BOWERS FLY BABY 1-A — Jefferson, GA, 2012

BOWERS FLY BABY 1-A — Jefferson, GA

1 fatal High-time pilot

Date	January 8, 2012
Location	Jefferson, GA
Aircraft	BOWERS FLY BABY 1-A (amateur-built)
Purpose of flight	Personal
Conditions	Day · Visual Meteorological Cond
Phase / occurrence	Prior to flight Aircraft maintenance event
Pilot age	50
Pilot total time	2,082 hrs · Experienced
Time in type	Unknown
Fatalities	1

Probable cause

The pilot’s failure to maintain airplane control which resulted in an aerodynamic stall and spin. Also causal was the partial loss of engine power during the initial climb due to the improper installation of a magneto. Contributing to the accident was the pilot's decision to take off with an engine problem and the mechanic’s failure to detect the missing magneto rotor cotter pins during the last engine overhaul.

NTSB findings

Aircraft-Aircraft power plant-Ignition system-Magneto/distributor-Incorrect service/maintenance - C
Personnel issues-Task performance-Maintenance-Installation-Other/unknown - C
Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Airspeed-Not attained/maintained - C
Environmental issues-Conditions/weather/phenomena-Temp/humidity/pressure-Conducive to carburetor icing-Not specified
Personnel issues-Task performance-Use of equip/info-Aircraft control-Pilot - C
Personnel issues-Action/decision-Info processing/decision-Decision making/judgment-Pilot - F
Personnel issues-Task performance-Inspection-Post maintenance inspection-Maintenance personnel - F

What happened

The airplane was about 200 feet above ground level when it stalled, spun about one-half turn to the right, impacted the ground in a nose down attitude, and burned. A witness reported that the pilot was attempting to diagnose an engine problem prior to departure. The witness also said that the engine was running rough and backfiring. A postaccident examination revealed that the right magneto distributor gear was unsecured inside the housing, and galling signatures were present. The galling signatures were consistent with damage found after the gear became loose while the engine was under power. Since limited maintenance records were available, it could not be determined how many flight hours had accumulated since the last engine overhaul; however, it is probable that the cotter pin was not installed in either magneto rotor drive shaft and that the right magneto’s castellated nut came loose during engine operation. It is probable that the unsecured distributor gear reduced engine performance, which resulted in a partial loss of engine power. The probability also exists that, at the time of the accident, the airplane was being operated in conditions conducive to serious carburetor icing at cruise power; however, the investigation could not conclusively determine that carburetor icing occurred.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.