7A real world performance - for those still building/deciding

[hecilopter]

Flying home yesterday in smooth air with Tru track AP on, decided to snap a shot of the panel doing its thing. XP-360, carb, mags, Hartzell blended airfoil F7696 blades.

5400 MSL, DA 6770 ft, OAT 62 F, 182 MPH indicated, 200 MPH true (see Dynon). 25" MAP full throttle, 2300 RPM, 100 ROP. I burn about 8 GPH at this setting. With tailwind was 197 knots across the ground (see GPS). This is about 65 - 67 % power according to Superior chart. I routinely see this at cruise.

 

[Russ McCutcheon]

Hi Rusty,

Cool, however at first glance it looks like your running 75%. I don?t have any fancy computers but 25+23=48, being ROP this is 75% power, that?s how we do it without the computers, might not be exact but close I?m told. Either way you?re doing well!

Russ

 

[hecilopter]

Percent power

My bad. The power chart below is for Sea Level, I don't have one for other altitudes so the percent power is more than stated below.

According to the chart I have from Superior:

http://www.superiorairparts.com/pdf/flliersdocuments/xp-360engine/xp360_specsht.pdf

MAP RPM %Power
25" 2700 81
25" 2600 77
25" 2500 73
25" 2400 69
25" 2300 65

100% power is obtained at 29" MAP and 2700 RPM.

75% Power is obtained at:

MAP RPM
27" 2350
26.5 2400
25.5 2500
24.5 2600
23.8 2700

 

[Randy]

As a point of reference from the alternative engine side:

Using turbocharged Subaru 150 Cubic Inch STI engine turning MT Electric Constant Speed prop.

At 4400 RPMs and 40" MAP I get a solid 8 GPH fuel burn and see 165 Knots TAS, at 8000'.

Power set to 45 "square" at 8000' gives 175 kts TAS, for this setting I do not have an accurate FF recorded but it will be very close to 9 GPH.

47 "square" at 8000' will take it over VNE , and burns more like 11.8 GPH.

Randy C
RV7A

 

[robertahegy]

My 7A would do 204 mph at 8000 msl WOT and 2400 rpm. The burn was just under 10 gph. I also ran a Lycoming 0-360 A1A with a 74" BA Hartzell. I had the thinner 96 blades. Those numbers were at the 1800 lb gross.

Roberta

 

[hevansrv7a]

It's personal preference, I know, but shouldn't your Dynon be set to put you in the yellow arc anywhere beyond manuvering speed (120 kts for the 7A, I believe)?

 

[n5lp]

It's personal preference, I know, but shouldn't your Dynon be set to put you in the yellow arc anywhere beyond manuvering speed (120 kts for the 7A, I believe)?

I'm not sure I can see exactly how his is set up but the yellow arc normally is the caution range, to be flown only under calm or light turbulence conditions. The bottom of this arc is quite a bit higher than maneuvering speed.

 

[videobobk]

For those deciding, another data point (although not from the same RV model.) I ran a test run Saturday in my 9A at 8000 DA and was indicating 8 gph. TAS was 192 mph but with an O-320 at about 75%, fixed pitch Catto three blade and P-Mags. Very close to the same horsepower and 4% more speed from the 7A, indicating it is faster. My 9A has to be higher to get that kind of speed. You could probably get 200 in an O-320 7A--amazing.

Bob Kelly

 

[frankh]

Yes but

I didn't see where the first airplane has EI, that will make a difference

Frank

 

[Webb]

7A with a Superior IO-360 (8.5:1 pistons - 180hp), MT 2 blade CS.

8,000 feet, 2250 rpm, 23.5 MAP, 9.5 gal/hr, 90-100 ROP, 160-162 knots TAS.

For flight planning, I plan 10 gal/hr at 160 knots TAS.

 

[frankh]

Really?

