Question about 175B

"Wayne" wrote in message ...
I am getting the 1961 175B Cessna that I mentioned before here. I am
trying to figure out how fast it should be. The owner said that it would go
GPH. Then I looked at the original specifications from Cessna. It
was supposed to cruise at 122 knots @ 75% power at 7500'. I had assumed that
he meant 125 MPH but that is only a little less than 109 knots.

Strange. I used to own a '59 Cessna and all of the performance
numbers from the factory were in mph back then. He probably meant 125
mph. The Skylark might be able to do 125 kts @ 75% @7,500' if the
plane is perfectly rigged and light, but the fuel burn he gave you
indicates that he's probably flying at 65% power. At 75% power
expect the O-360 to burn around 10.5 gph.

This has the
Lycoming O360 conversion with a constant speed prop, I would think that
would make it slightly faster and surely better on takeoff performance.

Why? The original Skylark made only 5 less horsepower and also had
a constant speed prop. Practically speaking I wouldn't expect 5 hp
to change the performance numbers a whole lot (particularly speed).

Real world, I'd expect to see 115-120 kts @ 75% @ 7,500' DA with
10gph for that plane, depending on its condition.

John Galban=====N4BQ (PA28-180)

On 5-Aug-2003, "Wayne" wrote:

I am getting the 1961 175B Cessna that I mentioned before here. I am
trying to figure out how fast it should be. The owner said that it would
go GPH. Then I looked at the original specifications from Cessna.
It
was supposed to cruise at 122 knots @ 75% power at 7500'. I had assumed
that he meant 125 MPH but that is only a little less than 109 knots. This
has
the Lycoming O360 conversion with a constant speed prop, I would think
that
would make it slightly faster and surely better on takeoff performance.
The 2003 172 that I fly is supposed to cruise at 115 knots @ 75% (I forget
the
altitude) so I wouldn't expect this one to fly faster than a new one with
the same HP and a fixed pitch prop. Anyone have a simular plane? Anyone
know what I should expect? Did Cessna stretch things that far in 1961?

Wayne


I don't have any experience with C-175s, either with the original geared
engine or with the 0-360 conversion. However, over hundreds of hours in a
C-172N (with the original 150 hp 0-320) I can state that it is a 112 kt
airplane at best. The important thing to remember is that, for a given
airframe, cruise speed will vary as the cube root of horsepower. Thus,
going from 150 hp to 180 hp, for instance, will increase cruise speed (at a
given percentage power setting) by only 6.3%. That would boost a 112 kt
cruise speed to 119 kts.

The idea that you can boost cruise speed with a modest power increase is
mostly wishful thinking. A bigger engine really helps mostly in takeoff and
climb performance (or, in some cases, allowing for more useful load). A
significant increase in cruise speed generally requires aerodynamic cleanup
of the airframe.

You will rarely meet a seller who can resist exaggerating the performance of
the plane he/she is selling. However, with the availability of handheld GPS
units, measuring cruise speed during a test flight is fairly easy. Just fly
in three headings 120 degrees apart, within a relatively small area (so the
wind will not change) and record groundspeed (from the GPS) for each
heading. From that data it is easy to compute the wind component, and then
the true airspeed. If the air is reasonably smooth you should be able to
calculate to within a knot or two.

-Elliott Drucker

Ok, thanks! I didn't realize that is had a constant speed prop before.
Wayne
"John Galban" wrote in message
om...
"Wayne" wrote in message
...
I am getting the 1961 175B Cessna that I mentioned before here. I am
trying to figure out how fast it should be. The owner said that it would
go
GPH. Then I looked at the original specifications from Cessna.
It
was supposed to cruise at 122 knots @ 75% power at 7500'. I had assumed
that
he meant 125 MPH but that is only a little less than 109 knots.

Strange. I used to own a '59 Cessna and all of the performance
numbers from the factory were in mph back then. He probably meant 125
mph. The Skylark might be able to do 125 kts @ 75% @7,500' if the
plane is perfectly rigged and light, but the fuel burn he gave you
indicates that he's probably flying at 65% power. At 75% power
expect the O-360 to burn around 10.5 gph.

