The A2, DJI's newest flagship flight controller, offers top of the line performance and features with an easy to use interface that makes it highly sought after for aerial photography and video. Before we dive into this review I'll start by saying that I have flown nearly every other brand of flight controller on the market. I've built multiwii boards from parts and sensors salvaged from Wii controllers, and I used to build multirotor copters for various purposes in a retail environment. I've practically seen it all and I find that most flight boards do a pretty great job. On some levels it can come down to preference and what you are familiar with. My preference for sport flying and aerobatics is Multiwii, but for FPV, and Aerial Video and Photography, I prefer to use DJI flight boards. I really appreciate the user experience and DJI's combination of user friendly software and flight performance is hard to beat. So in this review, I'm going to give my honest thoughts and opinions, even if it does sound a bit fanboyish. That said, on with the review!
|Supported Multi-Rotor:||Quad-Rotor: +4,x4; Hex-Rotor +6,x6,Y6,Rev Y6; Octo-Rotor +8,x8,V8|
|Supported ESC Output:||400Hz refresh frequency|
|Supported Tx For Built-In Rx:||Futaba FASST Series and DJI DESST Series|
|External Receiver Supported:||Futaba S-Bus, S-Bus2, DSM2|
|Recommended Battery:||2S ~ 6S LiPo|
|Operating Temperature:||-5°C to +60°C|
|Assistant Software System Requirement:||Windows XP SP3 / 7 /8 (32 or 64 bit), Mac OS X 10.6(Lion) or above|
|Other DJI Products Supported:||Z15,H3-2D,iOSD,2.4G Data Link,S800 EVO|
|Hovering Accuracy(In GPS Mode):||Vertical: ± 0.5m, Horizontal: ± 1.5m|
|Maximum Wind Resistance:||< 8m/s (17.9mph/28.8km/h)|
|Max Yaw Angular Velocity:||150 deg/s|
|Max Tilt Angle:||35°|
|Flight Controller:||54mm x 39mm x 14.9mm|
|IMU:||41.3mm x 30.5mm x 26.3mm|
|GPS-Compass Pro:||62mm (diameter) x 14.3mm|
|LED-BTU-I:||30mm x 30mm x 7.9mm|
|PMU:||39.5mm x 27.6mm x 9.8mm|
The box contains the main control module, IMU module, GPS unit, LED unit, PMU, 2 male to male servo cables, a USB programming cable, 3 sizes of carbon rods to mount the GPS unit and some mounting accessories.
When you open up the box you're greeted with a few of the modules front and center. The cases are all aluminum and really feel like quality products. I use a Wookong on one of my Octocopters and the A2 certainly has a more professional look to it. No manual is included in the box so you can either print it out or view the manual from an iPad which is what I prefer to do.
Having a receiver as part of the flight controller simplifies the wiring and setup process. The A2 receiver works native with Futaba FASST or DJI DESST transmitters. Users with Spektrum transmitters can connect two satellite receivers to the flight controller. The manual says to use DSM2 satellites, but I used DSMX satellites on mine and it worked just fine. You'll need to bind the satellites using the flight controller LINK button. You can also use your own S-BUS or PPM receiver and connect it directly to the flight controller. To use traditional receivers you'll need the DJI D-BUS Adapter to connect it to the flight controller.
There are 9 types of traditional multirotors available to choose from in the software. If you have a unique airframe not listed there, the A2 has a custom mixer that allows you to setup the motor parameters to fit your needs.
This a cool feature that uses the GPS and Compass data and allows the copter to know where it is in relation to the takeoff point and forward direction as well as a user defined point of interest. There are three modes you can select. Course Lock (CL), Home Lock (HL), and Point of Interest (POI).
In Course Lock you can face the copter in a direction that you want to be the "course" or forward direction. Once you have a GPS lock and it knows its position you can take off. You can yaw and rotate the copter to face any direction and when you push forward on the control stick, the copter will move in a straight path along the "course" or direction it was facing before you took off. When in this mode the nose of the copter is irrelevant to the flight path.
In Home Lock you can take off after getting a GPS lock and position recorded, fly out to wherever you want in any direction. When HL is selected, you can simply pull back on the control stick and the copter will move towards the "home point." This is useful when flying far away and if you lose your orientation, you can select HL and pull back to bring the copter back to you. In the same way as CL, the actual direction the nose of the copter is facing is irrelevant to the flight path.
