Schleicher ASW20C and Schleicher ASW27 mid-air collision near Clayton, California, November 7, 2020
On November 7, 2020 at about 8:51 pm local time, 2 aircraft, Schleicher ASW20C (N18MA) and Schleicher ASW27 (N81KP), were involved in a mid-air collision near Clayton, California. 2 people were seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure of both pilots of each glider to see an avoid one another while maneuvering, which resulted in a mid-air collision.
The failure of both pilots of each glider to see an avoid one another while maneuvering, which resulted in a mid-air collision.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 7, 2020 · about 8:51 pm local time
- Place
- Clayton, California · map
- Type
- Accident · mid-air collision
- Injuries
- 2 people were seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Schleicher ASW20C, built 1986 · all ASW20Cs on the register
- Registration
- N18MA · no longer on the register · serial 20844
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
- Aircraft 2
- Schleicher ASW27, built 1997 · all ASW27s on the register
- Registration
- N81KP · registry record · serial 27041
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative for the Schleicher ASW20C final · quoted from the NTSB record
The pilot of an ASW-20C glider reported that, while following lift under cumulus clouds, he observed another glider, an ASW-27 traversing from right to left. He entered into a steep dive in an attempt to avoid the other glider, however, the ASW-20C impacted the ASW-27 glider. Following the collision, the ASW-20C entered a steep descent and rolled inverted before the pilot elected to bail out and parachute to safety. The ASW-20C pilot added that the glider was equipped with a FLARM collision system, and prior to the collision, did not receive any alerts of additional traffic. The pilot of an ASW-27 glider reported that while maneuvering, another glider suddenly appeared to his left and followed by a collision. The pilot stated that his glider immediately entered a descent and was out of control. The pilot of the ASW-27 subsequently bailed out and parachuted to safety. The glider was equipped with a FLARM collision system but was inoperative awaiting an annual software update. The ASW-20C glider sustained substantial damage to the left wing. The ASW-27 glider sustained substantial damage to the left wing and aft fuselage. Both glider pilots reported that there were no preaccident mechanical failures or malfunctions with the gliders that would have precluded normal operation.
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 Schleicher ASW27 final · quoted from the NTSB record
The pilot of an ASW-20C glider reported that, while following lift under cumulus clouds, he observed another glider, an ASW-27 traversing from right to left. He entered into a steep dive in an attempt to avoid the other glider, however, the ASW-20C impacted the ASW-27 glider. Following the collision, the ASW-20C entered a steep descent and rolled inverted before the pilot elected to bail out and parachute to safety. The ASW-20C pilot added that the glider was equipped with a FLARM collision system, and prior to the collision, did not receive any alerts of additional traffic. The pilot of an ASW-27 glider reported that while maneuvering, another glider suddenly appeared to his left and followed by a collision. The pilot stated that his glider immediately entered a descent and was out of control. The pilot of the ASW-27 subsequently bailed out and parachuted to safety. The glider was equipped with a FLARM collision system but was inoperative awaiting an annual software update. The ASW-20C glider sustained substantial damage to the left wing. The ASW-27 glider sustained substantial damage to the left wing and aft fuselage. Both glider pilots reported that there were no preaccident mechanical failures or malfunctions with the gliders that would have precluded normal operation.
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 Schleicher ASW20C from the NTSB's investigation tables, in plain English
What happened, in order
- Midair collision during maneuvering defining event
The NTSB's findings
- Environmental issues › Physical environment › Object/animal/substance › Aircraft › Effect on equipment
- Personnel issues › Psychological › Attention/monitoring › Monitoring other aircraft › Pilot
Pilot
- Certificate: private
- Ratings: single-engine land; instrument: airplane; rotorcraft: glider
- Flight time: 1,847 hours in all; 186 in this make and model; 31 in the last 90 days; 10 in the last 30 days; 1,800 as pilot in command
- Last flight review: February 7, 2020
- Medical certificate: BasicMed (with waivers/limitations)
- Seat: sngl
- Injury: minor injuries
The aircraft
- Airframe total time: 1,431.7 hours
- Last inspection: annual inspection, February 22, 2020
- Maximum gross weight: 1,001 lb
- Seats: 1
- Landing gear: retractable
The flight
- Departed from: C83 Byron CA at 7:50 pm
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: at 5 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 61°F (16°C), dew point 32°F (0°C)
- Altimeter: 29.73 inHg
- Observation at 12:53 pm from KLVK, 11 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
The factual record for the Schleicher ASW27 from the NTSB's investigation tables, in plain English
What happened, in order
- Midair collision during maneuvering defining event
The NTSB's findings
- Environmental issues › Physical environment › Object/animal/substance › Aircraft › Effect on equipment
- Personnel issues › Psychological › Attention/monitoring › Monitoring other aircraft › Pilot
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; instructor: glider; instrument: airplane; rotorcraft: glider
- Flight time: 2,794 hours in all; 31 in the last 90 days; 7 in the last 30 days; 2,723 as pilot in command; 888 on instruments
- Last flight review: February 9, 2020
- Medical certificate: BasicMed (with waivers/limitations)
- Seat: ctr
- Injury: serious injuries
The aircraft
- Airframe total time: 4,245 hours
- Last inspection: annual inspection, March 3, 2020
- Maximum gross weight: 1,103 lb
- Seats: 1
- Landing gear: retractable
The flight
- Departed from: C83 Byron CA at 8:05 pm
- Flight plan: none
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 August 20, 2021. 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 | N18MA Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | N81KP Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 3 | Record of Phone Conversation (N18MA Pilot) | PDF, 1 page | View Download |
| 4 | Damage Photos | PDF, 3 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.