What happened
On 2 November 2015, a Boeing 737-8AS, registration EI-ESZ, arrived at Dublin Airport from London Gatwick. After landing, the aircraft taxied toward its assigned parking stand, during which time the crew shut down the right-hand engine to save fuel. While waiting for ground personnel to marshal the aircraft into its final position, the aircraft stopped adjacent to an active construction worksite.
As the aircraft began maneuvering into its final parking spot, the pilot increased power to the remaining engine. This increase in thrust created a powerful jet blast that struck two workers who were repairing a fence at the worksite. The force of the exhaust blew the workers backward and knocked over several sections of the site's fencing. Both individuals were transported to a hospital with bruising injuries, though no fractures were sustained.
The investigation
The investigation focused on the engine thrust levels and the proximity of the worksite to the aircraft's path. Data from the Flight Data Recorder (FDR) revealed that while the aircraft was stationary, the left engine was at 20% N1. However, during the final turn toward the stand, the N1 reading peaked at 55%.
Investigators compared this thrust level to manufacturer data, which indicated that at 40 meters from the tail, an engine setting of this magnitude could produce exhaust velocities exceeding 50 mph. The investigation also reviewed the operator's manuals, which advise minimizing breakaway thrust and caution against excessive jet blast when taxiing on a single engine. Additionally, the Dublin Airport Authority's (DAA) risk assessments for the worksite were examined, noting that while the risk of jet blast was identified, it had been categorized as a 'remote' possibility.
Findings
- The primary cause of the incident was the use of excessive engine thrust during the aircraft's final maneuvering onto the stand.
- The necessity of stopping the aircraft to wait for a marshaller led to a requirement for higher breakaway thrust, which increased the jet blast hazard.
- The use of single-engine taxiing procedures exacerbated the risk, as the increased power required to restart movement from a standstill created a concentrated blast directed toward the worksite.
- The worksite was positioned directly in the path of the engine exhaust during the aircraft's right-hand turn.
Safety action
Following the incident, the aircraft operator implemented several safety measures, including publishing safety reminders to flight crews regarding jet blast hazards and producing a safety video specifically addressing the risks at the Dublin Airport worksite. The operator also issued guidance against using single-engine taxi-in procedures when parking near this specific area.
In response, the Dublin Airport Authority updated its policy for airside construction, mandating the installation of jet blast fencing for future projects where such risks are present. The DAA also provided specialized fencing to contractors and improved the process for involving operators in site risk assessments.