About this objectCompass, P11 collected by school boy Geoff Greensmith. He often used to swap his finds with his friends. He traded a piece of his radio collection for this compass with a friend from Downe School.
The P11 compass and its variants was a standard piece of navigational equipment for Hurricanes and Spitfires and several other aircraft during the early days of the Second World War. It is liquid damped to stabilise its movement and in common with all compasses, points to the magnetic North Pole, which is somewhere to the top right of the Hudson Bay in Canada. Its actual position varies slightly year by year, either to the east or to the west and its current deviation must be accurately known for successful navigation.
For the successful navigation and accurate knowledge of the winds’ speed and direction must also be known, and this together with the aircrafts cruising speed enables ground speed to be calculated and ground speed against time and direction gives distance, and with luck one should arrive at the desired destination without the many radio navigational aids, not to mention the GPS which modern aviators take for granted.