# NTSB ERA21LA056: Cessna 172, N8125U, Atlanta, GA, November 25, 2020

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: November 25, 2020, 00:09 local (05:09 UTC)
- Place: Atlanta, GA
- Coordinates: 33.876002, -84.302031 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.8760&lon=-84.3020&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining events: [Landing-landing roll: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); [Landing-landing roll: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Eastern Region Aviation
- Parties: FAA/FSDO
- NTSB case key (mKey): 102341
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA21LA056
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102341/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102341
- Page: https://openairdocs.org/ntsb/ERA21LA056

## Probable cause (aircraft 1)

The Cessna pilot’s failure to tune his radio to the common traffic advisory frequency, which resulted in a lack of awareness of the other aircraft operating at the airport. Contributing to the accident was the Cessna pilot’s lack of understanding of the airport lighting system.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Action: forgotten action/omission](https://openairdocs.org/ntsb-findings/02041035): Personnel issues › Action/decision · Pilot (probable cause), aircraft 1; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/02041035/cases.md?model=2072414), [All aircraft, 440 cases](https://openairdocs.org/ntsb-findings/02041035/cases.md)
- [Knowledge: aeronautical knowledge](https://openairdocs.org/ntsb-findings/02032035): Personnel issues › Experience/knowledge · Pilot (probable cause), aircraft 1; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/02032035/cases.md?model=2072414), [All aircraft, 7 cases](https://openairdocs.org/ntsb-findings/02032035/cases.md)
- [Communication system: vHF/HF radio](https://openairdocs.org/ntsb-findings/03016010): Environmental issues › Operating environment · Compliance w/ procedure (probable cause), aircraft 1; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/03016010/cases.md?model=2072414), [All aircraft, 6 cases](https://openairdocs.org/ntsb-findings/03016010/cases.md)
- [Action: forgotten action/omission](https://openairdocs.org/ntsb-findings/02041035): Personnel issues › Action/decision · Pilot of other aircraft (probable cause), aircraft 2; cases with it: [Aero Commander 500-B, 1 case](https://openairdocs.org/ntsb-findings/02041035/cases.md?model=0141106), [All aircraft, 440 cases](https://openairdocs.org/ntsb-findings/02041035/cases.md)
- [Knowledge: aeronautical knowledge](https://openairdocs.org/ntsb-findings/02032035): Personnel issues › Experience/knowledge · Pilot of other aircraft (probable cause), aircraft 2; cases with it: [Aero Commander 500-B, 1 case](https://openairdocs.org/ntsb-findings/02032035/cases.md?model=0141106), [All aircraft, 7 cases](https://openairdocs.org/ntsb-findings/02032035/cases.md)
- [Communication system: vHF/HF radio](https://openairdocs.org/ntsb-findings/03016010): Environmental issues › Operating environment · Compliance w/ procedure (probable cause), aircraft 2; cases with it: [Aero Commander 500-B, 1 case](https://openairdocs.org/ntsb-findings/03016010/cases.md?model=0141106), [All aircraft, 6 cases](https://openairdocs.org/ntsb-findings/03016010/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Landing-landing roll: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) (defining event), aircraft 1; cases with it: [Cessna 172F, 5 cases](https://openairdocs.org/ntsb-events/490/sequence.md?model=2072414), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)
- [Landing-landing roll: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) (defining event), aircraft 2; cases with it: [Aero Commander 500-B, 1 case](https://openairdocs.org/ntsb-events/490/sequence.md?model=0141106), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)

