Racal Avionics said it's beginning installations of its Modified-Automatic Dependent Surveillance systems on Norwegian helicopters, ahead of legislation requiring all North Sea operators to be equipped by January 1. M-ADS, which transmits an aircraft's GPS position, ground speed and direction by Inmarsat to Stavanger air traffic control center, has been undergoing evaluation in two Norwegian helicopters for the past 18 months. The contract from Kongsberg Aerospace covers 40 Racal satellite transceivers. Trials of a similar system aboard RAF Sea King rescue helicopters will begin later this year as part of a Racal bid for an expected contract to upgrade Mk 3 avionics to the Mk 3A standard of more recent deliveries.