jstrach

Irelocated from the San Francisco bay area to the Denver area, so we're sitting at 5280 ft. +/-250 ft.

I quasi-recently got back into the hobby and built a couple electric planes; TopFlite Cessna 182 and GPElectriCub. I configured both planes with the recommended electric power configuration and the recommended props but BOTH planes when at full power are barely above stall speed. It's disconcerting to say the least.

One of my fellow club members mentioned that it's probably related to our altitude. It was suggested Idrop an inch on my prop size.

I wanted to start this thread to discuss experiences or opinions around altitude and performance. I'm looking for words of wisdom, strategies, thoughts about how much or how little the 5280 ft. altitude would impact the planes and their power performance. My electric ParkZone Corsair flies with plenty of power, but it's a 2.7 lb foamy with a three-blade prop. My Cessna is 13 lbs. and my ElectriCub is 4.8 lbs.

Anyone want to offer any opinions, insights, formulas, etc.? I would surely be grateful. Before Istart throwing bigger electric motors into the plane, I'd like to get some more data on the subject.


Thanks so much!

jzrf6c

I'd be very interested in hearing anyone's reply to this question. I'm planing on moving to an are where the altitude is 4500 ft higher than I now fly. Besides the altitude what about the humidity and tempature?

jamesc43

My Feedback: (2)

jstrach,

Have you ran a watt meter on your set up? You might need to tweek the prop size and pitch for the altitude. The air is thinner in Denver than it is in San Francisco.

Have you checked your batteries for overall condition since moving to Denver?

jstrach

Hello Jamesc43,

Technically, no, I haven't run a watt meter on my setup. Idefniitely believe I have to tweek my prop size; but one club member said make the prop smaller - yet someone on RCU told me yesterday to make the pitch more aggressive and INCREASEthe diameter, so now I'm confused. The air is definitely thinner in Denver, yes.

The batteries and ESC and two planes in fact were purchased in Denver - never flew them in the Bay Area. Batteries should be fine but it's hard to know for sureI guess....

Jerome

jeffk464

Electrics shouldn't loose power with altitude like a glow or gas engine but there is less air for the prop to bite into so wouldn't you need a prop with a slight pitch increase? Not sure I might have that backwards.

gyrocptr

First, increase the propeller-pitch: Since the air is less dense, the motor will be able to spin a higher-pitch prop without drawing excessive current; also the plane needs to move faster to generate the needed lift. Increased prop diameter will increase static thrust but may not generate the needed increase in airspeed.
FWIW: you really should invest in a watt-meter. Whatever prop you select, you need to check the current draw to make sure it's within the limits/capabilities of your ESC and motor.