Bad crash with Cinestar/Mikrokopter and Graupner MX20 combo

Discussion in 'Cinestar 8' started by Tim Sessler, Sep 28, 2014.

  1. Dave King

    Dave King Well-Known Member

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    Yes. Holgers response at that time was that the come home altitude (50 meters) but like I mentioned above I find that having that kind of CH altitude is necessary to clear tall trees for safety reasons. Here's the old thread that talks about what I tested and Gary's input.
    http://forum.freeflysystems.com/ind...-0-91-as-of-14-06-2013.1674/page-2#post-21421

    It's my opinion that the emergency landing procedures are not setup correctly in the software for heavy payloads.
     
  2. Holger Göhr

    Holger Göhr New Member

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    I work as a Firefighter.
    Our current standing orders are to extinguish LiPo fire with water or co2.
    Reason for that is what is called 'thermal runaway'.
    To make it short, water and co2 are cooling which is the most important thing to stop the next cell from blowing up.
    Sand would work to isolate the fire, but you'll need a lot (several buckets) and you wouldn't stop the runaway.
    D class is definitely not required as the lithium content is too low.
    ABC is ok, but can be corrosive and gets into the slightest crack and will render all your motors and electronics useless.
    Same applies to water (the useless part).
    People are always scared of putting water on as it could create a shortcut, but the shortcut is what made the battery blow up in the first place and stopping the runaway is the important thing.
    So CO2 it is for me.
    Will extinguish the fire,allows you to 'ice' the battery (cool it) but will evaporate and not create any secondary damage.
    I know there is a lot of discussion about this, but this is what we learned in a specific training session and is in line with our current standing orders.
    Just my two cents.
     
  3. Steve Maller

    Steve Maller UAV Grief Counselor

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    Great info, Holger. Thank you for your expert information!
     
  4. Ozkan Erden

    Ozkan Erden Distributor

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    To clear the failsafe emergency gas value:

    If you select "vario control", the value is relevant to hover gas.

    %100 means, the copter holds the altitude. %95 means, it will descend very slowly.
     
  5. Mark Harris

    Mark Harris Member

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    A few other points for you.

    This is a crash of mine from earlier this year:
    [​IMG]
    This is after 7 months of no rain, on a 43c day. I was extremely fortunate to have a fire truck next to me, and that it crashed less than 100m away. If this had crashed on the other end of it's photo run several kilometres away, it would have been a couple of days worth of firefighting involving dozens of fire trucks. The farmer was returning from priming windmills and dropped by to see how things were going. The autopilot thought an inverted full power dive would be a fantastic idea not long after this - impact was well over 150km/h, parts of the aircraft were upto 50m away on an almost vertical crash. Fire was coming out of the lipo upto my knee.

    As a result of this, uavs in summer *only* fly LiFE cells. LiPo exhibits cascading failure, where one cell fails internally and gets warm, the next cell gets hot and vents, the third cell catches fire, and it goes downhill very rapidly from there. LiFe does not have cascading failures, does not plate lithium on the electrodes (meaning many dozens-hundreds of times more life than a lipo) when over discharged or just used agressively, and they dont tend to puff up. They are extremely tolerant of punctures. The big down sides are lower voltage per cell and much lower watthour/cm3 and watthour/kg. For example, one of my planes that runs on 6S/11600mah LiPO now runs on 8S/8400mah LiFE for the same volume, power and weight. However the LiPO can only be about 70% discharged safely, the life can be run to the bone if need be and not mind overly much. A lipo run to the end (in an emergency) needs to be discarded.

    To stop a cascading failure on a LiPO, you must cool it to the point the next cell doesn't start thermal runaway. Once it starts to get above 70-80c it will not stop heating up until all its energy is spent.

    If there is a fire risk, do not fly LiPO. Period.

    I highly recommend going to A123's website and checking their white paper on LiFE batteries, its quite a fascinating read. I tell every one of our commercial clients to do this, the liability for burning down several hundred thousand acres of dry farmland is more than my insurance would pay, nevermind criminal liability.

    Do not trust R/C 2.4ghz systems, i am biased in that I design a UHF RC system here, however I know of at least $5million of copters and camera gear that has been destroyed on customers who have come desperately to DragonLink to fix their R/C link issues. DragonLink works to 10km in adverse environments, the record is 140km or so if that gives you an idea of what a bad RF environment does to range. A 2.4ghz R/C system has a max range of 1-2km in the best RF environment.
     
  6. Ryan McMaster

    Ryan McMaster Active Member

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    We have been playing with a 915 link that works quite well out to 10km and acts as a grounds station link.

    Seems to be a lot of fails lately in the 2.4 range on the MC-20.
     
  7. Mark Harris

    Mark Harris Member

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    2.4ghz of any system is pretty awful. I see in my inbox an average of about $100k of crashed gear a week from people flying 2.4 and looking for a better solution. Its not a pretty world out there for 2.4. The fun ones are where they have a 2.4ghz remote focus, video link, or other 2.4ghz transmitter on the copter and expect it to still get an r/c signal through.
     
