Stinson 108 accident near Lampasas, Texas, March 4, 2023
On March 4, 2023 at about 5:00 pm local time, a 1948 Stinson 108, registered N6532M, was substantially damaged in an accident during enroute near Lampasas, Texas. It was a personal flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Improper case hardening of the crankshaft timing gear, which resulted in the fatigue failure of the gear and a total loss of engine power.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 4, 2023 · about 5:00 pm local time
- Place
- Lampasas, Texas · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Stinson 108, built 1948 · all 108s on the register
- Registration
- N6532M · registry record · serial 108-4532
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
While enroute during a cross-country flight, the engine lost total power and the pilot performed a forced landing to a bridge. During the landing, the airplane contacted a cable placed across the bridge and nosed over, which substantially damaged the rudder. Examination of the engine revealed that three teeth of the crankshaft timing gear had separated, and approximately 60 to 90 percent of the remaining gear teeth had been deformed and flattened, which stopped rotation of the camshaft and resulted in a total loss of power. The liberated teeth exhibited evidence of fatigue cracks and subsequent overstress fractures. The crankshaft timing gear and liberated teeth did not meet the 50 HRC (513 HV) standard for case hardening. No evidence of the engine overheating was found, which eliminated the possibility of an altered case hardening of the crankshaft timing gear via engine heat. A review of maintenance records revealed that the engine had been overhauled about 58 operating hours before the accident and all ferrous metal parts were non-destructive tested (NDT), including the crankshaft timing gear; the testing did not identify surface or subsurface cracks. An annual inspection of the engine was performed about 8.4 flight hours before the accident and revealed no anomalies. The accident crankshaft timing gear was likely the original gear to the engine.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (partial) during enroute defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Engine (reciprocating) › (general) › Fatigue/wear/corrosion
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 1,537 hours in all; 1,475 in this make and model; 6 in the last 90 days; 2 in the last 30 days; 1,474 as pilot in command
- Last flight review: October 17, 2022
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 3,044.8 hours
- Last inspection: annual inspection, October 17, 2022
- Seats: 4
- Landing gear: fixed
- Engine: Franklin 6A4165 SERIES (piston); 0 hours total
The flight
- Departed from: F69 Plano TX at 3:30 pm
- Destination: 17T San Antonio TX
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 240° at 9 knots, gusting 15
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 68°F (20°C), dew point 32°F (0°C)
- Altimeter: 29.95 inHg
Weather report (METAR): METAR KLZZ 041655Z AUTO 24009G15KT 10SM CLR 20/05 A2995 RMK AO2 T02040047
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number WPR23LA117.