# NTSB DEN93FA099: Piper PA-32-300, N479KC, Delight, AR, August 6, 1993 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: August 6, 1993, 11:40 local (16:40 UTC) - Place: Delight, AR - Coordinates: 34.020004, -93.499946 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.0200&lon=-93.4999&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 6 fatal - Status: Completed, report June 22, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 11084 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN93FA099 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/11084/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=11084 - Page: https://openairdocs.org/ntsb/DEN93FA099 ## Probable cause THE FAILURE OF THE VACUUM PUMP, AND AN INOPERATIVE TURN COORDINATOR. FACTORS WHICH CONTRIBUTED TO THE ACCIDENT WERE: THE PILOT'S LOSS OF CONTROL OF THE AIRPLANE AS A RESULT OF SPATIAL DISORIENTATION, THE PILOT EXCEEDING THE DESIGN STRESS LIMITS OF THE AIRPLANE, AND THE WEATHER CONDITIONS (CLOUDS). ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - normal - engine accessories,vacuum pump - failure,total (cause) - flight/nav instruments,turn and bank indicator - inoperative (cause) - Loss of control - in flight, maneuvering - weather condition - clouds (contributing factor) - aircraft control - uncontrolled, pilot in command (contributing factor) - spatial disorientation, pilot in command (contributing factor) - design stress limits of aircraft - exceeded, pilot in command (contributing factor) - In flight collision with terrain/water, descent - uncontrolled ## Analysis AFTER BEING CLEARED FOR THE LOCALIZER APPROACH TO THE TEXARKANA AIRPORT, THE PILOT CANCELLED HIS IFR FLIGHT PLAN, AND SAID HE WOULD PROCEED VFR TO NASHVILLE, AR. SHORTLY THEREAFTER, THE PILOT REPORTED HE WAS IN THE CLOUDS AND THAT HE HAD LOST HIS VACUUM, THE TURN COORDINATOR DID NOT WORK, AND HE WAS ON THE VERGE OF VERTIGO. THE CONTROLLER ATTEMPTED TO VECTOR THE PILOT BACK TO TEXARKANA, BUT NOTED HE WAS HAVING DIFFICULTY HOLDING A HEADING. THE AIRPLANE BROKE UP IN FLIGHT. THE LEFT WING SPAR WAS FOUND TWISTED UP AND AFT, THE RIGHT WING SPAR WAS BENT SLIGHTLY DOWN AND AFT, AND THE VERTICAL STABILIZER SPAR WAS BENT AFT. LABORATORY EXAMINATION OF THE VACUUM PUMP REVEALED THE DRIVE SHAFT HAD SHEARED IN TORSION, THE ROTOR HAD BROKEN IN OVERSTRESS, AND THE VANES WERE WORN. IT COULD NOT BE DETERMINED IF THE INOPERATIVE TURN COORDINATOR, WHICH HAD AN ELECTRICAL IMPEDANCE OF 10,000 OHMS, HAD FAILED PRIOR TO OR ON THE ACCIDENT FLIGHT. ## Factual narrative HISTORY OF FLIGHT On August 6, 1993, at approximately 1140 central daylight time, a Piper PA-32-300, N479KC, was destroyed when it broke up in flight and impacted terrain about seven miles southeast of Delight, Arkansas. The pilot and five passengers were fatally injured. Visual meteorological conditions prevailed at the site: however, the airplane was in instrument meteorological conditions when contact was lost. An IFR flight plan had been filed. The pilot contacted the McAlester (OK) Flight Service Station via radio at 0924 while in flight and, after receiving a briefing on weather conditions in the Texarkana, Arkansas area, filed an IFR flight plan. At 1035, he requested clearance from the Fort Worth Air Route Traffic Control Center (ARTCC) to descend from 5,000 feet to 4,000 feet "to see if we can make a visual approach into Nashville, Arkansas." The controller said this was not possible due to the minimum vectoring altitudes (MVA) in the area, but cleared him to "cruise" to the Nashville Airport at 5,000 feet. At 1047, after reporting he was still in the clouds and could not see the airport, the pilot was given radar vectors to intercept the localizer course at Texarkana Airport, and was cleared to descend to 2,100 feet. At 1059 the pilot asked, "Can we go ahead and go on our own and get back to Nashville now and go through the clouds. I see a shot where we can make it." He then cancelled his IFR flight plan and radar services were terminated. At 1110, the pilot reported back on the Fort Worth ARTCC frequency and said, "We've lost our