525 

Federal Aviation Administration, DOT 

Pt. 135, App. C 

Parameters Range 

Installed system

1

minimum 

accuracy (to recovered data) 

Sampling inter-

val (per second) 

Resolution

4

 

read out 

Roll attitude ............................

±

60

° 

or 100% of usable 

range, whichever is 
greater.

±

2

°

.........................................

1 ........................

0.8

° 

Stabilizer trim position ............

Full range .......................

±

3% unless higher uniquely 

required.

1 ........................

1%

3

. 

Or 

Pitch control position ..............

Full range .......................

±

3% unless higher uniquely 

required.

1 ........................

1%

3

. 

Engine Power, Each Engine 

Fan or N

1

speed or EPR or 

cockpit indications used for 
aircraft certification.

Maximum range ..............

±

5% .......................................

1 ........................

1%

3

. 

Or 

Prop. speed and torque (sam-

ple once/sec as close to-
gether as practicable).

.........................................

................................................

1 (prop speed), 

1 (torque).

Altitude rate

2

(need depends 

on altitude resolution).

±

8,000 fpm .....................

±

10%. Resolution 250 fpm 

below 12,000 ft. indicated.

1 ........................

250 fpm Below 

12,000 

Angle of attack

2

(need de-

pends on altitude resolu-
tion).

¥

20

° 

to 40

° 

or of usable 

range.

±

2

°

.........................................

1 ........................

0.8%

3

 

Radio transmitter keying (dis-

crete).

On/off ..............................

................................................

1.

TE flaps (discrete or analog) ..

Each discrete position 

(U, D, T/O, AAP).

................................................

1.

Or.

Analog 0–100% range ....

±

3

°

.........................................

1 ........................

1%

3

 

LE flaps (discrete or analog) ..

Each discrete position 

(U, D, T/O, AAP).

................................................

1.

Or.

Analog 0–100% range ....

±

3

°

.........................................

1 ........................

1%

3

. 

Thrust reverser, each engine 

(Discrete).

Stowed or full reverse ....

................................................

1.

Spoiler/speedbrake (discrete) 

Stowed or out .................

................................................

1.

Autopilot engaged (discrete) ..

Engaged or disengaged

................................................

1.

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

If data from the altitude encoding altimeter (100 ft. resolution) is used, then either one of these parameters should also be re-

corded. If however, altitude is recorded at a minimum resolution of 25 feet, then these two parameters can be omitted. 

3

Per cent of full range. 

4

This column applies to aircraft manufacturing after October 11, 1991. 

[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] 

A

PPENDIX

C 

TO

P

ART

135—H

ELICOPTER

F

LIGHT

R

ECORDER

S

PECIFICATIONS

 

Parameters Range 

Installed system

1

minimum 

accuracy (to recovered data) 

Sampling inter-

val (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 ..................

V

m

in to V

D

(KIAS) (min-

imum 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 sec-

ond where 
peaks, ref. to 
1g are re-
corded).

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

°

. 

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