## Analysis (aircraft 1)

The private pilot of the Cessna was landing while the airline transport pilot of the Aero Commander was landing on the opposite runway during night visual meteorological conditions, after the airport control tower had closed. The Cessna pilot activated the runway approach lighting system and mistakenly believed that the green threshold lights indicated the direction for landing on the active runway. The pilot-controlled lighting system used a separate radio frequency from the common traffic advisory frequency (CTAF) at this airport. The Cessna pilot stated that he then “switched radio channels” and made “routine calls.” The Aero Commander pilot made radio announcements on the CTAF during each leg of the traffic pattern, announcing his location and intentions. Contrary to the Cessna pilot’s belief that the green lights he observed indicated the active runway (and the one on which he intended to land), they denoted the location of the (displaced) runway threshold of the adjacent runway. During landing rollout, the right-wing tip of the Cessna contacted the underside of the right wing of the Aero Commander, which had landed on the opposite runway, resulting in substantial damage to the Cessna’s right wing. The Cessna pilot reported that he did not hear any radio transmission from other aircraft operating at the time, and the pilot of the Aero Commander did not hear any radio transmissions from the Cessna pilot. Audio recordings of the CTAF frequency captured the radio transmissions made by the Aero Commander pilot (and other traffic) but did not capture any transmissions from the Cessna pilot. It is therefore likely that the Cessna pilot kept his single communications radio tuned to the pilot-controlled lighting frequency rather than change it to the CTAF as indicated in the airport/facility directory, which resulted in his communications not being heard by other pilots in the vicinity and his lack of awareness of the Aero Commander pilot’s position.

## Factual narrative (aircraft 1)

On November 25, 2020, at 0009 eastern standard time, a Cessna 172 N8125U, was substantially damaged when it collided with an Aero Commander 500, N777CM, during landing at Dekalb-Peachtree Airport (PDK), Atlanta, Georgia. There were no injuries. The Cessna was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The Aero Commander was operated as a Title 14 Code of Federal Regulations Part 135 flight. According to the Cessna pilot, while en route to PDK, his home base, he deviated around fog, which delayed his arrival until after the control tower had closed. Upon arrival near PDK, he listened to the automatic terminal information service, and reported that he “wrote down the radio channels and headed in, thinking how much (he) hated being without air traffic control.” As he neared the airport, he activated the pilot-controlled lighting, and the runway lights. He saw green lights at the approach end of what he believed to be runway 21R and stated that these lights indicated the direction he was supposed to land on the active runway (the lighting the Cessna pilot observed actually indicated the displaced threshold for runway 21L). He stated that he then “switched radio channels” and made “routine calls.” He did not hear any radio transmissions of other traffic operating at or near PDK. He reported that he had his landing lights and navigation lights on while on approach. During landing on runway 21L, about 200 ft past the runway numbers at an altitude of about 10-15 ft above the runway and at 65 knots, the Cessna pilot saw a “tiny white light approaching extremely fast.” About 3 seconds later, he heard a “bang” and the airplane “pitched hard” to the right He maneuvered the airplane back to the runway centerline and landed. He stated that he exited the runway at taxiway F, did not make any further radio calls, and taxied to his parking spot. An airport security guard met him and informed him that he had collided with another airplane. According to the Aero Commander pilot, he opted to land on runway 3R “because other aircraft were landing on 3R.” He followed an emergency medical services (EMS) helicopter that was landing on runway 3R. He entered a right downwind traffic pattern leg and “made the appropriate CTAF [common traffic advisory frequency] calls” on frequency 120.9. He turned to a right base and entered a ½ mile final for runway 3R, announcing each leg on the CTAF frequency. He reported that he typically does not adjust the intensity of the runway lights when landing at PDK, and he noticed that the light intensity increased while on approach. After landing, he saw “some lights” and was initially unsure what they were. He subsequently “realized it was an oncoming aircraft landing on runway 21L.” He reported that both airplanes swerved, and the right wingtip of the Cessna contact the right outboard wing section of the Aero Commander. A review of Federal Aviation Administration (FAA) automatic dependentsurveillance-broadcast (ADS-B) tracking data (see figure 1) revealed that the Cessna approached the airport from the northeast and flew a straight-in approach to runway 21L. Figure 1 - ADS-B tracking data showing the ground track of the Cessna (yellow) and the Aero Commander (red). A review of FAA recordings of the CTAF frequency 120.9 revealed that about 0005, the pilot of the Aero Commander initially announced that he was on a left downwind for runway 21L. About 2 minutes later, the pilot of an EMS helicopter, advised that he was on a modified base leg for runway 3R. The Aero Commander pilot then advised he was on final for runway 21L. The EMS pilot then advised that he had the Aero Commander in sight, acknowledged the potential conflict, and offered to approach the “shorter runway” (3L) instead. The Aero Commander pilot acknowledged and told the EMS pilot that he would instead go-around and enter a right downwind leg for runway 3R. The Aero Commander pilot subsequently transmitted his position as he entered the downwind leg and again as he made the turn to the final approach leg. Just after his turn to final, the EMS pilot announced that he was clear of the runway and hovering over the ramp. The Aero Commander pilot acknowledged and advised he had the helicopter in site. FAA tracking data (see figure 1) showed that at the time the Aero Commander pilot advised that the had the helicopter in sight, the Cessna was on final, about ½ mile from the displaced threshold of runway 21L. The recording did not include any radio calls from the Cessna pilot. Examination of both airplanes revealed that the Cessna sustained substantial damage to the right wingtip, including the outermost wing rib, and bending of the right aileron. Postaccident testing of all of the airplane’s lights (with the exception of the right wingtip navigation light, which was separated from the wing) revealed no anomalies. Postaccident ground testing of the single communication radio revealed successful transmission and reception. Examination of the Aero Commander revealed minor scrapes/paint transfer to the underside of the right wing near the outboard edge of the wing flap, and minor damage to the right-wing flap. According to the FAA airport/facility directory, the CTAF frequency at PDK is published as 120.9, which is the same frequency for the air traffic control tower when it is operating. When the tower is closed, the high intensity runway lights (along the runway edges) for runway 3R/21L are turned on and preset to medium intensity. The pilot-controlled lighting system uses a separate radio frequency, 120.0, which can be used to perform the following three functions: 1) increase the intensity of the runway edge lights, 2) activate the runway 21L approach lights (Medium Intensity Approach Lighting System with Sequenced Flashers or MALSF), which include green lights that mark the runway threshold, and 3) activate the taxiway lights. The green threshold lights, orientedtransverse to the runway centerline, denote the location of the (displaced) runway threshold. These lights are not an indication of the “active runway” in use.

