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Electric Aircraft

 

Electrics Explained By Harry Harris

 

Although I do own quite a few electric models I don't claim to be an expert on electric flight. If you you plan to get into this side of the hobby in a serious way it can get VERY technical. As with other sections on this site, I offer the following as a guide to those interested in flying electric powered models.

Electric model aircraft really have come of age in the last couple of years. This is mainly due to the availability of brushless motors and Lithium battery packs.

A brushless motor commonly delivers 20% more power then your standard brushed motor. The lithium batteries are less then half the weight of the equivalent powered Nicad or Nickel Metal Hydride.

Recently the Precision Aerobatics (Pattern Flying) in the USA was won with an electric powered model. At the time of writing this, the world's fasted model aircraft is electric powered.

A word of caution at this point, Lithium batteries behave very differently to Nicads (NiCd) and Metal Hydrides (NiMH) and can only be charged with a Lithium charger.

NEVER CHARGE A LITHIUM BATTERY WITH A NiCd OR MiMH CHARGER OR ANY OTHER HOUSEHOLD CHARGER.

It is important to know what rate a Lithium battery pack can be charged at and this varies with different cell configuration. Never use a mobile phone Lithium charger as you don't know what cell configuration it is set up for. If handled incorrectly Lithium explode and catch fire, the chemical reaction can continue even after the battery has been disconnected from the charger.

If you are new to electric flight start off start off by talking to someone who 'Knows What They Are Doing'. If you have not already done so read the article on electrics by Harry Harris.

Okay, now that I have scared you out of ever going near a Lithium cell, electric flying is great.... no messy fuels, no glow plugs, no noise, no cleaning up after flying etc. Almost every type model that uses a petrol engine can be converted to an electric power. Have a look at our Photo Section to see a small sample.

Electric powered models use the same radios as gas powered models with one exception, the throttle is operated by an electronic speed controller. This replaces the throttle servo in the gas powered models.

Speed controllers have to be matched to the type of motor you plan to use and the amount of current (power measured in Milliamps or Amps) the motor is capable of pulling out of the battery. If you don't get this match right you'll just be burning up money... literally. Brushless motors must be used with a brushless speed controller.

Indoor electric flying is very popular... by that I don't mean flying in the HOUSE, but in basketball stadiums or large sheds etc. There is a whole range of models manufactured especially for indoor flying. In my arsenal of indoor models I have a Tiger Moth, a helicopter and a helium filled Blimp. The great thing about indoor flying is that you don't have to worry about the weather, just load up and go flying. Indoor flying is not difficult but probably not a great place to learn to fly... the walls and roof come up very quickly !!!

The big challenge with electric flying is keeping the weight down. Remember, you have lug around the battery pack. There is a whole range of special gear around to help keep the weight down, mini servos, micro receivers, tiny speed controllers.

Motors come it all different configurations, some have reduction gear boxes to swing big props and a huge variety of armature windings. Just as a rule of thumb, the less the windings the slower it will turn but the more torque it will have, but also will require more current to turn it. Then you get single turn motors or 2 turn motors... gets tricky doesn't it.

My first attempt to drop an electric motor into a trainer I had ended up in a disaster.... I got this 'Beaut' buggy motor and bolted it in. Then made up a great 8 cell pack and got a speed controller to match. Off I went to the field with my 'Speed Machine' all charged up with all my mates in tow. We fired it up and threw it into the air. To say it was less then impressive would be an understatement, but I eased it up to a decent height and puttered around for a few minutes and then landed. Carrying the model back I noticed the bottom of the fuselage was a bit hot and it didn't smell too flash either. When I opened the battery bay this puff of blue smoke came out. I decided to get the batteries out ASAP only to find that not only had the shrink wrap around the pack totally dissolved but so had the plastic covering on the cells. When I held the pack by the cable all the cells just hung like a bunch of grapes... it was then I decided I had better read up a bit about this electric stuff and chat to someone who knew what they were talking about. The 'beaut' motor is back in my son's buggy and my $60 homemade battery pack is no more.

Electrics are great, but be very careful, the motors nowadays draw huge currents and the battery packs very powerful and if shorted the consequences can be serve.

There is a huge number of different chargers available ranging from the old basic resistor type up to the wizz bang microprocessor pulse ones that do everything but make a cup of tea for you.

Treating your batteries properly will ensure you get the maximum amount of use and power out of them. Correct cycling, minimum discharge levels, charge rates are all important.

If you want to have a dabble in electric flying there is huge selection of 'Ready To Go' models in the Hobby and Toy shops. There is a brand called GWS who make a great selection of scale and sport electric models, there are thousands of them out there flying. I recommend you start off with one of these types and work you way into the wizz bang 'pocket rockets'.