P mode is preferred for most flying scenarios, it is the most automatic flight mode relying on GPS outdoors, or the vision system when indoors. Users can switch to A mode when P mode is unavailable, or the UAV is behaving erratically. Be aware that position hold is NOT available for A mode, be cautious when flying in A mode, and practice, practice, practice.
Note: By default from DJI, the Flight Mode Switch is locked to P mode (the switch does nothing). To unlock other flight modes (A(TTI) and F(unction) the “Enable Multiple Flight Modes” must be turned on in the menus, tap the P-GPS or P-OPTI icon on the App --> Advanced Settings --> Enable Mult......
1) P mode (Positioning): P mode works best when the GPS signal is strong, or indoor where P-OPTI will show. There are three different states of P mode, which will be automatically selected by the Phantom 3 depending on GPS signal strength and Vision Positioning sensors:
a) P-GPS: GPS is strong, and the aircraft is using GPS for position hold, meaning the Phantom will attempt to maintain the same horizontal/vertical position in space (holds the aircraft in a fixed and stabled hover) by automatically adjusting the UAV when you take your hands off the controls.
b) P-OPTI: If GPS is unavailable, the aircraft will try to use the VPS to hover. The VPS may NOT work properly when the Phantom 3 is flying over water, over surfaces not well defined (like people), or in a low light environment.
c) P-ATTI: When neither GPS nor VPS is available, the aircraft is using only its barometer, only altitude is controlled. If this mode is shown likely Return To Home will NOT WORK!!!
2) A mode (Attitude-ATTI): The GPS and Vision Positioning System are NOT used for positioning. The aircraft only uses its barometer to maintain altitude. ***IF it is still receiving a GPS signal, the aircraft can automatically return home if the Remote Controller signal is lost and if the Home Point has been recorded successfully. The Phantom will attempt to hold height, orientation and keep itself level by means of the Compass and IMU. your craft will drift with the wind or in the direction the UAV was heading when you use a stick input, after you let go of the stick it will still drift (i.e. no horizontal positioning). It has momentum and will continue flying in whatever direction it was moving until you counter that momentum with a different direction of thrust. Laws of physics apply!
Why use this? This can be used for extremely smooth flights for video, keeping a constant velocity can be easier in this mode.
Need to Know: You should practice ATTI flying mode, You have greater control of the aircraft rather than relying on automatic systems, that can and do fail without warning. Google Flyaway, most can be saved by going into ATTI Mode
A switch to ATTI mode is always a good idea if the UAV starts flying unnaturally, it can save your investment.
3) F mode (Function): Intelligent Navigation Modes will be available when switching to F mode. Familiarize yourself with these modes before use. Note: Intelligent Navigation Modes are only available when sufficient GPS signal is available and compass is working.
Course Lock (CL): The nose direction, at the time that CL is set (power on), will remain the forward direction regardless of how the YAW of the aircraft changes. It's like flying on an invisible, fixed grid. Example: If it took off with the nose pointing north, forward will always send it north, back will always send it south, left will always send it west, and right will always send it east. When flying in Home Lock or Course Lock you can change YAW, while remaining on course.
Home Lock (HL): Record a Home Point (HP) and enter HL mode. This mode lets the Phantom be controlled intuitively regardless of the orientation of the camera (where it is pointed). The "front" of the craft is no longer defined. Think if a circle that can grow and shrink around the HP. When you right stick forward the UAV goes away from the HP, when pull back it comes closer (smaller circle). When you push left or right the Phantom will move a complete circle around the HP at the radius it is at. You still control YAW.
Point-of-Interest (POI): Select a point on a map and fly a perfect circle around the point while the camera is aimed at center of the circle, the camera captures a 360 degree video of the point selected. You select the radius and height of the circle of flight.
Waypoints: You input points on a map and tell it what height (above takeoff, NOT above ground level) it should fly past the waypoint, you can concentrate on pointing the camera at the shot you want to capture. The flights save and you can recall them at a later date to allow you to fly the same route again.
Follow Me: The Phantom will follow you, this can only be enables after hovering off the ground. It will use the GPS location of the smartphone or tablet connected to the remote control *** Many tablets do not have GPS chips, an add on bluetooth GPS may be needed. Most cellular capable tablets will have GPS. The Phantom will follow you while aiming the camera picture at you / the device.
*Credit for info and ideas interpreted from personal experience and Fantomas Help Guide for the Phantom 3 (Adv/Pro)