After US Airways Flight 1549 accident, the NTSB recommended modifying engine certification test standards.
The Department of Transportation (DOT) has added a new testing requirement to the airworthiness regulation addressing engine bird ingestions. New turbofan engines will now have to be able to continue operating after ingesting medium flocking birds (MFB) while operating at a lower fan speed associated with climb or approach.
Preventing a new Flight 1549
On January 15, 2009, US Airways Flight 1549 had an accident after taking off from LaGuardia Airport in New York City. While climbing at approximately 2,800 feet above ground level, the airplane –an Airbus A320– struck a flock of migratory Canada geese. Both engine cores suffered major damage and total thrust loss, forcing the crew –commanded by Captain Chelsey Sullenberger– to land in the Hudson River. This is one of the most famous accidents –if not the most famous– in recent memory and has now forced changes in how the DOT tests turbofan engines and their manufacturers.
After the accident, the National Transportation Safety Board (NTSB) recommended modifying engine certification test standards. Additionally, the Federal Aviation Administration (FAA) also began studying how to improve engine durability related to core engine bird ingestion. On Tuesday, the new testing requirement was published in the United States Federal Register. It said,
“The FAA is amending the airworthiness regulations related to engine bird ingestion testing (…). This final rule (creates) an additional bird ingestion test for turbofan engines. This new test ensures that engines can ingest the largest MFB required for bird ingestion testing into the engine core at climb conditions.”
Why do engines require new testing?
In the past, engine tests were conducted with the engine operating at 100% takeoff power or thrust. This setting, while ideal for testing the fan blades, does not represent the lower fan speeds used during the climb and approach phases of aircraft flight, said the DOT.
A higher fan speed makes bird material less likely to enter the engine’s core during the test compared to the new climb flocking bird test. Therefore, the previous test didn’t simulate lower fan speed phases of flight during which a bird is more likely to enter the engine core if ingested.
What will the new testing look like?
There will be two parts to the new testing. One will review how the engine reacts during climbing and the other how it reacts during approaching.
Photo: Jaromir Chalabala/Shutterstock.
According to the information available in the Federal Register, to test the engine reaction during climbing, the test bird must be fired at 261 knots (which is 250 knots indicated airspeed (KIAS)). The mechanical engine fan speed has to be set at the lowest expected speed when climbing through 3,000 feet altitude on a standard day. After the bird ingestion, the engine must comply with new post-test run-on requirements for large flocking birds, with the exception that, depending on the climb thrust of the engine, during the first minute after bird ingestion, the engine may produce less than 50% takeoff thrust.
To test the engine reaction during approach, the bird must be fired at 209 knots (200–KIAS). The engine must be set at the lowest fan speed expected when descending through 3,000 feet on approach. This test only requires six minutes, since during approach “the airplane will already be lined up with the runway,” said the DOT.
The new testing does not impact current engine designs. This rule will apply only to newly certified engines.
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