Here is the list of major changes (a more detailed list can be found in the release notes):  

• Alt hold using inertial navigation (Leonard, Randy, Jonathan)
  • AUTO_VELZ_MIN, AUTO_VELZ_MAX parameters control the max climb/descent rate for the autopilot (cm/s)
  • PILOT_VELZ_MAX controls max climb/descent rate for the pilot (in cm/s)
• Landing improvements (Leonard/Randy).  Copter will descend to 10m or until an object is sensed with the sonar.  Then slows to 50cm/s descent (speed can be adjusted with LAND_SPEED parameter). (video).
• Surface tracking with sonar (Randy/Leonard).  Copter will attempt to maintain current distance from objects in front of sonar regardless of altitude.  Only used in alt-hold and loiter, not used for missions.  Sonar can be enabled/disabled with CH7 switch. (video)
• Failsafe improvements (Randy/Craig/John Arne Birkeland) including bug fixes, additional check for PPM encoder failure and implementation of battery failsafe.  Set-up instructions are here.
• Mediatek gps driver accuracy improvements and use of SBAS [Craig].  Instructions on upgrading your mediatek to firmware 1.9 are here.
• Traditional Heli improvements (Rob) including (a) bringing heli code back into the fold, (b) enabled rate controller (previously only used angle controllers). (c) fix to rotor speed controllers - now operates by switching off channel 8.  (d) allow wider collective pitch range in acro and alt hold modes vs stabilize mode  (e) bug fix to allow collective pitch to use the entire range of servos
• Acro trainer (Leonard). Copter will return to be generally upright if you release the sticks in acro mode.
  • ACRO_TRAINER : set to 1 to enable the auto-bring-upright feature
  • ACRO_BAL_ROLL, ACRO_BAL_PITCH : controls rate at which roll returns to level
• Camera control improvements (Randy/Sandro Benigno):  (a) AP_Relay enabled for APM2  (b) Trigger camera with CH7 or DO_DIGICAM_CONTROL command  (c) Allow pilot override of yaw during missions and fixed CONDITIONAL_YAW command.
• PPM sum support for transmitters with as few as 5 channels (Randy/Tridge/John Arne Birkeland).
• Performance and memory useage improvements (Tridge).

As per usual PIDs are optimised for the 3DR/jDrones 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 feel free to report issues you find in the discussion below and/or add them to the issues list.

If you are still having trouble with performance please make sure that the vibrations are not causing the problems

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!

This guide will walk you through the construction for your Arducopter 3DR frame and Power Distribution board.

Main frame parts included with your Arducopter Quadcopter Frame

Screws and other hardware included with the quadcopter frame.  Take note of the colours of the screws as they help when looking at the assembly pictures below.

The first step it to solder/ assemble the Power Distribution Board (PDB) sot hat you can power all four of your ESC from a single battery. 

To begin, take out the PDB board and run the two sets of narrow gauge wire through the central hole. 
The stripped ends of the wires should all emerge on the bottom side of the PDB, the side that says “This Side Down”.

Now you need to  solder a Female Dean’s Receptacle onto the exposed pads on each edge of the PDB.  The connectors straddle the PCB board with one connection on one side and the other connection on the opposite side. The positive and negative sides are marked near each pad, be sure to match the markings on the PDB with the markings on each Dean’s Receptacle.

Alternatively you could also just solder the ESC wires directly to each of the Pads 

The final step before mounting the PDB onto the fibreglass plate is to put the velcro strap through the slits, then mount the PDB on the bottom main plate.  The PDB is mounted to the frame using 4 of the M3x5mm black plastic crews, with the black plastic M3x8mm spacers, and the 4x M3 black plastic nuts.  It is reccomended that you use CA glue to secure the threads.

Something to keep in mind during this build is which configuration your vehicle will be flown in. This is later chosen when setting up your APM in the Mission Planner. There is no effect on performance it is just a matter of personal preference. Both the + (Top) 
and X (Bottom) configurations are pictured above. The blue arms indicate the front of the vehicle. This manual will continue building the vehicle in X configuration. Please adjust accordingly.

