What happened
On October 20, 2023, a Boeing 737-800, registration SP-RKI, operated by Ryanair Sun S.A., was performing a scheduled flight from Santiago de Compostela (ESGG) to Kraków (EPGD). At 09:43 UTC, immediately after takeoff, the aircraft experienced a bird strike involving a medium-sized bird (kestrel), which entered engine number 1.
Although the crew felt vibrations through the airframe, engine parameters initially remained within normal limits, leading the crew to continue the flight toward the destination. During the climb, vibrations in engine number 1 increased to over 4.0 units. The crew leveled off at FL150 and executed the "High engine vibration – non-icing conditions" procedure from the Quick Reference Handbook (QRH). This procedure did not mandate an immediate landing at the nearest airport.
Upon reaching the cruising altitude of FL300, the crew reviewed the weather forecast for Kraków, which indicated wind gusts of up to 25 knots. The crew deemed these conditions unsuitable and decided to divert the aircraft to the alternate airport, Przemyśl (EPMO). The investigation concluded that this diversion was operationally unjustified, as the additional 20 minutes of flight time unnecessarily increased the risk of damage to engine number 1.
Following the landing at EPMO, a post-flight inspection confirmed the bird strike and revealed deformation of several fan blades in engine number 1.
The investigation
The PKBWL reviewed documentation provided by the investigating entity to establish the sequence of events and the decision-making process regarding the diversion. The investigation focused on the impact of the bird strike on engine integrity and the operational necessity of the diversion based on weather forecasts.
Findings
- The primary cause of the incident was a bird strike that resulted in the deformation of the fan blades in engine number 1.
- The decision to divert to an alternate airport due to forecasted wind gusts was considered unjustified and lacked operational necessity.
- The extended flight duration caused by the diversion increased the exposure of the damaged engine to potential further damage.