Ideal forward speed for max. distance on a charge?

[GadgetGuy]

EXCELLENT, COMPLETE, TOTAL ANSWER FARRARIPT!!!!!!!!!!!

Many other guesses and discussions of what effects speed and efficiency, but at the end of the day, none of those gave a definitive answer. YOU DID!

Maybe it would make sense to restate your definitive conclusion so there is no ambiguity or further second guessing:

MOST EFFICIENT BATTERY USAGE ON THE DJI MODEL YOU TESTED IS MAX THROTTLE SETTING. PERIOD. 100% ACCURATE.

WELL WELL DONE!!!!

Now, the only additional info I could add is this: the initial question was not quite correct. As lots of folks stated, effectivee ground speed varies with flight conditions. So there is no correct answer to the initial question. BUT there is a definitive answer to the ACTUAL question, and stated the way it was intended that question is:

"What is ideal forward THROTTLE SETTING for max distance on a charge?"

THIS the question that was answered definitively by Farrript and none of that other parameters have any effect on it.

Which begs the question of why DJI sets the RTH speed to a meager 22mph, and also throttles the maximum speed on the P3 to 35mph, even in a tail wind, at the very time, while returning home, when you need max distance out of the remaining battery, to be sure the battery lasts long enough, to make it back to the Home Point...

 

[TheLightSpeedz]

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

Let me put all this nonsense to bed... 29 to 31 mph is the perfect distance speed in perfect conditions.

As for the "idiots" Miller for president refers to flying beyond 3 miles, I happen to be one of those said idiots. You're not an idiot for flying that far, you are an idiot for saying stupid things on a forum. Also, everything in this hobby has to be done with precision and caution for others. If you're careless it doesn't matter how far you fly.


Sent from my iPhone using PhantomPilots mobile app

 

[Ed209]

Let me put all this nonsense to bed... 29 to 31 mph is the perfect distance speed in perfect conditions.

As for the "idiots" Miller for president refers to flying beyond 3 miles, I happen to be one of those said idiots. You're not an idiot for flying that far, you are an idiot for saying stupid things on a forum. Also, everything in this hobby has to be done with precision and caution for others. If you're careless it doesn't matter how far you fly.


Sent from my iPhone using PhantomPilots mobile app

Any data to back that statement up? What tests have you done to find the sweet spot at 29-31mph? I see you mentioned 30.5mph in another thread so you must've done some sort of testing and analysis to increase the max speed to 31mph. What were the conditions when conducting these tests? Any battery mods on board or extra weight beyond stock? What props?

 

[TheLightSpeedz]

Any data to back that statement up? What tests have you done to find the sweet spot at 29-31mph? I see you mentioned 30.5mph in another thread so you must've done some sort of testing and analysis to increase the max speed to 31mph. What were the conditions when conducting these tests? Any battery mods on board or extra weight beyond stock? What props?

If you can hold it at 30.5 that's awesome, but I try to keep it at 29-31 in that range. What data? I was as high at #8 on the distance leaderboard at 24,000ft+ With a P4... No mods. I believe to go further closer to 29 is better than 31.

Have to go fast enough to get the distance but not so fast that you drain the battery too fast.


Sent from my iPhone using PhantomPilots mobile app

 

[TheLightSpeedz]

It's all conditional on the wind, etc. but there is a point a where to get max speed, and max distance without excessive drain on the batteries.


Sent from my iPhone using PhantomPilots mobile app

 

[Ed209]

If you can hold it at 30.5 that's awesome, but I try to keep it at 29-31 in that range. What data? I was as high at #8 on the distance leaderboard at 24,000ft+ With a P4... No mods. I believe to go further closer to 29 is better than 31.

Have to go fast enough to get the distance but not so fast that you drain the battery too fast.


Sent from my iPhone using PhantomPilots mobile app

So you're stating 29-31mph based on your experience with a P4?

 

[Mark The Droner]

If you can hold it at 30.5 that's awesome, but I try to keep it at 29-31 in that range. What data? I was as high at #8 on the distance leaderboard at 24,000ft+ With a P4... No mods. I believe to go further closer to 29 is better than 31.

Have to go fast enough to get the distance but not so fast that you drain the battery too fast.


Sent from my iPhone using PhantomPilots mobile app

But this is a P3 forum.

 

[MikeyOnline]

Because multi-rotors expend most of their energy maintaining altitude, the best range speed (as opposed to max endurance) is max throttle, esp if flying in a headwind, as the less time spent in the headwind, the better.

