# NTSB CEN18FA023: Beech V35B, N777PH, Alva, OK, November 4, 2017

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: November 4, 2017, 17:28 local (22:28 UTC)
- Place: Alva, OK
- Coordinates: 36.787776, -98.670555
- Nearby events: https://openairdocs.org/map.md?lat=36.7878&lon=-98.6706&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach: Miscellaneous/other](https://openairdocs.org/ntsb-events/900)
- Highest injury: Fatal
- Injuries: 2 fatal
- Status: Completed, report May 29, 2019
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: Flight Standards District Office, Textron Aviation, Continental Motors, American Bonanza Society
- NTSB case key (mKey): 96285
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18FA023
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96285/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96285
- Page: https://openairdocs.org/ntsb/CEN18FA023

## Probable cause

The flight instructor's and pilot's failure to recognize that a high descent rate had developed on short final, likely due to their distraction by an open engine cowling, and the unexpected strong pitch-down force during flap extension due to the installation in the airplane of a Short Takeoff and Landing system.

## Findings

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

- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Instructor/check pilot (probable cause); cases with it: [Beech V35B, 16 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=1151548), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Beech V35B, 16 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=1151548), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Performance/control parameters: pitch control](https://openairdocs.org/ntsb-findings/01062022): Aircraft › Aircraft oper/perf/capability · Design (probable cause); cases with it: [Beech V35B, 1 case](https://openairdocs.org/ntsb-findings/01062022/cases.md?model=1151548), [All aircraft, 526 cases](https://openairdocs.org/ntsb-findings/01062022/cases.md)
- [Performance/control parameters: descent rate](https://openairdocs.org/ntsb-findings/01062037): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Beech V35B, 1 case](https://openairdocs.org/ntsb-findings/01062037/cases.md?model=1151548), [All aircraft, 242 cases](https://openairdocs.org/ntsb-findings/01062037/cases.md)
- [Info processing/decision: understanding/comprehension](https://openairdocs.org/ntsb-findings/02041515): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Beech V35B, 1 case](https://openairdocs.org/ntsb-findings/02041515/cases.md?model=1151548), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/02041515/cases.md)
- [Info processing/decision: understanding/comprehension](https://openairdocs.org/ntsb-findings/02041515): Personnel issues › Action/decision · Instructor/check pilot (probable cause); cases with it: [Beech V35B, 1 case](https://openairdocs.org/ntsb-findings/02041515/cases.md?model=1151548), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/02041515/cases.md)
- [Aircraft](https://openairdocs.org/ntsb-findings/01030000): Aircraft › Aircraft structures · Inadequate inspection (probable cause); cases with it: [Beech V35B, 2 cases](https://openairdocs.org/ntsb-findings/01030000/cases.md?model=1151548), [All aircraft, 72 cases](https://openairdocs.org/ntsb-findings/01030000/cases.md)
- [Info processing/decision: identification/recognition](https://openairdocs.org/ntsb-findings/02041510): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Beech V35B, 2 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md?model=1151548), [All aircraft, 559 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md)
- [Info processing/decision: identification/recognition](https://openairdocs.org/ntsb-findings/02041510): Personnel issues › Action/decision · Instructor/check pilot (probable cause); cases with it: [Beech V35B, 2 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md?model=1151548), [All aircraft, 559 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md)
- [Inspection: preflight inspection](https://openairdocs.org/ntsb-findings/02061510): Personnel issues › Task performance · Pilot; cases with it: [Beech V35B, 3 cases](https://openairdocs.org/ntsb-findings/02061510/cases.md?model=1151548), [All aircraft, 551 cases](https://openairdocs.org/ntsb-findings/02061510/cases.md)

