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  #1  
Old 04-19-2022, 11:16 AM
Wahi-Air Wahi-Air is offline
 
Join Date: Apr 2022
Location: Hamburg, Germany
Posts: 2
Unhappy RV9a Performance: Need your x-check

Hi folks,

I am writing you as I need some guidance on where my speed is missing....

Summary:
  • I believe to be at least 10-15kt short of TAS at cruise. Question is aerodynamics vs. engine performance... I can´t think of aerodynamics...
  • Would be great if you can let me know where to look for some more knots


The plane:
  • RV9A / (Y)O-320-D2G (ordered from Vans), carburated, fixed pitch Sensenich 70CM7S9-0-79, dual mag ignition, all flaps and controls even and on surface, gear boots installed

My performance (all measured with Dynon HDX):
  • 5000ft, 77%, 2500RPM throttle wide open, lean, 35L/h (9.2USgls), 144KTAS (166TAS mph)
  • at take-off on MSL I am reading 2200RPM

The performance of a build-alike RV9a, same config:
  • 6000ft, 77%, 2500RPM, 39L/h, 161KTAS (186TAS mph)
  • 6000ft, 63%, 2300RPM, 34L/h, 145KTAS (167TAS mph)

Here´s a link of a 2.5h flight showing the same data:
https://apps.savvyaviation.com/fligh...9-4ef7574aa473

I AM REALLY GRATEFUL FOR ANY THOUGHTS AND INSIGHTS!!!
Cheers
Sunit
__________________
______
Sunit | RV-9A | D-ESVM
> (Y)O-320-D2G, FP, Dynon HDX, flying since 04/2014
> Homebase EDHS / Hamburg / Germany
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  #2  
Old 04-19-2022, 02:32 PM
edclee edclee is offline
 
Join Date: Aug 2008
Location: Lancaster, SC
Posts: 265
Default Speed?

The performance of a build-alike RV9a, same config:
  • 6000ft, 77%, 2500RPM, 39L/h, 161KTAS (186TAS mph)
  • 6000ft, 63%, 2300RPM, 34L/h, 145KTAS (167TAS mph)

Here´s a link of a 2.5h flight showing the same data:
https://apps.savvyaviation.com/fligh...9-4ef7574aa473

I AM REALLY GRATEFUL FOR ANY THOUGHTS AND INSIGHTS!!!
Cheers
Sunit [/quote]

I have a 9A, same engine but fuel injected. My TAS is essentially the same as your example similar aircraft, that is: pretty close to 186 mph TAS at that power setting and altitude. Mine pretty much holds that TAS at higher altitudes at WOT and leaned to best power, although I seldom run it at best power, normally at LOP about 50 deg F but naturally lower airspeed.

I suspect your indicated (and therefore reported TAS) is not accurate. Have you and this other aircraft flown side by side to verify the airspeed indications correspond?
Ed
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Sonex/Corvair 2016 Finished, Sold 2020
RV-9A 2005 Purchased
IO-320 160 hp
Exempt but happily paid for 2022
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  #3  
Old 04-20-2022, 10:32 AM
Snoho3 Snoho3 is offline
 
Join Date: Dec 2012
Location: Snohomish, WA
Posts: 171
Default I have the same engine/set up as you...

and will replicate your conditions and advise. Hopefully today if the weather holds.
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RV-9A - Flying as of 12-20-2020
2022 Dues+ Paid and worth it.
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  #4  
Old 04-20-2022, 06:55 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 1,026
Default Altitude?

Is the altitude quoted MSL or DA?

When I had that prop (Sensenich fixed) mounted, 2400 would give me 151 kt TAS AT 6500 ft DA and 21.5”of MAP, approx 71% power per the Dynon...after the static system was corrected. At WOT, 8000’ DA, 2610 rpm, 167 kt TAS, still showing 23.1” MAP. Before correction I would read low. I don’t recall what I would hit at 2500 down low.

Now, wIth the Sensenich GA mounted and set a smidge favoring climb, 8000’ DA and 2700 rpm gives me 166 kts consistently, a little leaning and I can hit 2750 and 169 kts+, with 23.1”-23.2” MAP. Things get busy at that speed. My data consistency got a lot better with the AP. .

I seem to be getting good pressure recovery in the airbox. My airbox is not quite standard. All data runs are solo full fuel at TO.

You do have your gear leg and wheel fairings mounted? That was worth 8-10 kt to me. I was shocked.

I suggest a couple three or four ways backed up by GPS before doing anything else.
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Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor

Last edited by rjcthree : 05-18-2022 at 06:18 PM.
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  #5  
Old 04-20-2022, 08:30 PM
Flying Canuck Flying Canuck is offline
 
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 620
Default

I've got a slow one, IO-320 C/S prop. Looks to be similar to yours. From my last flight:

7500', 22.5", 2350 RPM = 69% Power
34 L/hr
143 KTAS

This is with most of my fairings installed, missing one upper intersection fairing (in a box, just need to install it). I don't think I've ever exceeded 148 KTAS in level flight and that isn't common. I plan 142 KTAS.

