Eurocopter is working to understand the scope of a problem that is affecting the fuel probes on some EC135 light-twin helicopters that could cause pilots to overestimate the amount of fuel remaining on board.
The company issued a safety information notice covering the type on 16 December pointing out that in the worst case this could cause an emergency low-fuel notification to appear - warning that there is just 8-10min of fuel remaining - without a prior amber caution notice displaying.
The move follows the discovery of the issue on EC135s operated by Bond Air Services in the UK. In each case the fuel probes, made in Italy by an unidentified manufacturer, in both engine feed tanks were found to be faulty.
Subsequent tests by other operators - one in the UK and another in Eastern Europe - revealed two further helicopters with the issue, although only one probe was faulty in each instance, says Eurocopter.
It is also waiting to establish if the latter finds are linked to those discovered on the Bond aircraft, says chief technical officer Jean-Brice Dumont. "We have found these two, but we don't actually know if the issue is the same.
"We will retrieve these probes and analyse them with a matter of urgency."
Typical failure rates on the component are "very low" he says.
The airframer is working to validate tests to enable operators to identify and replace the affected components where necessary, says Dumont. He hopes to receive a snapshot of the scale of problem across the globe "in the coming days" before deciding on what action is required.
However, Eurocopter is at pains to temper speculation linking the fuel probe fault with the fatal crash of a Bond Air Services EC135T2 in Glasgow on 29 November.
"There is no obvious link with the Glasgow crash, but it is premature to state there is no link" while the investigation proceeds, says Dumont.
However, he notes: "This aircraft [G-SPAO] had much more than 10min of flight time with the fuel that was found in its tanks."
Separately Bond has mandated that its EC135s fly with a minimum of 90kg of fuel in their tanks.