Airbus A320 N649JB incident near Jacksonville, Florida

Probable cause

The loss of both Integrated Drive Generators (IDG) due to worn fixed cylinder block bores, which caused the IDGs to be tripped offline and caused the airplane to enter an emergency electrical configuration.

NTSB analysis

Information received from JetBlue maintenance and the download of the number 1 generator control unit (GCU) indicated that the number 1 integrated drive generator (IDG) had tripped offline twice over the five days before the incident flight. The digital flight data recorder (DFDR) and GCU data showed that, during the incident flight, the number 1 IDG tripped offline, followed by the number 2 IDG. The loss of both IDGs caused the airplane to enter the emergency electrical configuration and deploy the ram air turbine (RAT). Given the electrical configuration of the airplane at the loss of the number 2 IDG (the APU was not online), the emergency electrical configuration change would cause a temporary loss of the flight deck displays as the electrical system transitioned to power from the RAT.

The examination of both the airplane’s IDGs revealed that all of the fixed cylinder block bores were worn beyond tolerance. The IDG manufacturer Collins Aerospace indicated that worn cylinder block bores would make it difficult for an IDG to maintain a constant and consistent frequency; fluctuations in the frequency of the IDG’s output power made it susceptible to faults that could cause the IDG to trip offline.

Text from the NTSB. Open the NTSB docket for ENG23LA033 for the full record.