Taking Off¶

This article explains how to get your Copter to take off.

At high level, the steps are: check that the vehicle is able to arm, set the mode to GUIDED, command the vehicle to arm, takeoff and block until we reach the desired altitude.

Tip

Copter is usually started in GUIDED mode.

For Copter 3.2.1 and earlier you cannot take off in AUTO mode (if you need to run a mission you take off in GUIDED mode and then switch to AUTO mode once you’re in the air).
Starting from Copter 3.3 you can takeoff in AUTO mode (provided the mission has a MAV_CMD_NAV_TAKEOFF command) but the mission will not start until you explicitly send the MAV_CMD_MISSION_START message.

By contrast, Plane apps take off using the MAV_CMD_NAV_TAKEOFF command in a mission. Plane should first arm and then change to AUTO mode to start the mission.

The code below shows a function to arm a Copter, take off, and fly to a specified altitude. This is taken from Example: Simple Go To (Copter).

# Connect to the Vehicle (in this case a simulator running the same computer)
vehicle = connect('tcp:127.0.0.1:5760', wait_ready=True)

def arm_and_takeoff(aTargetAltitude):
    """
    Arms vehicle and fly to aTargetAltitude.
    """

    print "Basic pre-arm checks"
    # Don't try to arm until autopilot is ready
    while not vehicle.is_armable:
        print " Waiting for vehicle to initialise..."
        time.sleep(1)

    print "Arming motors"
    # Copter should arm in GUIDED mode
    vehicle.mode    = VehicleMode("GUIDED")
    vehicle.armed   = True

    # Confirm vehicle armed before attempting to take off
    while not vehicle.armed:
        print " Waiting for arming..."
        time.sleep(1)

    print "Taking off!"
    vehicle.simple_takeoff(aTargetAltitude) # Take off to target altitude

    # Wait until the vehicle reaches a safe height before processing the goto (otherwise the command
    #  after Vehicle.simple_takeoff will execute immediately).
    while True:
        print " Altitude: ", vehicle.location.global_relative_frame.alt
        #Break and return from function just below target altitude.
        if vehicle.location.global_relative_frame.alt>=aTargetAltitude*0.95:
            print "Reached target altitude"
            break
        time.sleep(1)

arm_and_takeoff(20)

The function first performs some pre-arm checks.

Note

Arming turns on the vehicle’s motors in preparation for flight. The flight controller will not arm until the vehicle has passed a series of pre-arm checks to ensure that it is safe to fly.

These checks are encapsulated by the Vehicle.is_armable attribute, which is true when the vehicle has booted, EKF is ready, and the vehicle has GPS lock.

print "Basic pre-arm checks"
# Don't let the user try to arm until autopilot is ready
while not vehicle.is_armable:
    print " Waiting for vehicle to initialise..."
    time.sleep(1)

Note

If you need more status information you can perform the following sorts of checks:

if v.mode.name == "INITIALISING":
    print "Waiting for vehicle to initialise"
    time.sleep(1)
while vehicle.gps_0.fix_type < 2:
    print "Waiting for GPS...:", vehicle.gps_0.fix_type
    time.sleep(1)

You should always do a final check on Vehicle.is_armable!

Once the vehicle is ready we set the mode to GUIDED and arm it. We then wait until arming is confirmed before sending the takeoff command.

print "Arming motors"
# Copter should arm in GUIDED mode
vehicle.mode    = VehicleMode("GUIDED")
vehicle.armed   = True

while not vehicle.armed:
    print " Waiting for arming..."
    time.sleep(1)

print "Taking off!"
vehicle.simple_takeoff(aTargetAltitude) # Take off to target altitude

The takeoff command is asynchronous and can be interrupted if another command arrives before it reaches the target altitude. This could have potentially serious consequences if the vehicle is commanded to move horizontally before it reaches a safe height. In addition, there is no message sent back from the vehicle to inform the client code that the target altitude has been reached.

To address these issues, the function waits until the vehicle reaches a specified height before returning. If you’re not concerned about reaching a particular height, a simpler implementation might just “wait” for a few seconds.

while True:
    print " Altitude: ", vehicle.location.global_relative_frame.alt
    #Break and return from function just below target altitude.
    if vehicle.location.global_relative_frame.alt>=aTargetAltitude*0.95:
        print "Reached target altitude"
        break
    time.sleep(1)

When the function returns the app can continue in GUIDED mode or switch to AUTO mode to start a mission.