Our latest S76C+ is equipped with an ADELT as it was a North Sea SAR machine. We also used to have ADELT fitted on our S76Bs when I was with Schreiner. These operated on both 121.5 and 243.0 MHz and also had an "I" band radar transponder. I never heard of a problem with inadvertent deployment from an aircraft on the ground. The beacon can be deployed by the pilots in flight and the spring ensures that the beacon is deployed far enough away from the aircraft that it isn't damaged. If not activated by the crew it deploys automatically by either:
- Frangible switches when a fragile structure deforms - in the case of the S76 this is normally on a chin window.
- Inertia switches which activate at 6G or a velocity increase of 3 feet per second
- A hydrostatic switch which normally activates at 5 bars or 10 feet
There is no magic switch which deploys it automatically until it contacts either land or water.
As Trogs says all our aircraft are also equipped with 406 Mhz transmitters, crew jackets have some form of SARBE and most of our aircraft also have beacons with the dinghy (ies) and often crew deployable beacons close to the pilots.
It is useless to speculate as to the cause at this stage and with all the information sources available to the various agencies investigating it shouldn't be too long before there is some indication as to the cause. It is notable that there has been no requirement to ground the S76 fleet.
Whatever the cause, i extend my condolences to the families of all the victims.