Engine power question???

[[email protected]]

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

[[email protected]]

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.

[Orval Fairbairn]

In article m>,
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.

[Scott[_1_]]

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)

[Vaughn Simon]

"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

[Stuart & Kathryn Fields]

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)

[[email protected]]

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 -

[J.Kahn]

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

[[email protected]]

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

[cavelamb himself[_4_]]

>
>
> 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

[cavelamb himself[_4_]]

J.Kahn wrote:

> 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.

You know, we ALL really ought to go get another hour in a 150 every once
in a while.

When I was in high school, the 150 was IT! WoW!

But I flew one a couple of years ago and the prevelant thought was,
"What happened? This used to be FUN".




> 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

[Dave S]

wrote:
> 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
>
>

For a given engine, the drop in static HP with altitude corresponds to
the drop in air density (and therefore air resistance) with altitude.

Air Density affects both factors equally.

[Dave S]

J.Kahn wrote:

>
> 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

But without that manifold pressure gauge on a fixed pitch prop, us
knuckledraggers are blissfully unaware of that fact. I did see at 152
with a MP gauge once.. nice "feature".

Dave

[Scott[_1_]]

OK, I guess I can buy into that one, but I'm still confused a bit. If
one is limiting it (the O-320) to a given RPM that gives 100 HP out,
wouldn't that same RPM give less than 100 HP at high density altitude
just as an O-200 would?

Scott


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)
>
>
>

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

[[email protected]]

On Oct 10, 7:14 am, Scott > wrote:
> OK, I guess I can buy into that one, but I'm still confused a bit. If
> one is limiting it (the O-320) to a given RPM that gives 100 HP out,
> wouldn't that same RPM give less than 100 HP at high density altitude
> just as an O-200 would?
>
> Scott

They're not deliberately limiting it to 100 hp. The fixed-pitch
prop does that on any airplane. Your O-320 will make any O-200 look
sick. You need to fly a 150 with the O-200, and you won't complain
anymore. A 150 with the O-200 on takeoff won't generate anywhere near
100 hp. In fact, I have my suspicions that it never did, even at 2750
RPM. We had those engines in a couple of 150s, and I flew an Aircoupe
with a C-90, 10 less hp than the O-200, and it took off much shorter,
climbed and cruised much faster than the 150. It generated that 90 hp
at a lower RPM, which means that less hp was lost to drag. The
airplane weighed only 150 lb less than the 150.
A guy in the US did some testing on a 150. He did a static
thrust test, full RPM with the airplane pulling on a hefty spring
scale. Got around 230 lb, IIRC. Then he took that O-200 out and put in
a 100 hp Subaru conversion and did the static test again and got
almost 300 lb. That wasn't with a lower-pitched prop, either; the
airplane cruised as well as before at a similar RPM. Makes one wonder
about hp claims.

Dan

[J.Kahn]

cavelamb himself wrote:
> J.Kahn wrote:
>
>> 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.
>
> You know, we ALL really ought to go get another hour in a 150 every once
> in a while.
>
> When I was in high school, the 150 was IT! WoW!
>
> But I flew one a couple of years ago and the prevelant thought was,
> "What happened? This used to be FUN".
>
>
>
>
>> 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

Actually, I'm starting to look for a 150 to play around with and for the
kids to learn in next spring. They fly about as well as most
airplanes, with a really good useful load for that size. The 150 does a
lot of things reasonably well and are becoming dirt cheap as the big
flight schools unload them. Where else can you get a 600 lb useful
load, electrics, really powerful fowler flaps, etc all for 20k.
Everybody else hates them, but I like the '64/65 straight tails. If
you block out the front half of the airplane in a picture, it looks like
an A-26.

Apparently aileron gap seals make the ailerons much lighter and
snappier, probably the biggest complaint in handling.

