Does altitude affect flight times?

[acall]

I live in the LA area and when I'm in the city, at sea level, I have a newer battery which usually gives me about 9 minutes (I have the Phantom 1). I'm up at Big Bear Lake this weekend, which is around 6500 feet elevation, and that same battery is only giving me about 7 minutes before it starts flashing red. It's rather frustrating and I'm just wondering if the elevation is affecting that at all? My 2 stock batteries that came with the Phantom are only getting 4 and a half minutes!

My apologies if this has already been discussed, I tried a search and didn't see anything but please link me to the thread if there is one already. Thanks.

 

[Michigan_PI]

Yes
Air is less dense at higher altitudes thus it takes more power to keep it flying which corresponds to lower flight times.

 

[d4ddyo]

yeah but it's not going to make a dramatic difference on this scale

 

[doug86]

yeah but it's not going to make a dramatic difference on this scale

won't the "difference" be the same, regardless of scale? I mean, the air density tables don't change whether I'm flying a 747 or Cessna. Density is dependent on altitude. The propellers generate less lift at 6500'.

I've flown out of Big Bear, and I sure ate up a bunch more runway to get airborne.

I'm with Mich_PI, about 2 minutes is probably the normal loss for 6500'. In fact, I wonder if that's not getting close to the ceiling of the Phantom

 

[usaken]

Also, Remember the compounding effect of temperature on performance. Density altitude is the altitude the drone feels it is at. Take a summer day at Lake Tahoe (about 6,000 ft) With an 85 degree temperature the Density altitude is around 9,000. You can sure bet that is going to affect performance.

 

[sar104]

yeah but it's not going to make a dramatic difference on this scale

won't the "difference" be the same, regardless of scale? I mean, the air density tables don't change whether I'm flying a 747 or Cessna. Density is dependent on altitude. The propellers generate less lift at 6500'.

I've flown out of Big Bear, and I sure ate up a bunch more runway to get airborne.

I'm with Mich_PI, about 2 minutes is probably the normal loss for 6500'. In fact, I wonder if that's not getting close to the ceiling of the Phantom

Not sure about the P1, but the P2 flies fine at 10000 ft. I haven't checked flight times at that elevation, but at 7500 ft a new battery gets better than 15 min on a 1350 g aircraft, depending on flight characteristics of course. Definitely reduced from sea level.

 

[usaken]

Another interesting angle to this Density Altitude stuff, is that in a propeller driven aircraft with a non fuel injected, non turbo engine the DA also affects the performance of the engine. We don't have that part of the problem with our quads, since they are driven by electric motors that are not affected. It would be interesting to know the service ceiling of our craft and how DA affects performance.

 

[MrTommy]

In fact, I wonder if that's not getting close to the ceiling of the Phantom

I took off and got some altitude at 7900 feet a few days ago while camped near Grand Canyon (not in the park, of course). Flytrex recorded it as 7923. But, I was only able to lock onto 4-5 sats due to heave tree cover. I figured if I got above the trees I'd get more sats and life would be good. There was an opening right above me. Bad plan! Having no GPS control, I was all over the place and consider myself lucky I got it down in one piece (though I did bury one prop in soft wood chips).

 

[doug86]

Another interesting angle to this Density Altitude stuff, is that in a propeller driven aircraft with a non fuel injected, non turbo engine the DA also affects the performance of the engine. We don't have that part of the problem with our quads, since they are driven by electric motors that are not affected. It would be interesting to know the service ceiling of our craft and how DA affects performance.

Yes, of course. Density alt affects the prop thrust, the wing, and the internal combustion engine. All the quad loses is some prop thrust. Amazed to read that post of ops at FL10.

 

[acall]

Thanks for all the input. I actually saw someone else flying a Phantom just now and went and chatted with him and he said the same thing - that his flight times were about 2 minutes less then when he's down in LA.