Elevation impact on IRIS+ flight times.

Posted by Justin H. on July 13, 2015 at 9:26am

Just a reminder that flying at high elevation can have a HUGE impact on flight times and can result in sudden failure. I flew at 9,600' this past weekend and my loaded IRIS+ (gopro, tarot 2d gimbal, secondary GPS) got to about 5:45 before the battery could not maintain enough thrust to keep it airborne and started dropping quickly. No warning, of course, since plenty of charge remained. Fortunately I was not flying past the cliff edge or the IRIS would have been unrecoverable; as it was, I suffered a hard landing that broke a leg off and took part of the motor housing with it. The more you know!

I normally get about 12:30 flight times from the same craft at 3,500'.

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Replies

  • Chris Hanson July 13, 2015 at 10:57am

    Has anyone calculated if different (bigger) props would improve the lift at altitude? Normally bigger props will have too much resistance, but in the thinner air, wouldn't it even out?

    • Gregg > Chris Hanson July 13, 2015 at 8:57pm

      More pitch on a prop will help. You live in Colorado Chris? Im In Denver.. wonder what my x8 would do at 10,400.

    • Chris Hanson > Gregg July 14, 2015 at 2:15pm

      Yes, I'm above Evergreen in Brook Forest. Come on up sometime and we can fly at Upper Maxwell Falls. This clearing where I've flown from before:
      https://www.google.com/maps/@39.5652182,-105.3793332,153m/data=!3m1!1e3!5m1!1e4

      is about 8400' MSL.

      We could also go up on Mount Evans if you like crashing.

    • Gregg > Chris Hanson July 14, 2015 at 8:02pm
      oh hell yah Im always looking for someone to fly with....notvsure about crashing..still licking my wounds over totalling my s900
    • David Ringler > Chris Hanson July 13, 2015 at 4:13pm

      I prefer using the original iris apc larger props on the iris+!

    • SkyRover > Chris Hanson July 13, 2015 at 12:00pm

      I haven't done any calculations, but at 4000+ I had trouble when descending and not being able to pull out. Switched to 10 in props and got a lot more punch as well as a few more min of flight. The extra time was because there was so little thrust as the bat voltage dropped off there wasn't any left to safely keep flying.

    • Justin H. > SkyRover July 13, 2015 at 1:01pm

      Great tip, I'll give that a shot. I seem to do most of my flying just around 3,500' and 4,500', and have had the same poor results in descent. I get other quirks. For instance, as soon as the battery comes off peak, underestimating the throttle needed to maintain altitude when switching from LTR to Stabilize results in that descent you mentioned that can't be pulled out of.

  • Chris Hanson July 13, 2015 at 10:55am

    Yeah. I fly at 8200' at my house here. ;) Hot & high is brutal. I tried flying in Telluride (9500') and could barely get off the ground. I wanted to fly at Bridal Veil falls (10,400') but I'm not sure I could even do so.

  • DavidFolts July 13, 2015 at 9:42am
    Justin...you described the "hot and high" mission limitation every DoD rotorcraft had in Afghanistan..and even at 3500 feet you have already lost an amount of prop efficiency due to thinner air...this is a big deal to a micro UAV.
    When I was living in Colorado Springs I had big issues during those early days of electric flight!
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