Links to competition classes

S1 Altitude

The altitude class is for models that are normally two stage and allowed 5 Newton Seconds (B Motor) impulse for seniors and 2.5 Newton Seconds (A motors) for juniors. The bottom stage must have a minimum of 40mm body diameter and the top stage must be at least 18mm for most of it's length. The class is changing from 2010 and a small peak altimeter will be mounted in the top stage to measure how high the model has flown.

Any one who has ever tried to fly a two stage model where the top stage motor is started by the bottom stage burning through, knows that as the motor in the 1st stage burns out the model arcs over. When the top stage then lights it shoots of at an angle. To combat this the two motors are sometimes both lit on ignition with a piece of slow match providing a delay before the top stage motor ignites. This should be carefully timed to start the motor just at the time the first stage is running out of power. The flight will then be straight and high. Alternatively a very short delay is required on the bottom stage, for example an A3-1 motor is often used. A flash tube is then used to carry the ejection charge to the top stage motor.

The heights achieved in this class are remarkable. The current world champion from Russia achieved 612 meters on a 5Ns B motor, that is just over 2,000 feet. The best junior achieved 325 meters on 2.5Ns A motor, which is 1,066 feet.

The change to the class to use small FAI specification altimeters to measure the peak altitude has two advantages. The first is that it will be more accurate and the risk of observers loosing track of the small upper stage is eliminated. The second is that the top stage has to be recovered and checked after the flight to read the altitude. This will ensure it meets the regulations and removes the temptation to put a "special" motor in the top stage.