## Sequence of events

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

- [Approach: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338); cases with it: [Beech V35B, 2 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=1151548), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md)
- [Approach: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) (defining event); cases with it: [Beech V35B, 3 cases](https://openairdocs.org/ntsb-events/900/sequence.md?model=1151548), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md)
- [Approach-VFR pattern final: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Beech V35B, 20 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1151548), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The private pilot had recently purchased the Bonanza airplane, which he and an experienced flight instructor were using to conduct his first training flight in a Bonanza. During a visual approach, the engine's left cowling opened. According to the pilot, who initially survived the accident, the flight instructor assumed control of the airplane. Based on video from home surveillance cameras, the descent rate for the approach increased to about 1,000 ft per minute about 100 ft above ground level. About 7 seconds later, the airplane impacted trees and a power line located 1/2 mile from the runway threshold. The airplane was one of three Bonanza airplanes modified with a Robertson Short Takeoff and Landing (STOL) system. The flight characteristics for this modification included a strong pitch-down force while extending the flap from 15° to 30° position, which is greater than in Bonanzas without this STOL system. The investigation could not determine if the pilot or flight instructor was aware of this unique flight characteristic, which was not described in the STOL certification information. The pilot had compiled a list of airplane discrepancies, which included "cowling latch - pilot's side rear spring." It is likely a latch for the left engine cowling opened in flight because it was not properly secured during the preflight. The flight instructor and pilot were likely distracted by the open engine cowling and did not expect the strong pitch-down force during flap extension, which resulted in a high descent rate on short final.

