Cessna 172 accident near Cottage Grove, Minnesota, September 13, 2020
On September 13, 2020 at about 7:32 pm local time, a 1968 Cessna 172, registered N8488L, was destroyed in an accident near Cottage Grove, Minnesota (So. St. Paul Municipal airport). It was a personal flight under general aviation rules (Part 91). 3 people were killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A steep descent and impact with terrain for reasons that could not be determined based on the available information.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 13, 2020 · about 7:32 pm local time
- Place
- Cottage Grove, Minnesota · So. St. Paul Municipal · map
- Type
- Accident
- Injuries
- 3 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 172 I, built 1968 · all 172s on the register
- Registration
- N8488L · registry record · serial 17256688
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The accident flight was a “discovery flight” arranged by the rear seat passenger for his girlfriend, the front seat passenger. A flight instructor was seated in the right front seat. Flight track information revealed that, about four minutes after departure at an altitude of about 1,900 ft, the airplane entered a steep descent that continued until water contact. The airplane was destroyed when it impacted the water. Examination of the airplane revealed no evidence of mechanical anomalies that would have precluded normal operation, and no evidence of a bird strike. Visual meteorological conditions were present in the area at the time of the accident. Available medical information provided no evidence that the CFI had any medical condition, substance use, or toxic exposure that contributed to the accident. Based on the absence of detected ethanol in the CFI’s urine, it is likely that ethanol detected in his cavity blood was from sources other than ingestion. Given the available information, the reason for the airplane’s impact with terrain could not be determined.
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
- Unknown or undetermined during unknown defining event
The NTSB's findings
- Personnel issues › Task performance › Use of equip/info › Aircraft control › Flight crew
- Not determined › Not determined › (general) › (general) › Unknown/Not determined
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: 300 hours in all; 300 in this make and model; 47 in the last 90 days
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: rgt
- Injury: fatal
The aircraft
- Airframe total time: 3,343 hours
- Last inspection: annual inspection, July 17, 2020
- Maximum gross weight: 2,299 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-320-E2D (piston); 3,242 hours total
- Operator: Harrier Aviation
The flight
- Departed from: SGS South St, Paul MN at 7:28 pm
- Destination: SGS South St, Paul MN
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 190° at 3 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 70°F (21°C), dew point 57°F (14°C)
- Altimeter: 30.10 inHg
- Observation at 7:35 pm from SGS, 6 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
14 documents, released by the NTSB on April 27, 2022. 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 | Accident Report Photographs | PDF, 9 pages | View Download |
| 2 | Maintenance Records Excerpts - N8488L | PDF, 3 pages | View Download |
| 3 | Opsview of Accident Flight (Plan View) | PDF, 1 page | View Download |
| 4 | Opsview of Accident Flight (Profile View} | PDF, 1 page | View Download |
| 5 | Cws Data | PDF, 6 pages | View Download |
| 6 | Attachment 2 - Video Recording - Specialist's Factual Report | zip file | Download |
| 7 | Attachment 3 - Video Recording - Specialist's Factual Report | video | View Download |
| 8 | Attachment 4 - Video Recording - Specialist's Factual Report | zip file | Download |
| 9 | Aircraft Performance Study | PDF, 5 pages | View Download |
| 10 | Weather Reports | PDF, 1 page | View Download |
| 11 | Satellite Weather | GIF file | Download |
| 12 | Instructor's Toxicology Report | PDF, 1 page | View Download |
| 13 | Statement of Party Representatives to NTSB Investigation | PDF, 2 pages | View Download |
| 14 | 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.