Cessna 172S accident near Seattle, Washington, July 31, 2017
On July 31, 2017 at about 7:30 pm local time, a 2002 Cessna 172S, registered N957TA, was substantially damaged in an accident during enroute (cruise) near Seattle, Washington. It was an instructional flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The total loss of engine power due to oil starvation as a result of the loose right magneto, which allowed oil to escape and the engine to seize. Contributing to the accident was inadequate maintenance, which failed to identify the loose magneto bolt.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 31, 2017 · about 7:30 pm local time
- Place
- Seattle, Washington · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 172S S, built 2002 · all 172Ss on the register
- Registration
- N957TA · no longer on the register · serial 172S9057
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
During an instructional flight, the engine started running rough and, shortly after the oil pressure light illuminated, subsequently quit. The pilot elected to ditch the airplane in the water close to the shoreline. An onsite examination of the engine revealed that the top bolt of the right magneto was loose and had backed off, which allowed the magneto to become partially separated, leaving a 3/8-inch gap at the top of the magneto where it mounted to the case, which allowed oil to exit the engine. Metal shavings were observed throughout the engine. A review of the maintenance records indicated that the magnetos were removed and overhauled about 9 months before the accident during a 500-hour inspection, which was 420.5 hours of flight time before the accident. The airplane had accumulated about 22 hours of flight time since its last annual inspection, and the loose magneto bolt should have been able to be identified at that time.
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 (cruise) defining event
- Emergency descent initiated during enroute (cruise)
- Ditching during landing (flare/touchdown)
- Collision with terrain or object (not controlled flight into terrain) during landing (flare/touchdown)
The NTSB's findings
- cause Aircraft › Fluids/misc hardware › Fluids › Oil › Fluid level
- cause Aircraft › Fluids/misc hardware › Fluids › Oil › Related maintenance info
- factor Personnel issues › Task performance › Maintenance › Scheduled/routine maintenance › Maintenance personnel
- factor Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng rear section › Incorrect service/maintenance
- factor Aircraft › Aircraft power plant › Ignition system › Magneto/distributor › Incorrect service/maintenance
- Environmental issues › Physical environment › Terrain › Water › Contributed to outcome
Flight instructor
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 490 hours in all; 57 in this make and model; 206 in the last 90 days; 64 in the last 30 days; 373 as pilot in command; 219 on instruments
- Last flight review: April 4, 2017
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: rgt
- Injury: minor injuries
Dual student
- Certificate: student
- Flight time: 0 hours in all; 0 in this make and model
- Medical certificate: Class 3 (without waivers/limitations)
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 5,539.9 hours
- Last inspection: 100-hour inspection, July 25, 2017; 22 hours since
- Maximum gross weight: 2,258 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming IO-360-L2R (piston); 918 hours total
The flight
- Departed from: BFI Seattle WA at 6:45 pm
- Destination: BFI Seattle WA
- Flight plan: none
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 010° at 10 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 79°F (26°C), dew point 52°F (11°C)
- Altimeter: 30.23 inHg
- Observation at 6:53 pm from BFI, 5 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
8 documents, released by the NTSB on August 24, 2020. 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 | Record of Telephone Conversation Between FAA and Lycoming Engines | PDF, 2 pages | View Download |
| 3 | Engine Examination Notes | PDF, 4 pages | View Download |
| 4 | Excerpts from Engine Logbooks | PDF, 18 pages | View Download |
| 5 | Statement of Party Representatives to NTSB Investigation | PDF, 1 page | View Download |
| 6 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 1 page | View Download |
| 7 | Evidence Control Form | PDF, 1 page | View Download |
| 8 | Photo Array | PDF, 6 pages | 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.