# NTSB WPR21LA032: Cessna 172, N124TW, Billings, MT, October 31, 2020 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Limited · Final report - Date: October 30, 2020, 19:05 local (Oct 31, 2020, 01:05 UTC) - Place: Billings, MT - Coordinates: 45.810806, -108.52258 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.8108&lon=-108.5226&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA-FSDO, Textron Lycoming, Textron Aviation - NTSB case key (mKey): 102218 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA032 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102218/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102218 - Page: https://openairdocs.org/ntsb/WPR21LA032 ## Probable cause The pilot’s failure to maintain the proper descent glide path while on final approach for reasons that could not be determined from available evidence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: descent/approach/glide path](https://openairdocs.org/ntsb-findings/01062040): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause) ## Analysis The pilot departed on the last leg of a multi-leg cross-country flight during dark night conditions. Air traffic control communications indicate he reported encountering wind shear, turbulence and difficulties continuing the flight at night with strong headwinds. The pilot also reported that he was not able to climb to an altitude to safely navigate mountainous terrain and needed to divert to another airport. During the approach the pilot was unable to identify the runway from other flashing lights that were likely part of a planned memorial procession and light display that was lined up near the airport. The controller gave the pilot a position report and the pilot reported that he thought he had the airport in sight. The controller advised the pilot to maneuver as necessary and to maintain an altitude of 4,500 ft mean sea level (msl) or higher. After some maneuvering the pilot reported that he did not have the runway in sight. The controller then requested that he pass over the top of the airport and the pilot replied he had the runway in sight. During the approach the pilot impacted trees and terrain about 3/4 mile from the runway. The accident site examination revealed that the airplane impacted a large tree and then terrain which was located along the runway centerline. Branches surrounding the large tree revealed propeller strike marks, suggesting an undetermined amount of engine power during the accident sequence. The postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. An airplane performance study revealed that airspeed and airplane attitude information estimated from automatic dependent surveillance-broadcast equipment and winds aloft data indicate that the airplane impacted a tree and terrain while in a controlled descent and that an aerodynamic stall was not likely a factor. The airplane was operating at altitudes between 7,000 and 11,000 ft msl for most of the 2 hour 6-minute accident flight, and it was night for the last 30 minutes with the airplane largely operating between 4,000 and 9,000 ft msl. The pilot’s severe cardiovascular disease placed him at increased risk of an acute cardiac event such as ischemia or arrhythmia that can cause sudden incapacitating symptoms and leave no evidence at autopsy. Whether the pilot was impaired or incapacitated by his cardiac disease or some other medical condition at the time of the accident could not be determined by this investigation. However, whether the cause of the airplane’s behavior was due to an incapacitating medical condition, distraction, wind shear, or some other factor is not known from the available operational information. ## Factual narrative According to a local news article, on the evening of the accident, at about 1900, a memorial procession involving emergency vehicles and tow trucks for a light display were lined up on Highway 3, located just to the south of BIL. At 1915 the procession was scheduled to move through town. On October 30, 2020, about 1905 mountain daylight time (MDT), a Cessna 172M airplane, N124TW, was substantially damaged when it was involved in an accident near Billings, Montana. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 cross-country flight. The pilot departed at 0739 central daylight time earlier in the day from the Dallas, Texas area and had flown four legs under visual flight rules before departing on the accident flight leg about 1652 MDT from Sheridan County Airport, Sheridan, Wyoming. According to air traffic control, the pilot reported windshear and turbulence and had difficulties continuing the flight at night with strong headwinds. The pilot also reported that he was not able to climb to an altitude to safely navigate mountainous terrain and needed to divert to Billings Logan International Airport (BIL), Billings, Montana. The pilot turned right and continued to BIL where he was instructed to land on runway 28R. As the pilot was approaching BIL, he was asked by the tower controller if he would like runway 25 because it was more aligned with the wind, to which the pilot agreed. As the pilot approached the airport, he advised, “I’m having trouble making out the airport from the rest of the flashing lights.” The controller gave the pilot a position report and the pilot reported that he thought he had the airport in sight. The controller advised the pilot to maneuver as necessary and to maintain an altitude of 4,500 ft mean sea level (msl) or higher. After some maneuvering, the pilot reported that he did not have the runway in sight. The controller then requested that he pass over the top of the airport and the pilot replied he had the runway in sight. The pilot reported that he needed to maneuver to lineup with the runway to which the controller issued wind information and cleared the pilot to land on runway 25 with additional instructions not to descend below 4,000 ft msl. As the pilot was lined up for runway 25, the