AD 71-21-10 ACTIVE

71-21-10 MICRODOT, INC.: Amendment 39-1316. Applies to all civil aircraft certificated in all categories in which a Microdot, Inc. Model 1410 Cockpit Voice Recorder is installed.

Compliance required as indicated.

To prevent inadvertent visual test circuit light illumination and reliance by flight crew members thereon, accomplish the following:

(a) Within five days of the effective date of this AD.,

(1) Remove the test light bulb from the CVR Control Unit and install a placard on the face of the CVR Control Unit adjacent to the test light thereon, which reads: TEST LIGHT INOPERATIVE, and

(2) Perform the following aural functional test (in lieu of the visual functional test) at least once each day during which the aircraft is flown:

(i) Plug low impedance headset (600 ohms) into the CVR audio jack, or into the CVR Control Unit audio jack, if connected.

(ii) Speak into the area microphone, or apply a speech signal to the CVR from any other monitored source.

(iii) Determine that recorded speech is satisfactorily reproduced in the headset (after a delay of approximately one second).

(b) The test light bulb should be replaced, the placard should be removed, and the aural functional test required by (a) above, may be discontinued after accomplishment of the modification described in Microdot, Inc. Service Bulletin No. 4-A, dated 14 September 1971, or later FAA approved revisions, or an equivalent modification approved by the Chief, Aircraft Engineering Division, FAA Western Region. This modification, when installed, will constitute terminating action under this AD.

This amendment becomes effective on October 13, 1971.