John

[[email protected]]

On Oct 10, 5:10 pm, "J.Kahn" > wrote:
> cavelamb himself wrote:
> > J.Kahn wrote:
>
> >> 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.
>
> > You know, we ALL really ought to go get another hour in a 150 every once
> > in a while.
>
> > When I was in high school, the 150 was IT! WoW!
>
> > But I flew one a couple of years ago and the prevelant thought was,
> > "What happened? This used to be FUN".
>
> >> 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
>
> Actually, I'm starting to look for a 150 to play around with and for the
> kids to learn in next spring. They fly about as well as most
> airplanes, with a really good useful load for that size. The 150 does a
> lot of things reasonably well and are becoming dirt cheap as the big
> flight schools unload them. Where else can you get a 600 lb useful
> load, electrics, really powerful fowler flaps, etc all for 20k.
> Everybody else hates them, but I like the '64/65 straight tails. If
> you block out the front half of the airplane in a picture, it looks like
> an A-26.
>
> Apparently aileron gap seals make the ailerons much lighter and
> snappier, probably the biggest complaint in handling.
>
> John

We're at 3000' ASL here. We found the 150 to be underpowered
and really tight inside, and the O-200 would usually give top end
problems by mid-life. There were days in the summer (30°C/85°F, 5000'
DA) when the dumb thing would climb at under 200 FPM and take all day
to reach circuit altitude. They might be OK near sea level.
The older straight tails, or at least the ones without the
back window, were lighter and faster. Not many of them around now. The
150's flaps are awesome, and the rudder has enough authority to deal
with strong crosswinds, better than the 172. And it'll spin readily,
something the 172 is really reluctant to do.

Dan

[Kyle Boatright]

> wrote in message
ups.com...
> On Oct 10, 7:14 am, Scott > wrote:
>> OK, I guess I can buy into that one, but I'm still confused a bit. If
>> one is limiting it (the O-320) to a given RPM that gives 100 HP out,
>> wouldn't that same RPM give less than 100 HP at high density altitude
>> just as an O-200 would?
>>
>> Scott
>
> They're not deliberately limiting it to 100 hp. The fixed-pitch
> prop does that on any airplane. Your O-320 will make any O-200 look
> sick. You need to fly a 150 with the O-200, and you won't complain
> anymore. A 150 with the O-200 on takeoff won't generate anywhere near
> 100 hp. In fact, I have my suspicions that it never did, even at 2750
> RPM. We had those engines in a couple of 150s, and I flew an Aircoupe
> with a C-90, 10 less hp than the O-200, and it took off much shorter,
> climbed and cruised much faster than the 150. It generated that 90 hp
> at a lower RPM, which means that less hp was lost to drag. The
> airplane weighed only 150 lb less than the 150.
> A guy in the US did some testing on a 150. He did a static
> thrust test, full RPM with the airplane pulling on a hefty spring
> scale. Got around 230 lb, IIRC. Then he took that O-200 out and put in
> a 100 hp Subaru conversion and did the static test again and got
> almost 300 lb. That wasn't with a lower-pitched prop, either; the
> airplane cruised as well as before at a similar RPM. Makes one wonder
> about hp claims.
>
> Dan

Don't confuse thrust with HP unless you're using the exact same prop and
prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of thrust
because of gearing, disc area, etc? But, that thrust is only effective in a
narrow (vertical) speed range. The same engine, combined with an RV-style
cruise prop, would only generate (WAG coming) 250 lbs of static thrust.

HP claims on certified engines were +/- 5% back in the day when most "100
hp" 0-200's were built, meaning that a "bad" engine generated 95 HP when it
was built.

KB

[cavelamb himself[_4_]]

wrote:
> On Oct 10, 5:10 pm, "J.Kahn" > wrote:
>
>>cavelamb himself wrote:
>>
>>>J.Kahn wrote:
>>
>>>>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.
>>
>>>You know, we ALL really ought to go get another hour in a 150 every once
>>>in a while.
>>
>>>When I was in high school, the 150 was IT! WoW!
>>
>>>But I flew one a couple of years ago and the prevelant thought was,
>>>"What happened? This used to be FUN".
>>
>>>>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
>>
>>Actually, I'm starting to look for a 150 to play around with and for the
>>kids to learn in next spring. They fly about as well as most
>>airplanes, with a really good useful load for that size. The 150 does a
>>lot of things reasonably well and are becoming dirt cheap as the big
>>flight schools unload them. Where else can you get a 600 lb useful
>>load, electrics, really powerful fowler flaps, etc all for 20k.
>>Everybody else hates them, but I like the '64/65 straight tails. If
>>you block out the front half of the airplane in a picture, it looks like
>>an A-26.
>>
>>Apparently aileron gap seals make the ailerons much lighter and
>>snappier, probably the biggest complaint in handling.
>>
>>John
>
>
> We're at 3000' ASL here. We found the 150 to be underpowered
> and really tight inside, and the O-200 would usually give top end
> problems by mid-life. There were days in the summer (30°C/85°F, 5000'
> DA) when the dumb thing would climb at under 200 FPM and take all day
> to reach circuit altitude. They might be OK near sea level.
> The older straight tails, or at least the ones without the
> back window, were lighter and faster. Not many of them around now. The
> 150's flaps are awesome, and the rudder has enough authority to deal
> with strong crosswinds, better than the 172. And it'll spin readily,
> something the 172 is really reluctant to do.
>
> Dan
>

Well, that's all right, I guess.
But it's sure no 65 HP Taylorcraft.
(Which gets off shorter, climbs better and is (no ****) faster!)

