Most economical long distance cruise speed

[skydriver]

I am planning a flight to an offshore lighthouse using a P4P. Distance one way over water is 1.7 miles. I want to arrive at the destination using the LEAST amount of battery energy. Assuming no wind, while cruising over water, is it better to fly in P mode or faster in S (sport). In other words, which is the most economical speed in terms of battery power used per mile flown? One past post suggests 29 MPH as being the "sweet spot". Does anyone have further input? Thanks for considering this.

 

[Beerock]

I would fly in atti mode.

 

[skydriver]

Is that based on experience?

 

[Meta4]

I am planning a flight to an offshore lighthouse using a P4P. Distance one way over water is 1.7 miles. I want to arrive at the destination using the LEAST amount of battery energy. Assuming no wind, while cruising over water, is it better to fly in P mode or faster in S (sport). In other words, which is the most economical speed in terms of battery power used per mile flown? One past post suggests 29 MPH as being the "sweet spot". Does anyone have further input?

Forget Sport Mode - it burns battery faster than any gains you may get from the speed - like driving your car at 100 mph.
Best fuel economy will be at just a little under full speed in P-GPS mode - not enough to make much difference, just use full speed in P-GPS mode.

Some things you need to consider:
First turn off obstacle avoidance - it only reduces speed and isn't much use over water.
Wind - can be critical. What will the wind be for the return trip?
Only attempt in light winds or winds that will give you a tailwind coming home.
You do not want to have to push against a substantial wind coming home.
Using atti mode if you have a tailwind to come home will give you a nice boost but won't do much to help otherwise.

 

[skydriver]

Thanks for your comments. With drones it is likely that you need to consider a number of variables: parasitic drag, which increases with air speed, translational lift that occurs when air passes over the rotor hub(s) and is most effective at a certain minimum speed, electric motor efficiency, percent of total electrical energy necessary to overcome the pull of gravity. All these factors would take a lot of testing to come up with an answer. My guess is what you have suggested; a little less than 100% in "P" mode. Of course if there are winds to consider, and there will be, that throws another factor into the equation depending on if you are dealing with a head or tail wind.

 

[Beerock]

I prefer atti mode. Has to use less power because it's not trying to hold gps position ever or trying to brake.

 

[sar104]

This was discussed last year, with both test results and calculations:

Physics of Drones

 

[NRJ]

I would fly in atti mode.

Maybe, but at what speed? That was the question.

 

[N017RW]

Under what conditions?

Indicated speed is based on Ground Speed via GPS. The 'effort' needed to achieve or maintain a specific GS depends on ambient conditions.

 

[Geoelectro]

Back in the P2 days, a discussion concluded that 30 mph was optimal.

Geo

 

[Beerock]

Maybe, but at what speed? That was the question.

At whatever speed is stated for best efficiency above but in atti mode

 

[Harleydude]

If I recall, Sport Mode gives you battery consumption data, which might aid in finding an answer to your question. Barring that....

It would be interesting to know if it's more economical to yaw into a side wind (like the big jets do) (ATTI mode), or if it's more economical to allow GPS mode to pitch the bird into the side wind. I've often wondered this myself. Because of the inherent inefficiency of a quadcopter (compare the energy used by a fixed wing for the same flight), I'd bet dollars to doughnuts that the difference between the fastest flight vs. the most economical flight are marginal. I mean, let's face it. A quad copter at ANY speed has the drag coefficient of a brick. And in most cases - like a car or fixed wing - wind drag is a major factor in finding the tipping point between "economy" and "diminishing returns." If one plots speed vs. fuel consumption on a graph, the point of diminishing returns becomes apparent because the curve is exponential. But in the case of a flying brick, I'd bet dollars to doughnuts that the curve is a little more linear because even it's most economical speed is still terribly UNeconomical. Let's face it. Even just hovering is a terrible waste of energy. I can't think of a better way to waste energy than to take a mass, strap 4 rotors to it, and hover. It would be like idling your car @ 4,000 rpm....leaving only 2,000 MORE RPM for top speed.

I'm just spit balling here. It think it makes for interesting discussion.

Discuss.

D

 

[PhantomPilotUK]

If I recall, Sport Mode gives you battery consumption data, which might aid in finding an answer to your question. Barring that....