I get 160kts TAS at 7 to 7.5GPH LOP..Might be a bit higher than 8k though and i run a Sam James cowl and a Hartzell 497 C/S

Frank 7a

 

[jthocker]

Rusty
100 deg. ROP at that altitude and 8.0 gph doesn't seem possible at full throttle, with your engine. 10 gph seems more normal to me in my experience with the same engine /prop on 4 planes. Your fuel flow gauge seems suspicious to me.
I hate it when someone nit pics my posts, but I have to remind you of the Hartzell restriction of "continuous rpm not below 2350 when MP above 22 inches".
Best regards

 

[Caveman]

More data to confuse us

Cruise Performance at 8,000? D.A./ 100 deg. Rich of Peak 195 HP IO360-M1B w/ 72" B.A. Hartzell -97 blades.

MPH
TAS RPM MAP F. Flow % PWR

197 2500 22.7? 11.3 70%
200 2600 22.6? 11.8 72%
193 2300 23.0? 10.3 65%
195 2400 22.8" 10.8 66%
174 2300 20.0? 8.7 55%
177 2400 19.5? 9.0 55%

* Indicated true airspeeds are reflected in chart above. Actual True A/S is 4 mph faster than that indicated at about 75% power and 2 mph faster at 65 and 55% power settings. (This is per GPS runs via methodology & spreadsheet provided on K. Hortons site).

This data was downloaded from an AFS 3500 EE while flying on A/P, w/alt. hold, during my phase one testing.

% Power numbers are from a spreadsheet with plug in factors for horsepower and compression ratio that was provided by one of our more mathmatically inclined forum members.

The airplane has a standard Van's F.I. cowl, external com, elt, and xpndr antennas and has no speed mods... yet.

 

[hecilopter]

Further clarification

Sorry if my fuel flow numbers are misleading, I don't have a fuel flow guage. I just divide the Gallons by hobbs time when I fill up on a trip and usually get 8 gals/hr. Sometimes less. This includes startup and taxi time so the number is artificially low. I'm sure it is closer to 9 to 9.5 gals/hr or so.

Per the Superior web site, the XP-360 burns about .5 gal/hr less than an equivalent Lycoming...

http://www.xp-360.com/faq.asp

4. How does that compare to a typical Lycoming 360?
The Lycoming O-360-A1A burns 10.5 GPH at 75% power (compared to 10GPH for the XP-360) and 9.0 GPH at 65% power (compared to 8.7 GPH for the XP-360).

Also in response to Jon's concern above, for the Hartzell Blended airfoil prop with F7496 blades, there are no RPM restrictions when installed on a Superior engine with mags installed.

Restrictions:
SUPERIOR XP-360 RESTRICTIONS:
Hartzell Propeller Model HC-C2YR-1BFP/F7496 is vibrationally approved when mounted on Superior Air Parts model O-360-B1A2 and IO-360-B1A2 engines rated at 180HP at 2700 RPM with magneto ignition and installed in Van's Model RV-6A and similar single engine tractor aircraft. There are no operating restrictions.

http://www.hartzellprop.com/kitplane/kitplanes.asp?kit=VAN003&manufacturer=Vans

Hevans, the bottom of the yellow arc (caution area, smooth air) is 193 mph in a -7. Vne is 230 mph. The Dynon is set at those numbers.

http://www.vansaircraft.com/pdf/speeds.pdf

 

[Randy]

An easy way to get very accurate fuel burn measurements:

Get established at the altitude and power setting you want to check. Start your stop watch at the same time you switch to a full tank of fuel. Fly at the same power setting for awhile and then note the time when you switch the fuel back off of that tank, then when back on the ground, note how much fuel is required to fill the tank. Some simple math will give very accurate results with this technique. It gets even easier if you do it for an even 30 minutes or 1 hour.

This method completley eliminates the climb and descent from the data.

Randy C

 

[sprucemoose]

It's personal preference, I know, but shouldn't your Dynon be set to put you in the yellow arc anywhere beyond manuvering speed (120 kts for the 7A, I believe)?

Actually, the yellow arc is set at Vno, or structural cruising speed. In the -6 its 156 kts, not sure what it is in the 7.

 

[Jamie]

Van's numbers for airspeed markings are here:

http://www.vansaircraft.com/pdf/speeds.pdf

That's what I used to set up the tapes on my Dynon EFIS.