Hex vs quad at high altitude?

[Joe B]

Hi all,

I have a question I haven't been able to find much about on online. Today I flew my F450 at a much higher altitude than usual-- just over 8000' versus about the usual 5200' or so around my normal flying areas. I of course experienced reduced flight time, pretty substantial, actually, and that got me wondering. Are hex rotors more efficient at high altitude than quads? For example, could I expect less of a reduction in performance with a hex since (given the same payload) a hex should have more power to spare, or would it be about the same performance loss for either one? Thanks for your input!

 

[sixshooterstang]

a hex is always less efficient as you have the energy lost to heat by 6 motors now rather than 4 motors.

 

[PeteDee]

That may be true but it will also depend on how efficiently you have your MR set up to start with, less to lose with a quad most likely.

Pete

 

[Joe B]

Interesting. I was thinking that living near Denver (5280 feet ASL) a hex might be a benefit compared to a quad at this altitude, all things being equal. To clarify, I do understand that more rotors will always require more power, but that's not what I mean-- I'm speaking more as to whether the flight times on either platform will drop off equally at high altitude. For example, if both a given quad and hex fly 10 minutes at sea level, would they both fly say, 5 minutes at 8000 feet, or would one fly a bit longer than the other?

 

[bensid54]

Am I reading this right! Are you actually flying 8000 feet off the ground? Air traffic in the area especially small planes could have a real problem if they flew into your quad, in my area here I can't legally fly above 400 feet due to the airport being about 5 to 6 miles away. This post got me thinking though I think once I get my Fat Shark I'm going to place my VU in sight of the camera so I can see the state of the batteries.

 

[FlyGirl]

Am I reading this right! Are you actually flying 8000 feet off the ground? Air traffic in the area especially small planes could have a real problem if they flew into your quad, in my area here I can't legally fly above 400 feet due to the airport being about 5 to 6 miles away. This post got me thinking though I think once I get my Fat Shark I'm going to place my VU in sight of the camera so I can see the state of the batteries.

I think he meant he was at a different 3000 foot higher elevation rather than a 3000' AGL difference. Sounds like he flies in a mountainous area...

Just a guess here but the lower air density of the higher elevation should affect a quad or hex's propellers (this is assuming the same prop on both aircraft) equally so if there is an advantage to a hex over a quad at lower elevations then that advantage should still be evident at the higher elevation. Being new to this, I don't know what if any advantages there are between the two yet but I would expect lifting capacity to be the main difference? I would think you would want a different propeller pitch and/or diameter for that great a difference of altitude no matter which platform you are flying...

 

[Joe B]

Yes, I live at about 5280 feet above sea level, but occasionally fly in the mountains near me. Taking off from there, my landing site is at already 8000+ feet ASL. Yes, that'd be pretty high if I was flying from sea level!

 

[Joe B]

Funny observation... just running the numbers on eCalc, it's saying that my flight times should increase for any given setup at higher and higher altitudes. Maybe it was just a matter of the temperature....

 

[bensid54]

Well that makes sense. I live at sea level or a bit above and thought you were talking about flying that machine 8000 feet above your head not 8000 above sea level.

 

[Thalios]

Higher altitude means the air is less dense, which means the props have to turn faster to produce the same lift. You'll see the same difference (or loss I should say) no matter which craft you're using.

Let's say it's 20% drop, it'll be 20% drop across the board, no matter quad, hexa, octo.

 

[Joe B]

That makes sense. Thanks, Thalios!

Higher altitude means the air is less dense, which means the props have to turn faster to produce the same lift. You'll see the same difference (or loss I should say) no matter which craft you're using.

Let's say it's 20% drop, it'll be 20% drop across the board, no matter quad, hexa, octo.