www.aircraft-spruce.com/da11.html