What happened
On 23 February 2017, a Let L-410 UVP-E, registration OK-LAZ, was operating a commercial passenger flight from Isle of Man (Ronaldsway) Airport to Belfast City Airport. The region was experiencing a deep low-pressure system characterized by intense surface winds. After an unsuccessful landing attempt at Belfast due to strong crosswinds, the crew diverted back to the Isle of Man.
Upon arrival at Ronaldsway, the aircraft encountered extreme conditions. During the landing roll, witnesses observed the aircraft rolling significantly, with the left wingtip descending to within approximately one metre of the runway surface. Following touchdown, the right mainwheel lifted off the ground before the aircraft stabilized. The crew subsequently attempted to taxi the aircraft, but the wind—gusting to 6/3 kt—exceeded the operator's established ground operation limits. Due to safety concerns regarding the risk of the aircraft being blown onto its wingtip, air traffic control and the local civil aviation authority directed the crew to halt the aircraft and shut down the engines into the wind.
The investigation
The AAIB investigation examined the flight's history, meteorological data, and cockpit voice recorder (CVR) transcripts. Investigators analyzed the aircraft's performance limitations, noting that the maximum demonstrated crosswind component for the Let L-410 is 19.4 kt. The investigation also reviewed the crew's pre-flight weather briefing, the operational flight plan (OFP), and the operator's manual regarding wind limits and fuel planning. Flight data recorder analysis revealed that the aircraft's airspeed fluctuated significantly during the approach, and the flightpath transitioned between climbing and descending as the aircraft encountered turbulence.
Findings
- The primary causal factor was the decision to land with a maximum crosswind component of 40 kt, which was approximately double the aircraft's maximum demonstrated certification value of 19.4 kt.
- The crew's weather assessment was insufficient, as they relied on limited reports without consulting meteorological charts to understand the storm's trajectory.
- The aircraft operator's procedures lacked adequate oversight, as neither the flight crew nor operational control reviewed the evolving weather threats with the pilot.
- Fuel planning was inadequate; the OFP did not account for correct contingency fuel, leaving the crew with much less margin than anticipated.
- There was a lack of effective Crew Resource Management (CRM), evidenced by the lack of verbal discussion regarding evolving threats and the failure to follow standard operating procedures when the approach became unstable.
- The crew attempted to taxi in winds that exceeded the operator's 45 kt ground limit and surpassed the conditions that had caused a similar accident for the same operator in 2007.