It would be interesting to know if it's more economical to yaw into a side wind (like the big jets do) (ATTI mode), or if it's more economical to allow GPS mode to pitch the bird into the side wind. I've often wondered this myself. Because of the inherent inefficiency of a quadcopter (compare the energy used by a fixed wing for the same flight), I'd bet dollars to doughnuts that the difference between the fastest flight vs. the most economical flight are marginal. I mean, let's face it. A quad copter at ANY speed has the drag coefficient of a brick. And in most cases - like a car or fixed wing - wind drag is a major factor in finding the tipping point between "economy" and "diminishing returns." If one plots speed vs. fuel consumption on a graph, the point of diminishing returns becomes apparent because the curve is exponential. But in the case of a flying brick, I'd bet dollars to doughnuts that the curve is a little more linear because even it's most economical speed is still terribly UNeconomical. Let's face it. Even just hovering is a terrible waste of energy. I can't think of a better way to waste energy than to take a mass, strap 4 rotors to it, and hover. It would be like idling your car @ 4,000 rpm....leaving only 2,000 MORE RPM for top speed.

I'm just spit balling here. It think it makes for interesting discussion.

Discuss.

D

How many doughnuts per dollar?

 

[sar104]

If I recall, Sport Mode gives you battery consumption data, which might aid in finding an answer to your question. Barring that....

It would be interesting to know if it's more economical to yaw into a side wind (like the big jets do) (ATTI mode), or if it's more economical to allow GPS mode to pitch the bird into the side wind. I've often wondered this myself. Because of the inherent inefficiency of a quadcopter (compare the energy used by a fixed wing for the same flight), I'd bet dollars to doughnuts that the difference between the fastest flight vs. the most economical flight are marginal. I mean, let's face it. A quad copter at ANY speed has the drag coefficient of a brick. And in most cases - like a car or fixed wing - wind drag is a major factor in finding the tipping point between "economy" and "diminishing returns." If one plots speed vs. fuel consumption on a graph, the point of diminishing returns becomes apparent because the curve is exponential. But in the case of a flying brick, I'd bet dollars to doughnuts that the curve is a little more linear because even it's most economical speed is still terribly UNeconomical. Let's face it. Even just hovering is a terrible waste of energy. I can't think of a better way to waste energy than to take a mass, strap 4 rotors to it, and hover. It would be like idling your car @ 4,000 rpm....leaving only 2,000 MORE RPM for top speed.

I'm just spit balling here. It think it makes for interesting discussion.

Discuss.

D

It's precisely because hovering requires a significant amount of energy that the speed makes a significant difference to the efficiency in J/m. But why all the speculation anyway - there is a quite detailed physical analysis that includes all the first order factors in the thread linked above. Did you read it? There is no real mystery to this issue.

 

[Harleydude]

How many doughnuts per dollar?

LOL...Touché, sir!

 

[Harleydude]

It's precisely because hovering requires a significant amount of energy that the speed makes a significant difference to the efficiency in J/m. But why all the speculation anyway - there is a quite detailed physical analysis that includes all the first order factors in the thread linked above. Did you read it? There is no real mystery to this issue.

I have not read all the replies. I'll go back and look for the article. Indeed, if this has been covered in detail via a funded study, then my ramblings are moot.

D

 

[sar104]

I have not read all the replies. I'll go back and look for the article. Indeed, if this has been covered in detail via a funded study, then my ramblings are moot.

D

Not moot - but the discussion might be more interesting once you have looked at that stuff.

 

[StanMI]

I'm not by any stretch of the imagination "In the Know" as to what the correct answer. These are just from my experience.

Flying out 1.7 miles, taking a few photos or short videos and returning to the launch point should not be a problem as long as you don't have a lot of wind in either direction. I really don't think the fact that it's over water would affect anything other then you have nothing to break up the winds.

Please post whatever you do wind up doing. Lighthouses can make for some amazing images. IMHO !!

 

[skydriver]

I'm not by any stretch of the imagination "In the Know" as to what the correct answer. These are just from my experience.

Flying out 1.7 miles, taking a few photos or short videos and returning to the launch point should not be a problem as long as you don't have a lot of wind in either direction. I really don't think the fact that it's over water would affect anything other then you have nothing to break up the winds.

Please post whatever you do wind up doing. Lighthouses can make for some amazing images. IMHO !!

I'll do that but it won't be until July. Thanks to everyone who responded to this question.

 

[PhantomWetSuits]

I am planning a flight to an offshore lighthouse using a P4P. Distance one way over water is 1.7 miles. I want to arrive at the destination using the LEAST amount of battery energy. Assuming no wind, while cruising over water, is it better to fly in P mode or faster in S (sport). In other words, which is the most economical speed in terms of battery power used per mile flown? One past post suggests 29 MPH as being the "sweet spot". Does anyone have further input? Thanks for considering this.

Are you by chance part of the group heading out together ?