What happened
On 17 June 2017, a Bolkow Bo208, registration D-EKMY, departed from Navan Airfield with the intention of flying to Biggin Hill, UK. Shortly after takeoff, while climbing to 2,000 feet, the aircraft's forward canopy unexpectedly opened. Although a restraining cable initially limited the opening to 25 mm, the fastener on this cable failed, allowing the canopy to swing fully open and strike the rear canopy. This impact shattered the Perspex.
The sudden change in aerodynamics caused the aircraft to pitch upward and subsequently invert. The pilot managed to recover the aircraft by applying full left aileron and using intermittent bursts of engine power to maintain airspeed and prevent a stall. Due to intense airflow causing breathing difficulties, the pilot executed a forced landing in an agricultural field in Carntown, Co. L．Louth. The aircraft sustained substantial damage to the tailplane and both canopies, but the pilot escaped without injury.
The investigation
AAIU investigators examined the aircraft's canopy latch and the aftermarket modification consisting of a bracket and restraining cable. The investigation revealed that the bracket and cable were not part of the original aircraft design and were not covered by any approved Service Bulletins or Airworthiness Directives. There was no evidence that this modification had undergone the required EASA 'Part 21' design approval process.
While the latch mechanism itself showed only minor wear and remained operational, the investigation noted that the restraining cable was likely an unapproved modification. The pilot had acquired the aircraft with this cable already installed, believing it served as a safety feature to prevent full canopy deployment.
Findings
- The primary cause of the incident was the unexpected opening of the forward canopy during flight.
- The unapproved modification of a restraining cable and bracket introduced unknown risks, as the hardware was not engineered to withstand the aerodynamic forces acting on the canopy.
- The failure of the cable's fastener allowed the canopy to move into a position that caused structural damage to the rear canopy and tailplane.
- The pilot's ability to land safely was complicated by the 'startle effect' and the physical difficulty of breathing due to high-velocity airflow in the cockpit.