This has the
Lycoming O360 conversion with a constant speed prop, I would think that
would make it slightly faster and surely better on takeoff performance.

Why? The original Skylark made only 5 less horsepower and also had
a constant speed prop. Practically speaking I wouldn't expect 5 hp
to change the performance numbers a whole lot (particularly speed).

Real world, I'd expect to see 115-120 kts @ 75% @ 7,500' DA with
10gph for that plane, depending on its condition.

John Galban=====N4BQ (PA28-180)

Thanks for the reply. I thought he meant MPH but what Cessna said about it
made me second guess.
Wayne
wrote in message
...

On 5-Aug-2003, "Wayne" wrote:

I am getting the 1961 175B Cessna that I mentioned before here. I am
trying to figure out how fast it should be. The owner said that it would
go GPH. Then I looked at the original specifications from
Cessna.
It
was supposed to cruise at 122 knots @ 75% power at 7500'. I had assumed
that he meant 125 MPH but that is only a little less than 109 knots.
This
has
the Lycoming O360 conversion with a constant speed prop, I would think
that
would make it slightly faster and surely better on takeoff performance.
The 2003 172 that I fly is supposed to cruise at 115 knots @ 75% (I
forget
the
altitude) so I wouldn't expect this one to fly faster than a new one
with
the same HP and a fixed pitch prop. Anyone have a simular plane? Anyone
know what I should expect? Did Cessna stretch things that far in 1961?

Wayne


I don't have any experience with C-175s, either with the original geared
engine or with the 0-360 conversion. However, over hundreds of hours in a
C-172N (with the original 150 hp 0-320) I can state that it is a 112 kt
airplane at best. The important thing to remember is that, for a given
airframe, cruise speed will vary as the cube root of horsepower. Thus,
going from 150 hp to 180 hp, for instance, will increase cruise speed (at
a
given percentage power setting) by only 6.3%. That would boost a 112 kt
cruise speed to 119 kts.

The idea that you can boost cruise speed with a modest power increase is
mostly wishful thinking. A bigger engine really helps mostly in takeoff
and
climb performance (or, in some cases, allowing for more useful load). A
significant increase in cruise speed generally requires aerodynamic
cleanup
of the airframe.

You will rarely meet a seller who can resist exaggerating the performance
of
the plane he/she is selling. However, with the availability of handheld
GPS
units, measuring cruise speed during a test flight is fairly easy. Just
fly
in three headings 120 degrees apart, within a relatively small area (so
the
wind will not change) and record groundspeed (from the GPS) for each
heading. From that data it is easy to compute the wind component, and
then
the true airspeed. If the air is reasonably smooth you should be able to
calculate to within a knot or two.

-Elliott Drucker

Wayne wrote:

Thanks for the reply. I thought he meant MPH but what Cessna said about it
made me second guess.

Bill Clarke quotes the Cessna specs as showing a cruise speed of 131 mph at
75% power with the original engine.

George Patterson
The optimist feels that we live in the best of all possible worlds. The
pessimist is afraid that he's correct.
James Branch Cavel

"Wayne" wrote in message ...
Just got the original POH, there was no CS prop on the 175 or 175
Skylark. On my plane the prop knob is in the cig lighter hole.

Really? Sorry about that. I've flown about 4 examples of the 175
over the years and half were O-360 conversions. I thought they all
had a CS prop. Oh boy. There go the brain cells :-(


They are claiming 175 HP at 3200 RPM. I believe it's a 150 HP engine
spinning at 3200 with the gear reduction rather than it's normal range of
what, 2500 RPM redline? They say 147 MPH for the 175, and 149 MPH max speed
at sea level for the Skylark.

It's the geared version of the 145 hp Continental O-300 used in the
regular 172. O-300 redline was 2700 rpm. 147mph ??? I'd say that's
pretty optimistic for the 175 unless it's going downhill :-)


The max recommended cruise is 140 and 142 MPH at 70% power and at 10,000
feet which must be full throttle and best power mixture wise.

That sounds more reasonable.

I agree that 5 HP shouldn't make much change, but the addition of a
constant speed prop should make more of a change. Am I correct? Obviously it
would make more change on takeoff, but I still expect an increase.

