Appendix F to Part 91 - Helicopter Flight Recorder Specifications
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                                                       Installed system
                                                          \1\ minimum      Sampling interval   Resolution 3 read
           Parameters                    Range           accuracy (to        (per second)             out
                                                        recovered data)
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Relative Time (From Recorded on   4 hr minimum......  0.125% per    1.................  1 sec.
 Prior to Takeoff).                                    hour.
Indicated Airspeed..............  VM in to VD (KIAS)  5% or         1.................  1 kt.
                                   (minimum airspeed   10 kts.,
                                   signal attainable   whichever is
                                   with installed      greater.
                                   pilot-static
                                   system).
Altitude........................  -1,000 ft. to       100 to        1.................  25 to 150 ft.
                                   20,000 ft.          700 ft.
                                   pressure altitude.  (see Table 1, TSO
                                                       C51-a).
Magnetic Heading................  360.........  5.....  1.................  1
Vertical Acceleration...........  -3g to +6g........  0.2g in       4 (or 1 per second  0.05g.
                                                       addition to         where peaks, ref.
                                                       0.3g          to 1g are
                                                       maximum datum.      recorded).
Longitudinal Acceleration.......  1.0g........  1.5% max.     2.................  0.03g.
                                                       range excluding
                                                       datum error of
                                                       5%.
Pitch Attitude..................  100% of usable      2.....  1.................  0.8
                                   range.
Roll Attitude...................  60 or 100%    2.....  1.................  0.8
                                   of usable range,
                                   whichever is
                                   greater.
Altitude Rate...................  8,000 fpm...  10%           1.................  250 fpm below
                                                       Resolution 250                          12,000.
                                                       fpm below 12,000
                                                       ft. indicated.
  1  1  1  1  1  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           High/Low..........  ..................  1.................  ..................
 (Discrete).
Radio Transmitter Keying          On/Off............  ..................  1.................  ..................
 (Discrete).
Autopilot Engaged (Discrete)....  Engaged or          ..................  1.................  ..................
                                   Disengaged.
SAS Status-Engaged (Discrete)...  Engaged or          ..................  1.................  ..................
                                   Disengaged.
SAS Fault Status (Discrete).....  Fault/OK..........  ..................  1.................  ..................
         Flight Controls
Collective......................  Full range........  3%..........  2.................  1%2.
Pedal Position..................  Full range........  3%..........  2.................  1%2.
Lat. Cyclic.....................  Full range........  3%..........  2.................  1%2.
Long. Cyclic....................  Full range........  3%..........  2.................  1%2.
Controllable Stabilator Position  Full range........  3%..........  2.................  1%2.
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\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.

[Doc. No. 18334, 54 FR 34328, Aug. 18, 1989; 54 FR 41211, Oct. 5, 1989; 54 FR 53036, Dec. 26, 1989]