vacuum. We're in the clouds. We're in a helluva bind...Nothing's working...My directional gyro I don't believe is working either. It went to spinning awhile ago." The controller attempted to vector him back to the Texarkana Airport, but noted the pilot was having difficulty holding a heading. At 1114, the pilot confirmed he was declaring an emergency. A 1127, another pilot who had been listening to the radio conversation suggested that he use the turn and bank indicator for attitude information. The pilot replied that it "does not work." Shortly thereafter, the pilot said, "I need to get above these clouds. I'm fixin' to get vertigo." He was cleared to 9,000 feet, and acknowledged the clearance at 1138. This was the last known radio communication with the pilot. PERSONNEL INFORMATION Flight times found in this report are based on a photostatic copy of a portion of the pilot's most recent log book. This document contained entries from December 28, 1989, to December 3, 1992, and indicated the pilot had obtained instrument competency checks on March 22, 1992, and March 11, 1993. According to the instructor who administered these checks, partial panel procedures were reviewed and the pilot's performance had been satisfactory. WRECKAGE AND IMPACT INFORMATION Wreckage was strewn through a heavily wooded area for about 1/4 mile on a magnetic heading of 005 degrees. The left wing outboard panel, with the aileron missing, was found on top of a shed in the rear of a residence. Across the street, in the back yard of another residence, was the left wing tip. The left wing inboard panel, with the landing gear still attached, was located in the woods behind this house. The inverted fuselage, with the right wing attached by aileron cables, was found about 1/4 mile away. The separated stabilator, vertical stabilizer, and rudder were in close proximity to the fuselage. The tops of several trees lay on the ground nearby. The left wing spar was twisted up and aft; the right wing spar was bent slightly down and aft. The front spar of the vertical stabilizer was bent aft. TESTS AND RESEARCH The vacuum pump, low vacuum annunciator light, vacuum gauge, and the filter from the gyroscopic artificial horizon vacuum were examined at NTSB's metallurgical laboratory. According to the metallurgist's factual report, the vacuum pump rotor was broken in three pieces "consistent with overstress breaks is castings." The vanes were intact but worn, measuring between 0.58 and 0.62 inch. The vacuum pump drive shaft coupling was fractured. On the engine (drive) side, the fracture was on helical planes "indicative of a brittle torsional separation...There was no evidence of ductility." On the pump (driven) side, there was "post fracture rotational damage...and the resulting shape was conical." The low vacuum annunciator light filament was stretched, "indicative of the filament being hot" on impact. The filter in the gyroscopic artificial horizon filter had two small tears and contained amounts of carbon, oxygen, silicon, sulfur, aluminum, potassium, calcium, and iron deposits. The vacuum gauge bore no evidence of needle indicator marks on its face. The turn coordinator was examined at AMR Combs, Denver, Colorado. Despite impact damage to the instrument, the turn needle and gyroscope were free to turn, but the slip tube glass was broken and the ball was missing. An electrical impedance test disclosed a 10,000 ohm resistance. It could not be determined if this resistance was a preexisting condition or the result of impact. ADDITIONAL INFORMATION The wreckage was released on August 7, 1993, and the turn coordinator, filter from the gyroscopic artificial horizon, and the vacuum pump, gauge, and annunciator light were released on January 26, 1994, to the John Ashford Company, Sherman, Texas. ## Aircraft - Registration: [N479KC](https://openairdocs.org/deregistered/N479KC-2012-09-20), registration cancelled 2012-09-20, S/N 32-7840019 (OpenAirDocs) - Reported make and model: PIPER PA-32-300 - Registry model: [Piper PA-32-300](https://openairdocs.org/model/piper-pa-32-300) (registry code 7103212) (OpenAirDocs) - Category: Airplane - Serial number: 32-7840019 - Airframe hours: 2497 - Engines: LYCOMING IO-540-K1G5D 300 horsepower reciprocating - Damage: Destroyed - Flight: Business, Part 91 - Registered owner: Mcglaughlin, Earl W. