What happened
On 24 March 2022, a Cessna 560 XL, registration D-CNOC, was conducting a non-commercial ferry flight from Almería Airport to Faro Airport. During the approach to runway 10 at Faro, the aircraft encountered heavy rain. The flight crew reported that the visibility through the cockpit windows was severely diminished, preventing a clear view of the runway environment. This led to two consecutive missed approaches.
Due to the degraded visibility, the crew decided to divert to their alternate aerodrome, Seville Airport. To minimize flight time and conserve fuel, the crew requested to land on runway 09 instead of the active runway 27. Air traffic control informed the crew that using runway 09 would require a declaration of an emergency. The crew subsequently declared a MAYDAY due to a perceived lack of fuel. The aircraft landed safely at Seville at 13:20 local time, with fuel levels remaining above the final reserve.
The investigation
The investigation focused on the condition of the aircraft's rain removal system, specifically the hydrophobic sealant coating on the windshield. Investigators found that the coating was in a degraded state, which caused raindrops to obscure the crew's view rather than bead and roll off as intended.
While the aircraft's maintenance records showed the coating had been re-applied in November 2020, the functional inspection due 12 months later had not been performed. The investigation also examined environmental factors, noting a Saharan dust intrusion over the Iberian Peninsula at the time. While the presence of dust is a known agent for coating deterioration, the investigation could not definitively confirm if the dust or an improper application caused the failure.
Findings
- The primary cause of the incident was the poor condition of the windshield coating, which prevented the crew from maintaining an adequate view of the runway during heavy rain.
- The flight crew's fuel planning was appropriate, and the aircraft landed with more than the required final reserve fuel.
- The aircraft operator had not performed the scheduled 12-month functional test of the windshield coating.
- The presence of Saharan dust in the region may have contributed to the deterioration of the hydrophobic sealant, though this was not definitively proven.