Cruise speed - 360 with a Fixed Pitch Prop?

[moespeeds]

For the guys running fixed pitched props with a 360, what kind of cruise speeds and climb rates are you seeing?

Anyone running a 3 blade FP?

Asking for a friend.

[bifft]

I'm running a O-360 with a Catto 3-blade on my 8A. I bought a used "RV-4" prop, design specs from the dataplate:
Diameter: 66 inch Pitch: 76" RV-4
Engine O-360 Design PM 2800
Prop Red Line RPM max 3200

For max speed I get 165 KTAS at 8000 MSL and 2800 RPM. But since the redline on the engine is 2700, I usually run it at 145-150 in cruise. 145 KTAS at 8000 MSL comes out to 8.5 gph.

On climb I get around 1250 fpm, that is also at 8000 MSL. The ground around here is 5000, so I did my climb testing up that high. I estimate I should get about 1400 fpm down at sea level, if I ever take my plane there.

[PhatRV]

I guess the top speed can vary with the ground adjustable fixed pitch propeller too.

[mike newall]

"Asking for a friend....."

Hahahahahahha

Love it.

Fit a C/S prop and enjoy the full fun that an 8 can provide

I'll get my coat.....

[moespeeds]

Originally Posted by mike newall

"Asking for a friend....."

Hahahahahahha

Love it.

Fit a C/S prop and enjoy the full fun that an 8 can provide

I'll get my coat.....

There's always that one guy....

I'm quite happy with my Whirlwind 200RV. I really am asking for a friend.

[Scott Hersha]

If your fixed pitch prop is pitched for cruise (2700 RPM @ WOT), then your top cruise speed should be the same with both props - both being limited to 2700. The fixed pitch might have a slight speed advantage because of its lighter weight. That’s what I found out when running against two O-360 powered RV8’s with carbon fiber Hartzells in my RV4 with it’s carbon GA Sensenich at WOT at about 1,000’ AGL. I was 1-2 knots faster. The trade off was in takeoff distance and initial climb. I could still get off the ground in less than 500’, and climb to pattern altitude by the end of our 5500’ runway, but the CS RV8’s could get off a little shorter and initial climb was better. Cruise climb at about 135 KIAS was about the same at WOT, the fixed pitch being at a lhigher RPM/ lower MP. The biggest difference I’ve seen in my airplanes is that for a given percentage of max power (ie. 65%), the fixed pitch will be running at a higher RPM - with a corresponding lower MP, because you can’t run WOT at 65% unless you are relatively high, and then you’ll likely see something close to 2700 RPM. There’s nothing wrong with this. Lycoming says you should be able to run this engine at 2700 to TBO without problems.

[YvesCH]

My specs are:

Engine: Superior IO-360-M2S with dual PMag

Prop: Catto 3 blade, 68" diameter, 76" pitch

75% Power:
@3000ft: 2510rpm / IAS 156kts / TAS 165kts / 24.4" MP / 8.9 usg/hr
@6000ft: 2610rpm / IAS 159kts / TAS 174kts / 22.8" MP / 9.1 usg/hr

55% Power:
@3000ft: 2220rpm / IAS 136kts / TAS 144kts / 20.1" MP / 6.8 usg/hr
@6000ft: 2220rpm / IAS 134kts / TAS 152kts / 19.1" MP / 7.1 usg/hr

Those are measured values of my flight testing... But not yet lean of peak.

Then also the climb performance as well as takeoff and landing performance. But they were done when I did not yet had to much experience (below 30 T/O and LDGs in total) thus they may could be improved.


Regards,

Yves Heller

[humptybump]

Originally Posted by moespeeds

fixed pitched props with a 360 - cruise speeds and climb rates

I flew and RV-8 with an O360 and a Catto 2-blade pitched for cruise.

The initial climb was 2000fpm at sea level and it tapered to 1500 rpm by 4000ft.

It would "frugal cruise" at 160kts. Above 6500ft the fuel flow was 8.5gph or less as altitude increased.

[wilddog]

Rv-8, Titan IO-370, WW GA prop, 1032#, WOT @ 7750’ measured with auto-pilot and 4way GPS runs avg. 179kts@2780rpm, 22.8”MP. Goes faster down low. Have not measured climb but it is sufficient. Engine is low CR on Mogas, Slick and SDS, AFP FI on cold air slump, 4pipe exhaust.

[WA85]

I know the thread was asking about 360 cruise speeds with a FP prop....but just a data point.

My RV-8 with an IO-320, W-W ground adjustable prop cruises at 155 kts true airspeed at 65% power (as computed by the Dynon SV) at 7.5 GPH rich or peak. 75% at 8.5 GPH is 163 kts true airspeed, WFO at 7500" DA is 173 kts true airspeed at 13.5 GPH. Reducing drag and weight are the keys to speed and climb. I have my W-W pitched for best climb (1200 fpm at 115 kts Indicated airspeed through 5000 DA), but this leads to slight prop overspeed at WFO. I have pitched the prop for best speed and made it to 177 kts true airspeed with a significant drop in climb performance. Yes, a C/S prop would be nice, but my engine isn't plumbed for a prop governor, so sometimes I just happy to have an RV-8 and the ability to go fly...