Help with Engine Sizing?

I fly in and out of high altitude airports [6,000 ft - 9700 ft] and am considering the purchase of a fixed pitch 150 hp RV6A. Can anyone comment as to the suitability of that power plant for high altitude?

Thanks,
Tim
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This should be interesting. You'll get a bunch of guys with O-360 powered RVs (and who have never flown a 150 hp RV) who will tell you that you "need" 180 hp. You'll also get responses from some 150 hp/FP RVers who have flown into Leadville, CO in the middle of summer who will tell you the aircraft does just fine.

How long are the runways you will use, and how hot does it get in the summer?

150 hp should be completely adequate, as long as you realize that it won't take-off like a Super Cub. Of course you can never have "too much" power, but that extra power comes with a price (and a weight).

Engines and altitude

Probably fly in and out of some of those same airports. Salida is second home and the mountains the playground. 160 hp fixed but would go with 160 or 180 CS if I had the choice now. Climb rate is fine by most measures but those mountains are close! It would be nice to point it in the direction you are going and head up rather climbing in circles. Note also that the turbulence and waves around the mountains often net out the first 500 to 1000 fpm of climb rate.

A light CS would be ideal.

I'd actually like a turbo or supercharger at times!

My biased opinion

Get 180 HP. CS is a great help too. Resale of a 150 HP, FP prop in this area will be poor IMO.

Hard to answer but some food for thought

timheavers said:

I fly in and out of high altitude airports [6,000 ft - 9700 ft] and am considering the purchase of a fixed pitch 150 hp RV6A. Can anyone comment as to the suitability of that power plant for high altitude?

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RV performs well but you left out type of runway, soft, slope, obstacles and weight you want to fly at (dual or solo).

If you are really going to fly out of high altitudes with two up, assuming the runway is short, obviously MORE HP and most definitely a constant speed prop are better. I would probably want a constant speed prop on a 160HP before a fixed prop on 180 HP, I think. The constant speed prop pays for it self on TAKEOFF, CLIMB and LANDING. The landing part is that a constant speed prop in low-pitch/high-RPM has more drag and less residual thrust than a fix prop, thus you can make steeper approach. Any way fixed props and clean RV's with simple hinge flaps can be a little challenge to slow down over obstacles. Slipping is a valuable technique and skill. However the C/S prop is kind of a speed brake.

My recommendation is a 180HP with the a hollow crank. If you can't pop for the C/S prop at first, you can plug the crank and try the fixed prop at first. The Sensenich is probably the best value and performing. The Hartzell BA best overall for C/S. If you go 150/160HP and fix prop and its not good enough, you can always sell the set-up and upgrade later.

Where are you flying? If Cessna 172's, Piper 140/160/180's are getting in and out of the strips you want to fly out of, then a 160hp/fix RV-6 might work fine. If all you see are C185's with STOL kits, Super Cubs and Maules, you might want to think twice about going in there at all. RV's do have small tires and need a fairly well prepared surfaces. Grass, dirt and gravel are fine, but RV's are not a BUSH PLANE. However compared to most 160/180HP/fixed pitch prop GA plane, the RV-6 out performers across the board, except say a Cub.

The resale comments above are good. However I understand budgets and like I said you can get flying with a lower hp fixed set up and upgrade later. It's better to get flying than dreaming about it.