The Australian Transport Safety Bureau (ATSB) ordered stub pipe inspections on only two specific versions of the Rolls-Royce Trent 900 engine as part of its investigation into an uncontained engine failure on a Qantas Airways Airbus A380 aircraft on 4 November.
The stub pipe inspections completed 8 November were on 45 Trent 900 engines which were exclusively "mod A" and "mod B" versions of the powerplant, a spokesman says. The latest version of the engine, "mod C", was not inspected.
The ATSB could not say what differentiated "mod A" and "mod B" versions from the "mod C" version.
Rolls-Royce had earlier said "there has been no design change relevant to this failure between A, B and C versions of the engine".
However, sources familiar with the matter say that the problem the ATSB identified last week in its preliminary report as the cause of the uncontained engine failure - an axial misalignment of the counter-boring in the stub pipe - is limited to early versions of the Trent 900.
"The suspected misaligned counter-boring stopped at a certain point in the production process," says one of the sources, who was unable to elaborate further.
The stub pipe inspections found three affected engines, all of which were removed from service.
"Based on Rolls-Royce's understanding of the cause of the problem, the inspection was focused on specific types of Trent 900 [engines]," the ATSB spokesman says.
"We identified the oil pipe affected and they identified the range of engines affected," he adds.
Rolls-Royce submitted to the ATSB the identification numbers of the affected engines, the spokesman says. All of those engines were either "A mod" or "B mod" versions.
The ATSB says it is continuing its investigation.