Auto land and directional control.

Discussion in 'ALTA 8' started by Rick Gerard, Jun 25, 2019.

Tags:
  1. Rick Gerard

    Rick Gerard Member

    Joined:
    Apr 22, 2017
    Messages:
    154
    Likes Received:
    21
    I posted this story on the Movi Pro/XL Facebook page but thought I should also post here.

    I had a very close call yesterday when landing my Alta 8. The battery warning had just come on, it was about a 97º F day. I set up the approach and started to land but just before touchdown, a gust blew me off course a bit. I climbed to about 10 feet and then started down slowly then the descent rate increased and I could not slow it down. I thought "Ok, my Alta is in Auto Land mode." The descent rate was a little higher than I wanted it to be but it still looked safe. When I tried to line up with the landing spot I realized I had no directional control over the drone. None. Full stick deflection did not move the Alta to the level spot I had chosen. I only needed to move about 2 feet.

    As soon as the up-hill gear leg touched down I cut power fearing a tip-over. The Alta settled for a moment then slowly tipped over because of the uneven ground. Fortunately, there was no damage. I didn't even have any dust on the motors or rotors.

    This could have been a disaster. Has anyone else ever experienced loss of directional control when auto-land takes over? That should not have happened.

    I have double checked the batteries that were being used and they both show healthy. I think the very short time between the battery warning and the auto-land was caused by the heat. I'm probably going to increase the warning voltage when flying in hot weather so I don't get into that kind of situation again. I hope that increasing the warning voltage does not also increase the switch to auto-land.

    I didn't have time to check the voltage while I was trying to land. I should have recorded the FPV video so I could see exactly what happened. I'll have to check to see if it is in the flight log to see if that info is there.
     
  2. Jason Smoker

    Jason Smoker Active Member

    Joined:
    Oct 23, 2012
    Messages:
    786
    Likes Received:
    62
    Can u post your Alta 8 gpx file that might have some clues to what happened? What flight mode where u in? maybe you hit the comehome button?

    Hot weather helps batterys not shorten them heat is your friend to a certain degree.
     
  3. Rick Gerard

    Rick Gerard Member

    Joined:
    Apr 22, 2017
    Messages:
    154
    Likes Received:
    21
    Screenshot_2019-06-28 10.36.56_942jyf.png
    This is a graph of all 8 battery voltages from the log. The battery took a dump at 595 seconds. About 10 seconds later it dropped below 19.5V then almost immediately dropped to an average of just above 14 volts. Autoland was initiated where the voltage spike is showing right around 600 seconds - 10 minutes into the flight. I was almost to the landing area when it happened. I verified the time by looking at the footage from the camera which was rolling for the entire flight.

    I'm not concerned by Autoland, I'm concerned that I didn't have directional control and after the voltage dropped below 19.5 I could not control the descent or position of the Alta.

    As for heat not being a problem, I disagree. The warmer the motors the more current they require to maintain the same power. High current means high discharge rates. When LiPO's get hot they get unpredictable.

    I have double checked the batteries I was using and they check as healthy and the discharge rates are completely normal. I was in Position mode, which is my usual mode for the approach to landing because it lightens the workload. I switch to manual at about 5 feet and activate the disarm safety as part of the landing checklist. The motors are killed as soon as the first gear leg touches down.

    I am going to raise the alarm voltage and the autoland voltage by a couple of 1/10's to give me more than 10 seconds to land.
     

Share This Page