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 12, 1993, 67 hours before - Departed: LNK, LINCOLN, NE - Destination: M77, NASHVILLE, AR - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 628 total, 29 in this make and model, 415 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 8 knots - Visibility: 5 statute miles - Lowest ceiling: 1,300 ft broken - Temperature: 81 °F, dew point 73 °F - Altimeter: 29.00 inHg - Observed at: TXK, 40 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 19930806028069A](https://openairdocs.org/incident/19930806028069A), Aug 6, 1993: Piper PA32300, Delight, AR, Destroyed, 6 fatal. Cancelled IFR after approach to txk proceed VFR to M77. Entered. Cloud lost vacuum. Lost control. Broke up inflight ## Docket (38 files) The files NTSB released with the investigation on June 3, 1995, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=11084. 4.3 MB in all. - Supplement A (item 1, .PDF, 237 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004686&FileExtension=.PDF&FileName=Supplement%20A-Master.PDF - Supplement B (item 2, .PDF, 375 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004687&FileExtension=.PDF&FileName=Supplement%20B-Master.PDF - Supplement K (item 3, .PDF, 420 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004688&FileExtension=.PDF&FileName=Supplement%20K-Master.PDF - Supplement S (item 4, .PDF, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004689&FileExtension=.PDF&FileName=Supplement%20S-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2 (item 5, .PDF, 648 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004690&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%2F2-Master.PDF - Factual Report from NTSB Metalurgy Lab (item 6, .PDF, 82 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40379159&FileExtension=.PDF&FileName=Factual%20Report%20from%20NTSB%20Metalurgy%20Lab-Redacted.PDF - Photo 1. Overall view of components as received. (item 7, .PDF, 25 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004692&FileExtension=.PDF&FileName=Photo%201.%20%20Overall%20view%20of%20components%20as%20received.-Master.PDF - Photo 2. view of vacuum pump internal rotor and vanes after removal of pump back arrowed "p" in figure 1, X2 (item 8, .PDF, 36 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004693&FileExtension=.PDF&FileName=Photo%202.%20%20view%20of%20vacuum%20pump%20internal%20rotor%20and%20vanes%20after%20removal%20of%20pump%20back%20arrowed%20%22p%22%20in%20figure%201,%20X2-Master.PDF - Photo 3. Closeup of bulb from low vacuum warning annunciator light, arrowed "b" in figure 1. X10 (item 9, .PDF, 27 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004694&FileExtension=.PDF&FileName=Photo%203.%20%20Closeup%20of%20%20bulb%20from%20low%20vacuum%20warning%20annunciator%20light,%20arrowed%20%22b%22%20in%20figure%201.%20X10-Master.PDF - Photo 4A. View left X4 and right X10, of Gyroscopic artificial horizon vaccum filter arrowed "f" in figure 1. (item 10, .PDF, 21 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004695&FileExtension=.PDF&FileName=Photo%204A.%20%20%20View%20left%20X4%20and%20right%20X10,%20of%20Gyroscopic%20artificial%20horizon%20vaccum%20filter%20arrowed%20%22f%22%20in%20figure%201.-Master.PDF - Photo 4B. Two views, left X4 and right X10, of Gyroscopic artificial horizon vacuum filter arrowed "f" in figure 1. (item 11, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004696&FileExtension=.PDF&FileName=Photo%204B.%20%20Two%20views,%20left%20X4%20and%20right%20X10,%20of%20Gyroscopic%20artificial%20horizon%20vacuum%20filter%20arrowed%20%22f%22%20in%20figure%201.-Master.PDF - Photo 5A. Views of separated drive shaft coupling on the pump side. Left view looking directly toward pump and right view is inclined to show coning. (item 12, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004697&FileExtension=.PDF&FileName=Photo%205A.