Speed vs Batt Life.

[Captain Jerry]

Does anyone have any info/experience on what is the optimum/most economical speed vs batt life for a P3P? For example at 90 in my car I am burning more fuel per mile than at 60...

For instance, if I were to plan a mission on Litchi mission planner, say at 30 mph, I would expect a shorter flight time than at 20 mph, however it would take longer to complete the mission at 20 mph. There must be a sweet spot in there somewhere for max distance vs batt life...

Thx!

Aerospace engineers are familiar with your thoughtful and perceptive question.

Let's review the factors involved:

1. In subsonic aircraft twice the speed requires four times the power. Higher speed means less range, but not always.
2. In hover mode range is zero.
3. Enter the velocity versus speed graph.
4. For aircraft, there does exist the sweet spot speed you mentioned called "Maximum Lift Over Drag Ratio". <--- the most lift for the least amount of power.

You can write down how much power you use versus speed at several different speeds to determine L/D Max.

In addition, always consider the wind.
If you fly 30 MPH into a 30 MPH headwind your ground distance covered versus power is zero!

Generally it's best to fly 10% faster into headwinds.

Now, after covering these factors, the Phantom can not fly very fast so differences will be less compared to big airplanes.

BUT! To answer your question answer the questions below.

How long can you hover?
How far can you fly at 1/4 speed?
How far can you fly at 1/2 speed?
How far can you fly at 3/4 speed?
How far can you fly at max speed?
The answer is in the experiment above...

Good luck and let's find out.

 

[Chad Mowrey]

I know this post is a little old but I did do some testing on this during multiple days with slightly different wind conditions (wind does make a huge difference). Based on my tests it seems that around 17 or 18 MPH is the right speed for maximizing the distance with relationship to the battery life. I assume you're asking because you plan on doing a long distance mission. If that's the case just remember that if you lose connection during the mission and you have it set to complete mission when the connection is lost the RTH button on the RC won't do anything and it'll TRY to complete the mission regardless of battery life. So if you think the distance is too great for the battery in the middle of the mission you might be out of luck if it disconnects before you hit the RTH button.

 

[solentlife]

True, as is fuel burn per hr increases with higher speed.
My example of 10 mph vs 15 mph by increasing speed if you had 6 minutes of battery left you would go 1 mile. By increasing speed you may lose up to 20 % battery life so would have 4.8 min at 15 speed so would go 1.2 miles. Someday that might keep you dry. Also usually lower altitudes have less wind so altitude is important.

Think you missed an important point in battery drain.

Unlike fuel which will create a curve graph ... which is a pure consumption graph. Batterys have 2 factors that alter to determine its watts output ... reducing voltage and increasing compensatory amps.

Basically gasoline / diesel has a fixed energy output per unit of fuel and makes no difference what level the tank is.

A battery on the other hand is seriously affected by its mA/hr reduction and voltage reducing as a consequence..... in effect the tank being used up affects that power output.