NTSB Identification: ATL89LA037.
The docket is stored on NTSB microfiche number 40078.
Accident occurred Monday, November 14, 1988 in LAWRENCEVILLE, GA
Probable Cause Approval Date: 01/16/1990
Aircraft: CESSNA R172E, registration: N96164
Injuries: 1 Minor,1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE CFI & STUDENT WERE PRACTICING TOUCH-&-GO LNDGS AT NIGHT WHEN THE ENG LOST PWR SHORTLY AFTER THE 5TH TOUCH-&-GO. SUBSEQUENTLY, THE ACFT WAS DMGD WHEN IT WAS LNDD IN TREES. DRG AN EXAM OF THE ENG, DARK, SOOTY DEPOSITS WERE FOUND ON ALL SPARK PLUGS. THE PLUGS WERE REINSTALLED & AN OPNL CHECK OF THE ENG WAS MADE. THE ENG STARTED ALMOST IMMEDIATELY & DEVELOPED PWR WHEN THE THROTTLE WAS OPENED. A FURTHER EXAM REVEALED THAT THE CARB HEAT DOOR ON THE CARB AIRBOX WOULD NOT MOVE TO THE FULL ON POSITION WHEN THE CARB HEAT CONTROL WAS ACTIVATED. THE AIRBOX HAD BEEN IMPROPERLY MODIFIED AND/OR REPAIRED. NO ENTRIES WERE FOUND IN THE ACFT LOGS CONCERNING THE AIRBOX. THE ACFT HAD FLOWN APRX 97 HRS SINCE THE PREVIOUS ANNUAL INSPN APRX 5 MOS BEFORE THE ACDNT. THE TEMP & DEW POINT WERE 61 & 45 DEG, RESPECTIVELY. ACCORDING TO ICING PROBABILITY CHARTS, CONDS WERE CONDUCIVE TO CARB ICE. THE CFI RPRTD THE CARB HEAT WAS USED PRIOR TO EACH LNDG.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

IMPROPER REPAIR AND/OR MODIFICATION OF THE CARBURETOR AIRBOX BY UNKNOWN PERSON(S), AND THE SUBSEQUENT FAILURE OF MAINTENANCE PERSONNEL TO DETECT THE IMPROPER REPAIR/MODIFICATION DURING ANNUAL INSPECTION(S), WHICH LED TO A LOSS OF POWER DUE TO CARBURETOR ICING. A CONTRIBUTING FACTOR WAS THE PRESENCE OF WEATHER CONDITIONS CONDUCIVE TO THE FORMATION OF CARBURETOR ICE.

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