# NTSB WPR13LA222: Robinson Helicopter R22 Beta, N5ZK, Honolulu, HI, May 9, 2013 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: May 8, 2013, 15:20 local (May 9, 2013, 01:20 UTC) - Place: Honolulu, HI - Coordinates: 21.311111, -157.859161 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=21.3111&lon=-157.8592&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed, report November 13, 2014 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 86843 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR13LA222 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/86843/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=86843 - Page: https://openairdocs.org/ntsb/WPR13LA222 ## Probable cause The mechanic’s failure to properly inspect the helicopter following maintenance performed by an apprentice, which resulted in a total loss of engine power due to the improper rigging of the mixture control assembly. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine controls: mixture control](https://openairdocs.org/ntsb-findings/01057602): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Robinson Helicopter R22 BETA, 5 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md?model=7640110), [All aircraft, 41 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md) - [Engine controls: mixture control](https://openairdocs.org/ntsb-findings/01057602): Aircraft › Aircraft power plant · Inadequate inspection (probable cause); cases with it: [Robinson Helicopter R22 BETA, 5 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md?model=7640110), [All aircraft, 41 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md) - [Engine controls: mixture control](https://openairdocs.org/ntsb-findings/01057602): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Robinson Helicopter R22 BETA, 5 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md?model=7640110), [All aircraft, 41 cases](https://openairdocs.org/ntsb-findings/01057602/cases.md) - [Inspection: post maintenance inspection](https://openairdocs.org/ntsb-findings/02061515): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Robinson Helicopter R22 BETA, 1 case](https://openairdocs.org/ntsb-findings/02061515/cases.md?model=7640110), [All aircraft, 57 cases](https://openairdocs.org/ntsb-findings/02061515/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Robinson Helicopter R22 BETA, 3 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=7640110), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Robinson Helicopter R22 BETA, 18 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=7640110), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis The pilot reported that, while he was maneuvering the helicopter about 3,000 feet above ground level (agl), the engine suddenly experienced a total loss of power, which was immediately followed by the activation of the low rotor rpm light and horn. In response to the engine failure, the pilot lowered the collective and entered an autorotation. She began to flare the helicopter at an altitude of about 40 feet agl. The helicopter touched down on a road and skidded into a parked automobile. A postaccident examination of the helicopter revealed that the mixture cable had fracture-separated from the mixture bellcrank control arm located on the carburetor. The bellcrank was positioned near the idle/cutoff position, and the spring was inserted in the wrong direction. The helicopter airframe had undergone an overhaul about 16 hours of flight time before the accident, and, during that overhaul, a mechanic's apprentice installed the mixture hardware. The apprentice improperly rigged the mixture-to-bellcrank hardware, which prevented the mixture cable from moving freely. The repeated stress on the mixture cable resulted in it breaking after a number of operation cycles. When the failure occurred, the bellcrank spring, which is designed to force the mixture to the full-rich position, instead pulled the mixture to the idle/cutoff position, which cut off the fuel. The mechanic overseeing the apprentice reported that he did not visually observe the misrigging and that, if he had performed a tactile inspection, he would have detected the error. ## Factual narrative On May 08, 2013, about 1520 Hawaiian standard time, a Robinson R22 Beta helicopter, N5ZK, was substantially damaged when it collided with an unoccupied parked automobile following a total loss of engine power while maneuvering over Honolulu, Hawaii. HLM Aviation owned the helicopter, and Hawaii Pacific Aviation (doing business as Mauna Loa Helicopters) operated the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certified flight instructor (CFI) was not injured, and the passenger sustained minor injuries. The local aerial observation flight departed from Honolulu International Airport about 1455. Visual meteorological conditions prevailed and no flight plan had been filed.The CFI stated that the purpose of the flight was for her to orbit the helicopter over an area known as Punchbowl