eLaws | eCases | United States Code | Federal Courts |
 Code of Federal Regulations (Last Updated: November 8, 2024)
 Title 14 - Aeronautics and Space
 Chapter I - Federal Aviation Administration, Department of Transportation
 SubChapter G - Air Carriers and Operators for Compensation or Hire: Certification and Operations
 Part 135 - Operating Requirements: Commuter and on Demand Operations and Rules Governing Persons on Board Such Aircraft

  Appendix C to Part 135 - Helicopter Flight Recorder Specifications  

Latest version.

  • Appendix C to Part 135 - Helicopter Flight Recorder Specifications

    Parameters Range Installed system1 minimum accuracy (to recovered data) Sampling interval (per second) Resolution3 read out
    Relative time (from recorded on prior to takeoff) 25 hr minimum ±0.125% per hour 1 1 sec.
    Indicated airspeed Vm in to VD (KIAS) (minimum airspeed signal attainable with installed pilot-static system) ±5% or ±10 kts., whichever is greater 1 1 kt.
    Altitude −1,000 ft. to 20,000 ft. pressure altitude ±100 to ±700 ft. (see Table 1, TSO C51-a) 1 25 to 150 ft.
    Magnetic heading 360° ±5° 1 1°.
    Vertical acceleration −3g to + 6g ±0.2g in addition to ±0.3g maximum datum 4 (or 1 per second where peaks, ref. to 1g are recorded) 0.05g.
    Longitudinal acceleration ±1.0g ±1.5% max. range excluding datum error of ±5% 2 0.03g.
    Pitch attitude 100% of usable range ±2° 1 0.8°.
    Roll attitude ±60° or 100% of usable range, whichever is greater ±2° 1 0.8°.
    Altitude rate ±8,000 fpm ±10% Resolution 250 fpm below 12,000 ft. indicated 1 250 fpm below 12,000.
    Engine Power, Each Engine
    Main rotor speed Maximum range ±5% 1 1%2
    Free or power turbine Maximum range + 5% 1 1%2
    Engine torque Maximum range ±5% 1 1%2
    Flight Control - Hydraulic Pressure
    Primary (discrete) High/low 1
    Secondary - if applicable (discrete) High/low 1
    Radio transmitter keying (discrete) On/off 1
    Autopilot engaged (discrete) Engaged or disengaged 1
    SAS status - engaged (discrete) Engaged/disengaged 1
    SAS fault status (discrete) Fault/OK 1
    Flight Controls
    Collective4 Full range ±3% 2 1%2
    Pedal Position4 Full range ±3% 2 1%2
    Lat. Cyclic4 Full range ±3% 2 1%2
    Long. Cyclic4 Full range ±3% 2 1%2
    Controllable Stabilator Position4 Full range ±3% 2 1%2

    1 When data sources are aircraft instruments (except altimeters) of acceptable quality to fly the aircraft the recording system excluding these sensors (but including all other characteristics of the recording system) shall contribute no more than half of the values in this column.

    2 Per cent of full range.

    3 This column applies to aircraft manufactured after October 11, 1991.

    4 For all aircraft manufactured on or after December 6, 2010, the sampling interval per second is 4.

    [Doc. No. 25530, 53 FR 26152, July 11, 1988; 53 FR 30906, Aug. 16, 1988, as amended by Amdt. 135-69, 62 FR 38397, July 17, 1997; Amdt. 135-113, 73 FR 12570, Mar. 7, 2008; 73 FR 15281, Mar. 21, 2008; Amdt. 135-121, 75 FR 17047, Apr. 5, 2010]