When the landing gears are up and the throttles are retarded, the warning horn will not sound if an open occurs in wire No. 6.

• A. No. 5
• B. No. 7
• C. No. 4
• D. No. 6

Answer: (D)

Warning horns only sound when there is a complete electrical path to energize them. In this setup, with the landing gear up and throttles retarded, the horn relies on a specific conductor to complete the circuit to the horn. If that conductor opens, the current cannot reach the horn, so no sound is produced even though the other interlocks are in place. The other conductors aren’t part of the same complete path under these conditions, so opening them wouldn’t have the same effect. Therefore, an open in the conductor that completes the horn circuit in this configuration will prevent the horn from sounding.