I thought I had plenty of reserve to return...and the forced landing warning was inducing panic

[albatross911]

The other day I was flying out to the sea going to a man-made island about 3.5km away, which has been on the local news lately. I flew with sports mode on and reached it with 78% battery left which means the distance used up just above 20%. I spent about 5 minutes filming there thinking of returning before reaching 50%, which should give me double the battery required to return in case of emergency. At about 58% it gave me a warning that I only have enough battery to return home. I thought for a few seconds and took the advice to start returning with sports mode on. I realized that I must be against wind as the battery kept dropping quicker than the way over, and I descended to about 20m over the water hoping to catch weaker wind...50%...40%...30%...20% and I was still 1km away...15% and 600m away, knowing that it will start forced landing at 10% I ascend to 35m to give me more time to pick a landing spot just in case...10% and 400m to go and reached land I kept it just above some rocks on the coast in case it drop out from the sky, but the forced landing warning is so rapid that my heart was pounding and palms sweating...

Finally it reached home point with 5% left. After turning off everything my hands were shaking...I have lost a Phantom 2 into the ocean before and been flying the Mavic for over 200 flights so I won't consider myself a novice, but that forced landing warning sound was really making me nervous. Also my girl friend heard it and kept asking me what's happening which further induced the stress. In less experienced hands a pilot can easily panic under the pressure and make the wrong decision.

Can DJI make the warning to sound just a few seconds and then go silent? I'm sure we can hear the warning when it goes off and attend to it. Keep it going for the entire duration from 10% onward really does not help the pilot handle it calmly.

Also when we go long distance always leave more reserve than you estimate to be enough. I looked at the log and on the way out the speed under full throttle in sports mode was 60km/h while on the way back was 45-50km/h. Another flight and another lesson for me.

 

[albatross911]

News about the island and a photo I took.

 

[albatross911]

The flight log if anyone is interested.

 

[RayOZ]

I wouldn't recommend using Sport mode for long distance flight. You pretty much half your air time in sports mode flying full throttle. You would be better of with P-Mode and OA off. Unless you are fighting strong wind.
Battery Consumption Experiment

 

[choo choo]

I agree. I stand to be corrected on this, sport mode doesn’t increase power, it only enables a greater angle of attack against a headwind. Thus enabling the aircraft to fly faster or make headway against wind. The greater angle of attack and faster speed will expose the craft to higher wind resistance thus not the most economical way to conserve fuel. (Battery) A debt of thanks must surely go to the OP for being brave enough to admit the error, but mostly from the rest of our community for the reminder to watch the wind/distance/ battery, even the most experienced can get caught out.

 

[albatross911]

Well it took me about 3.5 minutes with a speed of 60km/h to fly the 3.5km distance to reach my destination. Then I got 5 minutes to film the island before reaching safe return limit (should have been 4 minutes to be safe in this case) and a total flight time of almost 16 minutes to reach 5% battery left. If I don't use sports mode with a speed of 30km/h it'd take double the time to reach there, so 7 minutes. Normally I keep at least 20% left to land and rarely go over 20 minutes total flight time. So I would have just under 6 minutes to film the island for a safe return, assuming all things equal. So yeah I would be better off to fly with P-mode and get more time at the island.

But flying a straight line over the water for 7 minutes is so boring...

 

[RayOZ]

You had quite strong wind on the way back. I think you would have to flick to sports mode on the way back either way. The battery temperature got pretty high on the return journey, if you haven’t noticed.
I did a similar flight in NZ. Ran a POI to circle an island, and returned with 30% battery. Spent almost 7 minutes around the island before returning.

 

[RayOZ]

I agree. I stand to be corrected on this, sport mode doesn’t increase power, it only enables a greater angle of attack against a headwind. Thus enabling the aircraft to fly faster or make headway against wind. The greater angle of attack and faster speed will expose the craft to higher wind resistance thus not the most economical way to conserve fuel. (Battery) A debt of thanks must surely go to the OP for being brave enough to admit the error, but mostly from the rest of our community for the reminder to watch the wind/distance/ battery, even the most experienced can get caught out.

It does increase power, you’ll see that with the rev on the motors. Higher angle of attack and higher speed also increase drag. And by the looks of it, generate a lot of heat.

