FAA proposes a new engine bird ingestion capability

Eleanor Steed
By Eleanor Steed July 12, 2018 15:30

FAA proposes a new engine bird ingestion capability

The FAA is proposing the addition of a new test requirement to the airworthiness regulation addressing engine bird ingestion. The current regulation ensures bird ingestion capability of the turbofan engine fan blades, but the existing test conditions do not adequately demonstrate bird ingestion capability of the engine core.
This proposed rule would require that, to obtain certification of a turbofan engine, a manufacturer must show that the engine core can continue to operate after ingesting a medium sized bird while operating at a lower fan speed associated with climb or landing. This new requirement would ensure that engines can ingest the largest medium flocking bird required by the existing rule into the engine core at climb or descent conditions.

Currently, the MFB test is conducted using 100 percent power or thrust and 200 knots airspeed, simulating takeoff conditions. Consequently, the current MFB test does not simulate lower fan speed phases of flight (such as climb and descent) during which a bird, if ingested, is more likely to enter the engine core. In addition, the higher airspeed in climb is not covered by the existing test. Therefore, the existing small and medium flocking bird tests do not provide the intended demonstration of core durability against bird ingestion for climb and descent conditions.

The proposed test consists of firing at the engine core one MFB, equivalent to the largest bird currently required by § 33.76(c) for the engine inlet throat area of the engine being tested, using either climb or descent testing conditions for an engine.

The FAA estimates the annualized costs of this proposed rule to be $4 million, or $52 million over 27 years (at a seven percent present discount rate). The FAA estimates the annualized benefits of $5 million, or $61 million over 27 years.

The FAA notes that this proposed rule may result in the engine manufacturer having to run an additional bird ingestion test. If the manufacturer discovers during the 250-knot climb test that no bird material enters the engine core, then it is required to run the 200-knot approach test. However, the FAA anticipates the two-test scenario is unlikely, because manufacturers would evaluate the design of its engine prior to engine bird ingestion testing. Thus, a manufacturer would be able to determine, prior to commencing certification testing, whether their engine will centrifuge all bird material away from the core. Based on this determination, the manufacturer would select the appropriate bird ingestion test (either the 250-knot climb or 200-knot approach test) proposed in this rule.

Comments are sought until September. Click here for the proposal in full.

Eleanor Steed
By Eleanor Steed July 12, 2018 15:30