What happened
On 18 August 2003, a Sikorsky S-61 N helicopter, registration EI-CNL, was conducting a pilot Operator Proficiency Check (OPC) at Shannon Airport. The flight crew, consisting of a pilot-under-test and a Type Rating Examiner (TRE), was performing a series of simulated training maneuvers. During the third circuit of the exercise, the TRE initiated a simulated engine failure, followed later by a simulated auxiliary hydraulics failure. The latter caused the automatic flight control system to disengage, making the flight controls significantly heavier and more difficult to manipulate.
As the aircraft approached runway 31, the crew became preoccupied with discussing another aircraft taxiing across their path. During the final stages of the approach, the pilot failed to perform the necessary landing checks. Consequently, the helicopter touched down with its main landing gear retracted. The impact caused damage to the aircraft's keel area and the underbelly anti-collision light. The crew was able to recover the aircraft into a hover, extend the gear, and land safely on the runway without further incident. There were no injuries to the crew.
The investigation
The investigation examined the cockpit voice and flight data recorders, as well as the aircraft's Audio Voice Alerting Device (AVAD) settings. It was established that the crew was utilizing a memory-based training checklist rather than a prompted, referenced checklist. Furthermore, the investigation looked into the RADALT bug settings, noting that the crew had configured the system in a way that inhibited the undercarriage warning.
Findings
- The primary cause of the accident was an oversight by the flight crew to properly configure the helicopter for landing.
- The crew's situational awareness was likely compromised by distractions regarding other aircraft movements on the taxiway.
- The use of a memory-reliant training checklist, rather than a formal prompted checklist, increased the risk of missing critical items.
- The crew's adherence to specific RADALT bug setting procedures effectively disabled the aircraft's automatic undercarriage warning system during the landing phase.
Safety action
- The investigation recommended that the operator review its RADALT DH bug setting procedures for onshore operations to ensure that the undercarriage warning system remains available during all phases of flight.