An image is provided for referance, but for more information about connecting your ardupilot mega electronics, please look at the arducopter quickstart guide.APM can be mounted using double sided tape (3M Scotch Exterior Mounting Tape is recommended) or it can be bolted to the carrier plate. The series of slots on the carrier plate allow your APM to be bolted in both + and X configurations. 
Note: In + mode the front of the APM should face arm 3. In X mode the front should be between arms 3 and 1.

To attach the propellers use the collets included. Cut the plastic ring included with the propellers that fits snug around the threaded collet and insert it into the slot in the back of the propeller. Place the collet on the motor shaft and tighten to keep the propeller in place. Make sure the writing on the propeller is facing up. Refer to the diagram above for correct prop rotation direction. Note: It is recommended that you balance your propellers prior to installing.

Functional Improvements over 2.7.1:

• Fast waypoints (Jason) - if the turn angle between two waypoint the copter is less than 60 degrees it does not slow down
• Navigation improvements and logging including switching to filtered location for distance calculations (jason)
• Flip improvements - more aggressive and flexible flip code based on attitude instead of timing (Jason)
• Improved camera control - you can now control any axis (roll, tilt, pan) with any rc channel.  it probably makes most sense that you will use 6 but others are possible too.  Unfortunately these changes required we change the set-up procedure so the mission planner gimbal set-up screen needs to be modified again.  Please refer to the AC_Camera wiki page for how to manually set-up the gimbal (Amilcar)
• Flybar acro mode for TradHeli (Robert)
• "Fast gains" - allows strong correction of attitude using accelerometers while the quad is stationary on the ground but relies more on gyros while flying (Tridge, Jason)
• Baro filtering improvements (Tridge)

Bug Fixes:

• DMP timing fix (Randy) - the MPU6000's dmp unit was inadvertantly turned on and caused timing delays in the main loop- xbee bricking issue (Craig / Tridge)
• Dataflash fixes (Jason)
• Engine ticking - was a combination of roll/pitch rate D term being too high and the dmp timing fix above (Randy, Emile)
• Faster heading correction on start-up - resolves issue with simple mode getting incorrect heading if you took off very soon after start-up (Tridge)

Code Cleanup:

• Increased maximum number parameters (Tridge)
• Formatting changes to code (Pat)
• Replaced "int" with "int16_t" everywhere (Randy)

As per usual PIDs are optimised for the 3DR/Jdrones 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.

There is still some question on whether the default Roll/Pitch Rate P (0.175) is high enough (it was 0.185 in 2.7.1) and also some people feel the Throttle Rate should be higher (currently 0.300 but some say 0.330 or even much higher would be better).

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

Thanks and enjoy!

This Hexa frame is based off the Arducopter 3DR Quadcopter, but includes 2 extra motors for added lift and stability in windy conditions.  This guide will show you how to assemble the kit

The Hexacopter power distribution board arrives as shown in the image above. To begin assembly, start by laying out the six female dean’s connectors in the appropriate spots around the PDB. They will be soldered at an angle so each lead makes contact with the pads on opposite sides of the board. Make sure you’re matching up the right pads by laying them all out before you start soldering. There should be exactly enough pads for the six connectors. Be careful to match up the positive and negative contacts properly as well. The connectors have raised lettering on the back that shows which tap is which.

Now attach the 3x4 right angle headers to the holes at the edge of the board.

Then add in the 2x3 pin right angle header next to it.

To begin assembling the Hexa 3DR frame, first get out the two parts pictured below. The piece on the left is the top half of the main frame and the piece on the right is the bottom

Lay them out in the same orientation shown above, we’ll start by adding the front and back arms.

Take an arm and line it up with the holes on the main frame pieces as shown below. Do the front and  the back arms first as the other four arms use different hardware. Make sure the arm is facing up as well,  there should be motor mounting holes facing up at the other end of the arm when it’s inserted as below.

Insert two M3x25mm (only four metal screw sizes are included, 5, 22, 25 and 35 mm) screws from the  bottom and fasten them on top with an M3 nut (color of the nut may vary but there’s only one size nut included in the kit).

