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.

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)

Interesting. I noticed on a flight the other day (first major flight since
Annual) that I was at or above redline on climbout, and had a lot of trouble
keeping it below redline at cruise. We'd almost never seen redline before
except on fast descents at cruise power. (1974 Archer). The muffler was
replaced at annual, and this problem has suddenly appeared. The prop was
filed and painted at Annual, but nothing else changed. I joked with my
partners that perhaps the prop was repitched, or that the engine was making
20% more power. Perhaps it IS now making more power. Guess we need to look
at the prop after all.

--
Bob (Chief Pilot, White Knuckle Airways)


wrote in message
oups.com...

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)

If your tach is accurate, my thought is does it ever go over redline?






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.

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.

Appreciate your thoughts.

Thanks,
Nathan

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.