Yes, but that's also true with the method of running the same circuit at different speeds. No difference.
What's the most efficent speed
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Yes, but that's also true with the method of running the same circuit at different speeds. No difference.
Agreed- your task however was to explain how knowing in flight power consumption might directly provide for determination of optimum speed for max distance. Seemingly it can’t.
Knowing the most efficient airspeed might prove to be just as relavent when flying into the wind- you won’t go as far as in still conditions or with a tailwind but you will get the maximum possible range for the conditions.
For multiple runs yes of course- however you are only using the power consumption and battery capacity to determine flight time. You can do this more accurately looking at your flight app or wristwatch. I was interested in your suggestion that looking at the power consumption at different speeds would allow you to determine optimum soeed for maximum distance. Quite simply, as might be expected, in the absence of multiple runs and other factors being considered it can’t.
Battery capacity or flight time are irrelevant to prove what you "tasked me" (?) to demonstrate. It's just a constant that I put in the example to make things simpler to understand. I clearly failed in my intent. Back to my example:
- Run 1: 10mph, power consumption 100W
- Run 2: 15mph, power consumption 120W
You can tell right away that Run 2 is more efficient, as it requires 8W per mph (Run 1 needs 10W per mph).
I think I showed you that power consumption at different speeds does indeed allow you to determine which speed - among those tested - would achieve maximum distance. If you mean to find the absolute optimum speed for that specific aircraft, then... well, the answer is still yes... you will need a few samples (5mph spacing would be enough, you don't need to go crazy), but you can definitely interpolate the results and find the lowest point of the curve (W per mph) with a good degree of accuracy. Heck, even by simply plotting the numbers on a chart would give you a good idea of what the best speed is!
I consider my "task" complete. If you don't agree, let's agree to disagree.
I am agreeing with what you are now saying, it’s obvious.... My question of you remains open as you haven’t addressed it. It concerned your comment “I wonder if one could come to the sameconclusion by looking at the power consumption at different speeds, as I suggested. In theory, yes“.. The answer to that is seemingly no. Which is fine.
I was hoping you might be able to demonstrate your theory.
When I wrote that, I was referring to the thread that @Oso mentioned, where someone did a series of runs (same path) at different speeds, and used the battery capacity left to determine empirically what was the most efficient speed. My comment was simply that "my" method of recording the power consumption at different speeds would in theory come to the same conclusion, meaning to identify the "best" speed.
I said that intuitively, but I actually found a way to demonstrate it, if this is what you want. Here's the reasoning: with my method, measurements come down to watts per mph for each run, with the lowest being the best. With the other method, they measure the capacity left for each run (the higher, the better). Since the battery doesn't change, that is equivalent to measuring the capacity used for each run (the lower, the better). And since they know how long was each run, this is equivalent to measuring the capacity used, per mile. Now, "capacity" is the total energy stored in the battery, so the actual unit of measure is Wh (watt-hour), which means that effectively their method comes down to measuring Wh per mile.
To recap, I have watt per mph, they have watt-hour per mile. But W/mph = W/m/h = Wh/m. Hence, we're ultimately measuring the same thing, and, in theory, we should come to the same conclusions.
I said that intuitively, but I actually found a way to demonstrate it, if this is what you want. Here's the reasoning: with my method, measurements come down to watts per mph for each run, with the lowest being the best. With the other method, they measure the capacity left for each run (the higher, the better). Since the battery doesn't change, that is equivalent to measuring the capacity used for each run (the lower, the better). And since they know how long was each run, this is equivalent to measuring the capacity used, per mile. Now, "capacity" is the total energy stored in the battery, so the actual unit of measure is Wh (watt-hour), which means that effectively their method comes down to measuring Wh per mile.
To recap, I have watt per mph, they have watt-hour per mile. But W/mph = W/m/h = Wh/m. Hence, we're ultimately measuring the same thing, and, in theory, we should come to the same conclusions.
