Seventeen people were injured when the jet they were travelling on sustained damage when it hit turbulence shortly before landing in Dublin.
The Air Accident Investigation Unit (AAIU) has published a reportinto the serious incident that occurred on October 20th, 2013, while the flight was on approach to Dublin.
An investigation was immediately launched, headed by the AAIU's chief inspector of air accidents Jurgen Whyte.
There were 131 passengers and a crew of eight on board United Airlines flight UA-23 from Newark to Dublin when the Boeing 757-200 hit turbulence.
The crew noted the presence of St Elmo’s Fire, where electrical discharge is seen when an aircraft flies through a heavily electrostatically charged atmosphere.
At the time, the aircraft was about 148km southwest of Dublin.
According to the report, as turbulence eased, the co-pilot noticed the airspeed as indicated was low. Fearing a stall, the co-pilot applied forward force on the control column and increased thrust.
After this the co-pilot reported the airspeed recovering, before falling again, and so repeated the manoeuvre.
The report said it was then determined the commander’s instruments were reading correctly, and the commander took control before handing back to the co-pilot. “Subsequently, the flight crew were alerted to a system message indicating a loss of hydraulic pressure in the centre hydraulic system,” the investigation found.
The crew told air traffic controllers of the turbulence and requested medical assistance and airport emergency services to be standing by. The aircraft landed at 5.22am.
The aircraft was found to have sustained damage to the centre hydraulic system service bay and ceiling panels in the cabin.
Eight passengers and two flight attendants reported minor injuries due to coming into contact with internal parts of the aircraft. They were attended to by airport fire and ambulance personnel. One passenger was treated in hospital and later released.
On December 2nd, 2013, weeks after the incident, a passenger contacted the AAIU and described how he was in a lavatory at the time and how he was injured.
The airline later informed the investigation that reports of minor injuries were subsequently received from four additional passengers.
In total, 13 passengers and four cabin crew staff were reported as hurt.
The “probable causes” of the incident were found to be temporary blockage of “the right main pitot probe due to ice crystal icing, leading to an unreliable airspeed indication” and “non-standard flight crew response to a low airspeed indication”.
The investigation made a total of eight safety recommendations.