Federal regulations · Through 2026-08-25 · Newer source version available

14 CFR Appendix C to Part 135: 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 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
Collective 4 Full range ±3% 2 1% 2
Pedal Position 4 Full range ±3% 2 1% 2
Lat. Cyclic 4 Full range ±3% 2 1% 2
Long. Cyclic 4 Full range ±3% 2 1% 2
Controllable Stabilator Position 4 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.

Where this section sits in the code

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

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 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

Collective 4 Full range ±3% 2 1% 2

Pedal Position 4 Full range ±3% 2 1% 2

Lat. Cyclic 4 Full range ±3% 2 1% 2

Long. Cyclic 4 Full range ±3% 2 1% 2

Controllable Stabilator Position 4 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.

Collected 2026-08-27T02:24:20Z. Source file · JSON

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