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Wh/unit distance is the relavent measurement here, and yes the less the better. Your suggestion lower power/unit speed being better can’t be right. . Lowest isn’t the best for your method. You won’t get the greatest distance at the lower power consumption which is somewhere between hover and 14ms. Time of flight is not an important consideration here. Max distance on a charge is.When I wrote that, I was referring to the thread that @Oso mentioned, where someone did a series of runs (same path) at different speeds, and used the battery capacity left to determine empirically what was the most efficient speed. My comment was simply that "my" method of recording the power consumption at different speeds would in theory come to the same conclusion, meaning to identify the "best" speed.
I said that intuitively, but I actually found a way to demonstrate it, if this is what you want. Here's the reasoning: with my method, measurements come down to watts per mph for each run, with the lowest being the best. With the other method, they measure the capacity left for each run (the higher, the better). Since the battery doesn't change, that is equivalent to measuring the capacity used for each run (the lower, the better). And since they know how long was each run, this is equivalent to measuring the capacity used, per mile. Now, "capacity" is the total energy stored in the battery, so the actual unit of measure is Wh (watt-hour), which means that effectively their method comes down to measuring Wh per mile.
To recap, I have watt per mph, they have watt-hour per mile. But W/mph = W/m/h = Wh/m. Hence, we're ultimately measuring the same thing, and, in theory, we should come to the same conclusions.
I believe it is and I even showed you (W/mph = Wh/m).
It is.
You are confusing power consumption with watts per mph. Run 1 in my example has a lower power consumption than Run 2 (100 vs 120W) but Run 2 has a lower W/mph (8 vs 10), so 15mph would be the speed that gives you the greatest distance.
I already answered this comment, see #26.
With this, I have nothing more to add. For each (detailed and articulated) answer I gave to your questions, you responded "agreed", "obvious", "of course" and went on to ask a different one. You seem to be on a quest to prove me wrong (don't know why, quite frankly), but you don't actually explain anything and you add nothing to the discussion. Now you clearly reached a point where you're repeating the same questions, so maybe my answers are not so obvious to you as you claim, and you need a bit of time to understand them. In any case, as I said I have nothing more to add on this subject, so consider this my last post.
That's interesting data, and seems reasonable. If we could get a continuous plot of power vs. pitch (which is going to be a single-valued transformation of power vs. airspeed), then the minimum for any given flight path and wind field could be computed.
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I agree with The Birds on 14ms or about 31 mph. This has been tested on some of our long range pilots who mostly agree on the 14 mps for battery life vs distance, gravity is the constant and wind resistance the variable. Last year in this forum a engineer did the physical calculation of the phantom that included pitch and the actual shape of the craft and he included all the math and the numbers came up to 13(point something) mps. At this speed I have noticed as I checked my flight records in GO that my right stick is about 75% (P mode), at this speed my P4 longest total distance is over 43,000 feet and landed at 20%.
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Its a bit tricky as we don't have airspeed, only speed over the ground which is only valid in no wind.
Generally faster is better up to the point where parasitic drag becomes dominant.
Again very generally, about half your maximum speed.
An OGE (Out of Ground Effect) hover has a very high power requirement.
Generally faster is better up to the point where parasitic drag becomes dominant.
Again very generally, about half your maximum speed.
An OGE (Out of Ground Effect) hover has a very high power requirement.
Thanks, for asking the question. I think it's a perfectly good one and I particularly liked the more knowledgeable answer from 120CCPM.
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Every single extra minute of flight time at your destination can be significant, when your destination requires travel time to and from of 7 to 10 minutes each way. Hence the previous demand on the P3P and P4 for even a few extra minutes of flight time by adding external batteries, despite their extra payload. The P4P finally delivers a true 23 minute flight time at a constant 30mph with OA turned on, without needing to resort to such extreme and impractical measures, using the high capacity P4P battery, which adds no weight, but adds 2 precious minutes of flight time.10 mile flight distances are now easily achievable with a fully stock configuration, using the Auto 5.8Ghz band for its very real 4.3 mile control range. Optimizing the flight distance per battery is now built-in to the P4P in P mode with OA turned on, limiting speed to 30mph at full throttle, which is close enough to the 31mph holy grail.
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