I'd love to find a few more knots for my long cross country flights, but I don't really need it most of the time.
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Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018

Added GPS 175 and authorized for IFR April 1, 2021

Interactive map of all of my flights here
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  #6  
Old 04-20-2022, 09:21 PM
cgeyman's Avatar
cgeyman cgeyman is offline
 
Join Date: Apr 2017
Location: Missoula MT
Posts: 270
Default My speeds

My 2003 RV9a with constant speed prop and o-320 DIA engine, faired fully with wheel pants runs 149 kts at 7500 feet MSL at 2400 rpm. I don’t usually run 2500 rpm as I don’t like the extra vibration and fuel burn. I think my plane is pretty average for an RV 9a.
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  #7  
Old 04-21-2022, 07:14 AM
edclee edclee is offline
 
Join Date: Aug 2008
Location: Lancaster, SC
Posts: 265
Default speed

Quote:
Originally Posted by edclee View Post
The performance of a build-alike RV9a, same config:
  • 6000ft, 77%, 2500RPM, 39L/h, 161KTAS (186TAS mph)
  • 6000ft, 63%, 2300RPM, 34L/h, 145KTAS (167TAS mph)

Here´s a link of a 2.5h flight showing the same data:
https://apps.savvyaviation.com/fligh...9-4ef7574aa473

I AM REALLY GRATEFUL FOR ANY THOUGHTS AND INSIGHTS!!!
Cheers
Sunit
I have a 9A, same engine but fuel injected. My TAS is essentially the same as your example similar aircraft, that is: pretty close to 186 mph TAS at that power setting and altitude. Mine pretty much holds that TAS at higher altitudes at WOT and leaned to best power, although I seldom run it at best power, normally at LOP about 50 deg F but naturally lower airspeed.

I suspect your indicated (and therefore reported TAS) is not accurate. Have you and this other aircraft flown side by side to verify the airspeed indications correspond?
Ed[/quote]

Just to clarify my post. The numbers I show here are based on the results of my flights usually by myself, about 1/2 fuel, no other baggage, so I am light. I dont recall my best speeds at near gross at best power since I normally fly LOP and accept the speed loss. I have never actually determined best speed at max gross. Also, my aircraft is polished, only paint is on the fiberglass parts. Also not sure if it makes any difference, but I have a slider, not tip up. I wonder if it makes any difference?
Ed
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Sonex/Corvair 2016 Finished, Sold 2020
RV-9A 2005 Purchased
IO-320 160 hp
Exempt but happily paid for 2022
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  #8  
Old 04-21-2022, 10:40 AM
Snoho3 Snoho3 is offline
 
Join Date: Dec 2012
Location: Snohomish, WA
Posts: 171
Default

-9A, painted, tip-up, all fairings installed except upper main gear intersection fairings. YO-320-D2G, FP Prop. Dynon avionics.

My numbers from yesterday:

5000' MSL
2500RPM
75%
9.2 g/hr
185mph TAS

6000' MSL
2300RPM
62%
7.7 g/hr
165mph TAS

6000' MSL
2500RPM
77%
10.1 g/hr
183mph TAS

This was a quick flight - might try again and take several data points.

To the OP - would be curious what you find if you continue to investigate your aircraft's performance.
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RV-9A - Flying as of 12-20-2020
2022 Dues+ Paid and worth it.
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  #9  
Old 04-21-2022, 04:04 PM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 434
Default Best Speed Altitude

Typically Best Speed will be at 7500' Density Altitude and Wide Open Throttle, which should give very close to 75% power.

Higher or lower than that will not be as good. NOTE, DA, not MSL.

If you are only turning 2400 rpm at that altitude then I don't think you'll see 75%.

All the gear fairings are important. Wheel pants (all 3), gear leg fairings (all 3) and intersection fairings (all 5). With none of that you'll be down around 15 mph.

Rigging can be huge. Make sure you don't have flap or aileron droop.

Run a 3 leg GPS test and plug it into the NTPS spreadsheet. [Search the forums...]
That will give you actual ground speed not some +/- 5% airspeed....

Took me a while, but I have book numbers now!
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Donation made Oct 2021
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  #10  
Old 04-22-2022, 01:25 AM
Wahi-Air Wahi-Air is offline
 
Join Date: Apr 2022
Location: Hamburg, Germany
Posts: 2
Default

thanks guys, really much appreciated.
Next week I will do a long X-country where I can test several settings. Will also check on the 3-leg flight test (though I am not expecting to see a huge change as my GS is always quite close in no wind conditions and does not show me the numbers like 160kts either...).

Will come back to you in a few days.
Cheers
Sunit
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Sunit | RV-9A | D-ESVM
> (Y)O-320-D2G, FP, Dynon HDX, flying since 04/2014
> Homebase EDHS / Hamburg / Germany
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