Theorie Basiskurs

Relative direction is often referred to by the hours of a clock.  12 o'clock is always ahead, 6 o'clock is always astern the aircraft.  3 o'clock is to the right and 9 o'clock to the left.  

Pilots often use this form of direction indication to indicate a direction of view (relative bearing). However, it is never used to indicate a direction to fly, i.e. A course.  

Example of a visual contact report:

"Contact, Left, 11 o'clock, high, far."

This tells a wingman where to look to see the contact.  In the example here, slightly to the left of the flight direction, slightly upwards and quite far away.  So he will have to look carefully to see the contact.  

The problem lies in the inaccuracy when the reference point (i.e. the reporter’s own location) is not absolutely clear.  If the wingman flies a slightly different heading, he also looks somewhere else, although he looks into the correct clock code.