 

[albatross911]

You had quite strong wind on the way back. I think you would have to flick to sports mode on the way back either way. The battery temperature got pretty high on the return journey, if you haven’t noticed.
I did a similar flight in NZ. Ran a POI to circle an island, and returned with 30% battery. Spent almost 7 minutes around the island before returning.

Yes I was not considering wind, just seeing if sports mode for long distance is good or not.

 

[tcope]

I agree. I stand to be corrected on this, sport mode doesn’t increase power, it only enables a greater angle of attack against a headwind.

It does increase the power to the motors. The motors are always generating lift and power is used in the process. If the aircraft is pitched more horizontally it need to generate more lift and use more power in doing so. Drones to not generate lift like an airplane wing does.

 

[choo choo]

Thanks guys, that makes sense, the larger angle of attack requires more energy/power to stay aloft. Thanks for the explanation.

 

[Kilrah]

People have done measurements and Sports mode typically does give you more travelled distance than P. Flight time will be significantly shorter though of course.

Now you know that if you got 3.5km with only 20% battery it means you got a lot of help and it will work against you for the return.

Always good to check what speed you get in both directions before heading out far.

 

[Lapeer20m]

I agree with post number 12.

Sport mode = greatest distance per battery

P-mode = longest flight time per battery.

 

[RayOZ]

I agree with post number 12.

Sport mode = greatest distance per battery

P-mode = longest flight time per battery.

Not true. I’ve done my own test. See link on post #4.

 

[Kilrah]

The point is there are threads where other people also tested and got the opposite result (I recall at least 2). They did not interpolate like you, they did the real thing.

Also your sports run estimates 8mins30 to 30%, I do that often and for sure get more. Something must be wrong with your procedure, or your battery is in bad condition. The meter takes that into account.

 

[Andyh77777]

The point is there are threads where other people also tested and got the opposite result (I recall at least 2). They did not interpolate like you, they did the real thing.

Also your sports run estimates 8mins30 to 30%, I do that often and for sure get more. Something must be wrong with your procedure, or your battery is in bad condition. The meter takes that into account.

Kilrah, could you please say whether you are replying to Lapeer20m (Sports Mode=Greater Distance) or RayOZ (P-Mode=Greatest Distance)

 

[genesimmons]

if worse came to worse,,,, could u have landed on that cool island and drove out there, that manmade road looks very cool, did u get any panoramas with the road in the back? can civilians drive out there or is it oil or millatary only, cool story and awsome lesson learned and ur mav flies another day whoohoo

 

[RayOZ]

The point is there are threads where other people also tested and got the opposite result (I recall at least 2). They did not interpolate like you, they did the real thing.

Also your sports run estimates 8mins30 to 30%, I do that often and for sure get more. Something must be wrong with your procedure, or your battery is in bad condition. The meter takes that into account.

Well, I've seen videos on youtube of someone doing this range thing, 8km out and back, with 1% battery left. They were flying in P-mode, OA off @ 50kph. I personally won't want to test it out myself, flying 4.5km out and back in Sports mode. There's no open field nearby me with that large/long open space for me to fly safely anyway.
My interpolation is using data point for sustained 60kph to 65 kph, straightline. Once you slow down, turn and do other maneuvers, the battery drain changes.
I guess the best confirmation would be from the guess doing their range test with stock batteries. Do the fly in Sports mode or P-mode with OA off?

 

[joejaxvic123]

if worse came to worse,,,, could u have landed on that cool island and drove out there, that manmade road looks very cool, did u get any panoramas with the road in the back? can civilians drive out there or is it oil or millatary only, cool story and awsome lesson learned and ur mav flies another day whoohoo

I think it's an entrance to an underwater tunnel?

 

[albatross911]

if worse came to worse,,,, could u have landed on that cool island and drove out there, that manmade road looks very cool, did u get any panoramas with the road in the back? can civilians drive out there or is it oil or millatary only, cool story and awsome lesson learned and ur mav flies another day whoohoo

The construction is not completed yet so it's not open to public. Unfortunately I did not take panorama as it can take a minute or more to complete and I'm more into video. Can post the video later though.