Tri-Pacer 150 Airspeed vs. RPM

[Subsonic]

Completed my 5 hour solo cross country requirement last weekend in my Tri-Pacer for my private certificate. Getting close to completion now. I did 2.2 hours CC Saturday, 164 nautical mile loop (OAR PRB KIC OAR) and 3.4 hours Sunday going 254 NM (OAR O27 FCH OAR). It was hot over mid-central valley of CA on Sunday, 110F in a lot of places on the ground and I was at 5,500' on the first two legs with oil temp running around 220F, OAT reading 83F so I had RPM set to 2,300 or so and IAS of 100mph to keep oil "cool". That 100mph airspeed was backed up by my GPS ground speed always within a couple miles an hour. Most of the time, the two speed indications matched. The last leg was flying due west back to my coastal hangar with the mountains in between forcing a climb to 6,500, again oil temps on climb out from Fresno Chandler was at 225-230F, so I was climbing slow at 3-400 FPM (2,450 RPM) to get to cruise alt and then setting power to about 2,300 RPM and observing 98 to 100 mph most all the way home. My initial full power take off and climb out was at around 900 to 1,000 fpm to 2,000 feet with oil temp going from 180 to 230F, so then I'd back it down because of the heat. Yes, I was leaning mixture beginning at 4,500' altitude. Anyway, that's a little background on my trips and I was wondering about cruise speed vs. RPM settings. Speed at 99 to 100mph with 2,300 RPM indicated was so consistent for so long I was wondering about other Tri-Pacer 150's demonstrated performance out there. I'm putting on wheel pants soon, and will make similar measurements to compare. Any comments?

[Glen Geller]

Sub, what prop do you run on your PA22?

GG

[Frank Green]

Typically run 2,400 at 105 mph with a 61" prop. I have a 58" I'm going to try.

[Subsonic]

Glen, My propeller record log says it's a Sensenich M74DM Serial #18688 manufactured in May of 1956. From my Owners Handbook it states the pitch is 61". I believe it to be original equipment.

[Subsonic]

Frank, I think your numbers are close to mine. If I increased RPM to about 2400 I'd see an extra 5 mph, and 2500 RPM would get me to 110 to maybe 113 mph. I'm looking at my "Altitude vs. True Airspeed and RPM At 75% Power Cruise" chart in section II, page 25 of my Owners handbook, and frankly that airplane characterized with those curves will outfly mine as the 75% power chart indicates 127 mph at 2,500 RPM at 3,000 feet. My previous speed testing around that altitude on a nice cool day shows about 120 mph at the same 2,500 rpm. I'm usually near full on gas, say 25 to 30 gallons onboard, and my plane weighs 1139# dry, I weigh 150#, and I have about 15 pounds of gear onboard. My lift struts are Airframes Alaska sealed and they're larger in cross section than the originals. My wing root strut fairings barely fit without the rubber trims, and the fairings at the fuselage anchor point where the V comes together needed significant trimming and work to get them to fit back on. All else is stock, so I'm thinking my plane has just a bit more aero drag than the mythical PA22-150 in the owners book. I've wondered about my somewhat ugly fabric covering on my wingtips leading edge as being a bit draggy, too. I've previously mentioned my engine mounting geometry is about a degree lower in angle than spec 4 degrees down. Does anyone out there achieve the Owners Handbook numbers?

[JPerkins]

I did when mine was still a Tri Pacer with 150hp and M74dm 58" pitch. Only time I'd see over 120 mph on the airspeed now is in a dive.

[Frank Green]

I tried pants, too hard to step over to get in. Easier to step on the tire. The nose pant made the rudder pedals feel funny. I don't run strut cuffs, I like too look at the forks and bolts on preflight. Otherwise I'm happy with the airplane the way it is and kind of figured the book #s were from the sales dept.