Richard

[[email protected]]

On Oct 10, 9:17 pm, "Kyle Boatright" > wrote:


> Don't confuse thrust with HP unless you're using the exact same prop and
> prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of thrust
> because of gearing, disc area, etc? But, that thrust is only effective in a
> narrow (vertical) speed range. The same engine, combined with an RV-style
> cruise prop, would only generate (WAG coming) 250 lbs of static thrust.

That Soob had the same diameter of prop and ran at the
same RPM. I'm aware of the diameter/RPM/pitch effects, and that's why
the results were so startling to me. The 150s performance was much
better with the Soob, confirming its output. So either the Soob
produced more power than claimed, or the O-200 was really sick. Yet
the guy said that the O-200 was OK and the 150's performance with it
was typical.

Dan

[Orval Fairbairn]

In article . com>,
wrote:

> On Oct 10, 9:17 pm, "Kyle Boatright" > wrote:
>
>
> > Don't confuse thrust with HP unless you're using the exact same prop and
> > prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of thrust
> > because of gearing, disc area, etc? But, that thrust is only effective in a
> > narrow (vertical) speed range. The same engine, combined with an RV-style
> > cruise prop, would only generate (WAG coming) 250 lbs of static thrust.
>
> That Soob had the same diameter of prop and ran at the
> same RPM. I'm aware of the diameter/RPM/pitch effects, and that's why
> the results were so startling to me. The 150s performance was much
> better with the Soob, confirming its output. So either the Soob
> produced more power than claimed, or the O-200 was really sick. Yet
> the guy said that the O-200 was OK and the 150's performance with it
> was typical.
>
> Dan

I have a friend who put a Soob in a homebuilt, with "help" from the Soob
conversion people. I told him that I was not impressed with some of the
design (especially the cooling installation) and to be sure to make a
lot of test flights.

Well, it lasted to just short of Oshkosh and then from Oshkosh to just
short of Dayton. Fortunately, the plane was relatively undamaged; my
friend's ego was his sole injury.

In short, tread carefully when going with someone's conversion.

[Andy Asberry[_2_]]

On Wed, 10 Oct 2007 19:10:18 -0400, "J.Kahn"
> wrote:

>
>Actually, I'm starting to look for a 150 to play around with and for the
>kids to learn in next spring. They fly about as well as most
>airplanes, with a really good useful load for that size. The 150 does a
>lot of things reasonably well and are becoming dirt cheap as the big
>flight schools unload them. Where else can you get a 600 lb useful
>load, electrics, really powerful fowler flaps, etc all for 20k.
>Everybody else hates them, but I like the '64/65 straight tails. If
>you block out the front half of the airplane in a picture, it looks like
>an A-26.
>
>Apparently aileron gap seals make the ailerons much lighter and
>snappier, probably the biggest complaint in handling.
>
>John

Here is one you can play around with a lot.
http://saltlakecity.craigslist.org/rvs/440160765.html

Would all this work qualify as a homebuilt?

--Andy Asberry--
------Texas-----

[Kyle Boatright]

> wrote in message
oups.com...
> On Oct 10, 9:17 pm, "Kyle Boatright" > wrote:
>
>
>> Don't confuse thrust with HP unless you're using the exact same prop and
>> prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of
>> thrust
>> because of gearing, disc area, etc? But, that thrust is only effective
>> in a
>> narrow (vertical) speed range. The same engine, combined with an
>> RV-style
>> cruise prop, would only generate (WAG coming) 250 lbs of static thrust.
>
> That Soob had the same diameter of prop and ran at the
> same RPM. I'm aware of the diameter/RPM/pitch effects, and that's why
> the results were so startling to me. The 150s performance was much
> better with the Soob, confirming its output. So either the Soob
> produced more power than claimed, or the O-200 was really sick. Yet
> the guy said that the O-200 was OK and the 150's performance with it
> was typical.
>
> Dan

I still think it is important to have the *exact same* prop, not just the
same diameter. Depending on prop pitch, chord, etc. you could get
significantly different amounts of thrust from props with the exact same
diameter.

