Definition

Simultaneous radio transmissions (SiT) are described as:

“Situations arise when two or more radio transmissions occur, simultaneously, on the same frequency. In this context ‘simultaneous’ is defined as two or more transmissions that overlap in such a way that the controller is not aware that more than one transmission has occurred leading to a potential safety hazard.” (VoIP - Air Traffic Management (ATM) system operational and technical requirements, EUROCAE, 2009-02)

Description

Simultaneous transmission by two stations result in one of the two (or both) transmissions being blocked and unheard by the other stations (or being heard as a buzzing sound or as a squeal). With the steady growth of air traffic worldwide there is a corresponding increase in the incidence of blocked or simultaneous transmissions. These frequently result in dangerous situations developing, especially when they go undetected.