General Electric expects to start a fleet-wide retrofit of variable geometry (VG) actuators on more than 360 CF34-8 engines in July after several incidents in which electrical signal faults occurred, at least one of which resulted in the full-authority digital engine control (FADEC) commanding the engine power to idle.
In the worst case to date, the problem caused an engine on a Lufthansa CityLine-operated Bombardier CRJ700 to reduce thrust to idle on the runwaybefore take-off. GE says no thrust reductions have occurred inflight, although the US Federal Aviation Administration (FAA) says the failure results in "loss of the ability to advance thrust above idle, and could result in a multi-engine loss of thrust if dual-channel faults occur on more than one engine simultaneously".
Inspection of the FADEC for master fault VG actuator messages and replacement of faulty actuators is being mandated by the FAA, which is expanding an existing airworthiness directive covering the -8C1 and -8C5 turbofans to embrace the -8E series now entering service on the Embraer 170.
The replacement effort is expected to take up to 18 months and involves new VG actuators for almost 130 CF34-8C1 powered CRJ700s, more than 40 -8C5 powered CRJ900s and 12 -8E powered Embraer 170s.
GE small commercial engines general manager Chip Blankenship says the company "is in the middle of building up inventory for a field change-out and next month we should have sufficient quantities to begin that".
Guy Norris / Los Angeles
Source: Flight International