controller advised the pilot the runway elevation was at 3,600 ft msl and that he could descend at any time. The controller also advised the pilot that the runway had Precision Approach Path Indicator (PAPI) lights, to which the pilot reported that he had them in sight. The controller lost sight of the airplane and lost all communication with the pilot. A security video shows the airplane’s navigation lights travel across the top of the screen at nighttime while on the approach to runway 25 at BIL. Near the end of the video, the airplane pitches downward and view of the airplane’s lights stop. Figure 1-Flight data track and accident site location. The pilot had reported havinghad coronary artery bypass procedures in 2004 and 2010 to the FAA. He had also reported having hypertension, cataract surgery (bilateral), and vascular surgery. At his last exam, he reported using losartan, amlodipine, aspirin, meloxicam, atorvastatin, and metoprolol to control his diseases. These are not considered impairing. At the time of the accident, the pilot was certified under BasicMed. According to the autopsy performed by the Department of Justice, Forensic Science Division, the cause of death was multiple blunt force injuries and the manner of death was accident. In addition, severe atherosclerotic stenosis (>75%) of left anterior descending coronary artery and moderate (<75%) atherosclerotic stenosis of right coronary artery was identified. A single patient graft to the left marginal artery was identified. The pathologist reported the presence of hypertensive cardiovascular disease based on elevated heart weight (wall thicknesses not described) and on the appearance of the kidneys. Toxicology testing identified losartan, amlodipine, and metoprolol, which are prescription blood pressure medications, in cavity blood and urine; metoprolol is also used to reduce the risk of recurrent heart attack. None of these medications is considered impairing. Zolpidem, a prescription sleep aid, was also identified in cavity blood and urine. Zolpidem carries warnings, including the potential for altered behaviors, agitation, hallucinations and performing complex behaviors. The level identified in the pilot’s specimens was at a level below that thought to cause effects. A surface analysis chart identified a cold front at 1800 MDT located across central Montana. A high pressure system was also located over western Wyoming. The accident site was located east of the cold front on the warm side of the boundary. Three hours later the cold front had moved through the BIL area and was located east of the accident site. The observations from BIL surrounding the accident time indicated VFR conditions with a southwest wind gusting to 27 knots in the hours leading up the accident time, and the wind becoming northwesterly at 1930 MDT and gusting to 42 knots at the surface at 1944 MDT. The observer also noted alto-cumulus standing lenticular (ACSL) clouds in the distance from the south, west, through the northeast prior to the accident. BIL weather observation at 1853 MDT, wind from 250° at 12 knots, visibility 10 miles or greater, few clouds at 9,000 ft above ground level (agl), few clouds at 13,000 ft agl, scattered clouds at 20,000 ft agl, temperature of 14°Celsius (C), dew point temperature of -2°C, and an altimeter setting of 29.60 inches of mercury (inHg). Remarks: automated station with a precipitation discriminator, sea level pressure 1002.2 hPa, temperature 13.9°C, dew point temperature -1.7°C. BIL special weather observation at 1917 MDT, wind from 240° at 14 knots, visibility 10 miles or greater, few clouds at 9,000 ft agl, few clouds at 13,000 ft agl,scattered clouds at 20,000 ft agl, temperature of 14°C, dew point temperature of -2°C, and an altimeter setting of 29.60 inHg. Remarks: automated station with a precipitation discriminator, temperature 13.9°C, dew point temperature -2.2°C. According to a family member, the pilot had flown this multi-leg flight numerous times. The airplane and pilot’s logbooks were not obtained during the investigation. An airplane performance study revealed that airspeed and airplane attitude information estimated from automatic dependent surveillance broadcast equipment (ADS-B) and winds aloft data indicate that the airplane impacted a tree and terrain while in a controlled descent and that an aerodynamic stall was not likely a factor. The airplane was operating at altitudes between 7,000 and 11,000 ft msl for most of the 2 hour 6-minute accident flight, and it was night for the last half hour with the airplane largely operating between 4,000 and 9,000 ft msl. It is not known whether the pilot was using supplemental oxygen; however, air traffic control communications indicate that he was having difficulty finding the airport at night. The FAA Airplane Flying Handbook, FAA-H-8083-3B, 2016, recommends using oxygen at night due to a “significant deterioration in night vision” at cabin altitudes as low as 5,000 ft. The handbook goes on to say that “flying over terrain with only a few lights makes the runway recede or appear farther away. With this situation, the tendency is to fly a lower-than-normal approach. If the runway has a city in the distance on higher terrain, the tendency is to fly a lower-than-normal approach.” Figure 11 shows the ADS-B ground track for N124TW and the surrounding terrain on final approach into Billings. Due to the Covid-19 pandemic, the National Transportation Safety Board did not travel to the accident site. Local law enforcement and the Federal Aviation Administration (FAA), responded to the accident site, and onsite photographic documentation was accomplished. The airplane impacted trees and rolling terrain about 3/4-mile east of BIL, near the approach end of runway 25. The accident site revealed that the airplane collided with a large tree before it impacted the ground. The wings and engine separated from the airplane during the accident sequence. The debris