Cessna 172S and amateur-built F1 mid-air collision near San Marcos, Texas, September 25, 2020
On September 25, 2020, 2 aircraft, Cessna 172S (N108VK) and amateur-built F1 (N540LK), were involved in a mid-air collision near San Marcos, Texas (San Marcos Regional Airport). 1 person was seriously injured and 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The F1 pilot’s failure to see and avoid the lower altitude Cessna while on final approach for landing. Contributing to the accident were the restrictions to pilot visibility inherent to low- and high-wing airplanes, and both pilots’ failure to recognize the conflict that developed between their airplanes.
The F1 pilot’s failure to see and avoid the lower altitude Cessna while on final approach for landing. Contributing to the accident were the restrictions to pilot visibility inherent to low- and high-wing airplanes, and both pilots’ failure to recognize the conflict that developed between their airplanes.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 25, 2020
- Place
- San Marcos, Texas · San Marcos Regional Airport · map
- Type
- Accident · mid-air collision
- Injuries
- 1 person was seriously injured and 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Cessna 172S, built 2001 · all 172Ss on the register
- Registration
- N108VK · no longer on the register · serial 172S8932
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
- Aircraft 2
- Amateur-built F1, built 2014
- Registration
- N540LK · no longer on the register · serial 021
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative for the Cessna 172S final · quoted from the NTSB record
A low-wing Team Rockets F1 airplane and a high-wing Cessna 172 airplane were involved in a mid-air collision on final approach for landing. The airplanes entered the downwind leg of the traffic pattern within one minute of each other, with the F1 in front of the Cessna. There were four other airplanes in the traffic pattern or communicating on the airport’s common traffic frequency at that time. Shortly after entering the traffic pattern, the F1 pilot announced and performed a right 360° turn to increase spacing with the preceding airplane. The instructor onboard the trailing Cessna could not see the F1 and asked if the F1 had completed the turn. The F1 pilot responded that he was about to turn base, but he saw a Cessna below him and that he would extend downwind before turning to final. The instructor onboard the Cessna began a turn to base and reported that they saw the F1. About 45 seconds later, the F1 pilot reported that he was on final approach over a highway about 2 miles from the runway, which indicates he did not extend his downwind sufficiently to attain sufficient separation. The Cessna crossed the highway about the same time and also reported a 2-mile final. About 45 seconds later, the F1 pilot reported a 1 mile final. The instructor onboard the Cessna then reported a .8-mile final. Shortly after the last radio calls from the two airplanes, the F1 impacted the Cessna on the Cessna’s top left side. Both airplanes impacted the ground short of the runway. The Cessna flipped over and the F1 came to rest against a fence and caught fire. The Cessna sustained substantial damage and the F1 was destroyed. The F1 pilot recalled an airplane making position calls on final, which he assumed was behind him. He said that he had a clear view of the runway while on final and he did not see any traffic between him and the runway. It is likely that the low-wing configuration of the F1 prevented the F1 pilot from seeing the Cessna below him. Likewise, the occupants of the high-wing Cessna were restricted from seeing the F1 above them. Although the F1 pilot stated that he would extend his downwind leg, he did not extend it enough to gain safe separation from the Cessna, which resulted in the F1 and the Cessna arriving at nearly the same geographical point on 2- mile final at the same time. The standard position reports issued by both pilots were sufficient for the pilots to have had awareness of each other’s position on final; however, neither comprehended the conflict between their airplanes, possibly due to the high volume of radio calls from other aircraft in the traffic pattern and both pilots’ increased attention on preparing for landing.
