{"data":{"id":"us/14-cfr-appendix-c-to-part-135","jurisdiction":"us","citation":"14 CFR Appendix C to Part 135","heading":"Appendix C to Part 135—Helicopter Flight Recorder Specifications","body":"Parameters Range Installed system 1 minimum accuracy (to recovered data) Sampling interval (per second) Resolution 3 read out\nRelative time (from recorded on prior to takeoff) 25 hr minimum ±0.125% per hour 1 1 sec.\nIndicated 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.\nAltitude −1,000 ft. to 20,000 ft. pressure altitude ±100 to ±700 ft. (see Table 1, TSO C51-a) 1 25 to 150 ft.\nMagnetic heading 360° ±5° 1 1°.\nVertical 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.\nLongitudinal acceleration ±1.0g ±1.5% max. range excluding datum error of ±5% 2 0.03g.\nPitch attitude 100% of usable range ±2° 1 0.8°.\nRoll attitude ±60° or 100% of usable range, whichever is greater ±2° 1 0.8°.\nAltitude rate ±8,000 fpm ±10% Resolution 250 fpm below 12,000 ft. indicated 1 250 fpm below 12,000.\nEngine Power, Each Engine\nMain rotor speed Maximum range ±5% 1 1% 2\nFree or power turbine Maximum range + 5% 1 1% 2\nEngine torque Maximum range ±5% 1 1% 2\nFlight Control—Hydraulic Pressure\nPrimary (discrete) High/low 1\nSecondary—if applicable (discrete) High/low 1\nRadio transmitter keying (discrete) On/off 1\nAutopilot engaged (discrete) Engaged or disengaged 1\nSAS status—engaged (discrete) Engaged/disengaged 1\nSAS fault status (discrete) Fault/OK 1\nFlight Controls\nCollective 4 Full range ±3% 2 1% 2\nPedal Position 4 Full range ±3% 2 1% 2\nLat. Cyclic 4 Full range ±3% 2 1% 2\nLong. Cyclic 4 Full range ±3% 2 1% 2\nControllable Stabilator Position 4 Full range ±3% 2 1% 2\n1 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.\n2 Per cent of full range.\n3 This column applies to aircraft manufactured after October 11, 1991.\n4 For all aircraft manufactured on or after December 6, 2010, the sampling interval per second is 4.","path":["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"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-14.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:20Z","sha256":"85ba1661ac1ede5db91254456e91b305bd1352a606a4fb0ae23800f01864a22f","source_id":"us-cfr","stale":true,"prev":"us/14-cfr-appendix-b-to-part-135","next":"us/14-cfr-appendix-d-to-part-135"},"notice":"GroundRules: Original legal text. Not legal advice."}