Description

On 31 July 2012, a Boeing 737-900 (N37420) being operated by United Airlines on a scheduled domestic passenger flight (UAL1475) from Dallas/Fort Worth to Denver hit a single large bird at 11500 feet during the descent to destination in day Visual Meteorological Conditions (VMC) and lost some flight instrument indications. The crew declared an emergency and were assisted by ATC in completing the approach without further event. After landing, a large hole was discovered in the radome together with other minor damage attributable to the strike.

Investigation

An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB) and the Flight Data Recorder (FDR) was removed and downloaded to assist. Recorded damage to the aircraft was documented as:

• a large hole in the radome
• a bent left side pitot head with a piece of broken radome lodged on it
• a dent to the leading edge of the vertical stabiliser

Bird remains were recovered from inside the radome, from the left side pitot head and from the vertical stabiliser leading edge. Following feather and DNA analysis, the species was identified as White‐faced Ibis. It was noted that this species is common in Colorado during migration and locally (although not within the airport perimeter) during breeding. The average weight of an adult bird was advised to the Investigation as being 1.3lbs (0.6kg) with a body length of 2' (60cm) and a wingspan of 3' (90cm).