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  1. etr102

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    I'm working on a Litchi mission that will require quite a bit of distance. The rule of thumb I've read is to try to keep your Litchi missions around 15 minutes (round trip) to get back with enough juice to have a safe and stress-free landing. The default cruising speed (30km/h or whatever it is) gives me an estimated 21 minute round trip, definitely too risky of a flight in my opinion. If I up the speed to the maximum of 54km/h, I can make it back in 13 minutes.

    Will increasing my speed that much cause my battery to die quicker? Would a 13 minute flight at 54km/h (still significantly slower than Sport Mode) drain the battery and make this flight risky?

    (I'm strictly asking about battery level management .. or "fuel economy")
     
  2. Rlisch

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    Location:
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    image.jpg View attachment 62312 image.jpg I get my best "fuel" efficiency using FPV Camara at around 33mph.
    I can make mission models beforehand at different speeds and the App tells me the approximate "fuel" consumptions
     
  3. ElGuapo

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    Your "fuel economy" depends on the weather you encounter the day you launch your mission. Let's say that you fly on gusts winds against 8 mph, that will require more battery power and have a direct impact in your fuel economy.

    I use Autopilot, I just ran a mission of a golf course when I planned my mission I was supposed to complete it with 50% of battery level and have plenty of juice left by the time I landed safely. The day I flew my mission was windy, I still completed my mission and landed safe buy I landed with 30% of battery.

    What I recommend you should do on the day of your mission is to keep an eye on the wind. Also if you have 2 batteries fly your mission manually trying to hit the points you have created in the App. When the AC returns home check how much juice is left, if the level is acceptable swap batteries and run your mission.
     
    #3 ElGuapo, Aug 16, 2016
    Last edited: Aug 16, 2016
  4. ElGuapo

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  5. Rlisch

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    Location:
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    Ponce, Puerto Rico
     
  6. ElGuapo

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    Boricua here..

    Been in California for 30 yrs or so.
     
  7. jogforfitness

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    I'm not sure this will help you but, Dirty Bird has designed missions traversing through Baltimore which I think are roughly 35,000 feet. If I recall he flys a P4 around 30 mph and the mission runs around 16 minutes. Roughly his battery is around 30 or so percent upon return. To verify I'd recommend searching through his forum posts.


    Sent from my iPad using PhantomPilots
     
    #7 jogforfitness, Aug 16, 2016
    Last edited: Aug 16, 2016
    Digdat0 likes this.
  8. jstjohnz

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    I'm sure there is an optimum flight speed to achieve maximum range but I don't know what it is. I've been meaning to fly a mission at various speeds to see if there is a "sweet spot" in terms of speed that gives the best range.

    Any calculation like that goes out the window though is you're dealing with winds.

    I would suggest flying a slightly shorter mission first to get a feel for your battery margin. I have flown 36,000 ft Litchi missions and I believe I calculated that a bit over 40,000 would be the max distance for me. Since you are over water you may stay in RC range the whole time, that's a big plud because if you do stay in range you can abort the mission early if battery looks iffy. I don't think that I belueve the Litchi battery percentage calculator.
     
  9. Rlisch

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    Flew many marginal long range missions but SRTH always brought the P4 back well on time, aborting the mission.
    Seems that it considers the tailwind if you are going down wind.
    From experience I also would say that 40,000' is about the limit in a stock setup with a safe return. Very windy and gusty conditions definitely will reduce this distance.
     
  10. Dirty Bird

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    Location:
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    I regularly run missions of 37,000-38,000' @ 30 mph and return with 30% battery remaining. Wind speed & direction can have a significant impact on the battery. My flights are usually in winds of 8 mph or less. Yesterday I ran a mission in 11 mph winds & returned with 25%. If you are heading directly into the wind on the long leg out or in expect less efficiency, especially over open water with unobstructed & potentially gusty winds.

    I think the sweet spot for efficiency in in the 24-28 mph range. I do not recommend running your mission at the max of 33.6 mph. This will likely result in terrible efficiency since you'll be running hammer down the entire flight trying to hit that mark. BTW Litchi estimated flight times are usually on the high side. Missions Litchi estimates @ 19 minutes generally complete in 16.

    Also should mention you'll probably have to disable Smart-RTH to complete a 35,000' mission unless you are just flying at a constant altitude. The flight computer is conservative & engages early. If you disable the bird will fly until the battery reaches 10% then auto-land engages. You can override with the sticks if you are in RC range.

     
    #10 Dirty Bird, Aug 17, 2016
    Last edited: Aug 17, 2016