Point of Interest is pretty neat also. Lets say you wanted to take a 360 degree video of an object. You can hover directly above that object and move the switch on your transmitter that you assigned to IOC control back and forth 20 times. The LED light on the copter will blink rapidly 20 times blue to indicate that it has recorded that position as the Point of Interest. Now you can use the pitch control to move the copter at least 5M away and up to 500M away from the object. You can simply move the roll stick left or right and the copter will fly a circle around the object keeping the nose of the copter pointed to the center. You can speed up or slow down by giving more or less roll control stick movement and you can move closer or farther away from the object using the pitch control. Forward stick will move the copter closer and backwards stick will move the copter farther away.
If your copter has retractable landing gear like the S800 Evo, you can use this function. In a situation such as failsafe, motor out, or auto landing from failsafe, the landing gear will automatically move to the down position so you don't land on your camera and gimbal. The landing gear will not retract up until you take off and move 5M above the take off altitude. This is great and saves your servos if you accidentally hit the switch before you take off.
Failsafe can be triggered manually from a switch on your transmitter or from a loss of signal from the transmitter. There are 3 modes you can select in the software to tell the flight board what to do when failsafe is activated. Hover, Go Home and Land, and Altitude Go Home and Land.
Hover is pretty simple, when failsafe is triggered, the copter will stop moving and hold its position waiting for the signal to return.
Go Home and Land is pretty amazing. When failsafe is triggered the copter will fly itself back to the take off point and autoland. If the copter is below 20M from the takeoff altitude it will first climb to 20M and then fly home. This is to avoid possible obstructions in the flight path. If the copter is above 20M it will stay at that altitude and fly home.
Altitude Go Home and Land is essentially the same thing, but you can assign an altitude that the copter should climb to before flying home.
This can save your copter and gear from being lost or damaged and it is definitely cool to see your copter fly all by itself and land without any input from you. I only recommend you test this function in a large open field. The GPS is very accurate and the copter usually lands within a few feet from the take off position, but you don't want to rely on it if it's not an emergency and using it after taking off underneath a tree or other obstruction could be a disaster. For these reasons, I recommend you fly home and land under your control and leave the failsafe to do its thing in an emergency situation.
This is a neat trick that DJI developed to keep the copter under control even if a hexacopter loses a motor. If an Octo loses a motor, it's no big deal, they can fly like nothing happening, but losing a motor on a hexacopter used to be devastating. Now it is relatively safe. When a motor stops spinning the flight controller will compensate by spinning the copter around the dead motor. You can throttle down to land or if you need to fly to a safer landing zone, you can put the controller in Course or Home lock and control the copter normally even though it is spinning. Watch the video by DJI below to see what I mean.
This is a feature that allows you to set the idle speed of your motors when armed. The recommended setting is perfect for most setups, but some motor/ESC combinations may like a higher or lower idle speed to start and idle smoothly.
The Gimbal function allows you to connect a 2-axis servo-driven gimbal to the flight board. The flight board will try to keep the gimbal level in pitch and roll and also gives you manual control to move the gimbal in pitch to point the camera where you want it. This function works ok for FPV use, but if you're wanting to shoot high quality video, it's best to use a Zenmuse or other quality brushless gimbal system.
The A2 gives you 2 levels of voltage protection with some options. Both levels are user defined and may vary depending on how you want it to work.
The first level has 2 options. LED Warning and Go Home and Land. The LED Warning will flash the LED light to alert you that the voltage has dropped to the user defined voltage. This can be a warning that you are getting low on battery and it's time to bring it home and land. The Go Home and Land option will bring the copter back home and land like failsafe, but is triggered by the battery voltage level set by the user.
The second level has 2 options as well. An LED warning or Descending. Descending will cause the helicopter to descend straight down while remaining level. You still have some throttle control and will need to move the stick to nearly full throttle to arrest the descent which is pretty fast before hitting the ground. It is best to use the first warning as a signal to land before it gets to the second warning since you may not be over a suitable landing zone when the second warning is triggered.
Limits allow you to set vertical and radius limits that will prevent the copter from flying higher than the set limit or farther away than the radius limit. This is great for some countries or areas that have strict guidelines on how high or far away you can fly.