## Factual narrative

The airplane, serial number D-9544, was issued a standard airworthiness certificate on October 17, 1973. The airplane was equipped with a Continental IO-520-BA10 engine, serial number 241368-R, and a three-bladed McCauley propeller. The airplane's last annual inspection occurred on May 1, 2017, at a total airframe time of 1,927.7 hours. A second control yoke was installed before the accident flight. In 1979, a Robertson Short Takeoff and Landing (STOL) system was installed in accordance with Supplemental Type Certificate (STC) SA503NW. The modification included removal of the ailerons; installation of full-span, single-slotted flaps; and installation of a spoiler roll control system. Flap positions for the STC modification were 0°, 15°, and 30°. The airplane was one of only three Bonanza airplanes modified by the STC. A handwritten list of airplane discrepancies, with penmanship matching entries in the pilot's logbook, was found in the pilot's hangar. One of the listed discrepancies was "cowling latch - pilot's side rear spring." A review of cowling latch part information indicated that each latch had two springs. One spring returned the latch jaws to the closed position when the bayonet fittings were pushed into the latch, and one spring exerted tension on the latch mechanism. The airplane flight manual contained the following information concerning the engine cowlings: The Bonanza is equipped with Hartwell latch mechanisms on the right and left upper engine cowling for quick and easy access to the engine compartments without the aid of tools. Each cowl latch (two per cowl) is locked and released by a single recessed handle located in the lower cowling panel on each side of the engine. To close the cowling, lower the cowling to the closed position with the handle in the prelatch position. The handle has three positions: flush with the fuselage is latched; held fully forward is unlatched; approximately 90° to the fuselage is prelatch (ready to close cowl). An audible click denotes the bayonet fittings, located forward and aft on the upper cowl, sliding into the latch safety catch. The cowl is locked by moving the latch handle to the full recessed position. The security of the forward latches can be checked by pulling out on the check tab attached to the lower forward edge of the upper cowling. If the cowling can be moved after latching, open the cowling, check the latch alignment and re-latch. A video of an exemplar engine cowling being shut and photographs of an exemplar engine cowling, latches, and bayonet fittings, are included in the docket for this investigation. In 1995, Beechcraft released a Safety Communique, which stated, in part, the following: Beech Aircraft Corporation continues to receive reports of accidents following the opening of a cabin door, baggage door, engine cowling, or fuel cap during takeoff or flight. In many cases, the pilot failed to make certain the cabin door, baggage door, engine cowling, or fuel cap was properlylatched and secured during pre-flight. In each accident, the pilot also failed to properly control the airplane and the airplane stalled at low altitude. THESE ACCCIDENTS SHOULD NOT HAPPEN! If a cabin door, baggage door, or engine cowling is not properly latched and secured, it will usually open during takeoff immediately before or at rotation, although there have been reports of unlatched doors and engine cowlings opening in cruise flight. On some models, additional noise is to be expected. Do not permit yourself to be distracted. ALWAYS MAINTAIN CONTROL OF THE AIRPLANE. On November 4, 2017, at 1728 central daylight time, a Beech V35B (Bonanza) airplane, N777PH, impacted terrain during approach to Alva Regional Airport (AVK), Alva, Oklahoma. The pilot and flight instructor were fatally injured, and the airplane was destroyed. The airplane was registered to the pilot who was operating it under the provisions of Title 14 Code of Federal Regulations Part 91 . Day visual meteorological conditions prevailed and no flight plan was filed for the local instructional flight, which departed AVK about 1710. According to a state trooper who spoke with the pilot at an emergency room, the pilot and flight instructor flew to Cherokee Municipal Airport, Cherokee, Oklahoma, for a practice approach and were returning to AVK when the accident occurred. The pilot stated that he and the flight instructor noticed that the left engine cowling had "popped up" during the approach to AVK. Subsequently, the flight instructor assumed control of the airplane. About 1/2 mile before reaching the runway 18 threshold, the airplane collided with trees and a power line, which were about 40 ft higher than the airport's elevation. The airplane came to rest inverted on its left side, and a postcrash fire ensued. The pilot and flight instructor egressed the airplane with their clothes on fire. The flight instructor was unable to move away from the wreckage during the postcrash fire and subsequent explosion and died at the accident site. The pilot climbed a hill next to the airplane, and responders helped him extinguish his burning clothes. The pilot was taken to an emergency room near the accident site and subsequently transported to the Integris Burn Center, Oklahoma City, Oklahoma, with burns on over 80% of his body. The pilot died on November 7, 2017, from the injuries he sustained. A segment of the final approach was captured by five home surveillance video cameras, and a video study was conducted, which confirmed that the left engine cowling was open during the final approach. During a 12-second period that corresponded to 1,500 ft of ground track, the airplane descended from about 250 ft to about 100 ft above ground level, and the airspeed decreased from 76 ± 4 knots to 71 ± 4 knots. The landing gear was extended and the flap positions could not be determined. At the end of the 12-second period, as the airplane approached the accident site, the descent rate increased to about1,000 ft per minute. The Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, performed an autopsy on the flight instructor and attributed his death to "smoke inhalation and thermal burns." The FAA's Bioaeronautical Research Sciences Laboratory Oklahoma City, Oklahoma, performed