# NTSB IAD98FA092: Austin Revolution Mini 500, N2XK, Northampton, PA, August 11, 1998 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: August 11, 1998, 18:32 local (22:32 UTC) - Place: Northampton, PA - Coordinates: 40.860851, -75.200958 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.8609&lon=-75.2010&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report September 7, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 47905 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=IAD98FA092 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47905/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=47905 - Page: https://openairdocs.org/ntsb/IAD98FA092 ## Probable cause the improper maintenance adjustment and the failure to properly torque the pitch-change link barrel by the owner/builder which resulted in main rotor to tailboom contact and main rotor separation. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Rotor failure/malfunction, maneuvering - misc rotorcraft,main rotor/tail boom contact - sudden stoppage - maintenance,adjustment - improper, owner/builder (cause) - condition(s)/step(s) in error, owner/pilot mechanic - rotorcraft flight control,pitch change horn - separation - rotorcraft flight control,pitch change rod/link - loose part/bolt/nut/clamp/etc (cause) - In flight collision with terrain/water, descent - uncontrolled ## Analysis The pilot departed his home in the home-built helicopter on a maintenance test flight. The purpose of the flight was to track the main rotor system after repair and re-assembly of the helicopter. The main transmission, transmission mast, main rotor system, and tailboom and associated components had been replaced following a rollover accident. The pilot changed the blade track by adjustment of the pitch change links during ground runs prior to takeoff. Witnesses to the accident reported unusual sounds from the helicopter before two sharp reports and an uncontrolled descent. One main rotor blade was found 400 feet from the main wreckage. Examination of the wreckage revealed rotor to tailboom contact. Fracture separation of one rotor blade and fracture of the pitch horn on the same side were due to overload. The pitch change link barrel was loose on the fractured horn with no torque applied to the barrel nuts. ## Factual narrative HISTORY OF FLIGHT On August 11,1998, at 1832 eastern daylight time, a homebuilt Revolution Mini 500 helicopter, N2XK, was destroyed during collision with terrain following an uncontrolled descent near Northhampton, Pennsylvania. The certificated commercial pilot was fatally injured. Visual meteorological conditions prevailed for the maintenance test flight that originated at Bangor, Pennsylvania, approximately 1800. No flight plan was filed for the flight conducted under 14 CFR Part 91. In a telephone interview, one witness stated his attention was drawn to the helicopter because it sounded unusual. He said the helicopter was maneuvering approximately 200 feet in the air. The witness said: "I saw it circle around but it didn't sound too good. I heard it making these weird noises. It stopped in the air and then turned towards my house. I heard it go 'pow' then another sharp 'snap'. It sounded like a gunshot. Then I saw this piece flying. The helicopter rotated approximately one-quarter turn, the tail came up, the nose dropped, and then the aircraft fell out of sight." In a telephone interview, a second witness said his attention was drawn by the sound. He stated: "It sounded like a helicopter, but it had a funny sound, it had a rat-a-tat-tat sound. I couldn't see it, then I saw him make a right hand turn heading due west gaining altitude. I heard a 'poof-poof'...Just the sounds of the rotors didn't sound normal. I heard the lighter 'pop' and then the louder 'pop'." The witness stated the helicopter then descended behind a tree line out of view. The accident occurred during the hours of daylight approximately 42 degrees, 28 minutes north latitude, and 76 degrees, 8 minutes west longitude. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with ratings for airplane single engine land and sea, multi-engine land, rotorcraft helicopter, and instrument airplane. His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on June 30, 1998. The pilot's family provided copies of the last 5 pages of the pilot's logbook. Examination of the pages revealed a total flight experience of 1,440 hours. The pilot had also accrued 98 hours of helicopter time of which 55 hours were in the accident aircraft. AIRCRAFT INFORMATION The helicopter was purchased as a kit, serial # 303, and was uncrated by the owner on March 26, 1997. The pilot's family provided copies of the helicopter's maintenance records to the FAA. Detailed construction and maintenance records begin March 26, 1997. A stamp dated February 2, 1998, certified an airworthiness certificate was issued for the helicopter on that date. The maintenance records end with an entry on April 11, 1998. However, the pilot's logbook reveals the helicopter flew, and maintenance was performed, between that date and April 20, 1998. A search of the pilot's