What happened
On 2 January 2014, an ATR 72-212A, registration EI-REL, was operating a scheduled passenger flight from Manchester to Cork. During its initial approach to Runway 25, the crew executed a go-around due to a sudden, significant increase in indicated airspeed caused by turbulent weather conditions.
Following the first go-around, the aircraft was vectored south of Cork Airport, flying at 3,000 feet near the coastline and occasionally over the sea. During this period, a thick, opaque layer of white residue began to accumulate on the front windscreens. By the time the aircraft attempted a second approach, the contamination had become so dense that the crew lost all necessary visual references, describing the effect as looking through frosted glass. This necessitated a second go-around.
In an effort to clear the obstruction, the crew utilized weather radar to locate areas of precipitation. By flying through light rain showers, they managed to clear a small gap in the residue on the commander's side of the windscreen. This allowed the crew to safely execute a third approach, which resulted in a successful landing as further rain at the airport helped finalize the cleaning of the glass.
The investigation
The AAIU examined the flight path, meteorological data, and the physical state of the aircraft. The investigation established that the aircraft's flight path between the first and second approaches placed it in an environment highly conducive to salt accretion. The investigation also reviewed the effectiveness of the aircraft's windscreen wipers, which were found to be unable to remove the dry, adhered salt.
Findings
- The primary cause of the loss of visibility was sea salt accretion on the front windscreens.
- The accumulation was driven by a specific combination of meteorological factors: high marine surface winds and a lack of significant precipitation to wash particles from the air.
- The aircraft's altitude of 3,000 feet placed it within a zone of high sea salt particle concentration.
- The use of windscreen heating may have inadvertently exacerbated the issue by drying the salt and helping it adhere more firmly to the glass.
- The crew demonstrated effective crew resource management by proactively seeking out rain cells to restore visibility.