top_shape

Merry Christmas everyone! I was having a disscussion, and it boiled down to: Given perfect conditions ie. no wind, infinte transmitter distance and battery power, how high could an RC heli reach? Specifically an electric heli on the smaller side.
For instance, I my friend was saying that he felt he could fly the heli off the side of a 10 story building if it wasn't windy. I was trying to tell him that if the heli could only power itself up to 9 stories, when he flew it off the side at 10 stories it would float down till it could keep that altitude. He was arguing that it didn't matter the power of the motor or rpm speeds, a RC heli could reach the same altitude as a real deal heli given perfect conditions.
Happy Holidays!

jamesc43

My Feedback: (2)

top_shape,

Altitude is a relative thing. I live in Colorado at around 6200 ft. I've seen electric helicopters fly alot and it is a far cry higher than a 10 story building. It is mostly down to air temperature, air density, and helicopter set up.

Rafael23cc

My Feedback: (6)

You are partially correct. Most aircraft have a service ceiling, based mostly on design limitations of the aircraft itself. But most of the time, it is limitations of other components. Take for example a naturally aspirated piston engine. How high can that engine still produce power efficiently?. And with the same token, how high do you believe a pilot can breathe, if the naturally aspirated engine cannot? Then we have electric RC helicopters that do not require air to "breathe".

Having said that, IF you could take an RC helicopter that high, you will not be able to open the door to let it out of whatever vehicle took you there. Then, only then, and RC helicopter might fall to it's service ceiling.

Rafael

top_shape

James, I was using 10 stories just for example, I do realize now that is a pretty low height. I figured that small helis like the picooz would only go 150-200 ft high because of mechanical limitations.
Rafael, I was mainly interested in small electric helis. Excluding the limitations of equipment, wind force and the logistics of being there to see and control the heli, if you could somehow lock the heli to fly at max power till it hits it's service ceiling, what is the max height it could reach?

Rafael23cc

My Feedback: (6)

I could not put a number to it, but I bet it would be pretty high. People like jamesc43 that live and play in the Colorado mountains could probably tell you a little better. They sometimes prefer electric helis spun at a higher rpm because the piston engines start loosing efficiency at their GROUND LEVEL.

Rafael

Rob2160

Hi, I used to fly real helis and have taken one to 10,000 feet - it flew fine, but we couldn't go any higher without oxygen masks.. (legally)

I fly TREX 450 clone helis and I think they would have NOproblem at all flying at 10,000 feet or even higher..

Here is my most powerful heli.. it has tons of power...

At 18,000 feet the atmopshere has half the densitiy of sea level, but I think this heli would still climb easily at that height...

You do strike some other interesting aerodynamics at high altitudes but its all on google if you are interested...

[youtube]http://www.youtube.com/watch?v=HYpqxY1ekZ8[/youtube]

jw637362

My Feedback: (1)

Wow thats Crazy, We walk / hike here in Colorado at 11,000' to 14,000' - Colorado 14'ers.
Surprising you would have to wear oxygen that low in a real heli, Now that I think about though we are acclimated to 6000', your acclimated to what 100..Sea level. I can see it..

Combustion is a little retarted at this altitude in the lower CI engines - .049 - .25, Gett higher than that and you dont really notice a loss of power to weight. but electric has no problem that I have noticed.

Interesting topic though.

homeunt

My Feedback: (3)

I can bring in the physics here lol,
air resistance is how helicopters and airplanes fly.
The speed of properlling component will give how fast it can move and also how high it can go for helicopters.
higher you get, air gets less dense and hard for even a well pitched high speed rotors to catch on and rise.

The max altitude for rotary flight depends on the following:
area of the blades/ surface area the blades create pi r^2
speed of the blades,
pitch, higher it is, higher it can go but anything above 30 degree is useless essentially. Imagine trying to fly the helicopter when the blades are perpendicular to the ground, not going to happen.

Overall what you're trying to see is the volume of air that the helicopter can replace by its rotary system then get the mass of the air that it replaces from the calculation (depends on altitude)
In order for helicopter to hover at its altitude, it has to replace the same mass of air as the mass of the airframe. (Quite similar how the floats work on the water)

You also have to remember the following, larger blade you get, slower the blades will spin, higher the pitch, more torque the motor needs and increasing each will increase the overall mass aswell.

If you are interested in more of this, i can show you the diagram and etc.

Bottom line, it depends on the aeroframe, air and weather condition and also wind.

Rob2160

Yes its just a legal requirement of our Civil Aviation Safety Authority (like your FAA)

Full info here http://www.casa.gov.au/wcmswr/_asset...cao20/2004.pdf

Here is the relevant part...