Irish investigators have cautioned over the use of single-engined taxiing after an incident in which jet blast injured two workers as a Ryanair Boeing 737-800 manoeuvred to park.
The aircraft had been taxiing with just its left-hand engine but had come to a halt while awaiting marshalling personnel for stand 111R.
Ireland’s Air Accident Investigation Unit says the engine speed, which had been around 20% of N1, increased to 55% as the jet turned to park.
It states that the breakaway engine speed – the level needed to start moving from stationary – is normally around 30-35% of N1.
As the aircraft turned into its stand, the jet blast struck two workers on a ramp site, some 40m (130ft) behind, and dislodged a set of fences. The workers were probably subjected to exhaust velocities exceeding 43kt, says the inquiry into the 2 November 2015 incident.
“The situation was compounded by the fact that the right-hand engine had been shut down and the use of left engine thrust in excess of the minimum required to break away exacerbated the hazard,” it states.
“In the circumstances, with the aircraft stopped in close proximity to the worksite, it would have been prudent to ensure minimum thrust was used or to consider re-starting the second engine or using a tug to manoeuvre the aircraft onto its stand.”
Both workers were taken to hospital but initial concerns of serious injuries proved unfounded. Ryanair carried out its own investigation and subsequently reminded crews of jet-blast hazards, giving guidance on single-engined taxiing, and the importance of using minimum thrust.