VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #1  
Old 11-11-2011, 10:44 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default 155kt cruise?

Hey guys, I'm asking this question for my dad who owns a very nice RV7 with 180 hp and a 3 bladed CS prop. I can't remember who makes the prop. Anyway, it has an amazing climb but cruise at 2450 or so is right at 155 kts true at 8.5 gph.

How is it that I'm seeing guys with less power cruising at 165 kts? I know the 3 bladed prop will have a better climb than a 2 bladed, but the cruise is going to be a little slower. How much slower? I think it weighs around 1100 full IFR, glass panel.

I just wanted to see how some of you guys are getting faster cruise speeds. I know Smokey's RVX can cruise at 160 KTS easily. Of course that's a light, slippery little plane.

Here's a quick video of the plane starting up last month.

http://www.youtube.com/watch?v=9-x-2UTXuGE

Last edited by steve91t : 11-13-2011 at 07:21 AM.
Reply With Quote
  #2  
Old 11-11-2011, 11:24 AM
Tandem46's Avatar
Tandem46 Tandem46 is offline
 
Join Date: Jan 2005
Location: Broomfield, CO
Posts: 639
Default

I've always got 170-172kts True above 8k on 8.5gph. That same 8.5gph down low only gives me 150-155kts true. I'm running IO-360 with CS prop. 1070lbs empty.
__________________
RV-7 Flying since 2004
1,100 hrs+
Reply With Quote
  #3  
Old 11-11-2011, 11:30 AM
craigvince's Avatar
craigvince craigvince is offline
 
Join Date: Sep 2006
Location: Stockton, CA
Posts: 1,207
Question Yeah, my first thought too....

At what altitude are you cruising at 155 kts?

I can pretty consistently get 170kts at 12k, which is where I prefer to ride, but down low you're not going to see that. By the way, I've had an RV-7A at 17,200 feet but it would only do about 140kts TAS.
Reply With Quote
  #4  
Old 11-11-2011, 11:32 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Sorry, this is 8000ft or so.
Reply With Quote
  #5  
Old 11-11-2011, 11:35 AM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,351
Default

As it has been mentioned, it depends on a number of factors including to check to see if you have an accurate pitot/static setup to get a good IAS.

My typical TAS/burn rate is very much in line with the above posters.
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
Reply With Quote
  #6  
Old 11-11-2011, 11:45 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Well, everything seems to match the GPS. We were at 9000 last month showing 155kts true. GPS said we had 7 kts on the tail, showing 162 across the ground.

What else could it be? From some of the comments he's gotten, especially from mechanics, it's one of the best built RV's they've seen. It's rigged perfectly, and the engine runs flawlessly.

Is it the prop?

I mean, 15-18 kts is pretty substantial.

Steve
Reply With Quote
  #7  
Old 11-11-2011, 11:55 AM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Just got clarification, 65% power, 2450 RPM in cruise at 8000 ft. The 155kt cruise matches Vans numbers if he were using 55% power.

Last edited by steve91t : 11-11-2011 at 11:59 AM.
Reply With Quote
  #8  
Old 11-11-2011, 11:58 AM
NDrv8r's Avatar
NDrv8r NDrv8r is offline
 
Join Date: Dec 2009
Location: Bismarck, ND
Posts: 212
Default

do a gps box to verify the speed. Then you know you have a power problem if the actual speed is verified low, or an indication problem if the actual speed is higher.

right now I am getting around 165kt cruise at around 8gph, 8000 da.

flat out 185kt at 3000 da, about 16gph.

I am looking for some missing manifold pressure from my snorkel. A winter project perhaps.
__________________
Larry Buller
RV7A slow build, Tip up, IO360 200hp, Catto 3 blade, Dynon Skyview, arinc 429, ems, SV transponder, Garmin GNS430w, Aera 560, Dynon D6.
FLYING!
Reply With Quote
  #9  
Old 11-11-2011, 12:13 PM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Engine is healthy. Just had an annual. If the engine is making proper MP, that means its developing the correct power, right? What is normal MP at 8000?
Reply With Quote
  #10  
Old 11-11-2011, 12:15 PM
steve91t steve91t is offline
 
Join Date: Nov 2010
Location: Huntersville, NC
Posts: 138
Default

Also, I know a 3 bladed prop isn't going to have the cruise of a 2 bladed. How much of a difference though? His is a light weight composite. Company is out of Florida.
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 06:57 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.