An air carrier captain reports that his first officer caused a stuck microphone.

Attributes
ACN	260026
Time
Date	199312
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : rno
State Reference	NV
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : aus
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 110 flight time total : 9700
ASRS Report	260026
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft was parked at the gate while we were preparing for departure of scheduled flight. First officer was on board performing his preflight duties. I joined him in the cockpit a short time later, and upon donning my headset, observed a side tone, and could hear muffled conversation from the cockpit coming through my earpiece. Obviously, a stuck microphone was indicated. I checked my microphone buttons and audio panel, and had the first officer do the same on his side, and I also looked at the observer station audio panel, but could not find the problem. We finally discovered that the first officer had hung his uniform coat on the microphone holder at the observer station, and the coat was pushing the transmit button on the hand microphone, hanging on the bracket. Once the coat was removed, the problem was solved. The problem of stowing flight crew coats, bags, etc, is a definite problem on the medium large transport aircraft. Some versions have a small compartment opposite the jump seat, but most have no cockpit storage at all. Usually, crew items are stowed in the passenger cabin, which means they are mixed in with the passenger carry-on baggage. This compromises the security of the crew's items.

Original NASA ASRS Text

Title: AN ACR CAPT RPTS THAT HIS FO CAUSED A STUCK MIKE.

Narrative: ACFT WAS PARKED AT THE GATE WHILE WE WERE PREPARING FOR DEP OF SCHEDULED FLT. FO WAS ON BOARD PERFORMING HIS PREFLT DUTIES. I JOINED HIM IN THE COCKPIT A SHORT TIME LATER, AND UPON DONNING MY HEADSET, OBSERVED A SIDE TONE, AND COULD HEAR MUFFLED CONVERSATION FROM THE COCKPIT COMING THROUGH MY EARPIECE. OBVIOUSLY, A STUCK MIKE WAS INDICATED. I CHKED MY MIKE BUTTONS AND AUDIO PANEL, AND HAD THE FO DO THE SAME ON HIS SIDE, AND I ALSO LOOKED AT THE OBSERVER STATION AUDIO PANEL, BUT COULD NOT FIND THE PROB. WE FINALLY DISCOVERED THAT THE FO HAD HUNG HIS UNIFORM COAT ON THE MIKE HOLDER AT THE OBSERVER STATION, AND THE COAT WAS PUSHING THE XMIT BUTTON ON THE HAND MIKE, HANGING ON THE BRACKET. ONCE THE COAT WAS REMOVED, THE PROB WAS SOLVED. THE PROB OF STOWING FLC COATS, BAGS, ETC, IS A DEFINITE PROB ON THE MLG ACFT. SOME VERSIONS HAVE A SMALL COMPARTMENT OPPOSITE THE JUMP SEAT, BUT MOST HAVE NO COCKPIT STORAGE AT ALL. USUALLY, CREW ITEMS ARE STOWED IN THE PAX CABIN, WHICH MEANS THEY ARE MIXED IN WITH THE PAX CARRY-ON BAGGAGE. THIS COMPROMISES THE SECURITY OF THE CREW'S ITEMS.

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.