# NTSB FTW98LA242: Grumman American AA-1C, N9606U, Roanoke, TX, May 29, 1998 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: May 29, 1998, 09:30 local (14:30 UTC) - Place: Roanoke, TX - Coordinates: 33.000915, -97.2303 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.0009&lon=-97.2303&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report December 1, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 20626 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW98LA242 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20626/pdf - Page: https://openairdocs.org/ntsb/FTW98LA242 ## Probable cause The loss of engine power resulting from an excessively rich mixture for an undetermined reason. 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, takeoff - initial climb - fluid,fuel - excessive flow/output (cause) - reason for occurrence undetermined (cause) - Forced landing, emergency landing after takeoff - In flight collision with object, emergency landing after takeoff - object - tree(s) - terrain condition - none suitable (contributing factor) ## Analysis During the initial takeoff climb, the engine gradually lost power, and the airplane descended into trees approximately 1/4 mile from the departure end of the runway. Examination of the engine revealed evidence that the power loss resulted from an excessively rich mixture. Black carbon deposits were present on the exhaust valves and exhaust stacks of two cylinders, and the engine oil drained from all the cylinders contained aviation fuel. Examination of the carburetor revealed no evidence of any discrepancies that would have resulted in a rich mixture. The reason for the excessively rich mixture could not be determined. ## Factual narrative On May 29, 1998, at 0930 central daylight time, a Grumman American AA-1C airplane, N9606U, was substantially damaged during a forced landing following a loss of engine power near Roanoke, Texas. The commercial pilot, owner/operator and sole occupant of the airplane, sustained minor injuries. No flight plan was filed and visual meteorological conditions prevailed for the Title 14 CFR Part 91 personal flight. When the accident occurred, the flight was originating from the Northwest Regional Airport, Roanoke, Texas, with an intended destination of Fort Worth, Texas. According to the pilot, the pre-flight inspection and run-up were "normal" with no discrepancies noted. During the takeoff roll on runway 17, the "RPM and ground acceleration were normal" as was the acceleration to a climb speed of 80 knots. When the climb was initiated, "engine power began to diminish, and continued to do so." The 9,213 hour pilot stated that he proceeded straight ahead and "reduced airspeed to best angle of climb speed (65 KTS) to clear trees." However, "engine power continued to diminish, and [the] aircraft settled into trees approximately 1/4 mile from the departure end of [the] runway." The pilot reported that the airplane came to rest inverted and sustained structural damage to the empennage and both wings. A witness, who observed the airplane begin its takeoff roll, reported that the "engine run up sounded normal;" however, at the start of the takeoff roll, the "engine sounded as if it was going rich (as if flooding was occurring)." Another witness, who observed the initial takeoff climb, reported that "the engine sounded weak, as if it was running very lean or very rich." On June 25, 1998, the engine, a Lycoming O-320-D2B, S/N L-5399-39, was disassembled under the supervision of the NTSB investigator-in-charge at the facilities of Air Salvage of Dallas, Lancaster, Texas. Tan colored deposits were noted on the exhaust valves and the exhaust stacks of the #1 and #2 cylinders, and black colored deposits were noted on the exhaust valves and the exhaust stacks of the #3 and #4 cylinders. The engine oil that drained from all four cylinders was a greenish brown color and smelled like aviation fuel. The carburetor, a Marvel-Schebler MA4SPA, S/N A-5-2919, was disassembled and found to be equipped with a metal float and a one piece venturi. The needle assembly was intact and free to move. No debris was found in the fuel inlet screen or in the bottom of the carburetor bowl. On August 19, 1998, the carburetor was reassembled and a fuel supply was connected to the inlet. After 1 hour, no leaks were noted. ## Aircraft - Registration: [N9606U](https://openairdocs.org/deregistered/N9606U-2001-10-12), registration cancelled 2001-10-12, S/N AA1C0071 (OpenAirDocs) - Reported make and model: Grumman American AA-1C - Registry model: [Grumman American Avn. AA-1C](https://openairdocs.org/model/grumman-american-avn-aa-1c) (registry code 3960100) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: AA1C-0071 - Airframe hours: 3741 - Engines: Lycoming O-320-D2B 160 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Francis P. Carr, Jr. - Airworthiness certificate: Standard, Utility - Last inspection: Annual, June 20, 1997, 59 hours before - Departed: 52F - Destination: NFW, FORT WORTH, TX - Airport: 52F, Northwest Regional, runway 17, 3,500 × 50 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 67; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 9,213 total, 47 in this make and model, 8,937 as pilot in command, 25 in the last 90 days, 5 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 225° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °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 19980529011529A](https://openairdocs.org/incident/19980529011529A), May 29, 1998: Gulstm AA1C, Roanoke, TX, Substantial damage. Acft engine quit on takeoff, other circumstances are unknown, Roanoke, TX (.4) during the initial takeoff climb, the engine gradually lost power, and the… 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.