The only real factor/variable that comes into play is additional wind resistance due to higher speed, (which increases as a square of the speed...like, go 2 times as fast and wind resistance increases by a factor of 4). But that doesn't much come into play at Phantom speeds, and in any case, the additional power needed by the Phantom to maintain a faster speed is much less than the additional power needed to fly for the additional time at the slower speed.

All the other variables, like temperature and air pressure (and altitude) and such, make a difference, but only if a person can choose the day/time they will have their emergency.

The only technique for getting more range (using less battery) would be to descend at a rate so the multi-rotor reaches the ground at the same time it reaches the landing zone, so you're not spending time descending from cruise altitude right over the landing zone.

This is exactly what I was thinking. Just thinking logically, at zero forward speed, you're spending all your battery power fighting gravity. If you inch forward at 1 m/s, you won't get very far before the battery runs out because the props are applying 2.8 pounds of force upward the whole trip, and very little forward force. Give it more pitch and go 10 m/s and it still has to apply the same 2.8 pound upward force but you're covering more ground distance while it is doing that so you get farther, quicker. So (again, just thinking out loud), the more forward vector you can give it, the farther you will get. I doubt wind resistance on an object with such small frontal area comes into play but something like prop efficiency-at-speed and motor efficiency-at-RPM might come into play. So there could be some difference near full throttle but I'd still expect the max efficiency to lie somewhere between 90% and 100% throttle

Mike

 

[yorlik]

It's all conditional on the wind, etc. but there is a point a where to get max speed, and max distance without excessive drain on the batteries.

Yep - and farraript told you where that was, based on science and facts: TOP throttle position. Nothing to do with mph units.

 

[yorlik]

I believe to go further closer to 29 is better than 31.

Have to go fast enough to get the distance but not so fast that you drain the battery too fast.

29 instead of 31 may be more efficient in a P4 - there was no P4 discussion here, it was P3. Tests were done to definitely show max efficiency on the P3 is at full throttle, not some lower throttle as you suggest based on feelings.

We all know wind, humidity, height, etc, will have some effect on the actual mph you get at different throttle positions. That is why the definitive answer was proven to be at full throttle - irregardless what speed is in reference to the ground.

We all know that power, going into and coming out of, the props goes up by the CUBE of the prop rpm. So as in any normal airplane, there IS some point of max efficiency where power usage will outgrow speed, but the proof was given that the P3 never increases prop rpm to that point - the proof showed straight lines, no curve showed up. Thus the P3 does not spin its props fast enough to get to that point of using more power than the return on speed.

Just accept it.

If you want to do the same definitive tests on your P4, that would be great! Your feelings that 29 is better than 31 may be proven as fact! If you do the tests and plot it, I suggest you plot throttle position rather than airspeed for a bit more accuracy - or plot both for comparison.

 

[TheLightSpeedz]

29 instead of 31 may be more efficient in a P4 - there was no P4 discussion here, it was P3. Tests were done to definitely show max efficiency on the P3 is at full throttle, not some lower throttle as you suggest based on feelings.

We all know wind, humidity, height, etc, will have some effect on the actual mph you get at different throttle positions. That is why the definitive answer was proven to be at full throttle - irregardless what speed is in reference to the ground.

We all know that power, going into and coming out of, the props goes up by the CUBE of the prop rpm. So as in any normal airplane, there IS some point of max efficiency where power usage will outgrow speed, but the proof was given that the P3 never increases prop rpm to that point - the proof showed straight lines, no curve showed up. Thus the P3 does not spin its props fast enough to get to that point of using more power than the return on speed.

Just accept it.

If you want to do the same definitive tests on your P4, that would be great! Your feelings that 29 is better than 31 may be proven as fact! If you do the tests and plot it, I suggest you plot throttle position rather than airspeed for a bit more accuracy - or plot both for comparison.

Conceptually speaking there are the same principals at play here. Maintaining a speed makes since despite the platform. On the P3, I don't remember flying at full throttle all the time for distance but I could be mistaken. So I will "accept it".


Sent from my iPhone using PhantomPilots mobile app

 

[Ed209]

Conceptually speaking there are the same principals at play here. Maintaining a speed makes since despite the platform. On the P3, I don't remember flying at full throttle all the time for distance but I could be mistaken. So I will "accept it".


Sent from my iPhone using PhantomPilots mobile app

It's quite obvious the same principals do not equal the same result when comparing a P3 to P4. Nothing is similar. Different motors, different weight, different surface area, different esc, different props, different firmware, different programming, different...everything.

So I will "accept" your claims of optimum speed for the P3 as unfounded.

 

[mikesmiley]

Just to make this all a little more fun, how much juice does it take to encode and write 2.7 or 4k video the entire time?

