Regulations last checked for updates: Jan 18, 2025

Title 14 - Aeronautics and Space last revised: Jan 16, 2025
All TitlesTitle 14Chapter IPart 135Appendix Appendix C - Appendix C to Part 135—Helicopter Flight Recorder Specifications
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Appendix Appendix C - Appendix C to Part 135—Helicopter Flight Recorder Specifications
Parameters Range Installed system 1 minimum accuracy (to recovered data) Sampling interval (per second) Resolution 3 read out
Relative time (from recorded on prior to takeoff)25 hr minimum±0.125% per hour11 sec.
Indicated airspeedVm in to VD (KIAS) (minimum airspeed signal attainable with installed pilot-static system)±5% or ±10 kts., whichever is greater11 kt.
Altitude−1,000 ft. to 20,000 ft. pressure altitude±100 to ±700 ft. (see Table 1, TSO C51-a)125 to 150 ft.
Magnetic heading360°±5°11°.
Vertical acceleration−3g to + 6g±0.2g in addition to ±0.3g maximum datum4 (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%20.03g.
Pitch attitude100% of usable range±2°10.8°.
Roll attitude±60° or 100% of usable range, whichever is greater±2°10.8°.
Altitude rate±8,000 fpm±10% Resolution 250 fpm below 12,000 ft. indicated1250 fpm below 12,000.
Engine Power, Each Engine
Main rotor speedMaximum range±5%11% 2
Free or power turbineMaximum range + 5%11% 2
Engine torqueMaximum range±5%11% 2
Flight Control—Hydraulic Pressure
Primary (discrete)High/low1
Secondary—if applicable (discrete)High/low1
Radio transmitter keying (discrete)On/off1
Autopilot engaged (discrete)Engaged or disengaged1
SAS status—engaged (discrete)Engaged/disengaged1
SAS fault status (discrete)Fault/OK1
Flight Controls
Collective 4Full range±3%21% 2
Pedal Position 4Full range±3%21% 2
Lat. Cyclic 4Full range±3%21% 2
Long. Cyclic 4Full range±3%21% 2
Controllable Stabilator Position 4Full range±3%21% 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]
authority: 49 U.S.C. 106(f), 40113, 41706, 44701-44702, 44705, 44709, 44711-44713, 44715-44717, 44722, 44730, 45101-45105; Pub. L. 112-95, 126 Stat. 58 (49 U.S.C. 44730)
source: Docket No. 16097, 43 FR 46783, Oct. 10, 1978, unless otherwise noted.
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