When a Routine Electrical Fault Becomes a Ramp Hazard
On July 18, 2025, an Airbus A319-131 (United Airlines Flight 2428, registration N822UA) arrived at Santa Barbara Municipal Airport. During taxi-in and gate arrival, the standard arrival sequence was interrupted by a cascade of ECAM cautions: an ELEC APU GEN FAULT and a brief fire warning for the shut-down right engine. The flight crew executed abnormal procedures, keeping the left engine (No. 1) running to maintain electrical power until a portable GPU arrived. The engine shutdown was delayed by approximately 10 minutes. Misinterpreted hand signals from the marshaller, incompatibility with jet bridge power while an engine was operating, and an unreceived radio warning resulted in a ramp agent entering the Jet Blast zone and sustaining serious injuries. This NTSB case provides a textbook illustration of an Interface Hazard: the hazard originated at the operational boundary between flight operations and ground handling.
ECAM FAULT CASCADE AND 10-MINUTE COCKPIT DELAY
Before stopping at the gate, the ECAM triggered an ELEC APU GEN FAULT caution. Following the routine shutdown of Engine No. 2, an intermittent right engine fire warning briefly activated. Unable to reset the APU generator and restricted from connecting jet bridge power while Engine No. 1 was operating, the crew maintained operation of the left IAE V2522-A5 engine for approximately 10 minutes until a mobile GPU was delivered and connected.
DESYNCHRONIZATION OF RAMP HANDLING PROCEDURES
The marshaller signaled stop and confirmed the nose gear was chocked. Standard operating procedures required wing walkers to wait for an explicit 'Safe to Approach' signal, as the continued operation of Engine No. 1 kept the Anti-Collision Beacon illuminated, maintaining the aircraft in an active hazard condition.
SIGNAL MISINTERPRETATION AND COMMUNICATIONS BREAKDOWN
The injured left wing walker perceived the marshaller lowering his hands as a signal to approach. Observing the operating engine and illuminated beacon, the ramp lead attempted to warn the agent over the radio, but the transmission failed to establish contact.
ENTRY INTO THE JET BLAST HAZARD ZONE OF THE IAE V2500 ENGINE
Carrying wheel chocks, the agent stepped behind Engine No. 1 operating at idle power. Exhaust blast from the engine knocked him to the concrete pavement, causing multiple serious injuries.
Investigation Findings
- The aircraft sustained no structural damage; cockpit cautions were triggered by electrical anomalies within the APU power generation system.
- The flight crew kept Engine No. 1 operating within established abnormal procedures while troubleshooting and waiting for external GPU power.
- Probable cause according to investigation materials: The ramp worker's premature entry into the jet blast hazard area due to a loss of situational awareness and misinterpretation of marshalling hand signals.
- Safety barriers (illuminated Anti-Collision Beacon, distinct marshalling signals, radio warning attempt) failed due to human factors and a disruption of the routine operational flow.
Official Sources
- NTSB — Investigation of UAL2428 / SBA, Airbus A319-131, N822UA