The A2 instruction manual is a 43 page downloadable pdf that you can get by visiting the DJI A2 Download Page. It's a good idea to read through the manual before installation so to keep this handy, you can either print it off or do like I did and use an iPad and choose to open and save it in iBooks. This lets me have an offline version of the manual that I can take anywhere.
The manual is fairly well written. On some items the English translations can be a little confusing, but overall I feel like they did a good job. I may have a bit of the curse of knowledge here with having set up many flight boards from DJI. Newcomers to DJI will want to read through the manual thoroughly to understand all the features and how they work before trying to set it up. There is a ton of information to cover since this flight board has so many features.
There are a lot of modules to connect together, but luckily DJI included a nice diagram in the manual showing how to put it all together. It should make sense when you have it all in front of you. Depending on the airframe you are using you can lay out the modules where they best make sense. The S800 Evo I'm using has lots of room to install the modules.
The IMU is the module that has most of the sensors in it and is used to supply data to the control board so it can make decisions on how to control the motors to make the craft stable. You can mount it in a few different orientations and tell the software which way it is facing. The sensors inside are internally dampened so you won't want to use thick gyro tape from a standard helicopter. Instead use the provided thin double sticky tape and secure the IMU to your airframe.
The main flight control board and PMU module can mount just about anywhere as long as the other connections can reach. You can use double sided tape or velcro to secure them to your airframe. Keep in mind that you may need access to these modules to disconnect wires for transportation, but this depends on your airframe.
The GPS unit can be mounted anywhere on your frame. It is best to mount it as high and as far away from the other electronics as possible to reduce possible electronic interference with the GPS receiver and compass. On top of the GPS unit is a red circle with an arrow. Make sure the red arrow is pointing towards the front or forward direction of your airframe.
The Bluetooth/LED Module can be mounted anywhere also but you'll want to put it somewhere that you will have decent visual access to during your flights. The LED lights will provide valuable information such as the number of GPS satellites acquired, flight mode, and battery status. On the S800 Evo, I chose to mount the module on one of the retract servos facing the rear. This gives me a great visual of the unit on the ground before take off and while in the air.
Once you have everything installed and connected its time to dive into the Assistant Software and program the A2. You can download a version of the software for PC and Mac. Make sure your props are not installed for this process. Turn on your radio, connect the battery to your main power connector and plug the USB cable from your computer into the LED module. Now you can open up the software on your computer and It should connect automatically.
DJI's Assistant program is the most user friendly software for programming a flight board that I've seen. The graphical interface is clean and it makes it easy to select the parameters you want. The first screen you see is an overview page that shows most of the important information. The programming functions are divided up into Basic and Advanced menus with several tabs for each menu. Once you make a change to any of the settings, just hit the enter button on your keyboard and the data is written to the flight board. You'll see items in RED that you have changed and when it has been saved to the flight board the color changes to BLACK. Watch the video below for a more in depth look at all the parameters in the Assistant Software.
|RCGroups.com DJI A2 Flight Controller Assistant Software (11 min 35 sec)|
If you don't feel like taking your computer to the field to fly and change parameters, you are in luck. DJI has a mobile application on iOS simply called DJI Assistant. You can find it on the iPhone app store. There is not an iPad version out currently, but the iPhone version still works and looks good with the 2X magnification on an iPad. The app connects to the flight board via Bluetooth and it allows you to change parameters wirelessly. No need for cables or computer drivers, it just works. The best part is that you can adjust the gain while flying. Of course you'll want to have a helper for this, but you can quickly tune the gains to suit your tastes in a matter of minutes.
Flying with the A2 is very similar to flying with any other DJI flight controller. To arm the motors, you need to give a stick command and push the sticks in either bottom corners. The motors will idle and you'll need to increase the throttle stick some or else the motors will auto shutdown after a couple of seconds. No change in rpm will be detected on the motors until you move the stick above half throttle. When you do, you'll hear the motors increase in speed and the copter will take off. You can use the gain settings to make the helicopter respond to your liking. Some like it snappy and responsive and others like it mushy and docile. There are several modes you can fly in depending on your style.
