Incident Details
On April 8, 2008, at about 1205 mountain daylight time, a Bombardier, Inc. CL-600-2B16 business jet, registration N483BA, struck birds during the initial climb after departing Colorado Springs Municipal Airport (COS), Colorado. The aircraft was operated by The Boeing Company Executive Flight Operations, based in Gary, Indiana, and registered to CEF 2002 Aircraft LLC, Danbury, Connecticut. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the Part 91 business flight. The captain, first officer, cabin attendant, and two passengers were not injured.
Flight and Bird Strike
The crew reported clear skies and light southerly winds. No bird activity advisories had been received prior to departure. After takeoff, air traffic control cleared the flight to a heading of 150 degrees and a climb to 10,000 feet mean sea level. The takeoff was normal. Approximately two minutes after takeoff, while passing through 8,000 feet at 230 knots, the crew observed large white birds. Immediately afterward, the aircraft impacted the birds. A loud bang followed by wind noise was heard. At least one bird penetrated the cockpit. The crew declared an emergency and requested a return to COS. The captain performed control checks and found them satisfactory, then slowed to 200 knots to reduce noise. The aircraft turned back.
Post-Strike Assessment and Landing
The left engine exhibited high vibration (4.0 mils), but engine instruments matched the right engine and throttles were not split. The N2 gauge REV (thrust reverser) light flashed intermittently amber. The captain deactivated the left thrust reverser for the remainder of the flight; the crew chose not to shut down the left engine due to weight, high airport altitude, and visibility considerations. On the downwind leg, flaps were set to 20 degrees and speed to 170 knots, with no control issues. During the turn to base, flaps 30 degrees and landing gear were selected, speed 150 knots. On final for runway 17R, flaps 45 degrees were set and speed maintained at 150 knots (Vref was 142 knots). The captain landed from the left seat; the first officer provided visibility assistance due to bird matter on the windscreen. The landing was uneventful, and the aircraft taxied to a fixed-based operator. No evacuation was necessary.
Aircraft Damage
Examination on April 9–12 by NTSB, operator, and airframe manufacturer representatives revealed a hole in the forward fuselage below the cockpit windows. The fuselage skin and forward pressure bulkhead were penetrated and contained bird matter. Left engine fan blades were damaged; the spinner was buckled and collapsed. The thrust reverser torque box assembly and pylon tracks were bent, and engine cowl supports were broken. The right engine inlet cowl leading edge was dented at the 12 o'clock position. Small bird remains were found on fan blades, inlet skin, and fan spinner. Bird matter was noted on cockpit windows, fuselage, and vertical and horizontal stabilizers.
Left Engine Examination
On May 20–21, the left engine was examined at General Electric’s facility in Arkansas City, Kansas. Bird remains and feather fragments were collected from the aft spinner, fan blade roots, and fan exit area. All fan blades were intact but most had leading edge and/or corner tip damage.
Bird Identification
Bird remains from the cockpit and left engine were sent to the Smithsonian Feather Identification Laboratory in Washington, DC. They were identified as American White Pelican (Pelecanus erythrorhynchos), with an average mass of about 7,000 grams (15.4 pounds). Colorado lies within the migratory path of this species, which typically travels from Montana/South Dakota to Mexico, mates in pairs, and moves in flocks of 4 to 12 birds.
Bird Avoidance Model
The United States Air Force’s Bird Avoidance Model (BAM) uses historical data to classify risk as Low, Moderate, or Severe based on bird mass per square kilometer. At the time of the accident, the BAM risk class for the Colorado Springs area was Moderate.