Narrative:

During climbout on the second leg passing FL180; we elected to turn the speakers on and remove our headsets. As the pilot monitoring I checked in with the center high controller and was given a climb to our filed altitude of FL390. As we continued climbing to our assigned flight level; I noticed a TCAS target about 5;000 ft above us and about 10 miles away at our two o'clock position. This flight crossed in front of our nose about 5 miles ahead and 1;500 feet above us; but the radio was silent; and I thought that strange; so I did a radio check with center. Immediately; the center controller came back with 'I have been calling you for 2 minutes! Turn 30 degrees right for traffic.' we complied with the vector and the captain asked me to query him if there was a loss of separation. He curtly replied 'I don't have time right now; I've been trying to reach you for 2 minutes.' once the radio traffic settled down; I queried him again; and he replied; 'it was close.' on our end; the TCAS target never became solid white and we did not receive a TCAS TA or RA. Prior to removing our headsets; the captain asked if I minded having the interphone on to improve inter-cockpit communication. I have never done this before on the B757; but agreed and that is how we operated. However; we did not return the interphone switches to the neutral position when we removed our headsets; and this may have caused our speakers to be inhibited. Once I called center however; two-way comm. Was restored. After the event; the captain checked in the aircraft systems manual to see if having both interphone switches on caused the speakers to be inhibited; but there was no information on this subject. Apparently; however; on this particular ics panel; if both interphone switches are on; the speakers are inhibited; effectively causing a loss comm. Situation. There are a couple ways: if above FL180; and the crew elects to 'go speaker' and remove their headsets; they must ensure that both interphone switches are in the neutral position. Secondly; when the crew does 'go speaker' they should do so during a center transmission to ensure that the speakers are working properly.

Google
 

Original NASA ASRS Text

Title: A B757 crew was unable to hear ATC on the overhead speaker because selecting overhead cockpit speaker and interphone muted radio calls and as a result the flight was NORDO with conflicting traffic.

Narrative: During climbout on the second leg passing FL180; we elected to turn the speakers on and remove our headsets. As the pilot monitoring I checked in with the Center High Controller and was given a climb to our filed altitude of FL390. As we continued climbing to our assigned flight level; I noticed a TCAS target about 5;000 FT above us and about 10 miles away at our two o'clock position. This flight crossed in front of our nose about 5 miles ahead and 1;500 feet above us; but the radio was silent; and I thought that strange; so I did a radio check with Center. Immediately; the Center Controller came back with 'I have been calling you for 2 minutes! Turn 30 degrees right for traffic.' We complied with the vector and the Captain asked me to query him if there was a loss of separation. He curtly replied 'I don't have time right now; I've been trying to reach you for 2 minutes.' Once the radio traffic settled down; I queried him again; and he replied; 'It was close.' On our end; the TCAS target never became solid white and we did not receive a TCAS TA or RA. Prior to removing our headsets; the Captain asked if I minded having the interphone ON to improve inter-cockpit communication. I have never done this before on the B757; but agreed and that is how we operated. However; we did not return the interphone switches to the neutral position when we removed our headsets; and this may have caused our speakers to be inhibited. Once I called Center however; two-way comm. was restored. After the event; the Captain checked in the Aircraft Systems Manual to see if having both Interphone switches ON caused the speakers to be inhibited; but there was no information on this subject. Apparently; however; on this particular ICS panel; if both Interphone switches are ON; the speakers are inhibited; effectively causing a Loss Comm. situation. There are a couple ways: If above FL180; and the crew elects to 'Go speaker' and remove their headsets; they must ensure that both interphone switches are in the neutral position. Secondly; when the crew does 'Go speaker' they should do so during a center transmission to ensure that the speakers are working properly.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.