# NTSB ATL93LA118: Cessna 188B, N731DH, Centre, AL, June 29, 1993 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 29, 1993, 08:05 local (13:05 UTC) - Place: Centre, AL - Coordinates: 34.150394, -85.670074 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.1504&lon=-85.6701&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 30, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 3231 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL93LA118 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/3231/pdf - Page: https://openairdocs.org/ntsb/ATL93LA118 ## Probable cause THE FAILURE OF MAINTENANCE PERSONNEL TO PROPERLY TORQUE THE CRANKCASE THROUGH BOLTS. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, maneuvering - aerial application - engine assembly,crankshaft - fatigue - engine assembly,crankshaft - failure,total - engine assembly,bearing - slipped - engine assembly,bearing - failure,total - maintenance,overhaul,major - improper, other maintenance personnel (cause) - Forced landing, descent - emergency - On ground/water encounter with terrain/water, landing - roll - ground loop/swerve - intentional, pilot in command ## Analysis THE PILOT REPORTED A LOSS OF ENGINE POWER DURING AERIAL APPLICATION MANEUVERS AND WAS FORCED TO LAND IN A SOYBEAN FIELD. DURING LANDING ROLL, THE PILOT INITIATED AN INTENTIONAL GROUND LOOP TO AVOID A RESIDENCE AT THE END OF THE FIELD, WHICH RESULTED IN THE COLLAPSE OF THE MAIN LANDING GEAR AND SUBSTANTIAL DAMAGE TO THE AIRPLANE. EXAMINATION OF THE ENGINE REVEALED A BROKEN CRANKSHAFT, A BROKEN MAIN CRANKSHAFT BEARING SHELL, AND EVIDENCE OF RUBBING BETWEEN THE CRANKCASE PARTING SUFACES DUE TO INSUFFICIENT TORQUE BEING PLACED ON THE CRANKCASE THROUGH BOLTS. ## Factual narrative On June 29, 1993, at about 0805 central daylight time a Cessna 188B, N731DH, lost engine power during an aerial application maneuver near Centre, Alabama. The airplane was registered to Charles Timmons, dba Aero Dusters, and operated by Vaughn Flying Service, Inc., under visual flight rules and 14 CFR Part 137. A flight plan was not filed for the aerial application flight. There were no injuries to the airline transport pilot, while the airplane was substantially damaged. Origination of the flight was Centre, Alabama, at about 0700 on the same day. The pilot reported that the engine lost power, at 200 feet, and the propeller ceased rotating, during the climb following a swath run. He force landed the airplane in a wet, slick, soybean field. Unable to stop, the airplane was intentionally ground looped to avoid colliding with a house. The left main landing gear collapsed and the wing collided with the ground. On site examination of the engine oil screen revealed metal in the oil. The aircraft's engine was examined and fretting was discovered along the main bearing support parting surfaces. The number two and three main bearing lock slots were displaced .06 inches and particles of the number two main bearing shell were found in the oil sump. The engine exhibited wear in several locations which indicated passage of bearing shell fragments throughout the engine during operation. The crankshaft was fractured from the number two main crankshaft journal to the number three crankcheek. The number three and four camshaft intake lobes and corresponding valve lifters were spalled and the number five counter weight pin was found in the oil sump. The number five counterweight retaining plate and snap ring were not found. On May 22, 1993, a top overhaul was performed on the engine, all cylinders were removed, and the number three cylinder was replaced. According to John V. Moeller, Aviation Safety Inspector, Manufacturing, this type of maintenance requires loosening of the crankcase throughbolts. He stated that the lack of sufficient torque placed on the crankcase throughbolts resulted in the fretting which was found on the crankcase. He also stated that the rubbing between the crankcase parting surfaces which causes this type of fretting allows the main bearings to move fore and aft, which eventually results in the breakup of the crankshaft bearings. Once a main bearing breaks up, the crankshaft is subject to surface origin fatigue like that found on the number two journal and the crankshaft may fail. ## Aircraft - Registration: [N731DH](https://openairdocs.org/deregistered/N731DH-2005-11-30), registration cancelled 2005-11-30, S/N 18802811T, built 1976 (OpenAirDocs) - Reported make and model: CESSNA 188B - Registry model: [Cessna A188B](https://openairdocs.org/model/cessna-a188b) (registry code 2073005) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 18802811T - Airframe hours: 4221 - Engines: CONTINENTAL IO-520-D 300 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Vaughn Flying Svc. Inc, doing business as Aero Dusters - Registered owner: Timmons,C. And Frost, J. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, May 22, 1993, 50 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; airline transport, commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 16,000 total, 2,800 in this make and model, 10,000 as pilot in command, 80 in the last 90 days, 55 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 220° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 70 °F - Altimeter: 30.00 inHg - Observed at: GAD, 26 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19930629022919A](https://openairdocs.org/incident/19930629022919A), Jun 29, 1993: Cessna 188B, Centre, AL, Substantial damage. Lost power during swath run turn around. Engine siezed. Engine recently top overhaul. Improper crankcase torque. ## Other investigations on N731DH (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB MIA77DKQ36](https://openairdocs.org/ntsb/MIA77DKQ36), Sep 12, 1977: Cessna 188B (N731DH), Sunflower, MS, destroyed From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.