NTSB Identification: MIA96FA100.
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Nonscheduled 14 CFR
Accident occurred Sunday, March 17, 1996 in KEY WEST, FL
Probable Cause Approval Date: 03/31/1997
Aircraft: Cessna U206G, registration: N9983Z
Injuries: 5 Fatal,1 Serious.
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.
After takeoff, according to radar data, the airplane climbed to 200 feet, then descended to 100 feet. The pilot was advised to turn right to pass behind the approach corridor for a departing airplane. Witnesses observed the airplane flying towards buildings, and stated that the airplane, which was about 50-100 feet above the water, started banking to the right which increased to near a 90-degree angle of bank. The airplane then pitched nose down and impacted the water nose and right wing low, rolled inverted and sank in about 6 feet of water about 20 yards from a seawall. Examination and testing of the right magneto revealed that the point gap was 0.018 inch, which is greater than specified by the manufacturer, and the magneto fired intermittently throughout the entire rpm range. After adjusting the point gap to within limits, the right magneto operated normally. The engine was then run with replacement magnetos installed with their point gaps set as found on the accident magnetos. During the right magneto check, the rpm drop was 156 rpm greater than the left magneto check. Damage was also noted to the #1 cylinder top ignition lead. Examination of the aft bottom section of the right float revealed numerous damaged rivets which join the keel to the bottom skin panel near the aft bulkhead.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's improper decision to continue the flight rather than making an immediate water landing due to the low altitude of the airplane and obstructions ahead, which led to his intentional maneuver to avoid the obstructions and subsequent inadvertent stall and loss of control. Contributing to the accident were: an inadequate 100-hour inspection of the airplane by company maintenance personnel for failure to fix a damaged ignition lead and a partially separated keel on one of the floats, the pilot's inadequate preflight of the airplane for his failure to pump a float to remove water, and the pilot's intentional operation of the airplane with an excessive magneto drop. Full narrative available
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