WeiXun LARK BIRD
The Lark Bird is a brilliant little model that is a great introduction to flying a powered model aeroplane. It flies really well and is virtually unbreakable but the instructions on the box are not very clear (and the QR code requires installation of the WeChat App). These supplementary notes should help you to put your model together safely and to get it flying as well as it can.
Assembly
The first item to attach is the yellow propeller guard. This is the hardest part. It has to be a tight fit on the motor in order to stay in place so it can be difficult to get it go on. The ring that fits over the motor should be towards the front. Hold the guard by the ring and ease it carefully over the end of motor. If you have small hands you might need to ask an adult to help with this bit. Once it’s on the motor make sure that the guard is not tilted one way or the other and then push it as far forward as it will go. Then push the propeller onto the motor shaft. The propeller will only fit one way as the hole doesn’t go right through. It’s a good idea to rotate the propeller with your finger at this stage to check that it doesn’t catch on the guard.
The wing and tailplane just push into the slots in the body (fuselage) but can be tight when they get towards the middle so take your time and push from as near the middle as you can, not from near the tips where it’s too bendy. The indented control surfaces (ailerons and elevators) should be on the top. This is marked as ‘up’ on the box but don’t bend them up – it just says that to make sure they are on the top.
That’s nearly all there is to it. As a final check hold the model at eye level pointing away from you and check that the wing and tail are properly centred and reasonably in line with each other, otherwise it will be difficult to get the model ‘trimmed’. If they are out of line, just give the fuselage a gentle twist to line them up.
Initial Trimming
Trimming is an important step in getting any model aircraft to fly properly. Before you start flying the Lark Bird it’s important to follow the step shown on the box to bend the wing tips up into a circle and hold them for three seconds. Don’t worry, they won’t break! When you let go this adds a little more upward curvature to the wing, known as dihedral, which makes the aircraft more stable in the roll axis. It’s then less likely to spiral into the ground and helps the model to recover if caught by a gust of wind. You may find you need to repeat this after a few flights as the wings will tend to straighten out again naturally.
The aim of initial trimming is to get the model to glide smoothly without zooming up and then dropping its nose (a stall), diving too steeply straight into the ground or spiralling too tightly one way or the other. This needs to be done without the motor running and is best done when there is little or no wind. Facing directly into the wind (if there is any) gently launch the model straight ahead with the wings level. Think of it like throwing a dart at a dartboard. Too slow and it will dive into the ground but too hard and it will zoom up and stall. You want to aim for a gentle glide at the speed at which the aircraft wants to fly. We have found that the model flies much better with a little more weight on the nose. A small piece of BluTack about the size of a 2p coin seems to be ideal (weighing about 1.5 to 2 grams). If the model spirals one way or the other and the wings and tail are not out of line, you can gently bend the rear fuselage a little (but not as severely as shown on the box!). Once you’re happy with the glide you can move on to powered flight.
Powered Flight
The first thing to consider before flying with the motor is that the Lark can fly a long way, even if there is just a gentle breeze. Somewhere the size of a football pitch is ideal. If there is a breeze, position yourself near the upwind end of the area. Briefly press the button to start the motor and wait for the propeller to spin up. Then launch the model gently directly into the wind the same way you did for the test glides – level or this time very slightly upward. Remember the dart board! There is no need to throw it hard – just a gentle push and let the motor do its work. The model should ideally gain speed and climb away in a gentle turn one way or the other. If it zooms up into a stall, try again but launch it a little slower. If it still wants to stall, or turns very tightly, add a little more nose weight. If it wants to spiral in under power, first check that that the wings haven’t lost their dihedral. If they have, bend the tips up again. If it still wants to spiral too steeply, try bending the fuselage a little the other way from the turn. When properly trimmed the model should climb to about two or three times the hight of a house and then cruise until the motor stops, before gliding back down to earth.
If your flying space is limited it’s a good idea to let the motor run for a few seconds before launching so the model doesn’t fly too high. It’s also advisable to get used to flying the model with a short motor run before trying the longer 20 second option. Otherwise, if there is any breeze at all you could be in for a long walk! If the model does head off downwind make sure that you or a helper watch it all the way down to the ground and note the line to follow in order to find it. The bright colour helps but small models can easily disappear in long grass or crops. And just in case you can’t find it, it’s a good idea to put your phone number on the model in permanent marker so you have a chance of getting it back if someone else comes across it.
Care of the Battery
The Lark Bird is powered by a small Lithium Polymer (LiPo) rechargeable battery. It should last for several years and being re-charged hundreds of times but there are a couple of things that will help to keep the battery in good shape. LiPos will last longer in storage if they are not kept fully charged or if the state of charge is not too low. If you’ve had a long flying session and have run the battery right down it’s a good idea to give it a short charge as soon as you get home. 10 to 15 minutes should do. Similarly, if you’ve charged it fully ready to go out but can’t fly for any reason and are unlikely to fly it again for more than a week or so then it’s worth taking a bit of energy out of the battery by running the motor through 5 or 6 power cycles whist holding the model in your hand. You can easily top it up again quickly the next time you want to go flying.
Final Thoughts
We hope that you’ve found these notes useful and have a lot of fun with your Lark Bird. Whilst it’s a small model that weighs only 25 grams it’s still important to remember to fly safely. Think carefully whether your flying area is suitable and ensure that you won’t annoy anyone or put them or yourself in danger.
If you’ve enjoyed flying your Lark Bird and want to try something a little more ambitious, you’ll find loads more information on the BMFA website at https://bmfa.club/. You could also check out the BMFA Flight School at https://www.bmfaflightschool.org/ for some simple projects or contact us at mailto:admin@bmfa.org and we can put you in touch with your nearest model flying club. Just scan one of the QR codes below for the appropriate link. Model flying is a great sport to have as a hobby that can last a lifetime. The most important thing is to Have Fun!
Happy Landings!
The BMFA
