|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

10-08-2011, 12:06 PM
|
|
|
|
Join Date: Feb 2011
Location: USA
Posts: 3,179
|
|
Performance numbers for RV-8 150hp
Vans does not post performance numbers for an RV-8 with only a 150hp engine but if it's safe to use 150/160ths of the 160hp numbers, then my airplane is about 1% faster than standard
(edit: using the data for 150hp vs 160hp from the RV-4 and RV-6, my plane is about 3% slower than standard for max cruise and 1.5% slower for 75% power at 8000ft.)
I an a buyer not a builder so today I went out and flew all the GPS boxes at 2000ft intervals up to 10,000 ft. The density altitudes were 3400ft up to 12200ft The numbers worked out to 165kts at 3,400ft down to 158kts at 12,200ft.
Throttle was WOT and leaned ROP. It is running a 150HP with a wood prop. Empty weight is 1085lbs (has a pretty massive weight at the prop).
Thanks Van for designing such a well behaved consistent performer!
Last edited by humptybump : 10-08-2011 at 01:21 PM.
Reason: New calculations
|

10-08-2011, 01:07 PM
|
 |
|
|
Join Date: Dec 2005
Posts: 976
|
|
Glad you like the RV-8
Quote:
|
but if it's safe to use 150/160ths of the 160hp numbers
|
Doubt it is... The 180HP "top speed (solo wt)" is 214mph. 160/180 x 214 = 190mph, but the 160HP is stated as 206mph.
If you take the ratio to the 3rd power (160/180) ^ 1/3 it gives 96%, and 214mph x 96% is 205.8mph - almost exact as given. So your 150mph top speed maybe should be (150/160) ^ 1/3 * 206mph = 201.6mph?
I'm sure this will provoke someone who knows what they are talking about to come along
Andy & Ellie Hill
RV-8 G-HILZ
RV8tors
|

10-09-2011, 05:08 PM
|
 |
|
|
Join Date: Dec 2005
Location: Sweden, 67" North
Posts: 68
|
|
All these KTS, MPH, KMH in aviation really confuses me 
__________________
Dennis Isaksson
G?llivare, Sweden
Grew up with an RV-4, SE-XIO
Now: RV-8, Showplanes Fastback. #83218 Under construction, SE-XXO
Engine and avionic installation in progress
|

10-09-2011, 05:11 PM
|
 |
|
|
Join Date: Jan 2005
Location: SC
Posts: 12,887
|
|
Quote:
Originally Posted by Dennis_I
All these KTS, MPH, KMH in aviation really confuses me 
|
It's simple. In the US, we knots for factory built aircraft but for kitbuilt aircraft we use MPH for performance comparison. When talking to Air Traffic Control, it is always in Knots.
I just wish the US would move to the metric system like the rest of the world and be done with it.
__________________
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
|

10-09-2011, 06:02 PM
|
 |
|
|
Join Date: Feb 2006
Posts: 359
|
|
not quite
Quote:
Originally Posted by humptybump
Vans does not post performance numbers for an RV-8 with only a 150hp engine but if it's safe to use 150/160ths of the 160hp numbers, then my airplane is about 1% faster than standard 
!
|
The horsepower required increases to the cube of the speed increase so if you add an extra 9% power you should expect the speed to increase roughly 3%.
So the difference in speed from 160 to 150 hp is actually relatively small.
__________________
---
David Edgemon
RV-9A N42DE
RV-8 N48DE
whats next ??
Track me!
|

10-09-2011, 07:00 PM
|
 |
VAF Moderator / Line Boy
|
|
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
|
|
Quote:
Originally Posted by N941WR
It's simple. In the US, we knots for factory built aircraft but for kitbuilt aircraft we use MPH for performance comparison. When talking to Air Traffic Control, it is always in Knots.
|
Huh Bill? YOU might use mph for kitbuilts, and a bunch of others do as well....but a lot of us follow the Knots rule for all aircraft. The only real reason to use mph is becasue the numbers sound bigger!
I had an aero professor who'd give you an "F" automatically if you didn't use knots - that was what the industry used, that's what you were going to use as an engineer!
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
|

10-09-2011, 08:35 PM
|
|
|
|
Join Date: Feb 2011
Location: USA
Posts: 3,179
|
|
As with all things, what's important is "I'm happy".
All things considered, the plane flies fast and sips fuel.
Trust me, 155kts at under 8gph is a big delta to my other flying favorite - a Stearman going about 100kts and burning 16-18gph. I don't think I'd trade either :-)
Last edited by humptybump : 10-09-2011 at 08:38 PM.
|

10-11-2011, 09:46 PM
|
|
|
|
Join Date: Jun 2005
Location: Hamilton, VA
Posts: 419
|
|
Quote:
Originally Posted by N941WR
It's simple. In the US, we knots for factory built aircraft but for kitbuilt aircraft we use MPH for performance comparison. When talking to Air Traffic Control, it is always in Knots.
I just wish the US would move to the metric system like the rest of the world and be done with it.
|
...just so long as we don't change first to altitude in meters and then convert altimetry to QFE down near the ground the way they do in Russia and China!!!! It makes my bunkie a very busy sort during the approach phase, calling out converted numbers and such!
__________________
Jeff
-8 wings, finishing up
-8 QB Fuse just arrived!!!
|

10-12-2011, 03:45 AM
|
 |
|
|
Join Date: Jan 2005
Location: SC
Posts: 12,887
|
|
Quote:
Originally Posted by Ironflight
Huh Bill? YOU might use mph for kitbuilts, and a bunch of others do as well....but a lot of us follow the Knots rule for all aircraft. The only real reason to use mph is becasue the numbers sound bigger!  ...
|
Sorry Paul, I was thinking about with regard to marketing and as you pointed out, the numbers sound bigger.
__________________
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
|

10-12-2011, 05:04 AM
|
 |
|
|
Join Date: Jan 2005
Location: Charlottesville, Virginia
Posts: 1,230
|
|
Quote:
Originally Posted by N941WR
Sorry Paul, I was thinking about with regard to marketing and as you pointed out, the numbers sound bigger.
|
I'm with Bill on this one!
The one question we as Rv'ers are asked a lot is "how fast does it fly?" and most of these questions are asked by automobile drivers, so it sounds very cool to be able to say "200mph" or just 200. This answer always get responses like WOW.......until some aviator asks the questions about mph or knots? Then we all know the discussion that follows but.......for a brief moment.....it was "200" 
__________________
Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
D100-KMD150-660-TT ADI2- AS air/oil seperator. Vetterman exhaust with turndown tips.
Louisa, Virginia KLKU N94TB
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 06:45 AM.
|