Large transport has brief period of lost communication due to stuck microphone.

Attributes
ACN	252974
Time
Date	199309
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mod
State Reference	CA
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 250 flight time total : 17000 flight time type : 300
ASRS Report	252974
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Communication with ZOA may have been lost due to a stuck microphone and the observers audio selector panel. The pilot and copilot audio selector panels were both checked for a stuck microphone. A few mins later, the observer's audio selector panel was found to have a hand microphone plugged in with the #1 UHF microphone selected. Removing the hand microphone from the observer's audio select panel cleared the airways or communication for the flight. Unless hand mikes are being used, they should be left unplugged, however, all audio selector panels should be examined at the same time. During the mins of lost communication at FL240, a TCASII alert was received from below FL230 -- an aircraft apparently climbed to that altitude. In compliance with far 91.185, a descent to cross cedes intersection on the modesto 2 arrival was about to be initiated. FL240 was maintained and code 7700 was selected with intention of squawking code 7700 for 1 min before changing to code 7600. It was during this time the copilot was successful in re-establishing communication with ZOA. Discovery of the hot microphone followed and subsequently an uneventful arrival and landing was accomplished.

Original NASA ASRS Text

Title: LGT HAS BRIEF PERIOD OF LOST COM DUE TO STUCK MIKE.

Narrative: COM WITH ZOA MAY HAVE BEEN LOST DUE TO A STUCK MIKE AND THE OBSERVERS AUDIO SELECTOR PANEL. THE PLT AND COPLT AUDIO SELECTOR PANELS WERE BOTH CHKED FOR A STUCK MIKE. A FEW MINS LATER, THE OBSERVER'S AUDIO SELECTOR PANEL WAS FOUND TO HAVE A HAND MIKE PLUGGED IN WITH THE #1 UHF MIKE SELECTED. REMOVING THE HAND MIKE FROM THE OBSERVER'S AUDIO SELECT PANEL CLRED THE AIRWAYS OR COM FOR THE FLT. UNLESS HAND MIKES ARE BEING USED, THEY SHOULD BE LEFT UNPLUGGED, HOWEVER, ALL AUDIO SELECTOR PANELS SHOULD BE EXAMINED AT THE SAME TIME. DURING THE MINS OF LOST COM AT FL240, A TCASII ALERT WAS RECEIVED FROM BELOW FL230 -- AN ACFT APPARENTLY CLBED TO THAT ALT. IN COMPLIANCE WITH FAR 91.185, A DSCNT TO CROSS CEDES INTXN ON THE MODESTO 2 ARR WAS ABOUT TO BE INITIATED. FL240 WAS MAINTAINED AND CODE 7700 WAS SELECTED WITH INTENTION OF SQUAWKING CODE 7700 FOR 1 MIN BEFORE CHANGING TO CODE 7600. IT WAS DURING THIS TIME THE COPLT WAS SUCCESSFUL IN RE-ESTABLISHING COM WITH ZOA. DISCOVERY OF THE HOT MIKE FOLLOWED AND SUBSEQUENTLY AN UNEVENTFUL ARR AND LNDG WAS ACCOMPLISHED.

Data retrieved from NASA's ASRS site as of July 2007 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.