Cessna 172H accident near Seattle, Washington, May 19, 2023
On May 19, 2023 at about 1:17 am local time, a 1967 Cessna 172H, registered N2550L, was substantially damaged in an accident during enroute (cruise) near Seattle, Washington. It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A stuck exhaust valve that resulted in a partial loss of engine power and a forced water ditching.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 19, 2023 · about 1:17 am local time
- Place
- Seattle, Washington · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 172H, built 1967 · all 172Hs on the register
- Registration
- N2550L · registry record · serial 17255750
- 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, as the airplane descended to 1,000 ft mean sea level (msl) crossing over a bay, the engine sustained a partial loss of power. The pilot declared an emergency and performed a forced water ditching. Examination of the engine revealed a stuck exhaust valve on the No. 4 cylinder. The No. 4 cylinder was removed for further examination. The exhaust valve guide exhibited evidence of oil coking along with an area of polishing on one side of the guide. A slight amount of discoloration consistent with corrosion was observed adjacent to the polished area. The exhaust valve stem was intact with some coking near the valve fillet and the intake valve exhibited moderate coking. It is likely that the coking resulted in the valve getting stuck. The Nos. 2 and 4 cylinder cooling fins exhibited thermal discoloration. A visual inspection of the internal area of the crankcase showed the crankshaft and camshaft did not reveal any anomalies or mechanical damage. The No. 4 cylinder had been serviced and reinstalled with a new cylinder kit 143 flight hours before the accident and the most recent annual inspection was about 11 months before the accident.
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 (cruise) defining event
- Ditching during landing
The NTSB's findings
- Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng cyl section › Damaged/degraded
- Aircraft › Aircraft power plant › Power plant › (general) › Related maintenance info
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 1,489 hours in all; 513 in this make and model; 63 in the last 90 days; 23 in the last 30 days; 1,143 as pilot in command; 435 on instruments
- Last flight review: May 25, 2021
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 4,030 hours
- Last inspection: annual inspection, June 9, 2022; 1,280 hours since
- Maximum gross weight: 2,300 lb
- Seats: 4
- Landing gear: fixed
- Engine: Continental O-300 (piston); 1,980 hours total
The flight
- Departed from: 0S9 Port Townsend WA
- Destination: S50 Seattle WA
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 240° at 5 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 75°F (24°C), dew point 61°F (16°C)
- Altimeter: 29.95 inHg
- Observation at 5:53 pm from KBFI, 4 miles away
Weather report (METAR): KBFI 190053Z 24005KT 10SM FU CLR 24/16 A2995 RMK AO2 SLP143 T02440156
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
4 documents, released by the NTSB on June 20, 2024. 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, 11 pages | View Download |
| 2 | Airframe and Engine Examination Report | PDF, 11 pages | View Download |
| 3 | Maintenance Records | PDF, 14 pages | View Download |
| 4 | 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.