# NTSB LAX05LA122: Robinson R22 Beta, N225G, Prescott, AZ, March 24, 2005 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 24, 2005, 12:07 local (19:07 UTC) - Place: Prescott, AZ - Coordinates: 34.676666, -112.410003 - Nearby events: https://openairdocs.org/map.md?lat=34.6767&lon=-112.4100&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 30, 2006 - Report: Approved by Office Director - Parties: Robinson Helicopter Company, Federal Aviation Administration - NTSB case key (mKey): 61212 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX05LA122 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/61212/pdf - Page: https://openairdocs.org/ntsb/LAX05LA122 ## Probable cause The company mechanic's improper maintenance actions, which resulted in the total failure of the main rotor drive belt system on approach to landing. A factor was the soft terrain. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - vfr pattern - base turn - maintenance,100-hour inspection - improper, company maintenance personnel (cause) - rotor drive system,clutch assembly - improperly serviced (cause) - rotor drive system,main rotor drive belt - failure,total (cause) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command(cfi) - Roll over, landing - flare/touchdown - terrain condition - soft (contributing factor) ## Analysis The helicopter's main rotor drive belts broke on the base leg and the helicopter rolled over during the subsequent autorotation and landing. The instructor said that he monitored his student during the preflight inspection of the helicopter. No evidence of any problem was detected. The instructor reported that there were no outstanding airworthiness issues with the helicopter. The accident occurred while he was preparing his student for the private pilot certification check ride. The lesson plan/maneuver that he intended the student to practice was a run-on landing. On base leg to runway 21R, while cruising about 60 knots at 300 feet above ground level, the helicopter's nose suddenly yawed left and then right. Concurrently the helicopter shook, and the clutch light illuminated. The instructor took the controls from his student and entered an autorotative descent. About 20 feet above ground level he commenced a cyclic flare for the landing. The underlying terrain was soft sand, and the helicopter rolled over during touchdown. Upon exiting the helicopter, the instructor observed that the V-belts were shredded. A company mechanic had performed a 100-hour inspection about 4.3 hours prior to the accident flight. During the inspection, he had loosened the self-locking nut on the belt actuator housing assembly and had rotated the down-limit stop screw upward until the screw bottomed out in the actuator housing in the full up position. The mechanic forgot to reposition the stop screw and tighten the nut. This action resulted in the main rotor drive V-belts becoming excessively loose. The belts exited their seated position on the lower pulley sheave and were severed. ## Factual narrative On March 24, 2005, about 1207 mountain standard time, a Robinson R22 Beta, N225G, experienced a mechanical malfunction on base leg to the Ernest A. Love Field, Prescott, Arizona. The certified flight instructor (CFI) took the flight controls from his student and performed an autorotation. The helicopter touched down hard, rolled over, and was substantially damaged. Neither the CFI nor the student pilot was injured during the instructional flight. Guidance Helicopter, Inc., Prescott, operated the helicopter. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was performed under the provisions of 14 CFR Part 91, and it originated from Prescott about 1200. The CFI reported to the National Transportation Safety Board investigator that he monitored his student as he performed the preflight inspection of the helicopter. No evidence of any problem was detected. The CFI reported that there were no outstanding airworthiness issues with the helicopter. The accident occurred while he was preparing his student for the private pilot certification check ride. The lesson plan/maneuver that he intended the student to practice was a run-on landing. On base leg to runway 21R, while cruising about 60 knots at 300 feet above ground level, the helicopter's nose suddenly yawed left and then right. Concurrently the helicopter shook, and the clutch light illuminated. The CFI additionally reported that he took the controls from his student and entered an autorotative descent. About 20 feet above ground level he commenced a cyclic flare for the landing. The underlying terrain was soft sand, and the helicopter rolled over. Upon exiting the helicopter, the CFI observed that the V-belts were shredded. The helicopter was recovered from the accident site. It was examined by the operator's personnel while under the direction of a Federal Aviation Administration (FAA) aviation safety inspector. In summary, on March 30, 2005, the operator's director of maintenance (DM) and the FAA inspector verbally reported to the Safety Board investigator the results of the examination. The DM reported that 2 days (and about 4.3 helicopter operation hours) before the accident he had performed a 100-hour inspection on N225G. Evidently, during that inspection he had loosened the self-locking nut on the belt actuator housing assembly. Thereafter, he had rotated the down-limit stop screw upward until the screw bottomed out in the actuator housing in the full up position. The DM further reported that, evidently, upon completing the helicopter maintenance, he had forgotten to reposition the stop screw and tighten the nut. The Robinson Helicopter factory participant indicated to the Safety Board investigator that, if the referenced self-locking nut on the belt actuator housing assembly was incorrectly positioned in the manner described by the DM (as evidenced during the wreckage examination), the main drive V-belts could have become excessively loose during shutdown on the flight previous to the accident, and remain so until start up on the accident flight. An excessively loose belt could fail to enter its proper sheave groove on start up, which could lead to a subsequent belt failure. ## Aircraft - Registration: [N225G](https://openairdocs.org/deregistered/N225G-2013-06-17), registration cancelled 2013-06-17, S/N 3563, built 2004 (OpenAirDocs) - Reported make and model: Robinson R22 Beta - Registry model: [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta) (registry code 7640110) (OpenAirDocs) - Registry engine: [Lycoming O-360 series](https://openairdocs.org/engine/lycoming-o-360-series) (registry code 41575, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 3563 - Airframe hours: 1060 - Engines: Lycoming O-360-J2A 124 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Guidance Helicopter, Inc. - Registered owner: Cheyenne Corporation - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, March 1, 2005, 4 hours before - Departed: PRC, Prescott, AZ - Destination: PRC, Prescott, AZ - Airport: PRC, Ernest A. Love Field, runway 21R, 4,846 × 60 ft, dirt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 22; injuries: none; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; last flight review March 1, 2004; seat: left; flight hours: 615 total, 470 in this make and model, 480 as pilot in command, 136 in the last 90 days, 55 in the last 30 days, 1 in the last 24 hours - Student pilot; age 19; injuries: none; student; medical: class 1, without waivers/limitations; seat: right; flight hours: 57 total, 57 in this make and model, 8 as pilot in command, 33 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: 4,100 ft broken - Temperature: 45 °F, dew point 28 °F - Altimeter: 29.96 inHg - Observed at: PRC, 1 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 20050324004899A](https://openairdocs.org/incident/20050324004899A), Mar 24, 2005: Robsin R22BETA, Prescott, AZ, Substantial damage. (-23) On a training flight, while approaching the airport, the rotor drive belts broke. The instructor pilot took control of the aircraft, accomplishing an… 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.