{"data":{"id":"us/14-cfr-appendix-b-to-part-121","jurisdiction":"us","citation":"14 CFR Appendix B to Part 121","heading":"Appendix B to Part 121—Airplane Flight Recorder Specification","body":"Parameters Range Accuracy sensor input to DFDR readout Sampling interval (per second) Resolution 4 readout\nTime (GMT or Frame Counter) (range 0 to 4095, sampled 1 per frame) 24 Hrs ±0.125% Per Hour 0.25 (1 per 4 seconds) 1 sec.\nAltitude −1,000 ft to max certificated altitude of aircraft ±100 to ±700 ft (See Table 1, TSO-C51a) 1 5′ to 35′ 1\nAirspeed 50 KIAS to V so, and V so to 1.2VD ±5%, ±3% 1 1 kt.\nHeading 360° ±2° 1 0.5°\nNormal Acceleration (Vertical) −3g to + 6g ±1% of max range excluding datum error of ±5% 8 0.01g.\nPitch Attitude ±75° ±2° 1 0.5°\nRoll Attitude ±180° ±2° 1 0.5°\nRadio Transmitter Keying On-Off (Discrete) ±2° ±2%\nThrust/Power on Each Engine Full Range Forward ±2° 1 (per engine) 0.2% 2\nTrailing Edge Flap or Cockpit Control Selection Full Range or Each Discrete Position ±3° or as Pilot's Indicator 0.5 0.5% 2\nLeading Edge Flap or Cockpit Control Selection Full Range or Each Discrete Position ±3° or as Pilot's Indicator 0.5 0.5% 2\nThrust Reverser Position Stowed, In Transit, and Reverse (Discrete) 1 (per 4 seconds per engine)\nGround Spoiler Position/Speed Brake Selection Full Range or Each Discrete Position ±2% Unless Higher Accuracy Uniquely Required 1 0.2% 2.\nMarker Beacon Passage Discrete 1\nAutopilot Engagement Discrete 1\nLongitudinal Acceleration ±1g ±1.5% max range excluding datum error of ±5% 4 0.01g.\nPilot Input and/or Surface Position—Primary Controls (Pitch, Roll, Yaw) 3 Full Range ±2° Unless Higher Accuracy Uniquely Required 1 0.2% 2.\nLateral Acceleration ±1g ±1.5% max range excluding datum error of ±5% 4 0.01g.\nPitch Trim Position Full Range ±3% Unless Higher Accuracy Uniquely Required 1 0.3% 2.\nGlideslope Deviation ±400 Microamps ±3% 1 0.3% 2.\nLocalizer Deviation ±400 Microamps ±3% 1 0.3% 2.\nAFCS Mode and Engagement Status Discrete 1\nRadio Altitude −20 ft to 2,500 ft ±2 Ft or ±3% Whichever is Greater Below 500 Ft and ±5% Above 500 Ft 1 1 ft + 5% 2 above 500′.\nMaster Warning Discrete 1\nMain Gear Squat Switch Status Discrete 1\nAngle of Attack (if recorded directly). As installed As installed 2 0.3% 2\nOutside Air Temperature or Total Air Temperature. −50 °C to + 90 °C ±2 °c 0.5 0.3 °c\nHydraulics, Each System Low Pressure Discrete 0.5 or 0.5% 2\nGroundspeed. As installed Most Accurate Systems Installed (IMS Equipped Aircraft Only) 1 0.2% 2\nIf additional recording capacity is available, recording of the following parameters is recommended. The parameters are listed in order of significance:\nDrift Angle When available, As installed As installed 4\nWind Speed and Direction When available, As installed As installed 4\nLatitude and Longitude When available, As installed As installed 4\nBrake pressure/Brake pedal position As installed As installed 1\nAdditional engine parameters:\nEPR As installed As installed 1 (per engine).\nN1 As installed As installed 1 (per engine).\nN2 As installed As installed 1 (per engine).\nEGT As installed As installed 1 (per engine).\nThrottle Lever Position As installed As installed 1 (per engine).\nFuel Flow As installed As installed 1 (per engine).\nTCAS:\nTA As installed As installed 1\nRA As installed As installed 1\nSensitivity level (as selected by crew) As installed As installed 2\nGPWS (ground proximity warning system) Discrete 1\nLanding gear or gear selector position Discrete 0.25 (1 per 4 seconds)\nDME 1 and 2 Distance 0-200 NM; As installed 0.25 1 mi.\nNav 1 and 2 Frequency Selection Full range As installed 0.25\n1 When altitude rate is recorded. Altitude rate must have sufficient resolution and sampling to permit the derivation of altitude to 5 feet.\n2 Per cent of full range.\n3 For airplanes that can demonstrate the capability of deriving either the control input on control movement (one from the other) for all modes of operation and flight regimes, the “or” applies. For airplanes with non-mechanical control systems (fly-by-wire) the “and” applies. In airplanes with split surfaces, suitable combination of inputs is acceptable in lieu of recording each surface separately.\n4 This column applies to aircraft manufactured after October 11, 1991.","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 121—OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS"],"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":"c2d75a04d689472f20f1924f5184f0a5e847ef3f5dd0aecf7688c39eca5a9fc6","source_id":"us-cfr","stale":true,"prev":"us/14-cfr-appendix-a-to-part-121","next":"us/14-cfr-appendix-c-to-part-121"},"notice":"GroundRules: Original legal text. Not legal advice."}