B737-300 crew had a stuck microphone departing mdw. A new microphone installation contributed.

Attributes
ACN	507850
Time
Date	200104
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : c90.tracon
State Reference	IL
Altitude	msl single value : 10000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : c90.tracon tower : mmsd.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 250 flight time total : 13000 flight time type : 1000
ASRS Report	507850
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 240 flight time total : 6000 flight time type : 3500
ASRS Report	507431
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera other controllerb
Resolutory Action	none taken : anomaly accepted other
Consequence	other other
Supplementary
Problem Areas	Company Aircraft
Primary Problem	Company

Narrative:

During climb phase of flight from mdw to ind, we were advised by ATC that there had been a stuck microphone on our frequency. After inquiring whether ATC thought it was us they replied 'yes.' no mention was made by ATC of this event causing any type of traffic conflict. To my knowledge/recall there was no deviation from procedures and/or standards. If there was, the deviation was not intentional. The aircraft involved had the 'new style' atscall microphone installed in the captain's position. This microphone is wider than the old style and as a result of this and the location is more prone to accidental pressing of the military microphone transmit button by one's leg. Some considerations that may prevent further events are: 1) more care when this style of microphone is installed. 2) positioning the microphone in the holder 'upside down' with microphone button near inner wall of center console. 3) moving holder 1 - 1 1/2 inches toward center console on microphone button is less exposed. 4) placing the atscall microphone back behind first officer's eat where previously located.

Original NASA ASRS Text

Title: B737-300 CREW HAD A STUCK MIKE DEPARTING MDW. A NEW MIKE INSTALLATION CONTRIBUTED.

Narrative: DURING CLB PHASE OF FLT FROM MDW TO IND, WE WERE ADVISED BY ATC THAT THERE HAD BEEN A STUCK MIKE ON OUR FREQ. AFTER INQUIRING WHETHER ATC THOUGHT IT WAS US THEY REPLIED 'YES.' NO MENTION WAS MADE BY ATC OF THIS EVENT CAUSING ANY TYPE OF TFC CONFLICT. TO MY KNOWLEDGE/RECALL THERE WAS NO DEV FROM PROCS AND/OR STANDARDS. IF THERE WAS, THE DEV WAS NOT INTENTIONAL. THE ACFT INVOLVED HAD THE 'NEW STYLE' ATSCALL MIKE INSTALLED IN THE CAPT'S POS. THIS MIKE IS WIDER THAN THE OLD STYLE AND AS A RESULT OF THIS AND THE LOCATION IS MORE PRONE TO ACCIDENTAL PRESSING OF THE MIL MIKE XMIT BUTTON BY ONE'S LEG. SOME CONSIDERATIONS THAT MAY PREVENT FURTHER EVENTS ARE: 1) MORE CARE WHEN THIS STYLE OF MIKE IS INSTALLED. 2) POSITIONING THE MIKE IN THE HOLDER 'UPSIDE DOWN' WITH MIKE BUTTON NEAR INNER WALL OF CTR CONSOLE. 3) MOVING HOLDER 1 - 1 1/2 INCHES TOWARD CTR CONSOLE ON MIKE BUTTON IS LESS EXPOSED. 4) PLACING THE ATSCALL MIKE BACK BEHIND FO'S EAT WHERE PREVIOUSLY LOCATED.

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.