# NTSB FTW99LA017: Grumman American AA-5A, N9956U, Scott, AR, October 29, 1998 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: October 29, 1998, 09:00 local (14:00 UTC) - Place: Scott, AR - Coordinates: 34.679615, -92.119522 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.6796&lon=-92.1195&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 2 minor - Status: Completed, report February 16, 2001 - Report: Approved by Office Director - ADs cited in the narratives: [AD 91-14-22](https://openairdocs.org/ad/91-14-22) (OpenAirDocs) - NTSB case key (mKey): 45169 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW99LA017 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/45169/pdf - Page: https://openairdocs.org/ntsb/FTW99LA017 ## Probable cause The disengagement of the crankshaft gear due to the maintenance personnel not installing the gear lockplate at the last engine overhaul, resulting in the loosening of the gear retaining bolt, and the subsequent fracture of the gear alignment dowel. A factor was the pilot's inadvertent stalling of the aircraft during the forced landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, descent - emergency - miscellaneous,bolt/nut/fastener/clamp/spring - not installed (cause) - maintenance,overhaul - inadequate, other maintenance personnel (cause) - miscellaneous,bolt/nut/fastener/clamp/spring - loose (cause) - miscellaneous,dowel/pin - fractured (cause) - engine assembly,gear - disengaged (cause) - Forced landing, descent - emergency - Loss of control - in flight, landing - flare/touchdown - stall - inadvertent, pilot in command (contributing factor) - Nose over, landing - flare/touchdown ## Analysis Following a total loss of engine power during the en route descent to the destination airport, the aircraft landed short of the runway. During the landing flare, the airplane stalled, bounced, landed on the main landing gear and nosed over. The aircraft had flown 852 hours since the last engine overhaul and 13 hours since the last annual inspection. Examination of the engine revealed a lack of gear train continuity. Disassembly of the engine accessory case revealed that the crankshaft gear lockplate was not installed and the crankshaft gear retaining bolt had backed out of the crankshaft approximately 1 3/4 turns. The crankshaft gear alignment dowel was fractured. Review of maintenance records indicated the engine was last overhauled in January 1987 and return to service by a FAA certified mechanic. ## Factual narrative On October 29, 1998, at 0900 central daylight time, a Grumman American AA-5A single engine airplane, N9956U, owned and operated by the pilot under Title 14 CFR Part 91, sustained substantial damage during a forced landing following a total loss of engine power. The private pilot and one of the passengers received minor injuries and the second passenger sustained serious injuries. Visual meteorological conditions prevailed for the personal cross country flight that departed Greenville, Mississippi, at 0800. A flight plan was not filed. During a telephone interview, conducted by the investigator-in-charge (IIC), the pilot reported that the flight departed Greenville with 3 hours of fuel aboard for the planned one hour flight to Little Rock, Arkansas. During the en route descent approximately 10 miles east of the destination airport, the "engine quit." The propeller continued windmilling. The Little Rock Control Tower provided vectors; however, the airplane landed short of the airport. During the landing flare the airplane stalled, bounced, landed on the main landing gear, and subsequently nosed over. The pilot, who had owned the airplane for 5 years, had flown the airplane 13 hours since the last annual inspection with no discrepancies noted. The local authorities and the FAA inspectors responding to the site reported that the airplane came to rest in a bean field after collapsing the nose gear and right main landing gear. Structural damage occurred to the lower engine cowling and fuselage. The left main gear was found separated from the airplane. The propeller blades were bent aft toward the engine cowling and an engine mount was found separated. The cockpit tachometer reading was 1460.63 hours. The FAA inspector's and the engine manufacturer representative's examination and disassembly of the engine at Clinton, Arkansas, revealed a lack of gear train continuity. Disassembly of the engine accessory case revealed that the crankshaft gear lockplate was not installed and the crankshaft gear retaining bolt had backed out of the crankshaft approximately 1 3/4 turns. The crankshaft gear alignment dowel was fractured. The crankshaft gear did not appear to have been modified according to Airworthiness Directive (AD) 91-14-22 and the Textron Lycoming Service Bulletin (SB) No. 475B. The AD and the SB require the crankshaft gear modification during engine overhaul. See the enclosed report for details of the teardown examination. A review of the maintenance records by the IIC did not reveal that the AD or SB had been accomplished. The tachometer reading at the annual inspection on August 20, 1998, was 1,448.4 hours. The aircraft had flown 852 hours since the last engine overhaul in January 1987 and return to service by a FAA certified mechanic. ## Aircraft - Registration: [N9956U](https://openairdocs.org/deregistered/N9956U-2001-01-12), registration cancelled 2001-01-12, S/N AA5A0356 (OpenAirDocs) - Reported make and model: Grumman American AA-5A - Registry model: [Grumman American Avn. AA-5A](https://openairdocs.org/model/grumman-american-avn-aa-5a) (registry code 3960106) (OpenAirDocs) - Category: Airplane - Serial number: AA5A-0356 - Airframe hours: 1463 - Engines: Lycoming O-320-E2G 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Collins E. Brent, doing business as Cheetah Aviation, Inc. - Registered owner: Cheetah Aviation, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 20, 1998, 13 hours before - Departed: GLH, GREENVILLE, MS - Destination: LIT, LITTLE ROCK, AR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; private; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 764 total, 314 in this make and model, 659 as pilot in command, 16 in the last 90 days, 7 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 9 knots - Visibility: 7 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 64 °F - Altimeter: 29.00 inHg - Observed at: LIT, 10 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 19981029030919A](https://openairdocs.org/incident/19981029030919A), Oct 29, 1998: Gulstm AA5A, Scott, AR, Substantial damage. Acft lost engine power and made an emergency landing in a bean field. (-23) on October 29, 1998, at approximately 099-0930, a gruman asaa, N9956U, registered… 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.