Do the same with the opposite side

Now insert one of the side arms. This time use a M3x25mm screw for the outer hole and use a M3x35mm screw for the inner hole. The longer screw is used to attach the removable stackup later on.

When you’re finished adding all the arms, the center should look like this. Double check that all arms are  oriented correctly with the motor mounting holes facing up.

Now pull out two leg pieces and line them up with the holes on the side of the front arm. Fasten them with M3x25mm screws and M3 nuts.

Then add a leg set to the two arms adjacent to the rear arm. When it’s finished, the legs should be installed like in the picture below, evenly spaced with one leg mounted facing directly forward (left in the picture below).

Next, take out 6 18mm plastic female-female spacers and 12 M3x5mm metal screws. Install them on each leg as shown below. This point doesn’t need to be very tight so don’t use too much force.

Once you’ve assembled your frame, mount the APM 2 board. It’s best to attach it with some double-sided foam tape to provide a bit of insulation and a solid base, then screw in a couple bolts in the mounting holes to keep in from moving.

Now, let’s temporarily mark each arm with the motor number assigned by the ArduCopter code for the hexa configuration, which I’ve done in the picture below (for a Hexa + configuration). You can also see the red tape on the front arm:

Now we’ll begin attaching the electronics. First, attach your motors to the end of each arm using the M3x22mm metal screws and included washers. If you have the UT 880kV motors as shown below, you will need to modify the aluminum arms a bit. The central hole needs to be slightly wider so it doesn’t restrict the movement of the black metal clip on the bottom of the motor. The easiest way is to use a drill with a bit slightly wider than that hole or a metal file would work as well. Increasing the hole diameter by about 1mm is enough.  Then feed the three wires through the center of the arm and retrieve them on the other side.

Plug the wires into an ESC and use a servo tester and battery to verify that the motor is spinning in the correct direction. Refer to the page - Arducopter Quickstart for which motors spin which direction. When the direction is confirmed, use zip ties to fasten the ESC to the arm as shown below. Try to get the ESC as flush to the arm as possible to assist in heat dissipation.

Once all the ESCs are plugged into their respective motors and attached, plug each of their signal wires into the back of the PDB as shown below. Start by plugging in the ESC attached to Motor  1 into the leftmost position and proceed through the rest to Motor 6.

Then place your power distribution board (PDB) in the gap between the main plates and connect all the Deans connectors to the ESCs. It doesn’t matter which connector goes to which ESC as they’re all just connected to battery power

Next add the rest of the stackup layers. Start by fastening 4 M3x30mm Spacers into the base plate with 4 M3x5mm screws.

Add a stackup board on top of the M3x30mm spacers then screw on 4 18mm female-female spacers.

Add another stackup board on top of that and then screw in 4 M3x5mm plastic screws into the spacers through the stackup.

Before mounting the stackup, put rubber washers onto the four longer screws on the main frame.

Finally, slide the stackup onto the main frame and screw it down using 4 thumb nuts. Be sure you’ve oriented it in the right direction so APM is facing forward.Then take the 4-pin connector and the two 2-pin connectors from the PDB and match them up to the RC outputs for each motor. The red and black cable should plug into the ground and power pin of RC Output 1 on APM.

Thats it, the last step is to connect your RC receiver and battery.  For more information please refer the the arducopter quickstart guide.

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

This guide will show you how to build the SIX600 Hexacopter frame.

This hexacopter frame is essentially the same as the X600 quadcopter frame, but has an extra 2 arms to make it into a hexacopter.  This frame also comes with high landing gear so you can easily mount a camera underneath the frame.

This will guide will walk you through the assembly process of the X600 Quadcopter frame.

The X600 quadcopter frame is an affordable quadframe that is great for anyone starting out, or for someone who wants a great test platform for trying new moves, or custom code.

Simply mount the arms onto your quadcopter frame using the remaining bolts and lock nuts.  Remember to attach your PDB onto the central plate before securing the top plate onto the frame 

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!