The XK 251 is a RTF (Ready to Fly) mid-sized (250 mm diagonal) quadcopter featuring brushless motors and carbon fiber arms and landing gear. Brushless motors are more efficient and more powerful than the brushed variety typically found on toy-grade models. They also have a much longer life span.
Here is an FAQ relating to the difference between brushed and brushless motors.
The XK 251 weighs in at 215 grams meaning that no FAA registration is needed. It is powered by a small 2s (7.4v) battery.
Audience for the XK 251
I would describe this XK model as a “light sport” quadcopter which would appeal to many types of pilots. It would serve as a good learning platform for newer pilots wanting to step up their skills from toy-grade models. More experienced pilots may enjoy flying it with or without add-on cameras, FPV or other modifications. While it may not be as fast or powerful than heavier racing drones, it will satisfy most who desire a “go fast” machine and cost MUCH less both initially and for upkeep.
In the Box
For a price of approx. $140 US (here is Banggod link) you get the following:
XK 251 Quadcopter complete
Remote Control(TX) – the TX is a step up from the toy grade models and can be programmed and adjusted in various ways to provide a custom flight experience.
Single 2s battery
Battery Charger for 2s Battery
Extra Propellers and small tools (hex and screwdriver).
No assembly or binding is required – this unit is ready to fly out-of-the-box. However, check and tighten the prop nuts and fully charge the battery prior to your first mission. You will need to provide 6 AA batteries to power the TX.
I would suggest the purchase of one or two extra batteries as well as additional propellers and prop nuts. These should be the only parts needed to keep the XK flying.
Insert the charged battery into the holder and plug it into the socket provided on the bottom of the XK 251. Place the quadcopter on a flat surface. Check the TX to make certain all switches are in their rear most position. Note – there is a switch on the upper right which is “throttle hold” – this will prevent the motors from spinning up – so if you are worried about accidental startup of the props, flip this forward.
Make sure the TX throttle (left stick) is in the lowest position (no throttle) and turn on the TX. It should take a couple seconds until the LED on the rear of the XK will then stop flashing and turn green. This means it is bound. Test the setup by slowing turning the throttle up (turn throttle hold off) and confirm that the props spin up.
If everything is working it’s time to take off. This is an outdoor machine – it’s too large for proper indoor use. First flights are best attempted in an open area on a day when the winds are fairly calm – this will allow you to master the machine before you lose it to a tree or other obstacle.
Machines of this type take off best with a fairly heavy dose of throttle. Attempting to take off too slowly may cause the quad to lean over with the props striking the ground. Goose the throttle and then quickly let up when the XK is a few feet above the ground.
Our companion video contains narration and a demonstration of the XK 251 in flight and also contains numerous hints on operation.
Our opinion is that this machine is well made and is very enjoyable to fly. Our XK had at least two flight modes – a tamer setup which is stock with all the switches pushed back and a more aggressive mode with one or two switches pulled forward. Owners report there are two different models of this quadcopter with slightly different options. Our had a D/R (dual rate) switch on the upper right which, when pulled forward, allowed the machine to attain steeper angles (more aggressive flight). It also had a “3d/6D” switch on the left which, in combination with the D/R switch, allowed for flips. This is demonstrated in our video.
The owner’s manual has decent diagrams but is written in “chinglish” so is not much good for understanding the capabilities of the XK 251. A little experimentation will allow owners to suss out the major features – those desiring more detail such as how to adjust the “gain” and other settings in the TX will need to consult some experienced owners at various forum threads which discuss this machine. Some links at the end of this article will steer readers to these resources.
Additions and Options
The XK can carry small payloads such as an 808 Keychain or Mobius camera and/or an FPV setup. For the technical minded, there are instructions for using some of the low priced FPV setups available for other machines…on the X251. However, if FPV and more completely camera control is desired out-of-the-box, XK makes a model which includes the camera and monitor. It’s called the X252 and here in the link (approx. $180 w/camera and monitor).
Payloads up to 50 grams could be lifted however performance and flight times are best with lighter cameras.
I placed my #808 16 Keychain camera on the XK 251 and used it for shooting some video as well as a couple still pictures. Video from such a setup will be very shaky – a sample is in our video review (included with this article). Still pictures, taken with interval shooting (picture every X seconds) can work to get decent pictures of your house, a local landmark or scenery. A couple samples are displayed below (click to enlarge).
Summary and Rating
The XK X251 has been getting rave reviews and we are going to chime in and agree. This machine is a good value for the money spent and has good flight manners. Unlike many of the cheaper toy models it could last a long time if properly cared for.
While it may be difficult for a total beginner (first time flyer), it should appeal to those who want their first step up from the starter machines. It’s a fun quadcopter to fly and should help educate those who desire to master manual flight.
Machines in this class do not have GPS or “active” braking – that means once headed quickly in one direction, inertia will make them want to continue along their present course – unless countered by a strong reverse of the elevator (right stick) or other similar moves. Mastering this type of flight is a good skill for all UAV pilots to acquire as even fancier GPS Camera Drones can go awry and require manual piloting skills to save them in an emergency.
In summary – the XK is highly recommended for those who have interest in this class of quadcopter. It’s 1/2 the price of popular models such as the Blade 200 and every bit as good. It is a great stepping stone for those on the way up the line to full power FPV models as well as a great all-around machine for park and large backyard practice.
Good Flight Manners
Decent Flight times
TX fine tuning and adjustment is possible.
No Propeller Guards
The prop nuts are M4 – you need to buy both CW and CCW.
RCGroups technical detailed forum discussion of XK X251
Our list of current suggested drone models (includes the XK X251).