%20%20Views%20of%20separated%20drive%20shaft%20coupling%20on%20the%20pump%20side.%20%20Left%20view%20looking%20directly%20toward%20pump%20and%20right%20view%20is%20inclined%20to%20show%20coning.-Master.PDF - Photo 5B. View of separated drive shaft coupling on the pump side. Left view looking toward pump and right view is inclined to show coning. (item 13, .PDF, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004698&FileExtension=.PDF&FileName=Photo%205B.%20%20View%20of%20separated%20drive%20shaft%20coupling%20on%20the%20pump%20side.%20%20Left%20view%20looking%20toward%20pump%20and%20right%20view%20is%20inclined%20to%20show%20coning.-Master.PDF - Photo 6A. View of separated drive shaft coupling on the engine side. Left side looking directly toward engine and right view is inclined to show helical fracture planes. (item 14, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004699&FileExtension=.PDF&FileName=Photo%206A.%20%20View%20of%20separated%20drive%20shaft%20coupling%20on%20the%20engine%20side.%20Left%20side%20looking%20directly%20toward%20engine%20and%20right%20view%20is%20inclined%20to%20show%20helical%20fracture%20planes.%20-Master.PDF - Photo 6B. View of separated drive shaft coupling on the engine side. Left view looking directly toward engine and right view is inclined to show helical fracture planes. (item 15, .PDF, 29 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004700&FileExtension=.PDF&FileName=Photo%206B.%20%20View%20of%20separated%20drive%20shaft%20coupling%20on%20the%20engine%20side.%20Left%20view%20looking%20directly%20toward%20engine%20and%20right%20view%20is%20inclined%20to%20show%20helical%20fracture%20planes.-Master.PDF - Photo 7. Higher magnification inclined view of separated drive shaft on the engine side with the coupling rotated somewhat form the position shown in right view in figure 6. (item 16, .PDF, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004701&FileExtension=.PDF&FileName=Photo%207.%20%20Higher%20magnification%20inclined%20view%20of%20separated%20drive%20shaft%20on%20the%20engine%20side%20with%20the%20coupling%20rotated%20somewhat%20form%20the%20position%20shown%20in%20right%20view%20in%20figure%206.-Master.PDF - Photo 8. SEM view of the origin area indicated by bracket "01" in figure 7. x 18.6 (item 17, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004702&FileExtension=.PDF&FileName=Photo%208.%20%20SEM%20view%20of%20the%20origin%20area%20indicated%20by%20bracket%20%2201%22%20in%20figure%207.%20%20x%2018.6-Master.PDF - Photo 9A. SEM photograph of main origin area, arrowed "0" on drive shaft coupling. (item 18, .PDF, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004703&FileExtension=.PDF&FileName=Photo%209A.%20%20SEM%20photograph%20of%20main%20origin%20area,%20arrowed%20%220%22%20on%20drive%20shaft%20coupling.%20-Master.PDF - Photo 9B. SEM photograph of main origin area, arrowed "0" on drive shaft coupling. (item 19, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004704&FileExtension=.PDF&FileName=Photo%209B.%20%20SEM%20photograph%20of%20main%20origin%20area,%20arrowed%20%220%22%20on%20drive%20shaft%20coupling.-Master.PDF - Photo 9C. SEM photograph of main origin area, arrowed "0", on drive shaft coupling.. (item 20, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004705&FileExtension=.PDF&FileName=Photo%209C.%20%20SEM%20photograph%20of%20main%20origin%20area,%20arrowed%20%220%22,%20on%20drive%20shaft%20coupling..-Master.PDF - Photo 9D. Photograph is higher magnification view of area outline by dashed line. (item 21, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004706&FileExtension=.PDF&FileName=Photo%209D.%20%20Photograph%20is%20higher%20magnification%20view%20of%20area%20outline%20by%20dashed%20line.-Master.PDF - Photo 10. Light microscope view of origin area on drive shaft coupling. X20 (item 22, .PDF, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004707&FileExtension=.PDF&FileName=Photo%2010.%20%20Light%20microscope%20view%20of%20origin%20area%20on%20drive%20shaft%20coupling.