Federal Aviation Agency AC NO: 121-6 AVESTION < AIR CARRIER AND
COMMERCIAL OPERATIONS
ADVISORY CIRCULAR EFFECTIVE :
1/5/66 SUBJECT : PORTABLE BATTERY-POWERED MEGAPHONES
1. PURPOSE. This circular sets forth an acceptable means for complying with rules (applicable to various persons operating under Part 121 of the Federal Aviation Regulations) that prescribe the installation of approved megaphones.
REFERENCE REGULATIONS. Sections 121.303(b) and 121.310(h).
3. ACCEPTABLE MEANS OF COMPLIANCE. A portable battery-powered megaphone is acceptable as "approved," under 0g 121.303(b) and 121.310(h), for a particular aircraft if -
a. Hearing range and intelligibility tests are conducted on the aircraft to show that the amplified speech is heard and clearly understood throughout the interior cabin region served by the megaphones, with the engines off and with all significant conditions associated with an accident (including the presence of passengers and the normallyattendant confused din) appropriately simulated; and
b. The megaphone reliably performs its intended function and is designed -
(1) For ease of handling, and use, with one hand,
(2) With sufficient acoustical feedback suppression, and
(3) With a volume control.
leT Walters Director Flight Standards Service