Beech B36TC accident near Los Banos, California, October 9, 2021
On October 9, 2021 at about 2:04 am local time, a 1984 Beech B36TC, registered N7220B, was substantially damaged in an accident during enroute (cruise) near Los Banos, California (Los Banos Muni airport). It was a business 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).
The NTSB's probable cause their words, unchanged
The total loss of engine power due to the improper installation of the No. 4 connecting rod bolt nut during a recent overhaul.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 9, 2021 · about 2:04 am local time
- Place
- Los Banos, California · Los Banos Muni · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Beech B36TC, built 1984 · all B36TCs on the register
- Registration
- N7220B · registry record · serial EA-425
- Damage
- Substantial damage
- Flight
- Business flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that he was on the return leg of a cross country flight, about 10,000 ft mean sea level, when the engine lost oil pressure and the manifold pressure dropped. He immediately diverted to the nearest airport. While in the descent to his divert location, the engine was initially producing partial power, but then exhibited serious vibrations and subsequently lost all power. During this time, the cockpit filled with smoke, and fire and sparks were observed exiting from the engine cowling. Due to the fire, the pilot elected to make a forced landing on a road near the approach end of runway. The airplane struck an object during the landing roll which resulted in substantial damage to the wings. A postaccident examination of the engine revealed that the No. 4 connecting rod bolt nut was missing. Prominent thermal distress was observed in the area where the No. 4 connecting rod connected to the crankshaft and was consistent with oil starvation. In June of 2020, the engine was disassembled for a propeller strike inspection. The inspection was about 27.3 hours before the accident. As part of the inspection, the connecting rods were overhauled and then reinstalled on the crankshaft using new bearings, rod bolts, and nuts. Given the recency of the work, it is likely that insufficient torque was applied during installation of the No. 4 connecting rod bolt nut, which subsequently became loose and separated.
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
- Emergency descent initiated during enroute (cruise)
- Off-field or emergency landing during approach
- Loss of engine power (total) during enroute (cruise) defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Power plant › (general) › Incorrect service/maintenance
- Aircraft › Aircraft handling/service › Maintenance/inspections › Unscheduled maint checks › Incorrect service/maintenance
- Personnel issues › Task performance › Maintenance › Installation › Maintenance personnel
Pilot
- Certificate: private
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 1,353.3 hours in all; 927.6 in this make and model; 17.3 in the last 90 days; 3.8 in the last 30 days; 1,469.6 as pilot in command
- Last flight review: March 15, 2021
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 5,356.9 hours
- Last inspection: annual inspection, September 8, 2021
- Maximum gross weight: 3,850 lb
- Seats: 5
- Landing gear: retractable
- Engine: Continental IO550B-AP (piston); 2,370 hours total
The flight
- Departed from: PRB Paso Robles CA at 1:29 am
- Destination: DVO Novato CA
- Flight plan: IFR
Weather at the time
- Light: dusk
- Wind: from 230° at 8 knots, gusting 14
- Visibility: 10 statute miles
- Sky: a few clouds at 5,000 ft
- Temperature: 57°F (14°C), dew point 46°F (8°C)
- Altimeter: 30.14 inHg
- Observation at 7:15 pm from KCVH, 28 miles away
Weather report (METAR): KCVH 090215Z AUTO 23008G14KT 10SM FEW050 14/08 A3014 RMK A01
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
5 documents, released by the NTSB on October 19, 2023. 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, 9 pages | View Download |
| 2 | Engine Examination Summary Report | PDF, 7 pages | View Download |
| 3 | Engine Data | data file | Download |
| 4 | Engine Logbook Excerpts | PDF, 2 pages | View Download |
| 5 | Release of Aircraft Wreckage, NTSB Form 6120.15 | 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.
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.