field was about 200 ft long and on a magnetic heading of about 277o. Multiple propeller blade strikes were found on broken branches near the large tree. All major structural components of the airplane were located within the debris field. The postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event) ## Aircraft - Registration: [N124TW](https://openairdocs.org/deregistered/N124TW-2022-07-30), registration cancelled 2022-07-30, S/N 17265696, built 1975 (OpenAirDocs) - Reported make and model: CESSNA 172 (M) - Registry model: [Cessna 172M](https://openairdocs.org/model/cessna-172m) (registry code 2072418) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17265696 - Year built: 1975 - Engines: Lycoming O-320 reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Donald C Nimmick - Registered owner: Donald C Nimmick - Airworthiness certificate: Standard, Utility; Standard, Normal - Departed: KSHR, Sheridan, WY - Destination: Same as departure - Airport: KBIL, Billings Logan International Airport, runway 25, 5,501 × 75 ft, asphalt - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 74; injuries: fatal; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; seat: left; restraint: lap only; flight hours: 851 total, 51 in the last 90 days ## Weather - Conditions: Visual (VMC), Night - Wind: 250° at 12 knots - Visibility: 10 statute miles - Temperature: 57 °F, dew point 28 °F - Altimeter: 29.60 inHg - Turbulence: Unknown - Observed at: KBIL, 1 nm away - METAR: SPECI KBIL 310117Z 24014KT 10SM FEW090 FEW130 SCT200 14/M02 A2960 RMK AO2 T01391022= ## 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 20201030018649A](https://openairdocs.org/incident/20201030018649A), Oct 30, 2020: Cessna 172M, Billings, MT, Destroyed, 1 fatal. N124TW departed sheridan Wyoming with a destination of three forks Montana. This was the last leg of a VFR flight. Approximately 55-60 southwest of Billings… ## Docket (20 files) The files NTSB released with the investigation on March 16, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102218. 102 MB in all. - Security video (item 1, MP4, 84.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12283660&FileExtension=mp4&FileName=2020_10_30__19_02_25_000__ProConnect_18198AJRNAEA_SOUTH_VIEW_b9967_-Rel.mp4 - Photo array-google earth flight track images (item 2, PDF, 5 pages, 862 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14790485&FileExtension=pdf&FileName=Photo%20Array-GE%20Flight%20Track%20Images-Rel.pdf - Photo array-accident site, courtesy of the FAA (item 3, PDF, 5 pages, 528 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15077302&FileExtension=pdf&FileName=Photo%20Array-Accident%20Site%20FAA-Rel.pdf - ADS-B raw data (item 4, PDF, 62 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14790674&FileExtension=pdf&FileName=20201030_A0644C_439189353_ADSB2pdf-Rel.pdf - NTSB wreckage examination summary (item 5, PDF, 8 pages, 9 photos, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14744572&FileExtension=pdf&FileName=WPR21LA032%20Wreckage%20Examination%20Summary%20Report-Rel.pdf - Record of memorandum b nimmick (item 6, PDF, 1 page, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14954044&FileExtension=pdf&FileName=Record%20of%20Memorandum-B%20Nimmick-Rel-Rel.pdf - Fuel receipt (item 7, PDF, 1 page, 670 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14954312&FileExtension=pdf&FileName=Fuel%20Receipts%20Oct%2030%202020_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-textron aviation (item 8, PDF, 1 page, 199 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14744747&FileExtension=pdf&FileName=Party%20Form-Textron%20Aviation_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation-lycoming (item 9, PDF, 11 pages, 245 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14744930&FileExtension=pdf&FileName=Party%20Form-Lycoming_Redacted-Rel.pdf - Weather factual report (item 10, PDF, 23 pages, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11798166&FileExtension=pdf&FileName=WPR21LA032_weatherfactualSuffernfinal-Rel.pdf - Weather attachment 1 (item 11, PDF, 1 page, 106 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11798176&FileExtension=pdf&FileName=attachment1_Pireps-Rel.pdf - Weather attachment 2 (item 12, PDF, 7 pages, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11798659&FileExtension=pdf&FileName=attachment2_GFAimagedata-Rel.pdf - Weather attachment 3 (item 13, PDF, 642 pages, 581 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11798296&FileExtension=pdf&FileName=attachment3_KBIL%2010-31-2020%200104UTC-Rel.pdf - Weather attachment 4 (item 14, XLSX, 219 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11798395&FileExtension=xlsx&FileName=attachment4_KBIL%2010-31-2020%200104UTC%20Winds-Rel.xlsx - FAA accident package ATC transcript excerpt (item 15, PDF, 5 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15164812&FileExtension=pdf&FileName=FAA%20Accident%20Package%20ATC%20Transcript%20Excerpt-Rel.pdf - Airplane performance study (item 16, PDF, 14 pages, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13135745&FileExtension=pdf&FileName=WPR21LA032_airplane_performance_study_v2-Rel.pdf - Toxicology report (item 17, PDF, 1 page, 180 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14744910&FileExtension=pdf&FileName=Tox1_Redacted-Rel.pdf - Memorandum of record-autopsy report summary (item 18, PDF, 1 page, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14749164&FileExtension=pdf&FileName=MOR%20Autopsy-Rel.pdf - NTSB medical factual report (item 19, PDF, 3 pages, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14790495&FileExtension=pdf&FileName=WPR21FA032_Medical%20Factual%20Report-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 20, PDF, 1 page, 183 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14744776&FileExtension=pdf&FileName=N124TW%20Wreckage%20Release%20Form%20Signed%2011%2018%2021_Redacted-Rel.pdf 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.