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Flight Times at High Altitude

Discussion in 'General Discussion' started by andreweio1, Mar 2, 2016.

  1. andreweio1

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    Hi Folks,

    We have a potential client who is in Santiago in Chile and he is asking how the performance is affected by altitude. His altitude is typically about 3000m, therefore can anyone on this forum who lives or has had experience of flying at higher altitude please advise on the typical percentage flight time loss, and confirm what altitude, and the typical temperature. I can then go back and advise on the expected flight times based upon normal altitude flight.

    Many thanks in advance
     
  2. The Editor

    The Editor Moderator
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    Might want to get yourself a set of two of the high altitude props as well.
    Official DJI Store
     
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  3. damoncooper

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    Also warm the batteries before flight to 25C if at all possible and try to keep them in the 20C - 40C optimal discharge temp during flight. Especially if ambient air temp is < 10C.
     
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  4. dogear

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    I am operating at 1800 meters above sea level and have noticed significantly lower flight times than normal. My theory is the motors are having to work harder in the thin air to produce the lift needed to operate the drone. I'm also a helicopter pilot and the performance of the machine is significantly reduced at high altitude reducing the useful loads the aircraft can maintain especially when the ambient temperature is high.
     
  5. damoncooper

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    Yes. Makes sense. Use increased pitch props if you can.
     
  6. dogear

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    Yup ordered some last thx for the advice.
     
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  7. dopeytree

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    Learn something new every day - I had no idea you could get those high altitude props! I've just flown the inspire pro on Sakran Mountain (Iraq) at 3587m. Flew fine but not for long as it was so windy I brought it down for safety. Probably 17-25mph winds. We were very lucky and able to drive 2 jeeps up so I used those as a wind break for takeoff. Also I used the DJI battery heater http://store.dji.com/product/inspire-battery-heater
     
  8. dogear

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    I do have the heater. As I said in an earlier post I think that there are a number of factors going on with high altitude ops. Firstly the props must turn faster in order to generate the lift in the thinner air therefore using more power from the batteries. Wind would definitely be a factor as well, and lastly the cold would also factor into shorter battery life. I think the service ceiling on the Inspire 1 is something like 14,000ft which isn't too shabby. I am not sure that the high alt props are going to extend the battery life. I think that they might just make the drone more responsive in the thinner air. Will be interesting to see. Cheers
     
    #8 dogear, Mar 5, 2016
    Last edited: Mar 5, 2016
  9. dopeytree

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    I wasn't flying very far away or high from take off point. Just circling our protagonist on the mountains tops. To show the guy & his surroundings (as much as you can while hiding the crew & 2 jeeps) It wasn't the biggest flying time as I wait until the ground camera filming was done so my flying time was limited to about the last 10 minutes of sunset. But we nailed it! It rained the day before & after too.

    How many batteries have you got?
     
  10. dogear

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    Got 4, two regulars and 2 of the "high capacities". As I said we will have to see what kind of flight times I get here at 1800 meters (6100ft). I ordered the high altitude props so I am looking forward to seeing what kind of performance I get. I am a retired helicopter pilot and have worked out of this area a lot. In the summer I had room in the machine for me (no pax) and very little fuel, just to be able to get the machine off the ground and down to where we could take on fuel, and we are talking an Augusta 109 (twin engine) which seats 6 including the pilot. It's very interesting to see what kind of performance the Inspire 1 gets at the same altitude. I am fascinated with the technology that they cram into such a small space. The Augusta that I flew was certified single pilot IFR which required it to have 2 "Heliflight" systems on board. Basically a stability augmentation system. These DJI drones have 20 times the sophistication of the Augusta at just a fraction of the cost!!! Now I've heard that they have added an anti collision system to the Phantom 4, unbelievable!
     
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  11. damoncooper

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    4500m ASL actually, according to specs
     
  12. Bryan Conover

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    So what's the result if used at sea level?
     
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  13. The Editor

    The Editor Moderator
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    Using s steeper pitch at sea level will draw more current from your battery and so you will get shorter flight times although the DJI offerings are not hugely different from stock.
    The side affect of drawing more current means everything will work harder and heat up. In extreme cases using a very steep pitch prop at low altitude can cause the motors to cavitate.
     
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  14. Bryan Conover

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    Thank You !
     
  15. Orchard

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    Editor: Are the high altitude props for the Inspire also compatible with the Matrice?
     
  16. The Editor

    The Editor Moderator
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    Providing your Inspire has the 1345s attachments then yes, the steeper pitch of 1360 should be fine to use at higher altitudes.
     
  17. jlrsn

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    I live 9 months a year up at 8,000' ASL at my Mountain Home up in the Rocky Mountains and 3 months of the year at my Sea Level home in the SF Bay Area where I bought and took delivery of my new Inspire 1V2. I regularly fly my I1V2 up thru 10,000'+ at my Mtn Home where the elevations vary up thru 14,000' ASL with 2,500' AGL vertical cliffs. I've only flown my I1V2 up at my Mtn Home since January with OATs from the low 20°Fs up thru about 35°F. The temps up at my Mtn Home can get down to -25°F or colder. I have a heavy Circular Rubber Landing Pad that I use in fresh powder snow surrounded by 100' plus high Ponderosa Pine Trees. A few things I've noticed is how the 1360T Props are quieter at altitude. Sudden high winds up in the mountains make landings interesting especially in confined areas. I reduced my gains using the 1360T Props according to a recommendation by DJI. DJI states that if the Zenmuse X3 gimbal and 3510H motors are used, gain adjustments are required. The recommended gain values are: Pitch = 90*, Roll = 90* and Yaw = 90*. My flight times are reduced due to the cold and elevations but not that greatly using TB48 Batteries. As a retired ATP Pilot I've flown both heavy Fixed Wing (Round Multi Engine Prop up through Heavy Multi-Engine Jet Airplanes) and Light Reciprocating Helicopters up thru Heavy Multi-Engine Turbine Helicopters. I've flown for decades throughout the Sierras with many landings up over 10,000' ASL both summer and winter. I've also crossed the Andes of Chile to Argentina many times with my Single Engine C210. I owned a home in Chile.
     
  18. Bryan Conover

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    And no one really cares.
     
  19. Richard G Hugh

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    What's your malfunction?
     
  20. licensed pilot

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    Aeronautical engineering is amazing...Do they make a low altitude/high heat propeller (I'm in the Arizona desert.):D
    In 1990 Phoenix hit 122 degrees, some airliners at Sky Harbor Internationals were grounded because their aircraft manuals density altitude pages didn't go past 120!

    I wasn't flying UAVs back then but I'm calculating at my elevation (1500) feet and standard altimeter setting setting, the density alt. was 5,755 that day, almost 6,000 feet! Not a good idea to fly my I1P at max TOW that day, eh?...