The A2 has an altitude hold mode that works when in the GPS Atti and Atti flight modes. It does not function when in Manual mode. To have the flight board hold the altitude, you move the throttle stick to the middle position. You can verify you are in altitude hold mode by looking at the LED unit on the copter. When the command is below or above the middle position the LED flashes twice every second or so. It will be either purple for GPS Atti or yellow for Atti mode. When the throttle stick is in the middle position the LED light will flash once every second or so. This gives you an easy visual cue to know that you are in altitude hold mode. I've used other flight boards that have this feature and I've never seen one work as well as any of the DJI flight boards. The A2 seems to hold as well as my Naza's and Wookong's which has always been excellent. Where I do see a difference in the A2 is holding altitude while moving. On the Naza and Wookong if you start out from a hover in altitude hold and then move forward you are likely to see a drop in altitude. With the A2 I noticed a much less drop off if any at all. On one shoot I had to fly down a stream about 150ft and under a bridge and I needed to be about 1ft off the water. The A2 was able to maintain a stable altitude while hovering and in the transition to moving forward.You might think that it's not a big deal and you could fly it manually and hold that altitude. You likely can, but having the board do it for you makes it easier and allows you to focus on being smooth with the movements and concentrate on the flight path. Being that low, any change in altitude is easily noticed in the frame and it can ruin a shot. The A2 helped me pull it off in one take.
I have to give the A2 a best in class rating for it's ability to lock in and hold position when asked to do so. The GPS unit is considerably larger than the Naza and Wooking versions, and I'm not sure what all the changes are, but the A2 holds it's position like its on a boom. I really can't find any faults in its operation, it just does what it's supposed to do.
Once you've adjusted your gains to suite your flying style, the A2 is a joy to fly. In GPS and Atti modes it will self level when you release the command sticks and overall it feels like you are a flying a normal helicopter with training wheels on. You can push the aileron or elevator sticks hard over and it will bank to about a 35 degree angle and hold there. In manual mode you have more power and the copter will not self level so the pilot will need to control it just like a normal helicopter. You can get more speed out of manual mode by increasing the tilt angle and in some cases manual mode can be smoother with altitude changes. Some will swear by flying in manual mode, but I say do what feels comfortable. The nice thing about the A2 is you have choices at the flick of a switch.
|RCGroups.com DJI A2 Flight Video (1 min 47 sec)|
I've used the A2 now for the last 2 months and it's been every bit as solid and reliable as I expected from a controller in this class. It has the features I need and the software makes it easy to setup and make changes or tune. It has the look, feel, and performance of a true professional class product. I like it so much that I'm actually planning to upgrade my Octo from the Wookong to an A2. This review may have sounded like a fanboy raving, but these have been my honest opinions. The proof is in the pudding as they say and the A2 has lived up to my expectations in the real world and I can't really ask for anything more than that.
Looks great! I'm glad to see this review because I had not heard any real details about the A2.
I'm especially pleased to hear that the alt hold and GPS hold work extremely well since when I shoot video, I do it as a 'one-man operation'.
I like the idea of the built-in receiver, but I suppose if I were to use it with a Turnigy 9X or with a new Taranis TX, then I would need to buy a spektrum module?
Anyway - I am certainly going to get one as soon as DJI comes out with a ZenMuse for the Panasonic GH4. Yes - I am using that - a mythical gimbal that has never been announced - as my excuse to not buy one . . . yet!
Thanks. You would need the spektrum satellites or you can use your own receiver with the optional module. Since the GH4 is the same body as the GH3, it should work just fine in my GH3 Zenmuse. I'm picking up the GH4 as soon as it's available so I'll know for sure then.
I had a motor fail on my hex, and the motor failure protection feature didn't work. According to DJI's video, the hex should have slowly revolved around the failed motor. In practice, my hex spinned as fast as it could around the center of the frame and eventually broke apart (presumably due to the sheer amount of centrifugal force resulting from spinning at mind-blowingly high speed).
This is Sai Krishna from India, I have a very serious issue regarding DJI A2.
ESC RCTimer 30Amp SimonK
Props: 1861 Foxtech Supreme
20,000mah 6S Lipo x1
After I finished my setup, I finished calibrating the compass and set all the gains to 140.
My takeoff is smooth, the pitch and roll are fine, but YAW input makes the craft horrible, it looses its balance, there is a rapid change in altitude and the LED flashes a few green lights. This is same for GPS and Atti mode.
I tried re-calibrating the compass several times, but no result.
Do I need to calibrate my ESCs, or any faulty hardware.
Please advise me.
Waiting for your reply.
Are you running the latest firmware, ie v2.2 ?
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