located about five nautical miles south of the airport. She departed as planned, proceeded to Punchbowl, and completed two orbits before slowing the helicopter to about 35 knots in an effort to help facilitate the passenger in taking his aerial photographs. While maneuvering about 3,000 feet above ground level (agl), the engine suddenly experienced a total loss of power, followed immediately by activation of the low rpm light and horn. The CFI reported that in response to the engine failure, she lowered the collective and entered an autorotation. She maintained a 60-knot airspeed, and maneuvered to land on a street. The pilot began the flare at an altitude of about 40 feet agl. The helicopter touched down on the road, and skidded into a parked automobile. A Federal Aviation Administration (FAA) inspector performed a post accident examination of the helicopter. He stated that the mixture cable was fracture-separated from the mixture bellcrank control arm on the carburetor. The bellcrank was positioned near the idle cutoff position, rather than the full-rich position. The spring did not drive the arm to the full rich position per design. The inspector noted that it appeared that the spring was not correctly connected to the mixture arm. The helicopter's maintenance manual stated that during inspection the mechanic must "Verify spring moves arm to full rich position." The mechanic who routinely maintains the helicopter stated that his company completed a 2,200 hour airframe overhaul of the helicopter on April 22, 2013, equating to about 16 hours of flight time prior to the accident. The mechanic recalled that at the completion of the overhaul, he inspected the helicopter which commenced with the tracking and balancing of the main rotor system, tail rotor system and engine. The mechanic further stated that he had accompanied the FAA inspector during the post accident examination. They determined that the mixture arm assembly was improperly rigged. The mixture to bellcrank hardware stackup was incorrect and did not allow the mixture cable to move freely and the spring was installed so that the arm was driven to the idle cutoffposition. The mechanic opined that the combination of the repeated stress on the mixture cable resulted in it breaking after a number of operation cycles. When the failure did occur, the bellcrank spring, which is designed to force the mixture to the full rich position, instead cut off the fuel by pulling the mixture to idle cutoff. The mechanic remarked that the rigging of the carburetor was accomplished by an apprentice who was under his supervision. The mechanic did not visually observe the misrigging, and reported that if he had performed a tactile inspection, he would have detected the error. ## Aircraft - Registration: [N5ZK](https://openairdocs.org/deregistered/N5ZK-2018-03-06), registration cancelled 2018-03-06, S/N 2158, built 1992 (OpenAirDocs) - Reported make and model: ROBINSON HELICOPTER R22 BETA - Registry model: [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta) (registry code 7640110) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 2158 - Airframe hours: 8800 - Engines: LYCOMING O-320-B2C 180 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Hawaii Pacific Aviation, doing business as Mauna Loa Helicopters - Registered owner: HLM Aviation - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, April 22, 2013, 15 hours before - Departed: Honolulu, HI - Destination: Honolulu, HI ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 30; injuries: none; commercial, flight instructor; instrument ratings: helicopter; medical: class 2, without waivers/limitations; seat: right; flight hours: 391 total, 319 in this make and model, 313 as pilot in command, 26 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 9 knots - Visibility: 9 statute miles - Lowest ceiling: 5,000 ft overcast - Temperature: 81 °F, dew point 64 °F - Altimeter: 29.96 inHg - Observed at: PHNL, 5 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 20130508006689A](https://openairdocs.org/incident/20130508006689A), May 8, 2013: Robinson Helicopter R22 BETA, Honolulu, HI, Substantial damage. While in cruise flight at 3000 feet MSL over Honolulu the aircraft experienced a sudden loss of power and the low rotor RPM horn sounded. Pilot immediatily… ## Docket (3 files) The files NTSB released with the investigation on October 7, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=86843. 6.5 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 6.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417442&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - FAA Inspector Statement (item 2, .PDF, 3 photos, 251 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417443&FileExtension=.PDF&FileName=FAA%20Inspector%20Statement-Master.PDF - Mechanic Statement (item 3, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417444&FileExtension=.PDF&FileName=Mechanic%20Statement-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.