Not quite without incident:
Date: 29 April 2004, aircraft type: Super Puma AS 332 L2, during the landing phase at airport. During the final approach of the helicopter to the airport (returning from offshore), one unidentified passenger used his mobile phone in flight about one minute before landing, which caused the loss of all the flight and navigation parameters of the four IFDS screens (Integrated Flight Display System).
The four screens became black during this critical flight phase for one second, and then returned to normal. In addition, there was illumination of the HUMS caution light, due to the loss of all the flight data of the HUMS (Health and Usage Monitoring System).
This incident is not an isolated occurrence: another incident has been reported on a Sikorsky S 76: a mobile phone - in the cargo bay, but not switched off - caused a false engine fire alarm during the flight. Mobile phone calls made by passengers on aircraft can seriously affect the aircraft's onboard equipment.
The UK Civil Aviation Authority carried out tests on two parked aircraft to find out the potential dangers of mobile phone use. It found evidence that calls produced interference levels which could disrupt aircraft systems. Faults that could be attributed to mobile phones use include false cockpit warnings, the malfunctioning of aircraft systems, interference in pilots' headsets and the distraction of cabin crews from their normal duties.
The CAA bans the use of mobile phones from its flights once engines start running.
In June 2003, a man was sentenced to 12 months in prison after being found guilty of "recklessly and negligently" endangering a British Airways flight. The Court jury heard that the man, an oil worker, had repeatedly refused to switch off his phone after being spotted with it on a Boeing 737.
Unless
you know better of course - after all you are professional pilots.