Is the ambient temperature and/or altitude a significant factor in the performance of the Phantom. Can't disregard that in a full scale heli. Wonder if it's something to evaluate during the hot summer months with the Phantom?
Air Density
- Thread starter jim81
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Both. Performance scales with air density, and air density decreases with increasing temperature, altitude and humidity. On the other hand these aircraft fly just fine in summer at 12,000 ft, so the only discernible difference that I've found is in flight time.
Is it a factor? YES!! Is it significant? Not really as much as many Manned Aircraft operators would think. My only guess is that due to light "wing loading" and usually not operating near design limits we don't see as much of a decrease when DA gets high.
I saw some testing in 2015 here in the Blue Ridge Mountains. They used Phantom3's and only noticed about a 5% decrease when flying at 1,500'MSL vs 6,000'MSL. We genuinely expected more of a difference but it just wasn't there.
About 20 years ago I did some flying in New Mexico and Colorado (single engine, fixed). What a dramatic difference from the nearly sea level airports I was used to in NY. There were two issues, altitude at take off and temperature at takeoff...all in relationship to density altitude. It took a while to get used to the long roll on takeoff and that's why high altitude airports have such long runways. But with vertical takeoffs this would seem to be much less of an issue. This was also with an aspirated carb. where density altitude is also an issue when it comes to icing. Again, not an issue with an electric motor.
Really its the same issue. In fixed wing aircraft, higher Density Altitude means that less air is being pushed across the wings to generate lift and by the props to create thrust. For our quads, less air being pushed down be the props so they have to spin faster to create the thrust needed to lift the UAV (Newton's second and third laws).
Thanks all. I am vaguely familiar with the physics but wondered in a practical sense if it was another possible cause of a fatal error if not taken into consideration with the Phantoms. 5% decrease doesn't seem like anything serious. If you are operating within little more than 5% error rate there are probably a lot of other things that would interfere more that ADA.
My very first "Flight Lesson" was in a Cessna 150 and the instructor was my size (I'm 6'4", 275lbs) on a hot HOT day on a very small airstrip that I think might have been a postage stamp previously LOL. We put enough full in the tank to putter around + reserve and the runway was short with "trimmed pines" at one end. I remember my instructor going into the grass on the far side of the runway instead of saying on the blacktop. I asked why and he said, "In this heat we need every inch of runway we can get" and he grinned this really sadistic grin and slammed the throttle to the wall. I remember when it FINALLY rotated and became "unglued" to the ground thinking, "what about those pines??"
I went back a few months later and we flew in that same plane but the air was COLD (I mean painfully cold) and the airplane left off the ground and climbed like a home sick angel. Talk about night & day difference.
N017RW
Premium Pilot
There's video out-there of a P1 or P2 flying at Everest base-camp, ~17kft.
Seemed sluggish if I recall. Battery capacity may have also been a factor as I don't recall temp. being mentioned.
Seemed sluggish if I recall. Battery capacity may have also been a factor as I don't recall temp. being mentioned.
That's just at, maybe even a bit above the published service ceiling for the Phantoms. Bet it was sluggish!! Just not that much air up there to push around!
The specified ceiling is 6,000 m (19,685 ft), and I have seen video taken at that elevation with a P4. There is clearly some margin in the specifications.
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