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!
We were lucky enough to be invited to the Natural History Museum in London for their 'Science Uncovered' event. We joined hundreds of other scientists who had stalls all around the museum sharing their science.
As well as a couple of drones we also had a flight simulator on a large TV screen so people could have a go at flying a remote control plane using one of our transmitters. This was pretty popular and demonstrated that age is no predictor of ability to fly!
On our stand we also had a compilation video of all the footage we have collected over the project, some bat calls on an iPad, and a bat detector for people to play with.
We took out newest plane, the talon, and our quad to show visitors. The quad was linked up to a laptop to show all the telemetry readings that are recorded in real time, and the plane was great for showing how light weight the air frames are, even little kids were able to hold it above their head with ease.
We were chatting to visitors pretty much continually for 6 hours so we were both pretty tired afterwards. If we are invited back we might have to employ some helpers!
There was a little time between Christmas and New Year when it was possible to nip out for a test flight of a new trainer plane.
The trainer is exactly as it sounds: a plane to aid the training of new pilots. This would potentially help both of us (Tom M and Tom A) to be able to fly and aid the training of others who wanted to invest in their very own bat drones (we're not aiming to sell anything but we can help people with building aircraft or provide advice on what to buy).
It's worth pointing out that we would always recommend that people start out with a simulator on a computer and then move onto a trainer plane. The first plane that we flew, the Bix 3, is actually a trainer. Check out one of our first blog posts here to see more about it.
There was a little spare foamboard left over after the build of the Mark 3 plane so we thought it would be useful to build a trainer aircraft with it.
The maiden flight of the plane was successful in that the plane landed in one piece. However, the weight of the plane is quite high relative to the wing area leading to a high wing loading and therefore relatively high cruise speed. This doesn't make for a perfect trainer and a lighter plane would be more desirable (either bought or built).
The design used was one from experimental airlines on Youtube; have a look at their channel here if you're interested. It was discovered recently that the foam we're using is circa 2.5x heavier than the foam experimental airlines uses which has lead to heavier than expected aircraft.
There's not many photos of the completed plane unfortunately so here's one of the better ones:
And, getting to the bit where it all went wrong, take a look at the video below:
So at least we know what the issue was and have learnt a lesson or two.
For a trainer we'll probably fix up one of the Bix 3's that we've been using as these are light and fly well.
When building further aircraft we'll use lighter foamboard. There's some available on Hobby King which is even lighter than the experimental airlines foamboard so this seems like a good option.
And finally, we'll not fly too far away from our transmitter without an autopilot failsafe in place! The flight controller for this plane doesn't have the ability to return to launch so this was not an option in this case.
Next up, we'll be test flying a new airframe - the Talon! Watch this space....