Investigators are recommending that European and US regulators consider extending tyre overpressure specifications retrospectively following a tyre-burst on a Bombardier CRJ200 which badly injured a technician.

The technician had been rectifying an under-inflated nose-wheel tyre on the CityLine aircraft at Manchester, on 13 November 2008, using a nitrogen pressure rig.

While attempting to inflate the tyre he unintentionally subjected it to six times its normal pressure of 163psi. It burst, scattering wheel fragments and inflicting serious injuries on the technician.

The Air Accidents Investigation Branch says the regulator on the rig had been set to deliver a particularly high gas pressure, but the usage pattern of the rig was not recorded which left the inquiry unable to determine how it had previously been adjusted.

While the rig's inflator was designed to limit the flow-rate of nitrogen into the tyre, it adds, the small volume of the nose tyre would have led to a much more rapid increase in pressure than in a larger tyre - too quickly for the technician to release the inflator's trigger lever in time.

The CRJ200 was certified before current regulations on overpressure burst protection were put in place.

"Had overpressure burst protection been fitted to this aircraft it is probable that the accident would not have occurred," says the AAIB. "This is not the first occasion on which such bursts have happened and previous such events have resulted in fatalities."

Source: Air Transport Intelligence news