workshop/hangar by the Safety Board investigator in the presence of the pilot's son and the family attorney revealed no additional maintenance records. According to the family's attorney, continued searches revealed no further maintenance records for N2XK. An examination of Revolution Helicopter Corporation's customer service records revealed that on May 13, 1998, the pilot sent purchase orders and work orders to the company for major drive train and airframe components. In a hand written work order, the pilot said, "[Transmission] mast bent-[Aircraft] suffered rollover damage." Company records further revealed complete overhaul of the main transmission to include replacement of the main rotor mast (bent) and the transmission case. The case was replaced due to elongation of the mount bolt holes. The tail rotor gearbox was also overhauled. The overhaul included the replacement of the gearbox output shaft, which was also bent. Among the parts purchased by the owner for the helicopter were: tailboom, tail rotor driveshaft, main rotor blades, and landing gear skid. The pilot remitted a check for $ 6,250.95 to Revolution Helicopter for "parts for #303" on May 13, 1998. Examination of National Transportation Safety Board records revealed that no accidents were reported for Mini 500, N2XK, between April 20, 1998 and May 13, 1998. On August 12, 1998, a Federal Aviation Administration (FAA) Aviation Safety Inspector visited the location where the helicopter was hangared and maintained. He found the construction manual for the helicopter opened to the section for the rigging and balancing of the rotor system and a copy of the "Revolution Helicopter Airworthiness Directive (AD) #09031997...New Dynamic Main Rotor System Balancing Procedures." According to Revolution Helicopter Corporation, Inc., the AD was "...Urgent (Must Be Complied With Before Further Flight)." The FAA Inspector interviewed the pilot's son regarding any work performed on the helicopter and the purpose of the flight. According to the Inspector's report: "His son informed me that he was assisting his father with rotor tracking by holding the tracking flag and his father was adjusting the blade track with the pitch change links. The son left prior to his father finishing the ground portion of the checks and when he returned the aircraft and his father were gone." METEOROLOGICAL INFORMATION Weather reported at Allentown, Pennsylvania, approximately 15 miles southwest of the accident was: few clouds at 3,000 feet with winds from 270 degrees at 7 knots. WRECKAGE AND IMPACT INFORMATION The wreckage was examined at the site on August 12, 1998, by a team of Federal Aviation Administration (FAA) Aviation Safety Inspectors. All major components were accounted for at the scene. According to one Inspector's statement: "The helicopter wreckage showed a vertical impact where the aircraft wreckage remained within a very confined area. No wreckage was more than a few feet from the fuselage. The only part of the aircraft not within the main fuselage was one main rotor blade that was discovered over 400 feet from the aircraft. Upon further investigation of the crash site, I observed that the pitch horn (a casting) was fractured on one of the main rotor hubs and disconnected. The blade yoke was still attached but only about twelve inches of the blade was attached. This part matched with the blade assembly that was over 400 feet from the wreckage. The rest of the hub assembly was found intact and all control rods and assemblies were attached. The mast showed no signs of mast bumping or deformation. The tailboom assembly and tail rotor assembly showed no signs of main rotor blade contact nor prior damage before impact...the pitch change rod to the hub with the missing main rotor blade was loose and the jam nuts to the rod and bearings were loose and not torqued at all." The FAA forwarded portions of the main rotor system to the NTSB Materials Laboratory in Washington, D.C. for further examination. The remainder of the wreckage was recovered and stored by a colleague of the pilot's. The wreckage was later moved to the NTSB Materials Laboratory in Washington, D.C. for further examination. MEDICAL AND PATHOLOGICAL INFORMATION The FAA Toxicology Accident Research Laboratory, Oklahoma City, Oklahoma performed toxicological testing for the pilot. Test results revealed Verapamil and Noverapamil were detected in the blood and urine. Dr. Samuel Land performed an autopsy on the pilot on August 12, 1998, for the Northampton County Coroner's Office. TESTS AND RESEARCH On October 9, 1998, the fractured main rotor blade and pitch horn were examined in the NTSB Materials Laboratory in Washington, D.C. According to the metallurgist's factual report, examination of the main rotor spar fracture and the pitch horn fracture surfaces revealed evidence typical of overstress fracture with no evidence of fatigue. On January 26, 1999, the engine was exa ## Aircraft - Registration: [N2XK](https://openairdocs.org/deregistered/N2XK-2000-03-31), registration cancelled 2000-03-31, S/N 0303 (OpenAirDocs) - Reported make and model: Austin REVOLUTION MINI 500 (REVOLUTION) - Registry model: [Austin Charles J MINI-500](https://openairdocs.org/model/austin-charles-j-mini-500) (registry code 05605ED) (OpenAirDocs) - Category: Helicopter, amateur-built - Serial number: 303 - Airframe hours: 55 - Engines: Rotax 582 80 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Personal, Part 91 - Registered owner: Charles J. Austin - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, February 2, 1998, 35 hours before - Departed: NONE, BANGOR, PA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; commercial; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; toxicology performed; flight hours: 1,440 total, 55 in this make and model, 1,222 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 63 °F - Altimeter: 29.00 inHg - Observed at: ABE, 15 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 19980811036079A](https://openairdocs.org/incident/19980811036079A), Aug 11, 1998: Amtr MINI500, North Hampton, PA, Destroyed, 1 fatal. (.19)On August 11, 1998, at 1832 eastern daylight time, a homebuilt revolution mini 500 helicopter, N2XK, was destroyed during collision with terrain following… ## Docket (15 files) The files NTSB released with the investigation on March 22, 2000, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=47905. 2.7 MB in all. - Supplement A (item 1, .PDF, 227 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120440&FileExtension=.PDF&FileName=Supplement%20A-Master.PDF - Supplement B (item 2, .PDF, 341 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120441&FileExtension=.PDF&FileName=Supplement%20B-Master.PDF - Summary of Witness Interviews (item 3, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423785&FileExtension=.PDF&FileName=Summary%20of%20Witness%20Interviews-Redacted.PDF - Witness Statements (item 4, .PDF, 183 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423786&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF - FAA Inspector's Statement (item 5, .PDF, 186 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120444&FileExtension=.PDF&FileName=FAA%20Inspector%27s%20Statement-Master.PDF - Work Order Request Forms with Parts List (item 6, .PDF, 318 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423787&FileExtension=.PDF&FileName=Work%20Order%20Request%20Forms%20with%20Parts%20List-Redacted.PDF - Materials Laboratory Factual Report (2) (item 7, .PDF, 855 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423788&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%20(2)-Redacted.PDF - Material from under bolt in tail boom (5x) Fibers typical of fiber glass matting, blue discoloration on surface, brown coating, paint chips - white (NTSB Mat Lab) (item 8, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120453&FileExtension=.PDF&FileName=Material%20from%20under%20bolt%20in%20tail%20boom%20(5x)%20%20Fibers%20typical%20of%20fiber%20glass%20matting,%20blue%20discoloration%20on%20surface,%20brown%20coating,%20paint%20chips%20-%20white%20(NTSB%20Mat%20Lab)-Master.PDF - Fractured edge of main rotor blade (5x) Fibers of fiber glass matting same size as above from bolt, blue discoloration, brown coating, paint-white (NTSB Mat Lab) (item 9, .PDF, 36 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120454&FileExtension=.PDF&FileName=Fractured%20edge%20of%20main%20rotor%20blade%20(5x)%20%20Fibers%20of%20fiber%20glass%20matting%20same%20size%20as%20above%20from%20bolt,%20blue%20discoloration,%20brown%20coating,%20paint-white%20(NTSB%20Mat%20Lab)-Master.PDF - Wreckage Release (item 10, .PDF, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423789&FileExtension=.PDF&FileName=Wreckage%20Release-Redacted.PDF - Toxicological Report (item 11, .PDF, 68 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40423790&FileExtension=.PDF&FileName=Toxicological%20Report-Redacted.PDF - Photo 1 - View of main wreckage facing direction of travel (FAA) (item 12, .PDF, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120449&FileExtension=.PDF&FileName=Photo%201%20-%20View%20of%20main%20wreckage%20facing%20direction%20of%20travel%20(FAA)-Master.PDF - Photo 2 - View of rotor blade resting-place marked by orange paint [400 ft from main wreckage] (FAA) (item 13, .PDF, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120450&FileExtension=.PDF&FileName=Photo%202%20-%20View%20of%20rotor%20blade%20resting-place%20marked%20by%20orange%20paint%20%5B400%20ft%20from%20main%20wreckage%5D%20(FAA)-Master.PDF - Photo 3 - View of separated main rotor fracture surface (item 14, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120451&FileExtension=.PDF&FileName=Photo%203%20-%20View%20of%20separated%20main%20rotor%20fracture%20surface-Master.PDF - Photo 4 - View of main rotor head, fractured pitch horn and pitch change link. (Note gap between pitch change barrel and lock nuts.) (item 15, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40120452&FileExtension=.PDF&FileName=Photo%204%20-%20View%20of%20main%20rotor%20head,%20fractured%20pitch%20horn%20and%20pitch%20change%20link.%20%20(Note%20gap%20between%20pitch%20change%20barrel%20and%20lock%20nuts.)-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.