## Aircraft 1

- Registration: [N8125U](https://openairdocs.org/aircraft/N8125U), registered now, S/N 17252025, built 1964 (OpenAirDocs)
- Reported make and model: CESSNA 172 (F)
- Registry model: [Cessna 172F](https://openairdocs.org/model/cessna-172f) (registry code 2072414) (OpenAirDocs)
- Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 17252025
- Year built: 1964
- Airframe hours: 6021
- Engines: Continental Motors O-300D 145 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Utility; Standard, Normal
- Last inspection: Annual, June 1, 2020, 15 hours before
- Departed: SAV, Savannah, GA
- Destination: Same as departure
- Airport: PDK, Dekalb-Peachtree Airport, runway 21L, 6,001 × 100 ft, concrete
- Equipment: ADS-B

## Aircraft 2

- Registration: [N777CM](https://openairdocs.org/aircraft/N777CM), registered now, S/N 1412-147, built 1964 (OpenAirDocs)
- Reported make and model: AERO COMMANDER 500 (B)
- Registry model: [Aero Commander 500-B](https://openairdocs.org/model/aero-commander-500-b) (registry code 0141106) (OpenAirDocs)
- Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 1412-147
- Year built: 1964
- Airframe hours: 24520
- Engines: Lycoming IO-540-E1A5 290 horsepower reciprocating; Lycoming IO-540-E1A5 290 horsepower reciprocating
- Damage: Minor damage
- Flight: Business, Part 135
- Operator: Central Air Southwest, doing business as Central Air Southwest
- Registered owner: Central Airlines
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, September 18, 2020
- Departed: BHM, Birmingham, AL
- Destination: Same as departure
- Flight plan: IFR
- Equipment: ADS-B, Handheld GPS

