I would think this has been asked before, but I couldn't find it. Maybe wording wrong. Anyway, as far as miles per battery goes, what is the most efficient speed for the standard?
Thanks,
Eddie
Thanks,
Eddie
What's the most efficent speed
- Thread starter AA5XA
- Start date
There are really too many variables to consider to answer that question in direct terms. When flying you have to consider, wind, temperature, and other factors as far as "efficiency" goes. It does not matter what aircraft you are flying.
The most effiicient speed is zero, however this negates most desired actions.
That's actually incorrect. I know you intended it as a joke, but I'm taking it literally to explain one concept: helicopters (and quadcopters) use less power in forward flight than when hovering, because of a phenomenon called translational lift. It's very tangible, and every RC helicopter pilot knows about it as you have to give more throttle (left stick = power + collective) when you stop to a hover, or the heli will lose altitude. You don't quite notice it on the P3S because (even in ATTI mode) it uses the barometer to maintain altitude, so it automatically compensates.
To the OP: I have a DashWare profile + gauge showing the instant power utilization (calculated as voltage x amps), and you can see it clearly dropping as soon as you start moving. This might not be accurate enough to find the "sweet spot" of the P3S (drag vs translational lift) but you can do some experiments using the logs: pick a day/time with calm conditions, bring the AC to a reasonable altitude, do 30 seconds or even 1 minute runs at 0mph (hover), 5mph, 10mph, up to max speed. Then download the logs (I use the Offline TXT FlightRecord to CSV Converter), isolate those runs by looking at the speed, and calculate the average power consumption for each.
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N017RW
Premium Pilot
Good points.
But as suggested flights are dynamic and worrying about one or a few more minutes of flight time seems to be opposed to the idea of gathering the intended data or images or just enjoying an ‘adventure‘. Not to mention the risk of trying to squeeze out flight time rather than maintaining a healthy margin of error.
But as suggested flights are dynamic and worrying about one or a few more minutes of flight time seems to be opposed to the idea of gathering the intended data or images or just enjoying an ‘adventure‘. Not to mention the risk of trying to squeeze out flight time rather than maintaining a healthy margin of error.
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Not only: finding the most efficient speed will have near-zero impact in practical terms. Just a bit of wind, and you will have to spend way more power to put the AC where you want it to be, than what you can save by flying at a specific speed.
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Just fly the darn thing... the battery capacity will be enough to keep you gasping hoping it'll make it back after that "CNN" moment...
Your question is a reasonable one and it has an answer- 14ms will give you best distance on a given charge for a P3 and it’s simillar for the 4 variants. Wind and other conditions may see the actual distance travelled as less or more over the ground however 14ms airspeed will give you greatest distance always. And yes, Transitional lift applies.
Thank you very much. I understand there are a lot of variables out there as to how much actual distance you can get out of a battery, but it seemed reasonable that there might be a sweet spot in there somewhere.
Oso
Premium Pilot
Check out these search results for additional interesting reading.
This particular thread has good data I think.
Cheers!
Yes- I posted this link long range drone DJI Phantom 3 professional in that thread.
The maths works. Proven out in the distance threads...
Pretty cool stuff, thanks for finding that thread! I wonder if one could come to the same conclusion by looking at the power consumption at different speeds, as I suggested. In theory, yes.
No- simply because maximum distance is attained at a specific power consumption is somewhat higher than the minimum that provides for level flight. We are looking for greatest possible distance flown as opposed to longest airtime (which could be determined by your method easily).
You are right that airtime doesn't equal distance, but airtime x speed does, so my method can still be used to determine what speed gives you more miles per battery.
How? Specifically how will knowing the instantaneous power consumption help?You are right that airtime doesn't equal distance, but airtime x speed does, so my method can still be used to determine what speed gives you more miles per battery.
Flying at a constant speed the steady state power consumption will give you time to empty. Factor in speed and you will have total range at that speed. You will still need to do a couple of runs and some trial and error to get to the magic speed for max distance.
It's very easy:
- Run 1: 10mph, power consumption 100W
- Run 2: 15mph, power consumption 120W
Say your battery has a usable capacity of 60Wh:
- Run 1 will last 0.6 hours, for a total of 6 miles
- Run 2 will last 0.5 hours, for a total of 7.5 miles
- Run 1: 10mph, power consumption 100W
- Run 2: 15mph, power consumption 120W
Say your battery has a usable capacity of 60Wh:
- Run 1 will last 0.6 hours, for a total of 6 miles
- Run 2 will last 0.5 hours, for a total of 7.5 miles
