Firstly, we'd like to give you a bit of background on why we're using the Talon at all:
In mid-2016 we set about designing and building a plane which would fulfil our needs for the project, we called the new plane the Mk3 (see the post here). There were various goals we wanted to meet. We wanted to have a big wingspan so we can carry heavy batteries and fly for a long time and also increase the distance between the propeller and the detector in order to cut down on noise.
During the build of the Mk3 plane we realised a couple of important points.
To further the aims of the project, it's more useful to find an off the shelf plane that people can pick up and put together themselves. That's where the X-UAV Talon comes in. X-UAV is actually a Chinese company that produces a number of UAV platforms, the Talon being one of these.
The Talon itself is actually based on a Lockheed Martin design of a UAV called a Desert Hawk. The photo below shows the original Desert Hawk, quite a similar design to the Talon:
The Desert Hawk design was put together by Lockheed's famous Skunk Works division which is responsible for advanced projects and prototyping. They're some of the best aircraft designers in the world and have a back catalogue to prove it (U2, Blackbird, F-117 stealth fighter for example all started life at Skunk Works). There's also a wikipedia page about the Desert Hawk if you're interested. Given the history of the designers, we expected a good airframe.
As a short aside, this is a nice re-purposing of the word drone from a military context into a more environmental/ecology context or to put it another way into a more humanitarian context. Drones can be viewed as tools like any other and although the initial use of these tools was often by the military, it's increasingly common to see commercial and hobby drones which may help to re-purpose the word itself.
Back to the Talon and happily, it does fly brilliantly and we're really pleased with its characteristics in the air. The airframe is a very smooth flyer and we're looking forward to investigating potential placements of the ultrasound recorder so we can get out for some field testing.
Below we've shown a couple of images taken from the telemetry on board showing the flight path. The one on the left is the maiden flight and the one on the right shows all the test flights performed:
For interest here's a video demonstrating some of the test flying:
If you're interested in potentially building your own bat sensing drone and the more technical aspects of the project then we're going to cover the components of the Talon and a comparison between the Talon and the Mk3 next.
If you're not interested in the more technical aspects of the project below then know that the Talon files well and meets the needs of the project so we'll be using it a lot more in the future!
The Talon is essentially meant to act as an easy to build replacement for the Mk3 plane. As such, it would be useful to provide a quick comparison between the two:
The most useful figures we're looking at are the wing loading and the cubic wing loading as because the two aircraft are similar in size these can be compared.
The numbers are close enough to tell us that the two planes will have similar stall, cruise and landing speeds (though a variety of other factors also come into play here). In practice this has also turned out to be the case.
A lower wing loading means that the wing needs to generate less lift for the plane to stay in the air and hence it can fly slower (which is good for slow landing speeds and cruise speeds). There are wing extensions available for the Talon though they have been difficult to find. We've luckily just managed to find some and they're 'winging' their way (it's the best I could come up with at short notice) over here from China as I type this.
They'll increase the wing area and reduce the loading to around 16.6 oz ft^-2 which will aid slower flight.
Finally, if you want to be able to reproduce what we've done then it would be useful to cover all of the bits and pieces that have gone into the Talon. Have a look at the table below for the full specification:
* We bought the Pixhawk 1 quite some time ago (in 2014) from 3DR. Since then they have stopped selling flight controllers and have moved onto closed systems. There are a couple of options available. A group of people who worked on the original Pixhawk 1 have launched a successor, called the Pixhawk 2.1. This would be the preferred option as it's a better flight controller. The second option is that because the Pixhawk 1 was open source there are a variety of clones which perform in exactly the same way. This would be less expensive and provide the necessary functionality. It's worth having a google for which are the best clones if you decide to go down this route.
*2 The original power module (this is the part which connects the main battery to power the Pixhawk) only accepts up to 4S batteries. As we're using 6S we needed a new one which could accommodate the higher voltage.
If you do decide that you'd like to go ahead and build a bat drone then do get in touch with us as we'd be happy to offer any advice. Our email is on the contact us page.
Next, we'll be posting about some acoustic testing with the Talon, watch this space!