What happened
On March 21, 2019, an Airbus H130 T2 helicopter, registration VT-GVO, was performing a routine shuttle service between Sanji Chhat Helipad and Katra Helipad. The aircraft, operated by M/s Global Vectra Helicorp Ltd, was carrying seven passengers at the time of the incident.
During the descent phase of the flight, at an altitude of approximately 5,500 feet, the pilot experienced a sudden, loud noise and a gust of wind inside the cockpit. Upon inspection, the pilot discovered that the glazed window ceiling panel located above the pilot's seat had detached and flown off the aircraft. The pilot immediately took corrective action by reducing the helicopter's airspeed and notified Katra ground control via radio. The pilot opted to cut the landing circuit short to perform an immediate landing. The helicopter arrived safely at the Katra Helipad at 17:40 IST, and there were no injuries to the crew or passengers.
The investigation
AAIB India investigators examined the maintenance history and the physical condition of the aircraft's interior. The investigation focused on the replacement of the left-hand window ceiling glazed panel, which had been replaced in October 201ered following the discovery of a crack during a 600-hour scheduled inspection.
Investigators scrutinized the timeline of this replacement, noting that the work was completed in only four days. This timeframe was found to be insufficient according to the Aircraft Maintenance Manual (AMM), which requires a 72-hour curing period for the adhesive. Furthermore, physical examination of the adhesive area revealed uneven surfaces and lumps, suggesting that the surface preparation and adhesive application were not performed with the required precision.
Findings
- The primary cause of the incident was the non-adherence to established maintenance procedures during the replacement of the glazed window panel.
- The replacement process lacked adequate surface preparation and did not allow for the necessary adhesive curing time.
- Inadequate bonding between the single-layer glazed panel and the aircraft surface led to gradual de-bonding over time.
- A crack likely originated from a glass alignment spacer and propagated until the panel failed during flight.
- The defect was not detected during the 150-hour/12-month scheduled inspection or during daily pre-flight inspections.