 

[Vertigo]

All aircraft have a speed where fuel economy is maximized. As speed increases, so does drag on the fuselage. At some point, the drag increases to a rate where fuel economy starts to drop.

I used to fly a Cessna 172. Best rate was 110 to 115 knots.

Yes, you can actually calculate your optimal cruise speed if you know all the variables. One key variable in this calculation is L/D (lift over drag, which is also your glide angle). On a cessna, thats around 10. On a multirotor, that is close to zero.

Ok, for the pedantic, the props are wings, and I guess you could autorate just a tiny bit. Ill be surprised if you achieved more than a 1:1 L/D ratio though. So for all practical purposes, you dont have a glide angle that is why full speed will always maximize your range on a multirotor; you dont have wings to generate lift.

 

[ferraript]

Just to make this all a little more fun, how much juice does it take to encode and write 2.7 or 4k video the entire time?

it's nothing easier than to start the Phantom (you don't even need to start the motors) and hit the record button
and then get the DAT log, convert it to CSV and look into the Watts column

 

[PVFlyer]

FPV Camera app has a battery consumption meter to show optimal battery economy as below.

Battery Consumption (Camera): Toggle On/Off Battery Consumption to show/hide real-time mAh/km (Metric) or mAh/mi (Imperial) in Battery Meter upon takeoff for optimizing economy cruise speed. It's similar to fuel economy (such as MPG or Litres/100km) of a car. The lower the value, the better battery consumption economy. When hovering with zero travel distance, battery consumption is the worst 9999 mAh/km.

This is designed for those long range junkie who need to fly the longest range per battery and squeeze all the performance of their gears. Experienced pilots know maximum pitch forward joystick (the highest speed) might not be the best battery economy, especially in windy condition.

 

[Ed209]

FPV Camera app has a battery consumption meter to show optimal battery economy as below.

Battery Consumption (Camera): Toggle On/Off Battery Consumption to show/hide real-time mAh/km (Metric) or mAh/mi (Imperial) in Battery Meter upon takeoff for optimizing economy cruise speed. It's similar to fuel economy (such as MPG or Litres/100km) of a car. The lower the value, the better battery consumption economy. When hovering with zero travel distance, battery consumption is the worst 9999 mAh/km.

This is designed for those long range junkie who need to fly the longest range per battery and squeeze all the performance of their gears. Experienced pilots know maximum pitch forward joystick (the highest speed) might not be the best battery economy, especially in windy condition.

I've been wanting to try this App but one thing that's holding me back is that I don't see if logs can be uploaded to healthydrones in any way. It seems your logs are proprietary. I rely on HD for keeping track of everything.

 

[Vertigo]

Been thinking this over some more, and perhaps what I said earlier isnt quite right. While you have no lift generated by wings, so traditional airplane wisdom of optimizing L over D goes out the window, there is another factor that still matter: the electrical efficiency of the motor and props at various RPM. At full throttle, they will be less efficient (as in grams of thrust per watt) and that may partially offset the loss induced by hovering for longer than needed. This makes it a non trivial question to answer even theoretically.

 

[RebelForGod]

I've done 38k ft Waypoint flights using 70% battery at 25mph.
Also, Have done waypoints at 55mph, by editing the mission file to this higher speed.
My top speeds are 72-77mph, but out of concern for malfunction, keep these speeds to 30 seconds or less duration.
Not tested yet, but suspect 45mph sustained may be a reasonable speed, for not overtaxing the equipment.
Unfortunately, since Jan 2016, haven't been able to do further testing, due to LOS restrictions.
See some of these old flights on: YouTube dot com/rebelforgod
Looking at flight data, hovering draws 14-16 amps, but a sprint surges 20-22 amps then reduces to 17-18 amps once speed is attained.
Also, using 9443 props extends my times by about 12% on the FC40 and P2v3.
With the P2v3, 9443s topped out at 77mph, but the 9450s reached 74mph(too close for a clear winner, since both tests were on low batteries amidst RTH to ATTI interruptions).
During Max-lift tethered tests, the P2v3 after 3min of ATTI max throttle, stumbled then recovered, so not sure if it was a battery or ESC overload that caused the stumble then recovery, but later the 3S battery recharged to 4450mah, instead of 5200mah.

 

[Nick93]

the maximum flight range is about 14 m/s and corresponds to 50 km/h.
At the optimum cruising speed of "DJI Phantom 3 professional" of about 14 m/s the estimated flight time is 17 minutes and the maximum range is over 14 km away.
long range drone DJI Phantom 3 professional