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 amateur-built F1 final · quoted from the NTSB record
A low-wing Team Rockets F1 airplane and a high-wing Cessna 172 airplane were involved in a mid-air collision on final approach for landing. The airplanes entered the downwind leg of the traffic pattern within one minute of each other, with the F1 in front of the Cessna. There were four other airplanes in the traffic pattern or communicating on the airport’s common traffic frequency at that time. Shortly after entering the traffic pattern, the F1 pilot announced and performed a right 360° turn to increase spacing with the preceding airplane. The instructor onboard the trailing Cessna could not see the F1 and asked if the F1 had completed the turn. The F1 pilot responded that he was about to turn base, but he saw a Cessna below him and that he would extend downwind before turning to final. The instructor onboard the Cessna began a turn to base and reported that they saw the F1. About 45 seconds later, the F1 pilot reported that he was on final approach over a highway about 2 miles from the runway, which indicates he did not extend his downwind sufficiently to attain sufficient separation. The Cessna crossed the highway about the same time and also reported a 2-mile final. About 45 seconds later, the F1 pilot reported a 1 mile final. The instructor onboard the Cessna then reported a .8-mile final. Shortly after the last radio calls from the two airplanes, the F1 impacted the Cessna on the Cessna’s top left side. Both airplanes impacted the ground short of the runway. The Cessna flipped over and the F1 came to rest against a fence and caught fire. The Cessna sustained substantial damage and the F1 was destroyed. The F1 pilot recalled an airplane making position calls on final, which he assumed was behind him. He said that he had a clear view of the runway while on final and he did not see any traffic between him and the runway. It is likely that the low-wing configuration of the F1 prevented the F1 pilot from seeing the Cessna below him. Likewise, the occupants of the high-wing Cessna were restricted from seeing the F1 above them. Although the F1 pilot stated that he would extend his downwind leg, he did not extend it enough to gain safe separation from the Cessna, which resulted in the F1 and the Cessna arriving at nearly the same geographical point on 2- mile final at the same time. The standard position reports issued by both pilots were sufficient for the pilots to have had awareness of each other’s position on final; however, neither comprehended the conflict between their airplanes, possibly due to the high volume of radio calls from other aircraft in the traffic pattern and both pilots’ increased attention on preparing for landing.
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 172S from the NTSB's investigation tables, in plain English
What happened, in order
- Midair collision during approach (VFR pattern final) defining event
The NTSB's findings
- Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot of other aircraft
- Personnel issues › Psychological › Perception/orientation/illusion › Perception › Instructor/check pilot
Flight instructor
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instrument: airplane
- Flight time: 342 hours in all; 108 in this make and model; 97 in the last 90 days; 36 in the last 30 days; 269 as pilot in command; 85 on instruments
- Last flight review: April 15, 2020
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: rgt
- Injury: minor injuries
Dual student
- Certificate: student
- Flight time: 16 hours in all
- Medical certificate: Unknown
- Seat: left
- Injury: serious injuries
The aircraft
- Airframe total time: 5,020 hours
- Last inspection: 100-hour inspection, August 20, 2020
- Maximum gross weight: 2,550 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming I0360 SER A&C (piston); 0 hours total
The flight
- Departed from: 50R Lockhart TX
- Flight plan: none
- Runway 08, 6,330 ft by 100 ft
- A second pilot was aboard
Weather at the time
- Light: dusk
- Wind: from 070° at 7 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 75°F (24°C), dew point 64°F (18°C)
- Altimeter: 29.92 inHg
- Observation at 6:56 pm from KHYI, 1 miles away
Weather report (METAR): KHYI 242356Z AUTO 07007KT 10SM CLR 24/18 A2992 RMK AO2 SLP123 T02440178 10272 20244 56007
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | 1 |
The factual record for the amateur-built F1 from the NTSB's investigation tables, in plain English
What happened, in order
- Midair collision during approach (VFR pattern final) defining event
The NTSB's findings
- Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
- Personnel issues › Psychological › Perception/orientation/illusion › Perception › Pilot
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 1,600 hours in all; 200 in this make and model; 1,500 as pilot in command
- Last flight review: January 1, 2020
- Medical certificate: Class 3 (without waivers/limitations)
- Seat: frt
- Injury: minor injuries
The aircraft
- Airframe total time: 170 hours
- Last inspection: condition inspection, September 15, 2020
- Maximum gross weight: 2,100 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming IO-540-C4B5 (piston); 170 hours total
The flight
- 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
11 documents, released by the NTSB on April 15, 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 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 N108VK | PDF, 11 pages | View Download |
| 2 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 N540LK | PDF, 11 pages | View Download |
| 3 | N108VK CFI Statements | PDF, 5 pages | View Download |
| 4 | Record of Conversation N540LK Pilot | PDF, 4 pages | View Download |
| 5 | Witness Statements | PDF, 2 pages | View Download |
| 6 | Record of Conversation Witness | PDF, 1 page | View Download |
| 7 | Ctaf Communications Transcript | PDF, 11 pages | View Download |
| 8 | Photos | PDF, 3 pages | View Download |
| 9 | N108VK ADS-B Raw Data | spreadsheet | Download |
| 10 | N108VK Flight Track | PDF, 2 pages | View Download |
| 11 | Onboard Image Recorder - Specialist's Factual REPORT_CEN20LA419 | PDF, 21 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.