Most helicopter don't transmit Extended Squitter - and are not required to do so. E.S. is additional data on the Mode S Squitter (spontaneous transmission) that carries position information from the GPS. This allows a device receiving the transmission to know the position of the transmitting aircraft without any triangulation/bearing/ range measurements. This is what the flight radar sites use to display the aircraft on maps.
ES is coming in, all offshore helis in Dutch airspace now require it so that the Dutch can provide a pseudo radar service with the aircraft in range only of a single mode S ground station (non-rotating antenna). It is easy to implement, just need a data cable from the Gps To the transponder (ie 2 wires) and the correct mod state and configuration of the transponder.
Bristow persuaded EC to do this on all our 225s after G-ZZSG and possibly other operators also now have this. However you won't find many 225s flying out of Aberdeen for the time being!
It's not currently available on the S92 or older helis.
Last edited by HeliComparator; 30th Oct 2012 at 11:27.
Two different methods in use. The Gulf of Mexico uses ADS-B so aircraft must be suitably equipped and can be picked up by the amateur ADS receivers. The North Sea is a combination of shore based radar and multilateration. The multilat can use ADS but works quite happily without it so operators don't have to equip.