Cessna 150L and Aeronca 11CC mid-air collision near Watertown, South Dakota, August 24, 1991
On August 24, 1991 at about 4:10 pm local time, 2 aircraft, Cessna 150L (N16098) and Aeronca 11CC (N4535E), were involved in a mid-air collision near Watertown, South Dakota (Unk airport). 1 person had minor injuries; 1 other was unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
ATTEMPTED FORMATION FLYING WITH N4535E BY THE PILOT OF N16098. FACTORS ASSOCIATED WITH THE COLLISION WERE: NONPERFORMANCE OF PREFLIGHT PLANNING, AND FAILURE TO FOLLOW PROCEDURES AND DIRECTIVES BY THE PILOT OF N16098.
ATTEMPTED FORMATION FLYING WITH N4535E BY THE PILOT OF N16098. FACTORS ASSOCIATED WITH THE COLLISION WERE: NONPERFORMANCE OF PREFLIGHT PLANNING, AND FAILURE TO FOLLOW PROCEDURES AND DIRECTIVES BY THE PILOT OF N16098.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 24, 1991 · about 4:10 pm local time
- Place
- Watertown, South Dakota · Unk · map
- Type
- Accident · mid-air collision
- Injuries
- 1 person had minor injuries; 1 other was unhurt.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Cessna 150L · all 150Ls on the register
- Registration
- N16098 · no longer on the register · serial 150-73475
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
- Aircraft 2
- Aeronca 11CC · all 11CCs on the register
- Registration
- N4535E · registry record · serial 11CC-243
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative for the Cessna 150L final · quoted from the NTSB record
TWO AIRPLANES COLLIDED WHEN THE PILOT OF AN OVERTAKING AIRPLANE N16908 ATTEMPTED TO JOIN AND FLY FORMATION WITH THE LEAD AIRPLANE N4535E. THE PILOT OF THE LEAD AIRPLANE WAS NOT AWARE OF THE OVERTAKING AIRPLANE. BOTH PILOTS PERFORMED EMERGENCY LANDINGS.
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 NTSB's narrative for the Aeronca 11CC final · quoted from the NTSB record
TWO AIRPLANES COLLIDED WHEN THE PILOT OF AN OVERTAKING AIRPLANE N16908 ATTEMPTED TO JOIN AND FLY FORMATION WITH THE LEAD AIRPLANE N4535E. THE PILOT OF THE LEAD AIRPLANE WAS NOT AWARE OF THE OVERTAKING AIRPLANE. BOTH PILOTS PERFORMED EMERGENCY LANDINGS.
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 for the Cessna 150L from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 467 hours in all; 467 in this make and model; 10 in the last 90 days; 3 in the last 30 days; 437 as pilot in command
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: unk
The aircraft
- Last inspection: inspection type not recorded; 0 hours since
- Maximum gross weight: 1,600 lb
- Seats: 2
- Landing gear: fixed
- Engine: Continental O-200 (piston); 0 hours total
The flight
- Departed from: 8D7 Clark SD at 3:30 pm
- Destination: ATY Watertown SD
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 160° at 16 knots
- Visibility: 12 statute miles
- Sky: scat at 25,000 ft
- Temperature: 75°F (24°C), dew point 66°F (19°C)
- Observation at 4:49 pm from ATW, 8 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
The factual record for the Aeronca 11CC from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: single-engine land; single-engine sea
- Flight time: 1,896 hours in all; 22 in this make and model; 10 in the last 90 days; 5 in the last 30 days; 1,843 as pilot in command
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: unk
The aircraft
- Last inspection: inspection type not recorded; 0 hours since
- Maximum gross weight: 1,450 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming O-235-C1B (piston); 0 hours total
The flight
- Departed from: 8D7 Clark SD at 3:40 pm
- Flight plan: none
- Runway 0
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
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.