public byte[] takeoff(float altitude)
{
MAVLink.mavlink_command_long_t req = new MAVLink.mavlink_command_long_t();//定义req为 MAVLink.mavlink_command_long_t类，填充常命令的数据包
req.target_system = 1;
req.target_component = 1;
req.command = (ushort)MAVLink.MAV_CMD.TAKEOFF; //‘COMPONENT_ARM_DISARM’代表你要发送什么类的信息（此处为解锁信息），可自己选择（看类里有多少种）
//req.command = (ushort)MAVLink.MAV_CMD
//req.param1 = armed ? 0 : 1;//此处发送解锁信息，只需用param1。其余param2—7注释掉
req.param1 = 0;
req.param2 = 0;
req.param3 = 0;
req.param4 = 0;
req.param5 = 0;
req.param6 = 0;
req.param7 = altitude;
byte[] packet = mavlink.GenerateMAVLinkPacket_APM(MAVLink.MAVLINK_MSG_ID.COMMAND_LONG, req);//把req数据包，按照mavlink协议打包成（定义了临时变量packet）
return(packet);
}