Flying Aeromodels

Flying aeromodels models are, as suggested by the name, model aircrafts capable of actual flight. While static models lay more emphasis on the external appearance of an aircraft, flying models need considerations of weight, balance and strength as well. Shape considerations tend to focus more on the aerodynamics or flight characteristics of the model than just the external looks such as paint and finish. Different building materials may be used for building flying aeromodels but they should have a good weight-strength ratio. Balsa wood and polystyrene foam meet these criteria and are choice materials for construction. Also, bits of glass fibre cloth, plywood and some plastic moulded parts such as propellers and spinner cones may be incorporated in the design. Just like the static models, it is always a good idea for beginners to go for kits rather than trying to build models from sheets of balsa wood!

Before we proceed to actually building a flying model, let us explore the different types of flying models. They may be classified very basically as: A. Powered or B. Unpowered whether they have a source of power (such as a motor or an engine) to assist their flying. Also, depending on the method by which they are controlled in flight, flying aeromodels may be classified as I. Free flight models (with only built-in controls) II. Control-line models or III. Radio-controlled models.

Unpowered aircrafts are without a powerplant and fly only using the initial force supplied during launching. The chuck gliders are launched in the air by the chucking action of the hand and are often flown indoors. Hence they are also known as 'Indoor models' Some chuck gliders are made using sheets / blocks of 'thermocol.'

Tow-line models are gliders which are launched using a long line with a ring hook, in the open against the wind direction. The launcher runs against the wind after the helper releases the aircraft. Once in air, the aircraft rapidly gains height until it is at the top most point called the 'zenith'. The model automatically detaches from the tow-line as the ring hook slips and glides back to earth in wide circles. The fin is off-set a couple of degrees while constructing, to aid the glider to descend in circles.

Rubber powered models also fall in the category of 'Indoor models' and are similar to chuck gliders, but made of balsa wood. They have a propeller which derieves power from the unwinding of a twisted rubber band. Special rubber powered motors are also supplied with some kits.

Catapult models are also similar to chuck models, except they are launched from a hand-operated catapult, rather than a chuck of the hand. These models are swift, have a longer range and are suitble outdoors. Catapult models need to be stronger than chuck gliders, hence are made of wood / plastic and not thermocol.

Free flight models are aircrafts fitted with an internal combustion, reciprocating engine (usually small compression ignition engines of capacity around 0.75 cc). They are launched in an open field and gain heigth as a virtue of pre-set elevators, as long as the engine is running. Calculated amount of fuel is filled in the tank to gain a desired height. When the engine cuts, the free flight model glides back to the earth, freely, just like a glider!

Control-line models are a stepping stone towards the radio-controlled models and are usually fitted with compression ignition engines from 1 - 3.5 cc capacity and are controlled by means of two metal cables, which control the elevators of the aircraft. A fixed rudder position in the design of the aircraft ensures that the aircraft flies in circles around the flyier but pulling away, to keep the control line taut at all times. Depending on the flight characteristics and the ease of maneuvering, the control-line aircrafts may be trainers or aerobatic models or speed models. Trainer models are sturdy and have low speeds and sluggish controls to allow a beginner to gain experience in flying powered aircrafts. The aerobatic models are light weight, overpowered and have sharp controls which allow the flyer to perform in-flight aerobatics with the model. Speed models are racing models, generally used in competitions and are dedicated to very high speeds. Some of the aerobatic and speed models are powered by glow-plug engines for an extra boost of power. Please check out these links to know more about control line aircrafts.

