ArduCopter 3.0.1 has been released and is now available in the Mission Planner, GitHub and the new Downloads Area.

• Warning #1: Compass calibration and reducing interference is far more important than with 2.9.1b
• Warning #2: GPS glitches can cause sudden and aggressive position changes while in loiter mode.  You may wish to reduce the Loiter PID P to 0.2 (from 1.0) to reduce aggressiveness (see image below of where this gain can be found in mission planner).
• Warning #3: optical flow is not supported but will be back in the next release (AC-3.0.2 or AC-3.1.0).
• Warning #4: This release has only been lightly tested on Traditional Helicopters.
  

Improvements over 2.9.1b include:

• Inertial Navigation for Loiter and Auto meaning much more accurate control (Randy,Leonard,JonathanC)
• 3D navigation controller follows straight lines in all dimensions between waypoints (Leonard,Randy)

         WPNAV_SPEED, WPNAV_SPEED_UP, WPNAV_SPEED_DN, WPNAV_ACCEL allows configuring speeds and acceleration during missions

• "compassmot" to compensate for interference on compass from the pdb, motors, ESCs and battery.  (Randy,JonathanC) (Set-up video here)
• Safety improvements:
  • simple Tin Can shaped Geo Fence
  • pre-arm checks to ensure all calibration has been performed before arming (can be disabled by setting ARMING_CHECK to zero).  (video description here)
  • GPS failsafe - switches to LAND if GPS is lost for 5 seconds
  • stability patch improvements to stop rapid climbs in very overpowered or overtuned copters
• Circle mode improvements including "panorama" when CIRCLE_RADIUS set to zero (Randy,Leonard)
• SONAR_GAIN parameter added to allow better tuning of sonar surface tracking
• CH8 auxiliary switch (same features as CH7)
• works on PX4 (some minor features still not available) (Tridge,PatH)

Arducopter 2.8.1 is now in the mission planner and in the downloads area! Remember to do your MP configuration again after loading this code, since it erases your EEPROM and sets it to the new defaults. 

Note: Issues with APM1 user's level feature not working are now resolved.  If you installed 2.8 we highly recommend you upgrade to 2.8.1 as 430 extra bytes of RAM have been freed up which reduces the chance of memory corruption (although we haven't seen any cases of this on the APM2 at least) .

Note #2: this release has not gone out for Traditional Helicopters until they can be tested fully.  Flip and Toy mode have also not been fully tested.

Improvements over 2.7.3:

• Improved ACRO mode (Leonard Hall)
• Improved stability patch to reduce "climb-on-yaw" problem (Leonard, Rob Lefebvre, Randy)
• Rate controller targets moved to body frames (yaw control now works properly when copter is inverted) (Leonard/Randy)
• Less bouncy Stabilize yaw control (Leonard)
• OpticalFlow sensor support for APM2.5 (Randy)
• DMP works again by adding "#define DMP_ENABLED ENABLED" to APM_Config.h You can also log DMP vs DCM to the dataflash by adding "#define SECONDARY_DMP_ENABLED ENABLED" (Randy)
• Watch dog added to shutdown motors if main loop feezes for 2 seconds (Randy)
• Thrust curve added to linearize pwm->thrust. Removes deadzone found above 90% throttle in most ESC/motors (Randy)
• More timing improvements (main loop is now tied to MPU6000s interrupt) (Randy)
• GPS NMEA bug fix (Alexey Kozin)
• Logging improvements (log I terms, dump all settings at head of dataflash log) (Jason)

Bug Fixes / Parameter changes:

• fixed skipping of last waypoint (Jason)
• resolved twitching when no GPS attached (Tridge)
• fixed loss of altitude if alt hold is engaged before first GPS lock (Randy/Jason)
• moved Roll-Pitch I terms from Stabilize controllers to Rate controllers
• TILT_COMPENSATION param tuned for TradHeli (Rob)

Code Cleanup:

• HAL changes for platform portability (Pat Hickey)
• Removed INSTANT_PWM (Randy)

As per usual PIDs are optimised for the 3DR quad with 850 motors and 10" props. If you're using more powerful motors/props and are seeing bad flight behaviour in stabilize, start by turning down Rate Roll P in 25% steps.

