Aircraft

The US NTSB has positively identified the biological remains found in both CFM56-5B/P engines on the US Airways A320 that ditched in the Hudson River on 15 January as belonging to Canada geese.

The Smithsonian Institution's feather identification library made the determination through DNA analysis as well as "morphological comparisons" where analysts compared feathers found in the engines with those in the museum's collections, says the NTSB.

Twenty-five samples of bird remains have been examined to date, reports the safety agency in its fourth update on the accident investigation, and additional work is being done to try to determine if the geese were resident or migratory.

"While no determination has been made about how many birds the aircraft struck or how many were ingested in the engines, an adult Canada goose typically ranges in size from 5.8 to 10.7lb," the agency says, adding that "larger individual resident birds can exceed published records."

NTSB says the bird ingestion standards in place when the engine was certified in 1996 called for withstanding the ingestion of a 1.8kg (4lb) bird without catching fire, without releasing hazardous fragments through the engine case, without generating loads high enough to potentially compromise aircraft structural components, or without losing the capability of being shut down.

"The certification standard does not require that the engine be able to continue to generate thrust after ingesting a bird 4 lb or larger," the report states.

ATI has previously reported that the disabled aircraft's left engine was running at a fan speed of 35%, which is roughly equivalent to flight idle, after the collision with the birds, a speed that would have kept essential systems operating buy wound not have been enough to maintain altitude. The aircraft's right engine was running at approximately 15% speed after the bird strike.