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High Altitude Runway Vs. CS prop?
I had a first time encounter with a runway at 7,000 msl, and upon entering the patern I got a "feel" for the prop speed and generally found there was more available thrust with the prop sped lever pulled back a bit.
I noticed it on takeoff as well, I was struggling to climb, but as soon as I pulled the speed lever back, I felt more thrust, and a much improved ability to climb.
I believe that that the best setting for takeoff at high altitude is to slow the prop speed a bit to help it grab a larger volume of air, rather than by relying upon an increase in prop rpm for thrust. This is contradictory to the POH and I want somebody to either yell at me or tell me im right for believing this.
This was in a Piper Arrow for the record.
5 Answers
- Anonymous5 years ago
No, no, no!
At high altitude the aircraft needs all the RPM it can get, you will not sustain climb in an Arrow unless you are in high RPM, it is like trying to tackle a hill in top gear. You might rush up on it, (what you were doing by increasing pitch) but you will soon run out of steam.
What is important is to apply as much power as you can to a climb at that altitude, you won't get full power and won't hurt the engine. You need to remember that you should climb at the best speed for climb at that altitude, which will be a little slower than it is at sea level, about a knot IAS per 1000 feet as a rule of thumb in an Arrow.
You also need to ensure the mixture is correctly leaned so that the engine is producing power most efficiently.
Climb is a function of excess power, above 7000 feet on a hot day, with a heavy load, the Arrow does not have a lot of excess power. You need to give it all the help you can
- Anonymous5 years ago
What you were feeling was a momentary burst of thrust that the engine has no way of maintaining. Kind of like dumping the clutch to get a good launch or pulling back on the stick to zoom--sacrificing airspeed for altitude.
Since we spend a long time climbing, pulling the prop back for that momentary extra thrust will not be beneficial in the long run.
Keep that prop lever if you want to climb the fastest. Also keep Vy.... adjusted for weight and altitude (indicated Vy decreases with DA, until it equals an increased Vx at the aircrafts absolute ceiling). Lots of people smarter than you or I figured that out a long time ago.
- Angela DLv 75 years ago
you know you're not supposed to ask real airplane questions around here. :-)
takeoff and initial climb are with the prop at highest rpm. there is a reason for that. then you set climb power. last time i did that it was "25 cubed" - 25", 2500 rpm, 125 mph.
Source(s): flights in cessna 182, piper arrow and piper seneca - 5 years ago
No, absolutely not. Takeoff at high rpm provides the greatest thrust and horsepower for climb. You are NOT smarter than the POH.
- ?Lv 75 years ago
Trust the POH. Hundreds of aviation engineers who know more about the aircraft than you do spent a lot of time putting it together.
