Cessna 421 accident near Rockport, Texas, June 24, 2023
On June 24, 2023 at about 4:15 pm local time, a 1968 Cessna 421, registered N123SM, was substantially damaged in an accident during enroute near Rockport, Texas. It was a personal flight under general aviation rules (Part 91). No one was hurt; 4 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure of the left engine starter adapter gear, which resulted in catastrophic damage to other engine components, and the subsequent loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 24, 2023 · about 4:15 pm local time
- Place
- Rockport, Texas · map
- Type
- Accident
- Injuries
- No one was hurt; 4 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 421, built 1968 · all 421s on the register
- Registration
- N123SM · no longer on the register · serial 421-0193
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that, while climbing through 6,000 ft above mean sea level (msl), the left engine tachometer generator went offline but the engine was still operating normally. He stated that about 2 minutes later, the left engine lost power and the airplane banked left. He attempted to stabilize the airplane with aileron and rudder control, but the airplane entered a spin. The pilot was able to regain control, but after the spin the right engine’s propeller was stopped and the left engine’s propeller was windmilling. The pilot executed a forced landing to a field and the airplane sustained substantial damage to the horizontal stabilizer. During a postaccident engine test run, the right engine operated normally. Examination of the left engine revealed the starter adapter gear had failed, which resulted in damage to other engine components that rendered the engine inoperable. The starter adapter was subject to an FAA Airworthiness Directive (AD), and an associated manufacturer mandatory service bulletin (SB). Maintenance records indicated that the AD and SB had been complied with less than 1 month and 10 operating hours before the accident. The mechanic that performed the SB inspection reported that he had performed this test numerous times in the past and did not find the procedures difficult but required patience. He recalled that the backlash on both starter adapter assemblies were well within the limits specified in the SB.
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 (total) during enroute defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng rear section › Failure
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 1,171 hours in all; 59 in this make and model; 105 in the last 90 days; 85 in the last 30 days; 983 as pilot in command
- Last flight review: October 31, 2022
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 6,831 hours
- Last inspection: annual inspection, June 2, 2023; 10 hours since
- Maximum gross weight: 6,800 lb
- Seats: 8
- Landing gear: retractable
- Engine 1: Continental GTSIO-520D (piston); 6,831 hours total
- Engine 2: Continental GTSIO-520D (piston); 6,831 hours total
- Operator: Fernair LLC
The flight
- Departed from: CRP Corpus Christi TX at 8:45 pm
- Destination: IWS West Houston TX
- Flight plan: VFR
Weather at the time
- Light: daylight
- Wind: from 140° at 14 knots
- Visibility: 9 statute miles
- Sky: clear
- Temperature: 91°F (33°C), dew point 77°F (25°C)
- Altimeter: 29.92 inHg
- Observation at 3:53 pm from KRKP, 4 miles away
Weather report (METAR): KRKP 242053Z AUTO 14014KT 9SM CLR 33/25 A2992 RMK AO2 SLP134 T03330250 56009 $
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
10 documents, released by the NTSB on July 16, 2025. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 12 pages | View Download |
| 2 | Engine Monitor Data | spreadsheet | Download |
| 3 | Airworthiness Directive 2007-05-15 | PDF, 7 pages | View Download |
| 4 | Continental Service Bulletin MSB94-4H | PDF, 18 pages | View Download |
| 5 | Aircraft Maintenance Records | PDF, 21 pages | View Download |
| 6 | Accident Photos | PDF, 11 pages | View Download |
| 7 | Statement of Party Representatives to NTSB Investigation (Continental) | PDF, 1 page | View Download |
| 8 | Left Engine Teardown Summary | PDF, 8 pages | View Download |
| 9 | Right Engine Test Run Summary | PDF, 5 pages | View Download |
| 10 | Memorandum - Mechanic Interview | PDF, 1 page | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Other NTSB records under N123SM the same tail number, which may have belonged to a different aircraft at the time
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.