  8. Ryan McMaster

    Ryan McMaster Active Member

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    In two years of flying I have never had an issue with a pair of 2.4 radios (mc32 and MX 20/D7xs for the Movi). Majority of radio related crashes I have seen are a direct result of poor planning or flying near things in the 2.4 range that over power the TX/RX. The longer range is related to using a fixed wing craft to survey high tension lines but works great with all my MK/graupner kit.
     
  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    I agree. While I've recently made the jump the the DragonLink UHF system on a couple of ships (not my heavy lifter), I still believe there's a place for 2.4 systems. They're definitely more susceptible to interference. But monitored and engineered carefully, they're usually not the primary cause of failure.
     
  10. Jeff Scholl

    Jeff Scholl Distributor

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    After spending way too much time with 433, 72, and 2.4 I still feel the 2.4 freq. hopping is the most robust.
    Having said that if anyone would like any Scherrer UHF Tx, RX, Booster gear let me know.

    Best,
    Jeff
     
  11. Mark Harris

    Mark Harris Member

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    That is absolutely true - if you are flying agriculture or realestate. On a movie set with 10 remote focus units on 2.4GHz on cameras for a stunt shot, in a downtown area with dozens if not hundreds of wifi APs, and all the other 2.4ghz remote or video systems around, 2.4ghz doesn't stand a chance. This is the scenario I see the most - the operator must operate in an RF adverse scenario and just doesn't have a choice, any time he flies near the 10 cameras with remote focus, he loses his link - but to get the shot he has to, its a $200k stunt setup, so they cant shoot it twice over - once with the uav once without. That specific shot didnt cause a crash, but came so close to losing shot several times.
     
  12. Holger Göhr

    Holger Göhr New Member

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    Problem is only that to my knowledge the UHF is illegal in Austrailia for controll purposes..
    So it's not rally an option for a commercial setup over here..
     
  13. Ryan McMaster

    Ryan McMaster Active Member

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    The Graupner 2.4 TX/RX system (I JUST got a Jeti DS 16 today, hoping it is on par) encoding and frequency hopping is quite robust. We have tried to get it to disconnect from a GR-24 in the middle of Downtown using a HACKrf (https://www.kickstarter.com/projects/mossmann/hackrf-an-open-source-sdr-platform) targeting the specific channels the Tx/Rx are on and not succeeded once. The only thing I have seen block the signal is a Cellphone blocker that runs 2.4, Cell towers (Helium balloon, 5v pack and Rx with some string to test this stupid idea) and certain microwave dishes.
     
  14. Mark Harris

    Mark Harris Member

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    433 is ISM in Australia, and telemetry/control is one of it items listed as legal to use. Up to you though ;)

    DragonLink should have its 900mhz FCC/IC certified system out by the end of the year (i think this is the first and only time this has been publicly mentioned ;) We're probably not going to be going for an ACMA approval right away though - sorry :( It will however be in the ISM band for Australia for unlicensed use - the transmitter just wont be certified. We'll see what the testing lab says about cost for EN 300 200 approval and autralian approval costs on top of the FCC and IC certs, if its only a couple of thousand who knows we might just go ahead and do it.
     
  15. Jose Martinez

    Jose Martinez New Member

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    Oh my, thats terrible brother.
     
  16. Cody Hanthorn

    Cody Hanthorn Member

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    Reading this is painful. Last year almost 2 months before you had your incident I had one. I had an I2C error. I went through the painful process of troubleshooting it. Metering all of the connections according to the MK wiki, Re-soldering connections on the main ESC board and did a test flight. 50 feet up and 4 minutes into the 2nd flight this time with wind...Beep beep beep inverted and pile drived into mother earth. My carnage was slightly less than yours. The guy I got it from swore there was nothing wrong with it when I got it. I purchased a new Esc board and changed out a motor. Lots of labor. This weekend the okto will get a test flight. For some reason I have anxiety.. If it goes well I will have another okto to fly. I will ensure the settings from your post are looked at at least one time..:)
     
  17. Mark Harris

    Mark Harris Member

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    Consider strapping your octo to a large heavy immovable object (my favourite is a table saw). You can then power it up to full/hover throttle and let it run without having it in the air, and therefore able to fall out of the air ;)
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I believe Mr. Maller uses the roof rack of his car -- this also has the advantage of blowing all the dust off the car.
    Or did you switch to using photog's sandbags in your studio (which then brushes the floor clean)?

    Andy.
     
  19. Steve Maller

    Steve Maller UAV Grief Counselor

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    I've used several things. The last big lifter I had (since sold) was a X8 which complicated things a bit so as to avoid those 4 lower props. My favorite method was a cinder block with a sandbag on it, but I once scared the hell out of myself when the copter actually lifted it mostly off the ground. That was about 30 pounds of dead weight. After that I went with a picnic table at the park, which was bolted to cement piers.

    I'm waiting for my ALTA, and we'll see how that bird gets its first few dry runs. ;)
     
  20. Cody Hanthorn

    Cody Hanthorn Member

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    The ALTA looks amazing. Congrats on the purchase. The movi and that should work well for you. I will look into a tiedown method till the machine performs. Sunday is the big day.
     

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