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PA28: Difference in constant speed prop vs fixed pitch



 
 
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  #1  
Old October 7th 04, 03:11 PM
Nathan Young
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Default 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!!!


  #3  
Old October 7th 04, 04:30 PM
zatatime
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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
  #4  
Old October 7th 04, 05:09 PM
G.R. Patterson III
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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.
  #5  
Old October 7th 04, 05:42 PM
Aaron Coolidge
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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
  #6  
Old October 7th 04, 09:02 PM
PaulH
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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.
  #7  
Old October 7th 04, 09:35 PM
MC
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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.)
  #9  
Old October 8th 04, 03:38 AM
Aaron Coolidge
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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
  #10  
Old October 8th 04, 11:58 AM
Matt Whiting
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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

 




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