A B737 crew lost communication and began transmitting blind on 121 pt 5. They could receive but could not transmit. Maintenance was unable to duplicate the problem.

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Attributes
ACN	449704
Time
Date	199909
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : grr.airport
State Reference	MI
Altitude	msl bound lower : 0 msl bound upper : 20000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	arrival star : polar 1
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	449704
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	atc equipment other atc equipment : freq 121.5 other controllera other flight crewa other flight crewb
Resolutory Action	other
Consequence	other
Supplementary
Problem Areas	Maintenance Human Performance Navigational Facility Flight Crew Human Performance ATC Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

While on polar one arrival to dtw we called ZOB, to ask for descent clearance. We were unable to establish communications. After trying several frequencys, I broadcasted in the blind on 121.5 and began our descent as per lost communication procedures. After much difficulty we found ourselves able to receive selfridge approach on 121.5, but unable to transmit. They relayed approach instructions to us and we continued on to dtw. Maintenance was unable to duplicate the problem. So, as a precautionary move, they replaced our #2 communication radio and switched #2 audio panel with the observer's. We did not encounter the problem again.

Original NASA ASRS Text

Title: A B737 CREW LOST COM AND BEGAN XMITTING BLIND ON 121 PT 5. THEY COULD RECEIVE BUT COULD NOT XMIT. MAINT WAS UNABLE TO DUPLICATE THE PROB.

Narrative: WHILE ON POLAR ONE ARR TO DTW WE CALLED ZOB, TO ASK FOR DSCNT CLRNC. WE WERE UNABLE TO ESTABLISH COMS. AFTER TRYING SEVERAL FREQS, I BROADCASTED IN THE BLIND ON 121.5 AND BEGAN OUR DSCNT AS PER LOST COM PROCS. AFTER MUCH DIFFICULTY WE FOUND OURSELVES ABLE TO RECEIVE SELFRIDGE APCH ON 121.5, BUT UNABLE TO XMIT. THEY RELAYED APCH INSTRUCTIONS TO US AND WE CONTINUED ON TO DTW. MAINT WAS UNABLE TO DUPLICATE THE PROB. SO, AS A PRECAUTIONARY MOVE, THEY REPLACED OUR #2 COM RADIO AND SWITCHED #2 AUDIO PANEL WITH THE OBSERVER'S. WE DID NOT ENCOUNTER THE PROB AGAIN.

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.