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What RPM for Takeoff

fbrewer

Well Known Member
In my RV-6, when taking off from KGTU (789' msl), I get appropriate manifold pressure of 29+ inches (depending on barometric pressure), but I only get 2340 rpm.

The motor has a fixed pitch prop.

Is this rpm appropriate for takeoff?

We have an IO360
 
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Right on

I have the same engine and a Sensenich fixed pitch prop. The quoted static RPM is around 2150 which is bang on. As the speed increases and the load on the prop decreases you'll get an increase in RPM obviously.

But yeah that's right on.

Simon
 
Just checked one of my flights.

Carb version of O-360 with the metal Sensenich prop at 83" pitch -

2206 RPM static

2250 RPM accelerating through 25 kts on the runway during take off

MAP was around 26" with a Density Altitude of 5600 ft. at an elevation of 2940 ft.

Sensenich states that the Static RPM should be 2050 to 2250, and interestingly I've never seen a correction for static rpm for differing Density Altitudes.
 
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Anyone have any numbers for an O-320? I' m seeing about 2200 static, but have told we should be seeing closer to 2350?
 
Y'all need to remember that there will be significant variation in static/takeoff rpm with various brands/pitches of fixed pitch props. 'Traditional' type fp props will have higher static if they're cut for climb, and lower if cut for cruise. Flexible props like the old Bernie Warnke 'almost constant speed' fp props will show higher static while maintaining the same cruise rpm as a 'cruise' prop, assuming same MAP.

So it's not really productive to ask someone else about their numbers, unless they have exactly the same airframe, t/o weight, engine, propeller, etc, as you.

The only really useful number to me is rpm at full throttle, leaned for best power, at ~8,000 feet, along with true airspeed at those settings. (Might not apply to the Sensenich metal f/p for 160HP, since you can't run it above 2600.)

Charlie
 
9:1 O-320, Vetterman crossover, mags, Carb that flows 14gph wide open in flight, 79 inch pitch 70CM6 (between cruise and climb), 2300 plus rpm once all unstalled at about 30 or so knots static std day about 800'msl.
 
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Most 360's with FP props around S/L produce about 150-155HP initially (depending on the health of yr power plant) which equates to around 2250-2350rpm. CS really makes a diff but there's other things to consider with a CS.
Formula: static RPM/rated RPM(2700)xHP
 
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I have a O-360 180hp with a FP prop in an -8 and regulatory fly from a field that is 1040MSL, and get 2300 on take off. Your numbers seem about right. Here inlies the problem with a FP prop! :)
 
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