Generally speaking, I've noticed that a CS prop makes less of a
performance difference with lower powered installations (i.e. below
200 hp). You're right that the CS prop should allow you to take
advantage of some extra horsepower for takeoff and climb. As for how
much, you'd have to have some hp/torque charts for both installations
to get a good idea of the difference.


Where did you get the idea that it had a CD prop from the factory? Maybe
a different year?

Like I said, that was probably a brain fart. So many 175s have had
the 180/CS conversion that I probably mixed up the two.

John Galban=====N4BQ (PA28-180)

Yeah, with a 1200 hours TBO, it wouldn't be a hard decision. As for the
prop, the way I figure, you could have a climb prop, or a cruise prop,
normally even the cruise prop would have to have enough climb in it to get
up and climb as needed at gross so a CS prop should get a fair amount of
cruise increase. Hope I get to fly a standard one and see the difference
sometime in the future.

Like I said, that was probably a brain fart. So many 175s have had
the 180/CS conversion that I probably mixed up the two.

The POH says it was a GO-300-D and rated 175HP@3200 I wonder if the 30
extra HP came from the increase in RPM alone or was there more to it. I have
heard that many people would not rev it that high though, thinking that it
would come apart although the prop RPM is the real reason for the lower
redline rather than a limitation of the bottom end itself. Or so I have
heard.

Isn't the O-200 the same as the O-300 with two less cylinders? and yet
it is rated at 100HP. Seems like the O-300 should be 150 HP. Someone please
catch me up on this.....

Wayne

It's the geared version of the 145 hp Continental O-300 used in the
regular 172. O-300 redline was 2700 rpm. 147mph ??? I'd say that's
pretty optimistic for the 175 unless it's going downhill :-)

John Galban=====N4BQ (PA28-180)

Wayne wrote:

Just got the original POH, there was no CS prop on the 175 or 175
Skylark. On my plane the prop knob is in the cig lighter hole.

Bill Clarke says there was. Also. Skylark is the name of the 175; there
is not a 175 and a 175 Skylark.

_The Illustrated Buyer's Guide to Used Airplanes_, Bill Clarke.

George Patterson
They say that nothing's certain except death and taxes. The thing is,
death doesn't get worse every time Congress goes into session.
Will Rogers

Hmmm, according to my POH, they are 2two different planes, although not much
different. The cover says
Your '61 Cessna 175B
and
Skylark
Owners Manual

Then in two separate rows, the specs for each. Shows the 175 having the
GO-300-C and the Skylark having the GO-300-D. The C is equiped with a
mechanically engaged starter and a vac pump on the right side of the prop

the D is all electric push button starter and the vac pump is on the rear of
the accessory case.

The dashes were different for the mechanical starter and many of the
"options" were standard on the Skylark.

I am only reading what I see, humbly, I am a 1967 model myself....
Wayne


"G.R. Patterson III" wrote in message
...


Wayne wrote:

Just got the original POH, there was no CS prop on the 175 or 175
Skylark. On my plane the prop knob is in the cig lighter hole.

Bill Clarke says there was. Also. Skylark is the name of the 175; there
is not a 175 and a 175 Skylark.

_The Illustrated Buyer's Guide to Used Airplanes_, Bill Clarke.

George Patterson
They say that nothing's certain except death and taxes. The thing is,
death doesn't get worse every time Congress goes into session.
Will Rogers

John Galban wrote:
: "Wayne" wrote in message ...
: Just got the original POH, there was no CS prop on the 175 or 175
: Skylark. On my plane the prop knob is in the cig lighter hole.

: Really? Sorry about that. I've flown about 4 examples of the 175
: over the years and half were O-360 conversions. I thought they all
: had a CS prop. Oh boy. There go the brain cells :-(

A guy on my field has a constant-speed prop on his GO-300 powered cessna.
It's a Cessna 172 "Powermatic", which is what they called the 175/Skylark
after it got it's bad reputation. The CS prop is from the factory, the prop
governor is mounted on the back side of the reduction gear housing on top
of the engine.

Any you guessed it, people wouldn't rev the engine high enough, AND they'd
use the prop to decelerate (backdriving the engine), which is a no-no with
a geared engine. So, these engines got a bad reputation.
--
Aaron Coolidge (N9376J)