Has anyone produced a table or calculation method to find the sweet spot of speed and flight time?
I live on a small Island and out to sea is a shipwreck exposed at low tide.
I am planning to visit by Mavic, but I need to be certain that the distance and timing are not going to be fatal unknowns.
I carried out an overland flight in sports mode to get a feel for range. 3.4km there with transmitters and probably other transmission weakening factors and this is a safe margin, because over sea distance to the wreck is 2.7km.
However, I need time to find the wreck, get the photos and return to land, on land.
Sport mode uses significantly more power than standard.
There must be a trade of between modes so I can spend maximum time over the wreck.
Do any of you have real test results rather than guesses as to the numbers?

I have some fly time Mavic can travel far away (i have ~7km away and the total of 14.5 km flight) - farthest distance it achieves at 45-50 km/h (sensors Off and full throttle).
Longest flight time is at ~25 km/h - hard to keep as You should either use fixed-wing mode with set speed at 25 or be Very precise with stick - I personally have it for about 25 minutes in air
Be careful of Wind all those Max's are in NO wind weather as Wind is an enemy of long flights   even when blowing sideways as the Mavic will struggle and fly longer for the same distance And never send Your drone on a far mission to the wind as it will be a lot harder to have him back
Hope it helps
And wish you Luck!

I've never done any methodical testing, but I have flown a bit and my longest distance was achieved flying at around 50 KPH, which is the Mavic's top speed in P-mode (non-Sport) when obstacle avoidance is disabled.

Your biggest enemy is going to be the wind. You will either have to do the flight in nil wind (and you would need to know the wind at the height you are flying at (windy.com can help with this) or fly out to the wreck with a low headwind so that you will have a tail wind on the way back.
Try a similar distance over land into a light headwind and note the battery percentage left. You would need to double that plus another 15 to 20 percent for video and finding the wreck but keep 30 percent battery up your sleeve.Exact calculations can be difficult because it will also depend on the state of the battery such as whether it is relatively new or has seen a number of flights.

I have a feeling your mavic will struggle on the way back with side winds or head on. Try keep your speed around 25km/h flying exactly straight.

I think you will have to try many flights, testing the wind conditions and battery life.

I feel that you are going to need to try multiple flights. I would fly out there and find it with fly 1. Maybe set up a waypoint and fly back. Do not go less than 50% battery. Fly back and see what percentage you have. Load up another battery and fly back out using waypoint and then snap some pics, maybe a video or 2 and when your battery gets to a point that when you fly back you will have about 20% battery left. And because you have it set as a waypoint you can pring it up anytime and fly out there.

jreynolds5 Posted at 2017-11-16 03:32
I feel that you are going to need to try multiple flights. I would fly out there and find it with fly 1. Maybe set up a waypoint and fly back. Do not go less than 50% battery. Fly back and see what percentage you have. Load up another battery and fly back out using waypoint and then snap some pics, maybe a video or 2 and when your battery gets to a point that when you fly back you will have about 20% battery left. And because you have it set as a waypoint you can pring it up anytime and fly out there.

The waypoint is a good idea.
I had to abandon today because the cross wind is much stronger than forecast.
There was a technical issue anyway. Take of/landing would be just inside the yellow NFZ marker and for some reason, the permission process failed with repeated unabletofindhost malarkey.
I am trying to sort this now at home.

jreynolds5 Posted at 2017-11-16 03:32
I feel that you are going to need to try multiple flights. I would fly out there and find it with fly 1. Maybe set up a waypoint and fly back. Do not go less than 50% battery. Fly back and see what percentage you have. Load up another battery and fly back out using waypoint and then snap some pics, maybe a video or 2 and when your battery gets to a point that when you fly back you will have about 20% battery left. And because you have it set as a waypoint you can pring it up anytime and fly out there.

Thank you. I was hoping for a comparative chart.
I have decided that non-sport is the best choice at just below max which is on a still day, in excess of 27kph
I am also aware of the variables with battery age etc.
At 27kph, the distance is 2.7km so travel out should be 6 minutes. The same back.
On my last test over land, 24 mins showed as I took off. Time lost because of NFZ matters.
The search area is about 0.5km and a convenient strip of rocks, so one pass should work.
Once found, I will return and try again. This time, and I thought the waypoint idea was a good one, I will overfly and try to video. At least I will get something.
Allowing for variations in battery capacity, i might decide on 6 mins over the site. Total 18mins. I think that is a safe assumption on timing.
I think that has answered my question and thank you all.