I was on a vacation in London, and after going through Hyde park a couple of times, I got a sudden urge to get a RC plane. After searching around a bit, I found “HobbyStores”, one located in Camden. The store was very nice, a huge selection of models, and they give the possibility to get more models from their other stores, transported over night.
I liked the service, they were quick to show models, and offered to test them in-store. As I was looking for something cheap and simple, I quickly found the RTF (Ready-To-Fly) Airhopper from Axion RC which was priced at about £45 GBP. It has 300m+ range and is suitable for indoor and outdoor flight (it suggests a 100mx150m flight area, so read “outside with indoor performance”). I didn’t get the chance to test it before we came home after our vacation though…
The plane is VERY small. I thought it looked cool, and it seemed like it could handle a crash or two. It also included two spare propellers. It is very light, weighing only 22 grams without the small 145mah 1S battery. It has a 415mm wingspan and is only 280mm long. This is a beginner plane, and does not have ailerons, you steer with the rudder and elevator, and of course the throttle. The rudder and elevator is controlled with the right stick, so the left stick is throttle only (even though it is a 4ch transmitter which does have a left rudder controller).
The charger is a bit strange. It is an USB charger, which is OK, but it has a potentiometer to choose the charge rate. The manual states that you should charge at a low rate to make the battery last longer. After my experiences, most batteries can handle 2C (charging at two times their capacity) giving approximately a 30min charge, but it is highly recommended to charge at 1C to prolong the battery life (1 hour charging time). I found out that the charger included has 1C with the knob turned at about 50 %, anything less and it took 2 hours to complete charging.
Assembly was easy. Click the landing gear and nose gear in, and you’re done!
After charging, and inserting the 6xAA batteries needed, I tested the plane. It had a very steep climb angle and did, well, hop in the air. If there was a slight bit of wind, it would raise the nose up, stall, then fall down, level and go into a new stall. As this is a 22g plane, adding nose weight is not an option. I pointed it towards the wind (almost no wind), put the elevator trim all the way up, and still had to keep pushing it forward to keep the plane level. If I eased down on the throttle it would descend to fast. Even though the plane doesn’t have ailerons, it was easy to make turns.
I could only fly for about 5 minutes before it started going very slow, and I had to take it down. The motor made a weird rattling noise, so I guessed it was just low battery. Went back in and charged it up for a new session.
So disappointed! My plane wouldn’t take off. It would glide for about 10 meters, then drop to the ground. The rattling noise was still there, so I took it in for a check.
First of all, I discovered that the elevator didn’t work. I could hear a sound like a motor spinning when I tried moving the elevator up or down… The only way to fix it? Cut the plane open. You could remove the wings, and there is a small opening through the fuselage to adjust the servos. Problem? The wings are glued to the fuselage, and impossible to remove without destroying the wings. I therefore tried cutting out a small door on the plane.
The servo horn had fallen off, in the picture I had just re-seated it. It is a stupid design. No collars keeping it in place. The servos are not actually servos, they are small motors, which spin, but will stop when they have too much resistance (and make a loud noise). The problem is that if the friction between the motor’s shaft and the servo horn is to low, it will continue to spin, and eventually push the servo horn off. You can’t hear this noise in-air, and can’t prevent it from happening. It should have been glued or fastened with a collar to prevent this in a plane which is sealed together like this. Very bad!
I tried another takeoff after a full charge. I charged the battery at 0.1A on my Accucel 6 charger, to make sure the battery would reach 4.20V at full charge. The battery is fine, and should not cause any problems. The same thing happened. I couldn’t get the plane up in the air, not even after adjusting the elevator trim all the way down. The motor still gave a rattling noise. What to do? Open the nose… Damn!
I quickly found the problem(s). The motors brass pinion was loose, and would spin at full throttle. I removed it, put a small drop of glue on the motor shaft, let it dry, then put the pinion back on. This made the motor shaft thicker, and the pinion didn’t spin.
The other problem was the propeller shaft being to loose. It was held in place by a plastic nut, which obviously had loosened during the first flight.
I tightened it up, put a drop of glue on it, and put the motor back in the plane and sealed it (I used CA glue, which did melt it a bit).
Even after all of these (unnecessary) fixes, the plane couldn’t get full throttle. As I was afraid I had tightened the propeller shaft to much, I punched a small hole through the nose, and loosened the nut a bit. The shaft could easily spin now. But still, the motor didn’t seem to reach its full potential, even with a freshly charged battery.
After trying to make it airborne for 10 minutes, I gave up, and did a bench-test. I could clearly hear a weird motor noise on full throttle, but I have no idea how to fix it. The motor seems to be of poor quality, and my plane is pretty much useless at this state – after ONE successful flight. I am very disappointed with this plane. It is underpowered, and has poorly designed servos. They are very week, and can’t control the elevator well. I did try to make the elevator push rod stiffer, but it still didn’t have enough power for liftoff.
This is a small plane which has the potential to be an excellent beginner, but fails completely. Any beginner in this hobby doesn’t expect to rip open a model like this. I did send an e-mail to HobbyStores about the poorly built plane, but didn’t get a reply. I was polite in the mail, explaining that I had a great experience at their store, but that the plane doesn’t perform as expected. I also sent a video of the motor rattling noise. Sending this back to London would cost more than £50 in shipping, so I’m stuck with a plane not working, with a 300m+ range transmitter which can’t be used with anything else than the combined ESC/Receiver in this plane. I can’t find any planes weighing 10-15 grams other than the rubber band planes, so I guess I’ll try modifying one of these to run on these electronics, and scrap the Airhopper plane.
It’s easy to say that I’m disappointed.
My tips for a beginner:
– If you’re looking for a RTF plane, invest $100-150 in the plane. This gives you more bang for the buck.
– Even though you want a small plane, don’t buy a very light plane. If it’s heavier, the motor has to be better. Go for 2-300grams or more flying weight.
– Look for 2S (battery around 350mah) required planes. These would normally have a wingspan around 550-650mm, is heavier and more stable, and you can easily re-use parts if you crash.
– Small planes aren’t always easier to fly. I’m a beginner, and I can handle simulators well after a couple of hours, but this plane was easily disturbed by wind, because of the low weight. You have to correct the plane at all times to keep it level.
– Read up on the model before you buy. And remember to not start too big and heavy, if you crash, it’s a lot of energy that will be concentrated on the part you crash with, which means you are likely to snap a wing in half, or break the cowl or the whole nose.
– If you should crash a small plane in the 550-650mm range, there’s a lot of kit models for a small price which you could transfer the electronics to.
Take a look at my HobbyKing Yak 12 950mm EPO
My biggest recommendation is to look at HobbyKing. This is now a nearly global store, and gives you a lot of choices for a reasonable price. I can recommend Turnigy batteries and transmitters. But you can also find cheap transmitters, like the HK6S for less than $30 USD, but expect a tricky battery compartment.
More on this in later posts.
Please comment if you have questions or suggestions!