The following is an update on the investigation of the crash involving a Cessna Citation II 550 business jet that occurred earlier this month.
On June 4, 2007, at 4:10 PM Central Daylight Time, a Cessna Citation II 550 business jet, N550BP, registered to Air Toy, Inc., and leased from Marlin Air, Inc., as a 14 CFR Part 135 air medical flight for the University of Michigan Health System, crashed into Lake Michigan shortly after takeoff from General Mitchell International Airport in Milwaukee, Wisconsin. Both flight crewmembers and all four passengers were killed. Instrument meteorological conditions prevailed and an instrument flight rules flight plan was filed for the 42-minute flight from Milwaukee to the airplane's home base in Willow Run Airport, Ypsilanti, Michigan.
AIR TRAFFIC CONTROL INFORMATION
A review of air traffic control (ATC) voice communications and recorded radar data revealed that the flight crew reported an emergency and their intention to return to MKE shortly after takeoff. During those communications, one of the flight crewmembers reported that they had experienced a runaway trim. In a later transmission, a pilot was heard telling the other pilot to hold the airplane's controls so that he could pull circuit breakers.
Initial examination of the radar data shows the airplane departing MKE and executing a climbing right turn to a northeast heading. The airplane's initial climb lasted for approximately one minute at which time the airplane leveled off for approximately 16 seconds at a pressure altitude of 3,900 feet. The airplane then began another climb at 1,300 feet per minute. This climb lasted for about 30 seconds at which time the airplane's pressure altitude was 4,400 feet. The radar data then shows the airplane in a descending left turn for the remaining 69 seconds of the data. The average descent rate during this period was 2,260 feet per minute. The last radar return shows the airplane at 1,800 feet pressure altitude. The wreckage debris field was located less than 0.2 nautical miles southeast of the last radar return.
COCKPIT VOICE RECORDER
The cockpit voice recorder (CVR) was located and sent to the NTSB Vehicle Recorders Laboratory in Washington, DC. The CVR's case was severely damaged, but information from the accident flight could be extracted. The information indicated that the flight crew had difficulty with the directional control of the airplane shortly after takeoff. A CVR Group was formed, and a complete transcript of the 30-minute recording is being developed.
WRECKAGE RECOVERY AND EXAMINATION
The main wreckage field was located near the last radar hit in about 60 feet of water depth. Although the CVR was recovered by a U.S. Navy contractor, the remainder of the wreckage was recovered by other contracted divers and taken to a facility near Poplar Grove, Illinois. The subsequent wreckage examination performed by the NTSB revealed pitch, roll, and yaw trim settings that were not in the neutral position. The Board will continue to assess the significance of these settings. Various flight control components and avionics units have been harvested for further testing and examination.
The investigation team has secured the maintenance records for the airplane. A preliminary review revealed that the autopilot engage relay was replaced in November 2006. No recent unresolved discrepancies were noted. Investigators will continue to review documents.
An aircraft performance study is being developed with information from the CVR, radar data, and flight control positions to describe the motions of the airplane during the accident flight. Additionally, plans are being developed to utilize a Cessna Citation II flight simulator to further explore possible failure scenarios.
Avionics units, including the airplane's Enhanced Ground Proximity Warning System (EGPWS) will be examined in order to have any potential non-volatile memory (NVM) extracted. These NVM data may provide clues to the motion of the airplane during the accident flight, and/or any equipment failures that may have occurred.
John Brannen of the NTSB's North Central Regional Office in West Chicago, Illinois, is the Investigator-in- Charge of this incident. Parties to the investigation include the Federal Aviation Administration, Cessna Aircraft Company, Marlin Air, Inc., Pratt & Whitney Engines, and Honeywell. The NTSB case number is CHI07MA160. A preliminary report of the investigation can be found at www.ntsb.gov.
Further information on the status of the investigation will be released at a later time.