NTSB Identification: CHI00FA003A
Accident occurred Friday, October 01, 1999 in OSWEGO, IL
Probable Cause Approval Date: 04/06/2001
Aircraft: Beech D-45, registration: N300SH
Injuries: 1 Fatal,1 Uninjured.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
N300SH, a Beech D-45, was destroyed on impact with terrain following a midair collision with N5367G, a Beech T-34, during a practice maneuver by the Lima Lima Flying Squadron. Both aircraft departed in sequence from 6-ship delta formation to perform a maneuver called a pop top break. The pop top break involved each aircraft to depart from the formation in sequence by entering a climbing 180-degree turn to follow the lead aircraft in trail. The narrow area of the human eye's visual field is approximately 10-15 degrees. A video tape of the accident flight shows a delayed entry into the turn by the D-45 relative to the T-34's entry into the maneuver. The pilot of the T-34 stated that he did not see the D-45 prior to the midair collision. The Lima Lima Flying Squadron did not have procedures in place to recover or adjust for maneuvers that were not successful.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the visual lookout not obtained by the pilot of the Beech T-34 and the inadequate procedure by the Lima Lima Flying Squadron. The delayed entry into the maneuver by the pilot of the Beech D-45 was a contributing factor. Full narrative available
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