%20%20X20-Master.PDF - Photo 11. Underside of the engine side portion of the coupling after removing from the drive spline. X4 (item 23, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004708&FileExtension=.PDF&FileName=Photo%2011.%20%20Underside%20of%20the%20engine%20side%20portion%20of%20the%20coupling%20after%20removing%20from%20the%20drive%20spline.%20X4-Master.PDF - Photo 12A. New coupling obtained from Airborne and subjected to torsional overstress to near breakage. X4. (item 24, .PDF, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004709&FileExtension=.PDF&FileName=Photo%2012A.%20%20New%20coupling%20obtained%20from%20Airborne%20and%20subjected%20to%20torsional%20overstress%20to%20near%20breakage.%20%20X4.-Master.PDF - Photo 12B. New coupling obtained from Airborne and subjected to torsional overstress to near breakage. X10 (item 25, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004710&FileExtension=.PDF&FileName=Photo%2012B.%20%20New%20coupling%20obtained%20from%20Airborne%20and%20subjected%20to%20torsional%20overstress%20to%20near%20breakage.%20X10-Master.PDF - Photo 13. Fracture surface of another new coupling overstress fractured in torsion. X4 (item 26, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004711&FileExtension=.PDF&FileName=Photo%2013.%20%20Fracture%20surface%20of%20another%20new%20coupling%20overstress%20fractured%20in%20torsion.%20X4-Master.PDF - Witness Statement, Jerry Mohler (item 27, .PDF, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40379160&FileExtension=.PDF&FileName=Witness%20Statement,%20Jerry%20Mohler-Redacted.PDF - Witness Statement, Kyle Andrews (item 28, .PDF, 12 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004713&FileExtension=.PDF&FileName=Witness%20Statement,%20Kyle%20Andrews-Master.PDF - Maps or Charts of Accident Area, VFR Sectional (item 29, .PDF, 441 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004714&FileExtension=.PDF&FileName=Maps%20or%20Charts%20of%20Accident%20Area,%20VFR%20Sectional-Master.PDF - Weather Reports and Records (item 30, .PDF, 184 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004715&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Reports from Federal Agencies - ATC Transcript (item 31, .PDF, 656 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40379161&FileExtension=.PDF&FileName=Reports%20from%20Federal%20Agencies%20-%20ATC%20Transcript-Redacted.PDF - Photo 1. The left outboard wing panel on roof of shed. (item 32, .PDF, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004717&FileExtension=.PDF&FileName=Photo%201.%20The%20left%20outboard%20wing%20panel%20on%20roof%20of%20shed.-Master.PDF - Photo 2. The left wing tip, found in the backyard of residence. Left outboard wing panel was found behind first residence across street (arrow) (item 33, .PDF, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004718&FileExtension=.PDF&FileName=Photo%202.%20%20The%20left%20wing%20tip,%20found%20in%20the%20backyard%20of%20residence.%20%20Left%20outboard%20wing%20panel%20was%20found%20behind%20first%20residence%20across%20street%20(arrow)-Master.PDF - Photo 3: The left wing and landing gear (item 34, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004719&FileExtension=.PDF&FileName=Photo%203%3A%20%20The%20left%20wing%20and%20landing%20gear-Master.PDF - Photo 4: Trees struck by falling aircraft fuselage (item 35, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004720&FileExtension=.PDF&FileName=Photo%204%3A%20%20Trees%20struck%20by%20falling%20aircraft%20fuselage-Master.PDF - Photo 5. Airplane wreckage (item 36, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004721&FileExtension=.PDF&FileName=Photo%205.%20%20Airplane%20wreckage-Master.PDF - Photo 6. Airplane wreckage (item 37, .PDF, 32 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004722&FileExtension=.PDF&FileName=Photo%206.%20%20Airplane%20wreckage-Master.PDF - Photo 7. Airplane wreckage (item 38, .PDF, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40004723&FileExtension=.PDF&FileName=Photo%207.%20%20Airplane%20wreckage-Master.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.