# NTSB FTW99LA227: Aeronca 11AC, N3184E, Rockwall, TX, August 14, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 14, 1999, 08:10 local (13:10 UTC) - Place: Rockwall, TX - Coordinates: 32.919818, -96.449043 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.9198&lon=-96.4490&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 30, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 47091 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW99LA227 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47091/pdf - Page: https://openairdocs.org/ntsb/FTW99LA227 ## Probable cause The mechanic's improper machining of the crankshaft during a major overhaul, which resulted in a fatigue crack and subsequent failure of the crankshaft. A factor was the lack of suitable terrain for the forced landing. ## 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, takeoff - initial climb - maintenance,overhaul,major - improper, other maintenance personnel (cause) - engine assembly,crankshaft - fatigue (cause) - engine assembly,crankshaft - failure,total (cause) - Forced landing, emergency descent/landing - On ground/water encounter with terrain/water, emergency landing - terrain condition - crop - terrain condition - none suitable (contributing factor) ## Analysis While maneuvering in the traffic pattern, the airplane experienced a total loss of engine power. The private pilot elected to land in a field that contained 5-foot tall maize crops. Examination of the Continental A-75-8 engine revealed that the crankshaft was separated aft of the #3 connecting rod journal. Examination of the crankshaft fracture revealed that a fatigue crack had developed in a secondary radius between the journal and the cheek. The secondary radius contained machining marks. The engine's maintenance records revealed that during the last major overhaul, the crankshaft had been ground .010 inches. ## Factual narrative On August 14, 1999, at 0810 central daylight time, an Aeronca 11AC airplane, N3184E, was substantially damaged during a forced landing following a total loss of engine power while maneuvering in the traffic pattern at the Rockwall Municipal Airport, Rockwall, Texas. The non-instrument rated private pilot, sole occupant, was not injured. The airplane was registered to the pilot and operated under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and a flight plan was not filed for the local flight, which originated from the Rockwall Municipal Airport approximately 0630. During a telephone interview conducted by the NTSB investigator-in-charge, the pilot stated that he had been practicing touch-and-go landings for about 30 minutes when, on the last takeoff, during the turn to crosswind, the engine lost power. The pilot performed the emergency checklist, which included checking the magnetos, the carburetor heat, and the throttle position; however, the power was not restored. The pilot elected to set up for a forced landing in a field, which paralleled the runway and contained a maize crop 5-feet tall. The airplane came to an "abrupt stop in a very short distance." The pilot, who is also an aircraft mechanic, stated that the right and left main landing gear were collapsed, the right wing v-strut was accordion crushed, and both the left and right wings sustained structural damage. The pilot also stated that the vertical stabilizer was structurally damaged. On August 17, 1999, the engine was examined by an FAA inspector and a representative of the engine manufacturer. The Continental A-75-8 engine (serial number 769219) was intact with no external damage. The crankshaft was rotated manually and a grinding sound was heard. The engine was disassembled and found to have a separated crankshaft. The crankshaft was removed for further examination. See the enclosed Manufacturer's Factual Report for more details concerning the engine examination. The crankshaft (with the connecting rods attached) was examined at the NTSB Materials Laboratory in Washington, D.C. The crankshaft was separated aft of the #3 connecting rod journal. The #3 connecting rod rotated freely and was removed for examination of the journal surface. Examination of the fracture surface revealed a "flat face with faint crack arrest markings, consistent with progressive fatigue cracking. The crack originated on the aft edge of the journal and progressed nearly all the way through the thickness of the cheek." The journal and fracture area were examined using a scanning electron microscope. Examination of the journal surface in the vicinity of the crack revealed that "all of the origins were located in a secondary radius that was located within the original radius between the rod journal and the cheek." The secondary radius was smaller than the original radius and contained machining marks, which were "found to be rougher than typically associated with a normal journal surface." See the enclosed Materials Laboratory Factual Report for more information. Review of the engine maintenance records revealed an entry, dated August 28, 1991, that read, "this engine was found installed in Aeronca 11AC-Reg. No. N3184E without current logbook or any other history of engine. Engine was removed, and major overhauled and reinstalled in same aircraft. See the following page for work accomplished during overhaul." On the following page, it stated that all steel parts had been magnafluxed. It also stated that the crankshaft had been ground .010 inches. During the last annual inspection, dated April 9, 1999, the engine had accumulated 170.9 hours since the major overhaul. At the time of the accident, the engine had accumulated 178.4 hours since the overhaul. ## Aircraft - Registration: [N3184E](https://openairdocs.org/deregistered/N3184E-2018-03-13), registration cancelled 2018-03-13, S/N 11AC-1529 (OpenAirDocs) - Reported make and model: Aeronca 11AC - Registry model: [Aeronca 11AC](https://openairdocs.org/model/aeronca-11ac) (registry code 0191102) (OpenAirDocs) - Category: Airplane - Serial number: 11AC-1529 - Airframe hours: 2581 - Engines: Continental A-75-8 75 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Charles D. Cawthon - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 9, 1999, 8 hours before - Departed: F46 - Airport: F46, Rockwall Municipal, runway 16, 3,400 × 45 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 41; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 540 total, 109 in this make and model, 439 as pilot in command, 10 in the last 90 days, 3 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 2 knots - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 77 °F ## 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 19990814046469A](https://openairdocs.org/incident/19990814046469A), Aug 14, 1999: Bbavia 11AC, Rockwall, TX, No damage. (-23)Crank shaft broken @ #2 crank cheek this occured on approach to landing at F46. Pilot lost power and landed in maze field adjacent to F46. 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.