<p>This chapter is a brief introduction to the way aircraft fly and are controlled. It is not essential to the game but it provides some background into how aircraft behave. An aircraft is free to move in any direction at any angle. It can fly upside down or dive straight towards the ground. This can cause problems with the meanings of words like up and down. In this chapter all these words are relative to the pilot of an aircraft and not to the outside world. This means that up is always the direction of the top of the head even if the aircraft is upside down and this direction points towards the ground.</p>
<p>A real aircraft is flown using a joystick and rudder pedals. The joystick moves freely backwards and forwards and from side to side. Sideways motion moves the ailerons, which causes the aircraft to rotate about the roll axis. Moving the stick right rolls the aircraft to the right. Backwards and forwards motion moves the elevator which causes the aircraft to rotate about the pitch axis. Moving the stick back pitches the nose up. The rudder pedals move the rudder, which causes rotation about the yaw axis. Pressing the right pedal yaws the nose to the right. Interdictor uses the left and right cursor keys in place of the rudder pedals.</p>
<p>The controls of an aircraft are such that it continues to move in a particular direction whilst there is control input and stops moving any further in that direction when the control is neutral. To level the aircraft an opposite control is required. For example if the aircraft is in level flight with neutral controls, and the joystick is moved left then the aircraft will roll left, the further the joystick is moved the faster the roll rate. When the desired angle of roll is reached the joystick has to be returned to neutral. To level the wings the joystick has to be moved right and then back to neutral when the wings are level. </p>
<p>An aircraft flies because its wing generates lift. This lift always points upwards. The aircraft also has weight which always points towards the ground, but not necessarily downwards. In level flight lift is equal to weight. The amount of lift depends on the speed of the aircraft and the angle of the wings to the airflow. This is known as the angle of attack. The slower the speed of the aircraft the higher the angle of attack must be to maintain lift.</p>
<p>In a trimmed condition at a given speed the angle of attack is kept -Page 51 - correct by the tailplane which acts in the same way as the flights on an arrow to keep the aircraft flying forwards. The angle of the tailplane is set by the elevator, which is a part of the tailplane that can be tilted by moving the joystick back and forward. Moving the joystick back tilts the elevator up. The elevator then deflects air upwards causing the tail of the aircraft to drop. This causes the angle of attack to increase, producing more lift and causing the aircraft to move up. This upward motion reduces the angle of attack and therefore the lift so the aircraft becomes stable at a new angle.</p>
<p>To the pilot this process is normally seen simply as the nose of the aircraft moving up whenever the joystick is moved back and vice-versa. However the situation is complicated because the wing only produces more lift at greater angles of attack up to about 15 degrees. At this point the lift suddenly reduces and the wing stalls. In level flight this means that the aircraft weight is greater than the wing lift so the aircraft starts to fall rewards the ground which causes the nose to drop, the speed to increase and the angle of attack to reduce until the lift is again sufficient to support the weight.</p>
<p>The other balance required for stable flight is between engine thrust acting forwards and drag acting backwards. Drag varies with speed squared, which means that the faster the aircraft goes the more power is required to cause a fixed speed increase. In steady flight for a given power setting there is a speed at which drag matches thrust. A high performance aircraft has a maximum thrust of over 1 g, which means it can climb vertically until the air becomes too thin to provide power. When pointing straight down gravity adds to thrust giving maximum speed.</p>
<p>The situation becomes more complex when the aircraft is rolled over. The lift from the wings always acts upwards, so if the aircraft is banked over at 45 degrees the lift has to be 1.4 times greater than normal to match the weight. At 60 degrees lift has to be twice normal. The diagram below shows this.</p>
<p>The extra lift acting at 90 degrees to gravity moves the aircraft sideways. Due to the stabilising effect of the tailplane and fin this causes the nose of the aircraft to turn. The maximum that most pilots can take is 8 times normal gravity, and this corresponds to an 80 degree bank turn. At more than 80 degrees, V the nose of the aircraft is level with the horizon the aircraft will lose height. A 90 degree bank turn can only be maintained by pointing the nose up with the rudder and using engine power for lift.</p>
<p>In a dogfight, high gravity (g) manoeuvres are normal and the extra Ig acting towards the ground becomes less significant. The important thing is to roll until the target is 'above' the aircraft so that the aircraft can be turned towards the target using only pitch. 'Above' means above the pilots head, which if the aircraft is flying upside down means towards the ground. The importance of gravity is to trade height for speed, which means the higher aircraft usually has an advantage. Therefore, a useful attack position is to be flying level upside down above the target. You can then use pitch only to position the target in your sights. </p>