toxicology tests on the flight instructor. The results were negative for all tests conducted. The Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, performed an autopsy on the pilot and attributed his death to thermal injuries. The FAA's Bioaeronautical Research Sciences Laboratory performed toxicology tests on the pilot. Therapeutic levels of morphine, which is commonly prescribed in an emergency medical setting, were detected. Flight Instructor The flight instructor, age 61, held commercial pilot and flight instructor certificates with airplane single- and multiengine land and instrument ratings. On his most recent Federal Aviation Administration (FAA) airman medical application, dated May 15, 2017, the flight instructor reported 2,529 hours of civil flight experience with 110 hours in the previous 6 months. On an insurance application dated May 1, 2017, the flight instructor reported 11,456 hours of total flight experience, which included his military flight experience. The flight instructor owned a Beech Bonanza airplane and frequently trained in them. Pilot The pilot, age 39, held a private pilot certificate with an airplane single-engine land rating. The pilot was issued a third-class medical certificate with no limitations on September 10, 2014. A logbook review revealed that the pilot had accumulated 231 flight hours as of June 1, 2017. The pilot had recently purchased the airplane and chose to receive training from the flight instructor based on the instructor's strong teaching reputation with Bonanza airplanes. The accident occurred during the pilot's first training flight and second flight overall in the accident airplane. STOL Modification In 2005, the American Bonanza Society (ABS) published an article describing the characteristics of a Robertson STOL-converted airplane. The owner of a Bonanza airplane with a STOL conversion wrote the article, which stated, in part, the following: Important handling characteristics: the modification provides a unique blend of speed, climb performance, STOL, and long legs, but the STOL modification brings some important handling characteristics. Most notable are larger trim changes with flap extension, needing full nose up trim, now 21 degrees, for landing at forward CG [center of gravity] with full (30 degrees) flaps. Following the accident, the author of the ABS article flew his STOL-converted airplane with another experienced Bonanza pilot who had never flown one with a STOL conversion. When the flap position was changed from 15° to 30°, the latter pilot commented that a much more pronounced pitch-down force occurred compared to a conventional Bonanza and that more pitch trim was required to offsetthe change in flap position. When the flaps were lowered from 15° to 30° without the pilots making a corresponding control input or trim adjustment, the airplane subsequently pitched down to about 20°, and the vertical airspeed increased to more than 1,500 ft per minute in about 5 seconds. Evidence indicates that the airplane impacted a tree, followed by a power line, before coming to rest inverted in a shallow wash adjacent to a steep hill. Most of the fuselage and the right wing were consumed by fire, and several trees near the accident site were burned. Examination revealed that the flight control cables were continuous from end to end. The cables had separated from the cockpit controls and empennage flight surfaces due to melting of the structure at the cable ends. The aileron bellcranks were intact with the control cables attached. The elevator trim actuator was not located in the wreckage. The left-wing flap was found extended 30°, and the landing gear were extended. Two control yokes were found in the wreckage. The engine was lying on its left side with the main wreckage. All six cylinders remained attached to the crankcase, and the magnetos remained attached to their respective mounting positions. The magneto housings and internal components were thermally damaged. The top spark plugs were removed and exhibited normal wear when compared to the Champion Check-A-Plug chart. The fuel pump exhibited thermal and impact damage. The drive coupling was fractured, and the fuel pump would not turn by hand. The fuel pump was disassembled, and the internal components were thermally damaged. The fuel manifold valve had separated from its mount and exhibited severe thermal damage. The fuel nozzles were removed and were free of debris. The cylinder combustion chambers were examined with a lighted borescope with no anomalies noted. As the crankshaft was manually rotated, thumb compression was obtained on all six cylinders, and continuity was established to the accessory gears. The muffler did not exhibit any breaches or signs of external sooting. The propeller governor was removed, and the control arm rotated freely by hand from stop to stop. The propeller governor drive rotated freely, and oil was discharged when rotated by hand. The propeller remained attached to the crankshaft propeller flange and exhibited thermal damage. One blade was relatively straight, the second blade was bent aft near the blade hub, and a third blade exhibited "S" bending. Examination of the engine and flight control system revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Three of the four engine cowling latches and three of the four bayonet fittings were recovered from the wreckage. Both left cowling latches were partially melted by postcrash fire. The right forward cowling latch remained attached to the structure and exhibited minimal fire damage. The rear half of the right cowling access doorframe was consumed bypostcrash fire. None of the three cowling latches recovered were engaged by a bayonet fitting. Two of the recovered bayonet fittings had their mounting brackets attached, but they were not attached to a cowling access door. Based on the design of the brackets, these two bayonet fittings were determined to be the forward bayonet fittings. The third bayonet fitting, an aft fitting, was found attached to a portion of a melted cowling access door. It could not be determined if the third bayonet fitting was from the left or right side of the engine. The exterior handles on both sides of the engine cowlings were found in the latched position.

