PA28: Difference in constant speed prop vs fixed pitch

I have a PA28-180 with a fixed 60inch pitch prop. I have always
wondered how much faster it would be if it had a constant speed prop.

I'm hoping someone with a PA28-235 (which has a constant speed prop)
could look up their speed for a reduced power setting, for example 57%
which would correspond to 135hp (which is 75% of my 180hp).

I know it isn't a 1:1 correlation because the 235 will be heavier, but
it is basically the same airframe, so it might be an interesting
comparison.

As a side note, My PA28-180 has an O-360-A4A, which has a solid
crankshaft, so the only CS option would be via an electric MT
propeller (for which they do have an STC). I'm told this is a $10k
prop, so you'd have to see a heck of a performance gain to make it
worthwhile!!!

I'd get maybe 125-130mph at 57% in my 235.


Trip


In article , says...

I have a PA28-180 with a fixed 60inch pitch prop. I have always
wondered how much faster it would be if it had a constant speed prop.

I'm hoping someone with a PA28-235 (which has a constant speed prop)
could look up their speed for a reduced power setting, for example 57%
which would correspond to 135hp (which is 75% of my 180hp).

I know it isn't a 1:1 correlation because the 235 will be heavier, but
it is basically the same airframe, so it might be an interesting
comparison.

As a side note, My PA28-180 has an O-360-A4A, which has a solid
crankshaft, so the only CS option would be via an electric MT
propeller (for which they do have an STC). I'm told this is a $10k
prop, so you'd have to see a heck of a performance gain to make it
worthwhile!!!

On Thu, 07 Oct 2004 14:11:19 GMT, Nathan Young
wrote:

I'm hoping someone with a PA28-235 (which has a constant speed prop)
could look up their speed for a reduced power setting, for example 57%
which would correspond to 135hp (which is 75% of my 180hp).


you'd be better off comparing to a 180 Arrow with the gear down. Same
engine, simialr weight and airframe.

z

zatatime wrote:
: wrote:
:I'm hoping someone with a PA28-235 (which has a constant speed prop)
:could look up their speed for a reduced power setting, for example 57%
:which would correspond to 135hp (which is 75% of my 180hp).
: you'd be better off comparing to a 180 Arrow with the gear down. Same
: engine, simialr weight and airframe.

I think the Arrow gear is much draggier than the fixed gear. Still, both
comparisons would be interesting.
--
Aaron Coolidge

Aaron Coolidge wrote:
I think the Arrow gear is much draggier than the fixed gear. Still, both
comparisons would be interesting.

It definitely is !
I lost about about 25 kts when a hydraulic leak caused the gear
to automatically deploy in an Arrow IV.
(I think most of the drag comes from the gear doors.)

MC wrote:

: I lost about about 25 kts when a hydraulic leak caused the gear
: to automatically deploy in an Arrow IV.
: (I think most of the drag comes from the gear doors.)

I was basing my judgement on (1) My Cherokee 180 glides like a rock, but (2)
compared to an Arrow with the gear out it seems like, well, a more
aerodynamic rock, anyway!
--
Aaron Coolidge

Aaron Coolidge wrote:

MC wrote:

: I lost about about 25 kts when a hydraulic leak caused the gear
: to automatically deploy in an Arrow IV.
: (I think most of the drag comes from the gear doors.)

I was basing my judgement on (1) My Cherokee 180 glides like a rock, but (2)
compared to an Arrow with the gear out it seems like, well, a more
aerodynamic rock, anyway!

Try adding a 3 blade prop to the Arrow. You then lose the aerodynamics
of the rock!


Matt

Nathan Young wrote:

I have a PA28-180 with a fixed 60inch pitch prop. I have always
wondered how much faster it would be if it had a constant speed prop.

FWIW -- Maule makes the MX-7-180 with both fixed pitch and CS props. They get 10 mph
faster cruise, 280 fpm better climb, and a 250' reduction in takeoff distance with
the CS prop.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

At any altitude that permits you to develop 75% power with your
current prop, a constant speed prop won't gain you an inch unless you
want to fly at a higher power setting.

What the CS prop primarily gives is better climb and increased drag in
descent if you need get down in a hurry.

On 7 Oct 2004 13:02:37 -0700, (PaulH) wrote:

At any altitude that permits you to develop 75% power with your
current prop, a constant speed prop won't gain you an inch unless you
want to fly at a higher power setting.

Can you better explain this? My understanding is that a fixed pitch
prop is typically a compromise in both takeoff pitch, and cruise
pitch. Using the typical car driving analogy - a prop that is stuck
in 3rd or 4th gear in a 5 speed transmission. So I would think a CS
prop would net gains at both cruise and takeoff/climb.

What the CS prop primarily gives is better climb and increased drag in
descent if you need get down in a hurry.

I've often thought a CS prop would be very beneficial in long
descents. I often cruise @ 8-11k feet, and during descent, it is easy
to redline the engine, so I have to remove some power, which decreases
the airspeed.