An embraer 135 in cruise declared an emergency due to dual navigation radio failure. Cause unknown.

Attributes
ACN	612442
Time
Date	200403
Day	Thu
Place
Locale Reference	atc facility : zau.artcc
State Reference	IL
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	Embraer Jet Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	612442
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
ASRS Report	612441
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During cruise, navigation #1 went to dashed display. Tried to tune the navigation, but it would not keep frequency. Tried to cross tune navigation #1 with rmu #2. This did not work. #2 navigation also went to dashes. We had no navigation function at all. Radioed dispatch and had patch through to maintenance. Explained problem and maintenance stated they did not have any information to help us. We declared an emergency. I flew the aircraft and the first officer tried to pull and reset navigation circuit breakers. He was able to recover navigation #2, but not navigation #1. He pulled and reset the rmu #1 circuit breaker. This worked and we recovered both navs. We landed without further incident. At the gate, both navs failed again. We followed all company manuals and procedures.

Original NASA ASRS Text

Title: AN EMBRAER 135 IN CRUISE DECLARED AN EMER DUE TO DUAL NAV RADIO FAILURE. CAUSE UNKNOWN.

Narrative: DURING CRUISE, NAV #1 WENT TO DASHED DISPLAY. TRIED TO TUNE THE NAV, BUT IT WOULD NOT KEEP FREQ. TRIED TO CROSS TUNE NAV #1 WITH RMU #2. THIS DID NOT WORK. #2 NAV ALSO WENT TO DASHES. WE HAD NO NAV FUNCTION AT ALL. RADIOED DISPATCH AND HAD PATCH THROUGH TO MAINT. EXPLAINED PROB AND MAINT STATED THEY DID NOT HAVE ANY INFO TO HELP US. WE DECLARED AN EMER. I FLEW THE ACFT AND THE FO TRIED TO PULL AND RESET NAV CIRCUIT BREAKERS. HE WAS ABLE TO RECOVER NAV #2, BUT NOT NAV #1. HE PULLED AND RESET THE RMU #1 CIRCUIT BREAKER. THIS WORKED AND WE RECOVERED BOTH NAVS. WE LANDED WITHOUT FURTHER INCIDENT. AT THE GATE, BOTH NAVS FAILED AGAIN. WE FOLLOWED ALL COMPANY MANUALS AND PROCS.

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.