VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 07-29-2012, 07:33 PM
Jeff R's Avatar
Jeff R Jeff R is offline
 
Join Date: Jun 2007
Location: Merritt Island, FL
Posts: 602
Default Right prop for RV-9 IO-320?

I am well into my flight testing but I don't think the prop I have (Sensenich 79" that Van's recommends and as supplied as part of my engine/prop package) is correct. At WOT (though at full rich), I get maybe 2,420 PRM in level flight. During takeoff, I get no more than 2,200 RPM, and this is with a fairly shallow departure (in order to keep CHT's down). This RPM makes me nervous, as Sensenich says to avoid operation between 2,150 to 2,300 RPM due to engine/prop resonances.

At a 2,300 RPM cruise with a Density Altitude of around 4,500 feet, I am indicating 120 kts with a TAS of 128 kts (148 mph). I don't have fairings, so this speed is somewhat reasonable. But, with the top RPM not very much higher than the restricted range, and with takeoff occurring in the restricted range, it would appear I have a mismatched propeller.

Any thoughts?
__________________
Jeff Rosson
Repeat Offender
RV14 - Working on Empennage/Tail Cone
RV9A - Completed! First flight on July 18, 2012!
Based at Merritt Island, FL (KCOI)
VAF Number: 1170


----
Star Trek Quote: "Logically, it could work. Also, logically, there are a hundred variables, any one of which could put us in a worse position than we're in now." Mr. Spock in Return to Tomorrow
Reply With Quote
  #2  
Old 07-29-2012, 07:52 PM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,887
Default

Dump the Sensenich and call Craig Catto.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #3  
Old 07-29-2012, 08:02 PM
Mel's Avatar
Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
Default

Don't make any rash decisions until you have all the fairings on.
An increase in airspeed will allow the rpms to come up.

On the other hand, I can't discount Bill's suggestion either. I'm a STRONG believer in Catto Props!
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
Reply With Quote
  #4  
Old 07-29-2012, 08:20 PM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,887
Default

Quote:
Originally Posted by Mel View Post
Don't make any rash decisions until you have all the fairings on.
An increase in airspeed will allow the rpms to come up.
...
Sorry, I missed that you didn't have your fairings on yet. As Mel said, wait until you have them all on before making any changes.

Remember, you will gain close to 10 MPH/Knots for the gear leg fairings and 5 MPH/Knots for the wheel pants. That will let the RPM come up. It will also help your cooling as you will be pushing more air through the cowling.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #5  
Old 07-29-2012, 08:35 PM
Jeff R's Avatar
Jeff R Jeff R is offline
 
Join Date: Jun 2007
Location: Merritt Island, FL
Posts: 602
Default

Sounds like good advice, but are there any comments on operating in the restricted range? I guess this applies for long term operation, but a lot of takeoffs and full power climbs eventually adds up to a lot of time.
__________________
Jeff Rosson
Repeat Offender
RV14 - Working on Empennage/Tail Cone
RV9A - Completed! First flight on July 18, 2012!
Based at Merritt Island, FL (KCOI)
VAF Number: 1170


----
Star Trek Quote: "Logically, it could work. Also, logically, there are a hundred variables, any one of which could put us in a worse position than we're in now." Mr. Spock in Return to Tomorrow
Reply With Quote
  #6  
Old 07-29-2012, 08:39 PM
ronoc74 ronoc74 is offline
 
Join Date: Jan 2005
Posts: 72
Default

I have a 160hp XP-IO-320 with an 81" Sensenich and it runs about 2220 rpm static and 2340 at 110 knots indicated while climbing at WOT. It will just exceed 2600 rpm in speed runs at 1000 ft and 7500 ft but I have all the fairings on. It may be worth checking your MP reading at WOT. Mine is 29.6" at 50 ft above sea level during the takeoff run. Maybe your throttle is not quite wide open.
__________________
Conor McCarthy
RV-9A 90990 flying
QLD, Australia
Reply With Quote
  #7  
Old 07-29-2012, 09:01 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
Join Date: Jan 2005
Posts: 3,646
Default

I may have the opposite problem with my Catto. With no fairings or wheel pants on and at about 75% power (about 2500 rpm), I'm showing around 135 knots TAS at about 5-6K density. At WOT, full rich, I can easily get it to go above the engine red line of 2700. I'm guessing I'll have more problems once I get the fairings on and once I start using the mixture knob. ???

For a prop pitched primarily for cruise, at what density altitude should full throttle in straight and level flight normally result in near-red line engine rpms? Stated differently, is there such a set of numbers one looks for to determine proper pitch on a prop?
__________________
Steve M.
Ellensburg WA
RV-9 Flying, 0-320, Catto

Donation reminder: Jan. 2021

Last edited by alpinelakespilot2000 : 07-29-2012 at 09:12 PM.
Reply With Quote
  #8  
Old 07-29-2012, 09:20 PM
ronoc74 ronoc74 is offline
 
Join Date: Jan 2005
Posts: 72
Default

Steve, it depends on your priorities. At about 8000' density altitude I can run WOT and LOP at just under 2400 rpm which is a good economical full throttle cruise. If I wanted better takeoff performance or to cruise LOP at 2500 rpm I would have a 79" pitch. But judging by the numbers you are getting with no fairings your prop needs to be re-pitched higher even to be a normal "climb" prop.
__________________
Conor McCarthy
RV-9A 90990 flying
QLD, Australia
Reply With Quote
  #9  
Old 07-30-2012, 07:40 AM
MS19087's Avatar
MS19087 MS19087 is offline
 
Join Date: Nov 2006
Location: West Chester, PA
Posts: 689
Default My Whirlwind GA200 has been great

I swapped out my Sensenich last year for a WW Ground adjustable prop. Took a few attempts to pitch it correctly, but now I have it dialled in nicely. As with any fixed pitch prop there are compromises, however I pitched mine for max RPM at cruise (in order not to redline). I get 2150 static. Solo I get 2200+ fpm climb - dual I get 1700++ fpm. It is always hard to give a top speed number due to test conditions . . . Im happy though getting 7.5-8.0 gph at 75% with cruise speeds (ranging from 145-160kts) Great all around performer.
__________________
Mark
RV-9A; Sold
RV-14A; Building
2020 =VAF= donor
Reply With Quote
  #10  
Old 07-30-2012, 09:48 AM
jclark jclark is offline
 
Join Date: Jan 2005
Location: Columbia, SC
Posts: 804
Default

Do NOTHING with the prop ...

Until you are sure that the plane is all cleaned up with fairings AND that you are getting good reading from ALL instruments.

I have run that combo (as well as the Catto). There are 10;s of knots still to be had.

James
__________________
James E. Clark
Columbia, SC
RV6 Flying, RV6A Cowling
APRS
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:03 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.