## Aircraft

- Registration: [N777PH](https://openairdocs.org/deregistered/N777PH-2021-03-06), registration cancelled 2021-03-06, S/N D-9544, built 1973 (OpenAirDocs)
- Reported make and model: BEECH V35B
- Registry model: [Beech V35B](https://openairdocs.org/model/beech-v35b) (registry code 1151548) (OpenAirDocs)
- Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: D-9544
- Year built: 1973
- Airframe hours: 1927
- Engines: Continental Motors IO-520-BA10 285 horsepower reciprocating
- Damage: Destroyed
- Fire: On-Ground
- Flight: Instructional, Part 91
- Airworthiness certificate: Standard, Utility
- Last inspection: Annual, May 1, 2017
- Departed: AVK, ALVA, OK
- Destination: AVK, ALVA, OK
- Airport: AVK, Alva Rgnl, runway 18, 5,001 × 75 ft, concrete
- Equipment: Stall warning system, Auto-pilot

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Flight instructor; age 61; injuries: fatal; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: right; toxicology performed; flight hours: 11,456 total, 1,302 in this make and model
- Pilot; age 39; injuries: serious; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; seat: left; toxicology performed; flight hours: 231 total, 1 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 4 knots
- Visibility: 10 statute miles
- Lowest ceiling: 20,000 ft broken
- Temperature: 63 °F, dew point 52 °F
- Altimeter: 29.79 inHg
- Observed at: KWDG, 48 nm away

## 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 20171104018209A](https://openairdocs.org/incident/20171104018209A), Nov 4, 2017: Beech V35B, Alva, OK, Destroyed, 2 fatal. On 11/04/2017, at appx. 1700 hrs CDT, acft N777PH (Beechcraft V35B) took off from Alva, OK (kavk) enroute to cherokee, OK, then back to kavk. At 1728 hrs CDT,…

## Docket (16 files)

The files NTSB released with the investigation on March 25, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96285. 23.2 MB in all.

- Witness Statement (item 1, .PDF, 166 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471359&FileExtension=.PDF&FileName=Witness%20Statement-Master.PDF
- Robertson STOL Conversion Brochure (item 2, .PDF, 904 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471360&FileExtension=.PDF&FileName=Robertson%20STOL%20Conversion%20Brochure-Master.PDF
- American Bonanza Society (ABS) Article on STOL Modified Airplane (item 3, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471361&FileExtension=.PDF&FileName=American%20Bonanza%20Society%20(ABS)%20Article%20on%20STOL%20Modified%20Airplane-Master.PDF
- STOL vs. Conventional Bonanza - Correspondence with ABS Article Author (item 4, .PDF, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471362&FileExtension=.PDF&FileName=STOL%20vs.%20Conventional%20Bonanza%20-%20Correspondence%20with%20ABS%20Article%20Author-Master.PDF
- List of Airplane Discrepancies Found in Pilot's Hangar (item 5, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471363&FileExtension=.PDF&FileName=List%20of%20Airplane%20Discrepancies%20Found%20in%20Pilot%27s%20Hangar-Master.PDF
- Excerpt of Pilot's Logbook (item 6, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471364&FileExtension=.PDF&FileName=Excerpt%20of%20Pilot%27s%20Logbook-Master.PDF
- Google Earth View of Accident Site (item 7, .PDF, 1 photo, 92 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471365&FileExtension=.PDF&FileName=Google%20Earth%20View%20of%20Accident%20Site-Master.PDF
- Photos of Wreckage (item 8, .PDF, 9 photos, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471366&FileExtension=.PDF&FileName=Photos%20of%20Wreckage-Master.PDF
- Toxicological Report - Flight Instructor (item 9, .PDF, 105 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471367&FileExtension=.PDF&FileName=Toxicological%20Report%20-%20Flight%20Instructor-Master.PDF
- Toxicological Report - Pilot (item 10, .PDF, 105 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471368&FileExtension=.PDF&FileName=Toxicological%20Report%20-%20Pilot-Master.PDF
- NTSB Video Study (item 11, .PDF, 3 photos, 490 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471369&FileExtension=.PDF&FileName=NTSB%20Video%20Study-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 12, .PDF, 530 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471370&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF
- Release of Aircraft Wreckage (item 13, .PDF, 328 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471371&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage-Master.PDF
- Safety Communique - Fly the Airplane (item 14, .PDF, 90 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471372&FileExtension=.PDF&FileName=Safety%20Communique%20-%20Fly%20the%20Airplane-Master.PDF
- Photos of Exemplar Engine Cowling, Latch and Bayonet Fitting (item 15, .PDF, 4 photos, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471373&FileExtension=.PDF&FileName=Photos%20of%20Exemplar%20Engine%20Cowling,%20Latch%20and%20Bayonet%20Fitting-Master.PDF
- Video of Exemplar Cowling Latch Operation (item 16, MOV, 13.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471374&FileExtension=mov&FileName=Video%20of%20Exemplar%20Cowling%20Latch%20Operation-Master

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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