# Rotorcraft servo system - Type: NTSB finding subsection - Path: [Aircraft](https://openairdocs.org/ntsb-findings/01) › [Aircraft propeller/rotor](https://openairdocs.org/ntsb-findings/0104) › [Rotorcraft flight control](https://openairdocs.org/ntsb-findings/010467) › Rotorcraft servo system - NTSB code: 01046730 - Cases: 6 - In the probable cause: 5 - Fatal cases: 5 - All cases: https://openairdocs.org/ntsb-findings/01046730/cases.md - Cases with it in the probable cause: https://openairdocs.org/ntsb-findings/01046730/cases.md?cause=1 - Page: https://openairdocs.org/ntsb-findings/01046730 ## Cases per year (in the probable cause / all) - 2008: 1 / 1 - 2011: 1 / 1 - 2012: 1 / 1 - 2014: 0 / 1 - 2015: 1 / 1 - 2020: 1 / 1 ## Defining events in these cases - [Loss of control in flight](https://openairdocs.org/ntsb-events/240): 4 cases - [Part(s) separation from AC](https://openairdocs.org/ntsb-events/338): 1 cases - [Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330): 1 cases ## Aircraft models (registry) - [Eurocopter France AS350B2](https://openairdocs.org/model/eurocopter-france-as350b2): 1 cases - [Eurocopter AS 350 B2](https://openairdocs.org/model/eurocopter-as-350-b2): 1 cases - [Aerospatiale AS 355F1](https://openairdocs.org/model/aerospatiale-as-355f1): 1 cases - [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii): 1 cases - [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44): 1 cases - [Bell UH-1H](https://openairdocs.org/model/bell-uh-1h): 1 cases ## Other findings in the same cases - [Performance/control parameters, general](https://openairdocs.org/ntsb-findings/01062000) (Aircraft): 2 cases - [Not determined, general](https://openairdocs.org/ntsb-findings/05000000) (Not determined): 1 cases - [Support/oversight/monitoring, general](https://openairdocs.org/ntsb-findings/04030000) (Organizational issues): 1 cases - [Availability of policy/proc](https://openairdocs.org/ntsb-findings/04021010) (Organizational issues): 1 cases - [Aircraft control](https://openairdocs.org/ntsb-findings/02063040) (Personnel issues): 1 cases - [Installation](https://openairdocs.org/ntsb-findings/02062035) (Personnel issues): 1 cases - [Maintenance, general](https://openairdocs.org/ntsb-findings/02062000) (Personnel issues): 1 cases - [Scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520) (Personnel issues): 1 cases - [Post maintenance inspection](https://openairdocs.org/ntsb-findings/02061515) (Personnel issues): 1 cases - [Alertness/Fatigue, general](https://openairdocs.org/ntsb-findings/02013500) (Personnel issues): 1 cases ## Newest cases - [NTSB WPR20LA211](https://openairdocs.org/ntsb/WPR20LA211), Jul 7, 2020: Bell UH1H (N623PB), Payson, AZ, destroyed, 1 fatal. Probable cause: A flight control malfunction due to either a hydraulic hardover or a flight control stiffness event, which resulted in a loss of control. - [NTSB ERA15FA164](https://openairdocs.org/ntsb/ERA15FA164), Mar 22, 2015: Robinson Helicopter R44 II (N30242), Orlando, FL, destroyed, 3 fatal. Probable cause: An inflight loss of control due to the likely detachment of the forward left servo control tube upper rod end attachment bolt. - [NTSB WPR14FA137](https://openairdocs.org/ntsb/WPR14FA137), Mar 18, 2014: Eurocopter AS 350 B2 (N250FB), Seattle, WA, destroyed, 2 fatal. Probable cause: The loss of helicopter control due to a loss of hydraulic boost to the tail rotor pedal controls at takeoff, followed by a loss of hydraulic boost to the main rotor controls after takeoff. The reason… - [NTSB ERA12FA563](https://openairdocs.org/ntsb/ERA12FA563), Sep 15, 2012: Aerospatiale AS 355F1 (N58020), West Windsor, NJ, substantial damage, 1 fatal. Probable cause: Disconnection of the upper rod end from the fore/aft servo due to severely worn threads, which resulted in a loss of control and separation of a main rotor blade during cruise flight. Contributing to… - [NTSB DCA12MA020](https://openairdocs.org/ntsb/DCA12MA020), Dec 8, 2011: Eurocopter France AS350B2 (N37SH), Las Vegas, NV, destroyed, 5 fatal. Probable cause: Sundance Helicopters’ inadequate maintenance of the helicopter, including (1) the improper reuse of a degraded self-locking nut, (2) the improper or lack of installation of a split pin, and (3)… - [NTSB ERA09LA051](https://openairdocs.org/ntsb/ERA09LA051), Nov 12, 2008: Robinson Helicopter R44 (N452JM), San Juan, PR, substantial damage. Probable cause: The detachment of the forward left servo control tube upper rod end attachment bolt during a hover due to separation of its retaining nut for undetermined reasons. NTSB has coded findings and defining events since 2008; earlier cases used its older occurrence and cause codes and aren't counted. Findings: https://openairdocs.org/ntsb-findings.md. Defining events: https://openairdocs.org/ntsb-events.md. Phases of flight: https://openairdocs.org/ntsb-phases.md. Every investigation, filtered by finding, event, phase, state, year or model: https://openairdocs.org/ntsb.md (for example ?state=MI&fatal=1). NTSB's definitions: Accident and incident, 49 CFR 830.2 (https://www.ecfr.gov/current/title-49/subtitle-B/chapter-VIII/part-830/subpart-A/section-830.2), CICTT occurrence categories (PDF) (https://www.ntsb.gov/safety/data/Documents/datafiles/OccurrenceCategoryDefinitions.pdf), CICTT phases of flight (PDF) (https://www.ntsb.gov/safety/data/Documents/datafiles/PhaseofFlightDefinitions.pdf), and NTSB coding manual, before 2008 (PDF) (https://www.ntsb.gov/GILS/Documents/codman.pdf). NTSB publishes no definitions for its findings, only their names. --- 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.