COMPONENT MAINTENANCE MANUAL
AVIATION RECORDERS
FA2100CVR
Rev. 15 Page 16
Apr. 14/16
Description and Operation
23–70–04
Use or disclosure of information on this sheet is subject
to the restrictions on the cover page of this document.
The Rotor Speed input is recorded as two words every 1/2 second. Rotor Speed
Word 1 (8-bits) provides the number of 400-Hz reference pulses counted during the
sample period. Word 2 (12-bits) contains the integer number of rotor pulse cycles
counted during the sample period. The average rotor pulse frequency is determined
from the word values with better than 1% accuracy using the following formula:
Rotor Pulse Frequency = (400 Hz) x (Rotor Pulse Count) / (Reference Count),
or Rotor Pulse Frequency = 400 x Word 2 / Word 1.
For displaying rotor speed the user must be able to select the display to be frequen-
cy or calculated revolutions per minute (RPM). To allow the conversion from frequen-
cy to RPM the user must provide a matching frequency to RPM ratio. For example,
6 kHz = 300 RPM. To determine the calculated RPM use the following formula:
RPM = Rotor Pulse Frequency x (Rotor RPM/Tach Frequency).
In the case of helicopter installations of the FA2100CVR, the Bulk Erase function is
inhibited until the rotors stop.
(4)
On board Maintenance System (OMS)
The OMS input signals are applied to the rear connector pins 39 and 40 as a low
speed ARINC 429 signal. The OMS output signal is sent out on pins 50 and 51 as a
high speed ARINC 429 signal, along with the Data Link output signal. The Recorder
records the FA2100 CVR OMS status word only, but is also used to send status
messages to the aircraft’s OMS computer.
Basically, there are two modes for sending messages to the OMS computer, Normal
and Interactive. When the aircraft’s recorder is in Normal mode, the CVR sends a
status message to the OMS computer four times per second. When the recorder is
in Interactive mode, the OMS computer can request the status of the recorder
through a series of menus. The OMS feature can be found on the FA2100 CVR p/n:
2100
−
1X25/1X26/1X27
−
( ) only.
(5)
Data Link
The Data Link input signals are applied to the rear connector pins 33 and 34 as a
high speed ARINC 429 signal. The Data Link output signal is sent out on pins 50
and 51 as a high speed ARINC 429 signal, along with the OMS output signal. The
Data Link Valid input signal is applied to pin 56. The Data Link Valid input signal noti-
fies the recorder to expect Data Link input signals.
When the Data Link system is energized, it sends an Aloha response message to
the recorder. If the recorder is in place and operational, the recorder records the
Aloha response message and returns a response message to inform the Data Link
The document reference is online, please check the correspondence between the online documentation and the printed version.