Please note that on this release we've moved the Roll and Pitch I terms from the Stabilize controller to the Rate controller. There's some evidence that says this can lead to flips on take-off if you move the roll or pitch sticks around as you take-off so we recommend you leave these sticks in the middle until you're in the air.

Please feel free to report issues you find in the discussion below and/or add them to the issues list.

Thanks and enjoy!

New and Improved:

• NEW: 3-axis camera stabilization
• NEW: AP_Limits library: Altitude limits and geofencing.
• NEW: Automatic Flip (Roll axis) is now enabled on Channel 
• NEW: GPS lag estimator
• Better altitude control in ALT_HOLD and better altitude transitions
• Better loiter, especially with the new 3DR uBlox GPS. Check out the video from Marco above!
• Better yaw control
• Better DCM implementation, resulting in noticeably smoother flight
• Better velocity control in Auto missions
• Etc

Bugfixes:

• Fix to dataflash erasing, which should resolve an issue some users were having
• Fix some MAVLink commands
• Fix Circle command
• Fix some units
• Etc

Notes:

No more 1280 support (out of program space)
AP_Limits documentation
Jason's explanation of several improvements

Here are two comparison videos of loiter mode for a tricopter fling the latest arducopter 2.6 code, compared to the previous v2.5.5 code.

Thanks to Dean for sharing the videos

Version 2.6 of the ArduCopter code is now available in the AP Mission Planner and in the downloads area!

Updates to MavLink 1.0 means you will need to use "ArdupilotMegaPlanner10.exe" to connect.  If you've updated your mission planner recently you should find this executable in the directory where the mission planner is installed.

The above video is done using a prototype 3dr ublox GPS which seems to have better accuracy than the standard mediatek.

Improvements over 2.5.5 include:
     - MavLink 1.0 support (use with ArdupilotMegaPlanner10.exe) [Tridge, Craig]
     - Stability improvements especially during level hover [Jason]
     - throttle range improvement (higher min and max) [Jason]
     - improved standard Loiter PIDs [Alan, Heino, Jason, Angel]
     - dataflash erase speed up ('+' messages removed but it only takes 6 seconds now) [Tridge]
     - Copter LEDs [Robert Lefebvre]
     - RTL loiter stage target set to home to improve final landing position [Jason]
     - flip & acro improvements [Jason]
     - circle mode target improvement for ground station [Jason]
     - Auto Approach [Adam Rivera / Marco]

Tuning:
PIDs are optimised for the stock Arducopter quad kit with 850 motors and 10" props.  If you're using more powerful motors/props and are seeing bad flight behaviour in stabilize, start by turning down Rate Roll P in 25% steps.

This time we spent some time optimising the loiter PIDs.  Tuning loiter can be tricky so please refer to the discussions which will appear below for more community feedback on what parameters work best.
 
All feedback welcome below.  Enhancement requests and bug reports can be put into the arducopter issues list.  When possible please include logs (tlog and/or dataflash) and tell us whether you're using APM1 or APM2 and what version of the software you're using (presumably 2.6 but tell us anyway!).

Happy flying!

Version 2.5 of the ArduCopter code is now available in the AP Mission Planner and in the downloads area!

Enhancements:

1. The first ArduCopter code release optimized for the APM 2.  Leans and drift should be much reduced or even eliminated for most users.  This was accomplished through a number of core improvements to the DCM implementation by Tridge like this one and this one.
2. Loiter and waypoint following should be improved due to a D term bug fix, some tuning and the improved DCM performance mentioned above.
3. On start-up, the yaw heading is updated with first successful mag read (so you should no longer see the slow rotation from north to your actual heading).
4. Increased output rate to ESCs to 490hz.  This update rate is also user selectable using the new RC_SPEED parameter.
5. hexa copter stability patch bug fix (should resolve slight flattening when pitching forward and accelerating very rapidly).
6. improved baro filtering
7. fix to dataflash logging of Mag heading
8. addition of H1 swash plate type and bug fix for proactive yaw compensation for collective pitch changes for TradHelis.