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot, aircraft N8125U; age 59; injuries: none; private; airplane ratings: single-engine land; medical: basicmed; seat: left; flight hours: 580 total
- Pilot, aircraft N777CM; age 67; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review June 30, 2020; seat: left; restraint: lap only; flight hours: 11,500 total, 3,500 in this make and model, 150 in the last 90 days, 50 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night
- Wind: 90° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 46 °F, dew point 36 °F
- Altimeter: 30.26 inHg
- Observed at: PDK
- METAR: KPDK 250453Z AUTO 09005KT 10SM CLR 08/02 A3026 RMK AO2 SLP252 T00830022 401440017

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20201125021421A](https://openairdocs.org/incident/20201125021421A), Nov 25, 2020: Cessna 172F, Atlanta, GA, Substantial damage. On November 25, 2020 at 0010 eastern daylight time (EDT), N8125U, a 1964 Cessna 172, and N777CM, a 1964 aero commander, struck each other after landing on the…

## Docket (12 files)

The files NTSB released with the investigation on September 28, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102341. 136 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 - N777CM (item 1, PDF, 10 pages, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664533&FileExtension=pdf&FileName=01-02%20-%206120%20-%20N777CM%20PDK%2011-25_Redacted_print-Rel.pdf
- Memorandum for record - information provided by Cessna (N8125U) pilot (item 2, PDF, 12 pages, 5.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12665385&FileExtension=pdf&FileName=01-02b%20-%20Memorandum%20for%20Record%20-%20Information%20from%20Cessna%20Pilot_ERA21LA056_Redacted-Rel.pdf
- Memorandum for record - information from FAA inspector (item 3, PDF, 1 page, 210 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664425&FileExtension=pdf&FileName=01-03%20-%20Memorandum%20for%20Record%20-%20Information%20from%20FAA%20Inspector_ERA21LA056-Rel.pdf
- Airport (pdk) security officer report (item 4, PDF, 1 page, 140 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12665477&FileExtension=pdf&FileName=01-05%20PDK%20Security%20Officer%20Report%20Incident%20Nov%2025%202020_Redacted-Rel.pdf
- FAA air traffic control audio/tracking data playback video (item 5, MP4, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664469&FileExtension=mp4&FileName=05-01%20Air%20Traffic%20Control%20Audio-Radar_Playback-Rel.mp4
- ADS-B track data- plot (item 6, PDF, 1 page, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12665487&FileExtension=pdf&FileName=05-02%20ADS-B%20Track%20Data%20-%20Plot%20-Rel.pdf
- ADS-B track data - tabular - N777CM (item 7, CSV, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664543&FileExtension=csv&FileName=05-03%20ADS-B%20Track%20Data%20-%20Tabular%20-%20N777CM-Rel.csv
- ADS-B track data - tabular - N8125U (item 8, CSV, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12665404&FileExtension=csv&FileName=05-04%20ADS-B%20Track%20Data%20-%20Tabular%20-%20N8125U-Rel.csv
- Airport diagram (item 9, PDF, 1 page, 156 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12669053&FileExtension=pdf&FileName=05-03%20Airport%20Diagram-Rel.pdf
- Description of approach lighting system - runway 21L at pdk (item 10, PDF, 2 pages, 701 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664479&FileExtension=pdf&FileName=05-05%20Description%20of%20Approach%20Lighting%20System%20for%20Runway%2021L%20at%20PDK_print-Rel.pdf
- Investigative photographs (item 11, PDF, 4 pages, 4 photos, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12665497&FileExtension=pdf&FileName=06-01-%20Investigative%20Photographs_ERA21LA056-Rel.pdf
- Security video recording (item 12, AVI, 119 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12664553&FileExtension=avi&FileName=08-01%20Security%20Video%20Recording-Rel.avi

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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