On March 4, 1999, a DC9-10 operated by USA Jet Airlines, at night and on final approach to land at Kansas City International Airport encountered a flock of large birds. Following the bird strike, several birds were ingested into both engines which resulted in a partial thrust loss on one engine and near total thrust loss on the other. The crew managed to regain sufficient thrust to continue the approach and land without further incident.
This is an extract from the official accident report (CHI99FA102) published by the National Transportation Safety Board (NTSB), USA:
[…] The first officer said that the airplane was on speed and course for the visual approach. "The captain had just called the 1,000 feet [above the ground] call when a flock of snow geese [was] suddenly illuminated in our lights, engulfing us from below, flying into us. No birds hit the windshields, but it was immediately apparent they had flown into the engines." The captain said that he had the airplane and directed the first officer to set the flaps to 30 degrees. The first officer said that she notified the Kansas City Air Traffic Control Tower (ATCT) of the bird strike. "When asked by [the] tower if we wanted to go around, we responded, negative.
The number two engine showed about 30 percent N1. The number one engine, when full thrust [was] applied, responded with fluctuating EPRs (engine pressure ratio gauge indications) and violent vibrations. We were able to land and taxi to the ramp with the thrust from [the] number one engine."
In his written statement, the captain said that on the descent into Kansas City international Airport, they received the current airport Automatic Terminal Information System (ATIS) broadcast. The ATIS information included the note, "migratory bird activity reported in the vicinity of the airport." Descending through 10,000 feet mean sea level (msl), the airplane's ground flood lights were turned on. Descending through 5,000 feet msl, the airplane's landing lights were turned on. […] "At 800 feet agl, we hit with no warning, a large flock of snow geese." The captain said that the airplane was three miles from the runway threshold. "Both engines compressor stalled, and I took control of [the] aircraft." The airspeed decayed and the airplane descended below the glide path. The captain advanced the power on both engines and ordered the flaps reset to 30 degrees, the single-engine flap position. "The number one engine continued to compressor stall. The number two engine went to a sub-idle run condition." The captain said that the number one engine compressor stalled at a rate of a surge/stall per second, and vibrated violently. The number two engine remained at 30 percent N1 with no response to the throttle position. The captain reduced the power on the number one engine "enough to lessen the surge/stall condition to a rate of once every two seconds, which allowed just enough thrust to maintain the approach and to lower the vibration… The number one engine continued to compressor stall/surge to touchdown." The touchdown was normal.
In the Airport Information section, the Report states:
Airport Remarks listed for Kansas City International Airport in the Airport/Facilities Directory, North Central U. S., covering Missouri, include an advisory for "Waterfowl on and in vicinity of airport from October 1 to December 15, and April 1 to May 30."
The Report further states that weather radar images […] were retrieved and compared with National Weather Service information to determine the likelihood of biological targets in the area during the time when the bird strike occurred. Analysis of the radar display information showed a wide area of returns consistent with a widespread northerly migration of birds. The broad-front nature of the returns indicated a large-scale migration. The overall density and pattern of targets in the reflectivity image suggested a migration of waterfowl through the area. […]
Following the investigation of this particular occurrence, together with other accidents involving birds strikes, the NTSB provided the following recommendations (for the complete list, see Further Reading):
- The Federal Aviation Administration (FAA) evaluate the potential for using Avian Hazard Advisory System (AHAS) technology for bird strike risk reduction in civil aviation, and if found feasible, implement such a system in high-risk areas, such as major hub airports, and along migratory bird routes, nationwide.
- In coordination with the U. S. Department of Agriculture, the FAA conduct research to determine the effectiveness and limitations of existing and potential bird hazard reduction technologies.
- In consultation with the U. S. Department of Agriculture, the FAA requires that wildlife assessments be conducted at all 14 Code of Federal Regulation Part 139 airports where such assessments have not already been conducted.
- The FAA require the development of a wildlife management program for all airports determined to need one as the result of the wildlife hazard assessment proposed in the previous recommendation.
- The FAA ensure that the wildlife hazard management programs are incorporated into the airport certification manuals and periodically inspect the programs' progress.
- The FAA require all airplane and airport operators to report bird strikes.
For further information see the NTSB Report (CHI99FA102)