What happened
On the night of 11 May 1999, an AS 355 N helicopter, operated by the Air Corps for the Garda Air Support Unit, was tasked with monitoring a VIP motorcade traveling from Shannon Airport toward Galway. The flight was being conducted under night Visual Flight Rules (VFR). While flying near Crusheen, north of Ennis, Co. Clare, the pilot attempted to reposition the aircraft to place the motorcade on the starboard side for better visibility and to increase distance from nearby high ground.
During this maneuver, the aircraft entered cloud cover, resulting in a loss of visual contact with both the motorcade and the ground. In an attempt to increase airspeed while in Instrument Meteorological Conditions (IMC), the pilot significantly increased the collective pitch. This action caused the aircraft to yaw violently and climb, eventually leveling off at 1,700 feet. Following the incident, the pilot requested radar vectors from Shannon, and the aircraft returned safely to Shannon Airport.
The investigation
The AAIU investigation examined the meteorological conditions, the aircraft's technical state, and the training protocols of the crew. Investigators found that the cloud base in the area was lower than the general area forecast had indicated. The investigation also reviewed the pilot's experience, noting that while the crew was professional, the pilot had relatively limited night flying and type-specific experience on the AS 355 N.
Technical examination of the aircraft, Air Corps No. 255, revealed no mechanical defects or deferred maintenance issues. However, the investigation noted that the aircraft was not equipped with a Cockpit Voice Recorder (CVR) or Flight Data Recorder (FDR). Additionally, a discrepancy was noted in the gyro compass, which showed an error of approximately 50 degrees upon landing.
Findings
- The primary cause of the incident was the inadvertent entry into cloud due to a lower-than-forecast cloud base and the pilot's late realization of the aircraft's position relative to the motorcade.
- The pilot's reaction to the loss of visual reference—increasing power—resulted in a violent yaw and an unplanned climb.
- The existing training and checking program for GASU pilots was found to be inadequate, specifically regarding night flying proficiency and regular competency checks by Air Corps instructors.
- There was a lack of sufficient supervisory flight checks due to the senior oversight officer not being type-rated on the aircraft.
Safety action
Following the investigation, several safety recommendations were issued, including:
- The immediate suspension of GASU night operations in rural areas until pilots completed an intensive night flying training program.
- The implementation of regular Base and Line checks for pilots to align with industry best practices.
- The consideration of retrofitting modern light-weight CVRs to operational aircraft to assist in future investigations.