AD 71-21-10
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Microdot | Cockpit Voice Recorder | Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Categories in Which A Microdot, Inc. Model 1410 Cockpit Voice Recorder is Installed |
| appliance | Microdot | Cockpit Voice Recorder | Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Categories in Which A Microdot, Inc. Model 1410 Cockpit Voice Recorder is Installed |
Unsafe Condition
Inadvertent visual test circuit light illumination and reliance by flight crew members thereon.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Remove the test light bulb from the CVR Control Unit and install a placard stating 'TEST LIGHT INOPERATIVE'. Perform a daily aural functional test using a 600 ohm headset, checking for satisfactory speech reproduction after a one-second delay. Replace the bulb and remove the placard once Microdot Service Bulletin No. 4-A or equivalent modification is installed.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within five days of the effective date of this AD
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
All civil aircraft certificated in all categories in which a Microdot, Inc. Model 1410 Cockpit Voice Recorder is installed.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Cockpit Voice Recorder
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_71-21-10.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 71-21-10 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Catego...Show more Subject: Cockpit Voice Recorder Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/13/1971 Make: Microdot Model: Cockpit Voice Recorder Product Type: Appliance Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 71-21-10 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1316 AD NUMBER: 71-21-10 SUBJECT HEADING: Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Categories in Which A Microdot, Inc. Model 1410 Cockpit Voice Recorder is Installed ACTION: SUMMARY: DATES: Effective October 13, 1971. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 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. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_71-21-10.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 71-21-10 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Catego...Show more Subject: Cockpit Voice Recorder Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/13/1971 Make: Microdot Model: Cockpit Voice Recorder Product Type: Appliance Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 71-21-10 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1316 AD NUMBER: 71-21-10 SUBJECT HEADING: Airworthiness Directives; MICRODOT, INC.: Applies to all Civil Aircraft Certificated in all Categories in Which A Microdot, Inc. Model 1410 Cockpit Voice Recorder is Installed ACTION: SUMMARY: DATES: Effective October 13, 1971. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 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. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.