[[email protected]]

On Oct 11, 8:44 pm, "Kyle Boatright" > wrote:
> > wrote in message
>
> oups.com...
>
>
>
> > On Oct 10, 9:17 pm, "Kyle Boatright" > wrote:
>
> >> Don't confuse thrust with HP unless you're using the exact same prop and
> >> prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of
> >> thrust
> >> because of gearing, disc area, etc? But, that thrust is only effective
> >> in a
> >> narrow (vertical) speed range. The same engine, combined with an
> >> RV-style
> >> cruise prop, would only generate (WAG coming) 250 lbs of static thrust.
>
> > That Soob had the same diameter of prop and ran at the
> > same RPM. I'm aware of the diameter/RPM/pitch effects, and that's why
> > the results were so startling to me. The 150s performance was much
> > better with the Soob, confirming its output. So either the Soob
> > produced more power than claimed, or the O-200 was really sick. Yet
> > the guy said that the O-200 was OK and the 150's performance with it
> > was typical.
>
> > Dan
>
> I still think it is important to have the *exact same* prop, not just the
> same diameter. Depending on prop pitch, chord, etc. you could get
> significantly different amounts of thrust from props with the exact same
> diameter.

Not so much. Efficiencies are typically in the range of
85-90% unless the prop is a real dog, and I don't think Cessna would
have continued using the prop they did on the 150 if it was a poor
performer.
We had an Ivoprop on a 135 hp Soob in a Glastar. Didn't trust
that prop, and had problems getting it to run smoothly. We eventually
put a Warp drive on it, three Blades instead of two, but the
performance was nearly identical even though there were big
differences in chord and planform.
The guy who put the Soob in the 150 may have used the same
prop, but I can't remember. Some of those Soob conversions used the
Lycoming bolt circle instead of the Continental, and the Cont's prop
wouldn't fit, of course.
As you mentioned, a larger, slower-turning prop is far more
efficient, so a redrive is better than direct drive, especially where
an auto engine is used. The airplane that became the Helio Courier was
a much-modified Piper Super Cruiser, IIRC, with a 125 hp Lyc driving a
big, slow prop through a redrive using several V-belts. Very rapid
acceleration and spectacular climb, aided by slats and flaps and the
usual STOL wizardry.

Dan

[J.Kahn]

Andy Asberry wrote:
> On Wed, 10 Oct 2007 19:10:18 -0400, "J.Kahn"
> > wrote:
>
>> Actually, I'm starting to look for a 150 to play around with and for the
>> kids to learn in next spring. They fly about as well as most
>> airplanes, with a really good useful load for that size. The 150 does a
>> lot of things reasonably well and are becoming dirt cheap as the big
>> flight schools unload them. Where else can you get a 600 lb useful
>> load, electrics, really powerful fowler flaps, etc all for 20k.
>> Everybody else hates them, but I like the '64/65 straight tails. If
>> you block out the front half of the airplane in a picture, it looks like
>> an A-26.
>>
>> Apparently aileron gap seals make the ailerons much lighter and
>> snappier, probably the biggest complaint in handling.
>>
>> John
>
> Here is one you can play around with a lot.
> http://saltlakecity.craigslist.org/rvs/440160765.html
>
> Would all this work qualify as a homebuilt?
>
> --Andy Asberry--
> ------Texas-----

Yikes too much work....

You could license it as a homebuilt if you did something like build up
the wings from parts so you could squeeze past the 51 percent rule for
the primary structure. You would have to be able to show that you were
at least equivalent to a "quick build" kit.

Here in Canada there is a category called "Owner Maintenance" where you
can buy one that is in annual but is maybe a bit rough, and license it
as OM (it has to have a current CofA to start, then you put X's on all
the data plates) then you can maintain and repair it yourself and use
uncertified parts, like a homebuilt. The number of airplanes converted
to date is limited, probably less than 100, mainly because the FAA
refuses to acknowledge the category so OM airplanes can't travel or be
sold to the US. If they treated OM the same as second owner homebuilts,
a major impediment would be removed and a LOT of older airplanes would
be converted. On an airplane that is airworthy but ratty and therefore
cheap to buy, it's still attractive even if you can't go south.

John