Event Description
On August 3, 2023, at 8:35 am eastern daylight time, JetBlue flight 18, an Airbus A320 (registration N649JB) experienced a loss of both engine integrated drive generators (IDG) while on approach to Jacksonville International Airport, Florida. The flight was a Part 121 IFR operation from Fort Lauderdale, Florida to Jacksonville. The airplane departed Fort Lauderdale International Airport (FLL) at about 0745, and the takeoff, climb, cruise, and descent were uneventful. At 0833:42, while descending through 2,330 feet pressure altitude, the number 1 IDG experienced an over frequency fault and was taken offline by its generator control unit (GCU). The electrical system automatically transferred AC BUS 1 to AC BUS 2, which then powered both systems. The flight crew began configuring the auxiliary power unit (APU) for start. At approximately 0834:25, the number 2 IDG also experienced an over frequency fault, causing its GCU to take it offline. With both IDGs lost and the APU not yet online, the airplane entered the emergency electrical configuration. The digital flight data recorder (DFDR) lost power for about 55 seconds, indicating the emergency electrical condition. The ram air turbine (RAT) deployed automatically. The airplane landed without further incident, and no injuries were reported by any occupants.
Electrical Power System
The Airbus A320 electrical power system (EPS) consists of a three-phase 115/200 Volt, 400 Hz AC system and a 28 V DC system. It comprises two main busses, AC BUS 1 (left) and AC BUS 2 (right), and an AC Essential Bus supplied by either main bus. Normally, two engine-driven IDGs provide power, each controlled by a GCU. In normal operation, each IDG supplies its own network independently. The EPS also includes an APU generator. In case of single IDG loss, the remaining IDG automatically supplies both busses. If both IDGs fail, the system reverts to emergency electrical configuration, powered by a RAT-driven emergency generator. In this configuration, electrical power to the DFDR is removed, but the cockpit voice recorder remains powered.
Integrated Drive Generator Failure
Each IDG contains a hydraulic pump and motor assembly that converts variable engine speed to constant output. Components include fixed and variable cylinder blocks with pistons. Over time, wear can enlarge cylinder bores. Collins Aerospace specifies maximum tolerances; worn bores can be repaired via FAA-approved re-sleeving. The GCU software monitors IDG output and can trip the IDG on detection of critical faults, such as over frequency. According to Collins, some IDG faults are associated with worn cylinder block bores that can limit stable frequency output.
Examination of Removed Components
Both GCUs were examined at Collins Aerospace facility in Phoenix, Arizona. Non-volatile memory downloads revealed that the number 1 IDG had previously tripped on July 29 and 30 due to over frequency faults. For the incident flight, the number 1 GCU recorded an over frequency fault at 0833:42, and the number 2 GCU recorded an over frequency fault at about 0834:25. The IDGs were examined in Miramar, Florida. Initial testing showed no significant findings externally. Upon disassembly, flecks of bronze-colored metal from cylinder block bore bushings were found on internal components and in hydraulic fluid filters. All four cylinder blocks (two variable, two fixed) were marked with "CB-31773", indicating FAA-approved re-sleeving. The two variable blocks showed minimal wear, but all nine bores of each fixed block exhibited significant wear and damage to the re-sleeved bushings, with some areas worn through to the cylinder block substrate. The air spindle test could not obtain accurate bore diameter measurements due to wear. According to Collins, such fixed block bore conditions would limit the IDGs' ability to maintain stable frequency during operation.