Cherokee 180 prop RPM

If your tach is correct within reason. It may not be the prop is under
pitched. But rather filed away too much and really under sized. Is it
really old?




Nathan Young wrote:

On Thu, 13 Apr 2006 19:51:47 GMT, "Mark" wrote:


I have a '71 PA28-180, with a fixed 60" pitch Sensenich prop. This is
the standard cruise prop for a PA28-180.

The POH indicates that 2700 RPM should only be able to be achieved
through 7000ft DA.

I am able to hit redline (2700 RPM) in level flight up to 11500 feet
density altitude. POH indicates that it should achieve about 2550.

It has operated this way as long as I can remember (several years) so
it is not a new phenomena.

So what could cause this? Prop pitch, poorly calibrated tach? Any
others? My plane has all of the K2U speed mods, so the reduced drag
probably plays a role.

I am able to achieve close to 150mph true airspeed at max cruise,
while the POH indicates 140mph for book. This makes me think the prop
RPM indications might be accurate.


You can check your tach for free with a portable computer and this program
http://www.tunelab-world.com/rpmsound.html


Cool thanks. I run a tablet PC in the plane, so that is an an easy
one to try.

-Nathan

On Fri, 14 Apr 2006 10:32:15 -0400, The Visitor
wrote:

If your tach is correct within reason. It may not be the prop is under
pitched. But rather filed away too much and really under sized. Is it
really old?

I do not know the actual age of the prop, but I did send it for an
overhaul last year and it passed. I know nothing of the fixed pitch
prop overhaul process, but I hope it involves checking the length,
ptich, and balance. Will have to talk to my A&P.

Nathan Young wrote:
: I have a '71 PA28-180, with a fixed 60" pitch Sensenich prop. This is
: the standard cruise prop for a PA28-180.

: The POH indicates that 2700 RPM should only be able to be achieved
: through 7000ft DA.

: I am able to hit redline (2700 RPM) in level flight up to 11500 feet
: density altitude. POH indicates that it should achieve about 2550.

Back when I had my Cherokee 180 I was able to pull well over redline
RPM at every altitude that I checked. This was a '68, no speed mods.
I think that I checked up to and including 11500 DA but I just can't
remember (and a test flight is out of the question!).
--
Aaron C.

On Fri, 14 Apr 2006 13:24:11 GMT, Nathan Young
wrote:

On Fri, 14 Apr 2006 13:06:55 +0000 (UTC),
wrote:

: landing gear/brake assembly fairing
Allegedly provide big benefit... +5mph or so. We're working on getting a field
approval for our PA-28-180 to use Warrior fairings.

This is true.

I take the fairings and wheel pants off occasionally to clean up the
brake fluid/dust (that gets everywhere) and to check on the status of
the brakes.

If I fly without the wheelpants, I notice a few mph difference, and
the plane floats less on landing.

A Cherokee that floats?

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

-Nathan

The Visitor wrote:
If your tach is correct within reason. It may not be the prop is under
pitched. But rather filed away too much and really under sized. Is it
really old?


I'll go with that answer! I always wondered why the prop on my
Cherokee 180 would turn redline speeds at 11K ft. when the book said it
shouldn't. When I put the new engine on last summer, I sent the prop
to the prop shop and found out why. 36 years of filing had left the
prop substantially thinner than standard (although it was still 76"
long). Prop shop said it was out of spec., so I had to shell out for a
brand new one. When I put the old and the new prop side by side, they
didn't even look like the same model.

With the new prop, the rpm now maxes out where the book says it
should.

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

Roger wrote:
: If I fly without the wheelpants, I notice a few mph difference, and
: the plane floats less on landing.

: A Cherokee that floats?

With aftermarket wingtips and VG's on it, a Cherokee actually floats quite a
bit in ground-effect. At least up to the point where it mushes.

-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

In article ,
wrote:

Roger wrote:
: If I fly without the wheelpants, I notice a few mph difference, and
: the plane floats less on landing.

: A Cherokee that floats?

With aftermarket wingtips and VG's on it, a Cherokee actually floats quite a
bit in ground-effect. At least up to the point where it mushes.

or was he getting at floating in water?

--
Bob Noel
Looking for a sig the
lawyers will hate

On Sun, 16 Apr 2006 13:59:21 +0000 (UTC),
wrote:

Roger wrote:
: If I fly without the wheelpants, I notice a few mph difference, and
: the plane floats less on landing.

: A Cherokee that floats?

With aftermarket wingtips and VG's on it, a Cherokee actually floats quite a
bit in ground-effect. At least up to the point where it mushes.

I would think that still means the landing is too fast. With STOL
mods that lower the stall speed the landing speed would be adjusted to
meet the new stall speeds.

Float normally means too fast. If the mods change the characteristics
so that float is still there at the corrected speeds I'd have some
concern.

Typically it takes a while to get used to flying the proper speeds
after adding mods that reduce the stall speed and increase lift at low
speed.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

-Cory

Quite true, but then the concept of "floating" is relegated to any
approach speed above stall-speed. How much speed margin is included in the POH
approach speed? Indeed, for a "slam-dunk" short-field approach, one hangs it on the
prop with a minimal speed margin that gust factor allows.

All I was trying to point out is that the (deserved) bad reputation of the
PA-28 gliding like a refrigerator with power-off can be partially mitigated by the VG
installation.

As a representative datapoint, I fly the approach in my PA-28-180 at 80mph IAS
with 2-notches. The book value says 85 mph (minus 2 x 3mph for the flaps) = 79mph.
With that speed, I've got just a second or two of "finesse" to do at the flare before
the energy is gone and it sinks on. At 75 mph it's a flare-drop-chunk one-motion.
Given the VG's and aftermarket wingtips on it, that's pretty much book corrected for
5mph or so.

Prior to the mods, coming in at 80mph with 2-notches had a pretty ugly sink
rate associated with it.

-Cory

: I would think that still means the landing is too fast. With STOL
: mods that lower the stall speed the landing speed would be adjusted to
: meet the new stall speeds.

: Float normally means too fast. If the mods change the characteristics
: so that float is still there at the corrected speeds I'd have some
: concern.

: Typically it takes a while to get used to flying the proper speeds
: after adding mods that reduce the stall speed and increase lift at low
: speed.

: Roger Halstead (K8RI & ARRL life member)
: (N833R, S# CD-2 Worlds oldest Debonair)
: www.rogerhalstead.com
:
: -Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

On Mon, 17 Apr 2006 15:23:42 +0000 (UTC),
wrote:

snip
All I was trying to point out is that the (deserved) bad reputation of the
PA-28 gliding like a refrigerator with power-off can be partially mitigated by the VG
installation.
snip

Ever driven a 114 Commander? You'd think it was a refrigerator with
the door open...

TC