Ideal forward speed for max. distance on a charge?

[mikesmiley]

I've been pondering this for awhile. Given the fact that a copter of any sort more or less maintains altitude by pure brute force, dawdling along at 5 or 10 mph is not going to give us the maximum range. But then, we've probably all gotten the "Propulsion output is limited.." warning towards the end of a charge, which tells me that balls out full speed is not the best way to make it home on a low charge. Which makes sense, because at some point, wind resistance on the aircraft itself will nullify the benefit of increased airspeed.

So, there's got to be a sweet spot, right? Anyone know what it is?

I'm thinking of trying some Litchi missions, all identical except for speed, and see where the bird comes home with the most charge remaining.

 

[flyNfrank]

Temperature, altitude, and wind speed direction are all contributors to inconsistencies. How can you be sure you will have a level playing field if you do such testing?

 

[mikesmiley]

Temperature, altitude, and wind speed direction are all contributors to inconsistencies. How can you be sure you will have a level playing field if you do such testing?

Without at least three or four identical aircraft with identical batteries, all sent out out the exact same time on the exact same mission, I obviously can't provide much more than anecdotal results. That's why I asked the question.

 

[mikesmiley]

If you have a better way of getting anywhere close to figuring the ideal speed, I am all ears.

 

[Yeager74]

It's a great question. While performing the RTH procedures, the P3P uses 10m/s (gps measured speed) as far as I remember, this being irrespective of wind (as it's gps speed!). This would lead me to guess that DJI have figured this out to be the max range speed (zero wind condition). There is no need to be to scientific about this, I'd think. In real world planes, rules of thumb are well used and appreciated, as a reference point. The external factors, such as wind, temp and altitude, will not be of great importance to quad choppers, like the P3, nor will the weight factor, as that's always going to be the same. I'd like somebody to provide a good speed, and elaborate on why that is. Until then, I'd say go with 10m/s, as per argument. Just my five cents.

 

[FantomFlier]

If you have a better way of getting anywhere close to figuring the ideal speed, I am all ears.

Your sarcasm not withstanding, FlyNFrank is exactly right. There is never going to be one ideal speed. Whether you like it or not you do have to take into account the temperature, altitude (including density altitude) , and wind speed and wind direction, for every individual flight.
When the quad can give you both groundspeed and airspeed, you may be a step closer.

 

[Mako79]

An Econo mode button. This would be good for RTH when battery is critical or if you wish to do long distance flights. I've seen healthydrones implement wind speed so I cant see why they cant introduce an eco mode.

 

[FantomFlier]

An Econo mode button. This would be good for RTH when battery is critical or if you wish to do long distance flights. I've seen healthydrones implement wind speed so I cant see why they cant introduce an eco mode.

HealthyDrones' wind speed is at best an educated guess and can only be calculated if you have flown for 5 seconds at full speed, and in P mode. Not practical for this discussion.

 

[MILLER4PRESIDENT2020]

I dont think the RTH 10m/s has anything to do with ideal speed. DJI probably wanted a speed fast enough to bring the bird home yet not too fast that the bird will do serious damage should it smack into something. Think about it....DJI knows that there will always be idiots who push the limit and fly 3 miles away. If RTH activates and it comes home at 30 mph and there is a building in between, that will do serious damage.

 

[Trackman1]

Since Low Power activates RTH I would think that DJI would design the P3 to return at it most efficient speed.

 

[mikesmiley]

Your sarcasm not withstanding, FlyNFrank is exactly right. There is never going to be one ideal speed. Whether you like it or not you do have to take into account the temperature, altitude (including density altitude) , and wind speed and wind direction, for every individual flight.
When the quad can give you both groundspeed and airspeed, you may be a step closer.

I completely understand that. But, there's got to be a general air speed range that's the most efficient, battery-wise. I'm just curious as to what that is.

 

[Yeager74]

I don't see anybody coming up with any speed. Try and press the RTH button and see what speed the manufacture (DJI) has chosen for the RTH functions. At least it's a speed and a starting point. Surely 15m/s with a high current is unlikely to be anywhere near best max range speed. A low speed of say 5m/s is probably not going to be all that great either, as the quad chopper will be in the air for longer. Until somebody can come up with a better number, I'd stick with something right in between the two numbers, and that's 10m/s (also the RTH speed that the manufacture has chosen). Cheers.

 

[flyNfrank]

The external factors, such as wind, temp and altitude, will not be of great importance to quad choppers, like the P3, nor will the weight factor, as that's always going to be the same.

What are you flying....a Hubacraft?

No great importance. Hahahahaaaa!

Btw, things are obviously different on this side of the planet.

 

[mikesmiley]

Thanks, Yeager. I plan to play around with it when I have some free time, just to satisfy my curiosity.

I figure a three mile Litchi mission, repeated a few times might give me a ballpark number. One at 20 mph, then again at 25, 30, and 35.

 

[mikesmiley]

What are you flying....a Hubacraft?

No great importance. Hahahahaaaa!

Btw, things are obviously different on this side of the planet.

Am I wrong, or do you have a problem with my question and my proposed way to find a ballpark answer?

 

[Yeager74]

What are you flying....a Hubacraft?

No great importance. Hahahahaaaa!

Btw, things are obviously different on this side of the planet.

Mate, the external factors are not of that great importance when choosing the optimum max range speed, but they are obviously of importance to the overall performance of the plane on that day.

So, while @flyNfrank sits at home making great calculations on what speed would be optimum for that particular day, the rest of us will be out flying with ball park numbers. It doesn't have to be rocket science to work, on either side of the planet. [emoji106]


P3P W323B GL300C, APP V.2.7.0, AIRCRAFT V.1.6.40, RC V.1.5.70, AUTOPILOT V3.2A.

Sent from my iPhone using PhantomPilots mobile app

 

[Yeager74]

Thanks, Yeager. I plan to play around with it when I have some free time, just to satisfy my curiosity.

I figure a three mile Litchi mission, repeated a few times might give me a ballpark number. One at 20 mph, then again at 25, 30, and 35.

That sounds great, please let us know what practical results you come up with, I'd appreciate this info.
Good stuff to know for those long range missions (preferably way beyond 3 miles and LOS!!!). Keep sending them up..


P3P W323B GL300C, APP V.2.7.0, AIRCRAFT V.1.6.40, RC V.1.5.70, AUTOPILOT V3.2A.

Sent from my iPhone using PhantomPilots mobile app

 

[mikesmiley]

Will do. May take me some time, but I'll report what I find,

 

[ray rokni]

Will do. May take me some time, but I'll report what I find,

All I can tell you is the long distance flyers ascend and descend at low speed, as threat seems to eat a lot of juice at full throttle and then once at their altitude they go full force forward.

But your idea of using litchi missions to get an idea of best speed vs battery is a good start, any experiment is fun and informative!
Good luck

 

[kennedye]

What you're looking for is the optimum cruise speed. I don't think DJI's published one have they?