Radio controlled models fly like real aircrafts and are a keen aeromodeller's ultimate dream. They are remotely controlled by means of a radio transmitter. The receiver fitted in the aircraft picks up the transmitted signals and manipulates the flight controls to fly and even perform aerobatics. Generally a 4 channeled radio with 4 servos fitted on the aircraft gives the flyer (pilot) control of the elevators, aielerons, rudder and the throttle. The more the channels on your radio the finer control you can exert on the aeromodel. These models are powered by a single / multi-cylinder glow plug reciprocating engine. There is a huge variety of engines available in several price ranges differing in their engine capacities, types (some are 2-stroke engines while others are 4-stroke), cylinder configurations, throttle controls and accessories. Some advanced models also incorporate jet engines or solid rock motors which use a solid propellant. this is where the rich-man's aeromodelling game begins. There is loads of literature available on the Internet on RC models, engines and accessories. An entire industry with engine manufacturers, kit manufacturers to accessory suppliers especially dedicated to aeromodelling is developed in the the west. A good point to start further reading is the Beginner's guide to R/C Flight by Howard Sullivan.

The flying models are available in standard and scale down kits. They are assembled as per the instructions provided with the kit. The angles of the wings, their flatness or camber must be equal on both the sides. No surface should be warped. Paint your model in a manner similar to the static models, avoid excessive use of filler paste or thick coats of paint as these add to the weight of the aircraft. When your flying model is finally ready, it may not be statically balanced i.e. either the nose or the tail may be heavier. This should be corrected by the addition of fixed ballast weights. The model should be balanced in the horizontal axis passing through the wings (around 20% from the leading edge) i.e. Add weight to the nose if the tail is heavy or make the tail heavy if the nose tips down. Then adjust the lateral balance along the long axis of the aircraft, although this is less significant as compared to the horizontal balance. The flight controls should be rigged with precision and the engines mounted firmly. Lock nuts are preferable as these do not loosen due to vibrations from the engine. Also you would realise how important is the quality of glue as models made using sub-standard glues rip open due to engine vibrations.

After painstaking efforts your model is ready for it's first flight. Test fly it gingerly, in a no wind condition, indoors, if that is possible. Before you proceed, please note the 3 basic controls, which determine the 3-dimentional stability of your model. The 'elevator', 'rudder' and the 'ailerons' are the basic control surfaces of any aircraft. Depending on the sophistication of your model, some of these may be pre-set or fixed.

Pitching control: The elevator which is situated in the tail plane, is the main control surface which makes your model go up or down. When the elevator is moved 'up' the aircraft goes 'up' and it goes 'down' when the elvator is moved 'down'. Never move the elvator more than 15 degrees up or down, as your model may stall or dive very sharply and you might crash!

Yawing control: The rudder, located in the fin is the control surface for turing your aeromodel left or right. When the rudder is turned 'left', your aircraft would turn 'left' and when the rudder is turned 'right', your aircraft wold turn 'right'. Again it is not wise to turn your rudder left or right more than 15 degrees, especially if you are not banking during the turn, or your aircraft would slip away and dramatically loose height!

Rolling control:A pair of ailerons, situated in the wings is used for banking an aircraft left or right. Ailerons are generally synchronised to move in opposite directions i.e. when the left aileron moves 'up', the right one goes 'down', effectively pushing the left wing down and pulling the right wing up. Effectively, the aircraft tilts (or banks) to the 'left'; the opposite happens while banking to the right. Ailerons are very sensitive and should not be operated more than 10 degrees, else your aircraft would go spinning in the air!

After some trial and errors, you will soon learn the basic skills of flying model aircrafts. Do not give up too easily, although there might be initial failures. It is easier said than done, as there are many frustrating moments while you learn to fly your model; but believe me the joy and satisfaction you get after you master the skys is so immense that I cannot help saying - It's worth it! For more details on the aerobatic maneuvres please refer to the web page called A Beginners Guide to RC Aerobatics, which gives brief descriptions on some of the most popular aerobatic stunts and how to do them.

So much for an 'Introduction' to the hobby of aeromodelling. My personal advice is that you should make a humble begining to flying models with a tow-line glider. When you are familiar with the behaviour of an aircraft out in open air, try for powered models like the control line models. Although RC aeromodelling is the pinnacle in this hobby, it should be noted that it is an expensive affair and it would be wise to invest in a radio, only after you are confident with control line models. Aeromodelling as a hobby is not so well developed and popular here in India, but with enthusiasts like yourself, we would soon be having a full-fledged aeromodelling activity here as well! Happy Aeromodelling...