Grumman G 164B accident near Sac City, Iowa, August 12, 2015
On August 12, 2015 at about 9:00 pm local time, a 1977 Grumman G 164B, registered N311AL, was substantially damaged in an accident during maneuvering near Sac City, Iowa. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). 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 loss of engine power 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
- August 12, 2015 · about 9:00 pm local time
- Place
- Sac City, Iowa · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Grumman G 164B, built 1977 · all G 164Bs on the register
- Registration
- N311AL · registry record · serial 255B
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
The airline transport pilot reported that he changed the engine oil the night before the accident flight. The next day, he performed a normal engine run-up and then departed on the agricultural application flight. The airplane's tail lifted when the airplane reached 60 mph, and the airplane then accelerated to 80 mph. Shortly after getting airborne, the pilot felt that the airplane was not performing as it should be and that the engine power was decreasing. He advanced the engine controls full forward and selected a cornfield for the forced landing. The pilot reported that he thought that the engine's blower/supercharger had failed because the engine did not stop but did seem to lose power. An engine examination was not performed; therefore, the reason for the loss of engine power 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
- Loss of engine power (partial) during maneuvering defining event
- Off-field or emergency landing during emergency descent
The NTSB's findings
- cause Not determined › Not determined › (general) › (general) › Unknown/Not determined
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Medical certificate: Class 2
- Seat: sngl
- Injury: no injuries
The aircraft
- Last inspection: inspection type not recorded
- Landing gear: fixed
- Engine: P&W 985 (piston); 0 hours total
The flight
- Departed from: KSKI Sac City Mun IA
- Destination: KSKI Sac City Mun IA
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 240° at 7 knots
- Visibility: 10 statute miles
- Sky: a few clouds at 4,300 ft
- Temperature: 82°F (28°C), dew point 66°F (19°C)
- Altimeter: 30.18 inHg
- Observation at 8:55 pm from KSLB, 15 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
2 documents, released by the NTSB on January 28, 2016. 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 | Memo | PDF, 1 page | View Download |
| 2 | Weather Reports and Records | 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.