ALTA 8 At High Altitude

Discussion in 'ALTA 8' started by Tom Comet, Aug 28, 2019.

  1. Tom Comet

    Tom Comet Member

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    Hello All. I have a gig coming up where we need to fly really, REALLY high. Think 20,000' +. Obviously this won't be happening with a stock A8 as the performance tables stop at 10,000' and, even there we loose 10lbs of carrying capacity. I did a search and found some info on high altitude props but not much in the way of real world results. How high can I really operate an A8 with the HA props? Obviously minimal payloads, lightest batts possible and HA props. Are there any other mods that will make our chances of success better??
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Whoa! That is reallly high, Tom. Gotta ask where?

    I've not heard of anyone operating that high -- you'll be breathing oxygen at that level. I've flown the sailplane up I used to own up to 22 grand, but it is really cold up there too.

    Cheers
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  3. Jason Smoker

    Jason Smoker Active Member

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    you flying on Everest? thats crazy high? you be better off asking Freefly send them a email then post a reply on here to keep everybody on the loop!
     
  4. Tom Comet

    Tom Comet Member

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    We will be flying all around the Himalaya and the Everest area. We have reached out to Freefly and they had very little comment on flights above 10'000' and suggested I try the forums. Hoping I can get a hold of someone with some real world experience. That being said, we are flying Inspire2s up high as well. Not a Freefly thing but any word there would be appreciated also.
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Tom:
    Check out this table of atmospheric data: https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html
    The air at 20,000 is considerably less dense and less viscous so the first thing I would be concerned about is whether the props will generate enough lift to carry the payload and/or the aircraft itself.

    You might be better off to contact some of the universities who teach aerodynamics or perhaps even NASA (there is on-going research for using multi-rotor copters on Mars which also has an extremely thin atmosphere.

    The FAA has also published data on helicopter performance: https://www.faa.gov/regulations_pol...helicopter_flying_handbook/media/hfh_ch07.pdf

    Hope this helps.
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Tom: Contact Larry Young at NASA Ames Research. He's leading the team creating a helicopter to fly on Mars.
    https://nari.arc.nasa.gov/young
    The article from I got his name is here: https://www.airspacemag.com/space/helicopter-dreams-of-mars-180971739/

    I've got to believe that either he knows some answers for you or can direct you to someone who does.
    Cheers
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  7. Tom Comet

    Tom Comet Member

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    If anyone would know that would probably be the guy...

    TC
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    One other problem you may have, Tom, is keeping the LiPos warm before you use them. When they get cold they tend not to give back as much charge as when they're warm. Of course, once you've flown a pair of them, then you can use them as Lipo Warmers® for the others.

    Cheers
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  9. Tom Comet

    Tom Comet Member

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    We are based in Canada so I have a lot of experience with COLD weather OPs. We have found that Batts charge very poorly in the cold as well. They appear full but that is not always the case. Planning on lots of warming strategies for sure.
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    In which case take two cases of beer: 1) Péché Mortel and 2) Lucky Lager. Keep the Lucky Lager very warm and surround the LiPos with it.

    The Péché Mortel? That should be kept cold. It's for drinking, eh?

    Cheers
    Andy
     
  11. Mike Hagadorn

    Mike Hagadorn Member

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    What camera\lens are you trying to fly? I just did some flights at 12,000 with a light red setup. (A far cry from 20,000) 15lbs of gimbal and 2x10,000 lipos and performance was good. I did add about 2lbs more to test a larger lens on a gusty day and it was not so good. Slightly sketchy. Soggy performance and not so much lift margin. it was 34f on that day. Later in the week was flying at 0deg F and performance was quite nice at 12,000 with a 7 min flight time. on the pair of older 10,000s Batteries MUST BE WARM. if they start cold your doomed.
     
  12. Rick Gerard

    Rick Gerard Active Member

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    Performance goes down logarithmically with altitude but performance increases as temperature decreases so you get a little bit of help in the mountains. Unfortunately, as the temperature drops battery performance also degrades quickly. If it is below freezing you are going to probably need heaters for the batteries. Chemical heaters would work and only add a little weight. I did a lot of filming on the North Slope of Alaska in November and December a long time ago and everything from the cameras to the batteries had to be in heater barneys to work. It was a real pain.

    You might be completely out of luck. If you are in the US Mt Ranier is a fairly easy climb over 2 days and that will get you to 14,500' but it's a national park so you would have to apply for a special waiver and probably wait more than 90 days to even know if you are going to get the waiver. Unfortunately, all of the high peaks in the US are national parks.

    The only other option I can think of for testing is to go up in an unpressurized cargo airplane, climb to 20,000', Teather the Alta. to some scales and see how much lift it can generate. The only other option is to project the performance charts using standard density altitude calculations. You can probably use this FAA paper as a starting point: https://www.faasafety.gov/files/gslac/library/documents/2011/Aug/56396/FAA P-8740-02 DensityAltitude[hi-res] branded.pdf

    Pay attention to the Koch Chart and you should be able to calculate the decrease in the rate of climb and relate that to performance. Before you did your weight and balance on an iPad we had to use this kind of info to safely fly in the mountains.

    Rick Gerard, FAA certified Commercial, Instrument, MEL, SEL, CFI pilot, and A&P mechanic.
     

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