Narrative:

On taxi out we were #3 or #4 in line for runway 32L from intersection T10 when we switched to north tower frequency of 126.9. We noticed that we did not hear the takeoff clearance for departing aircraft. Switched to south tower frequency and still heard nothing. Returned to north tower frequency and they told us, as we were approaching the #1 position, to contact tower 132.7. This frequency is not published on the airport diagram chart, 10-9. We probably could have waited to change from ground control to tower, but the transmission volume is so large at ord, we assumed the north tower frequency was the correct one and that the timing was right for the frequency change. Last clearance received was 'taxi to runway 32L, intersection T10.' the 132.7 frequency is new to me as I've never seen it on a chart or been given it before. Callback conversation with ord tower and ord TRACON revealed the following information: callback was made to ord tower and ord TRACON. TRACON stated that the frequency the flight crew was told to use is a #3 spare frequency. There are 3 frequencys that are to be used whenever the main frequency is blocked by an emergency, maintenance work, or aircraft bomb threat. The frequency assigned (132.7) was used with no prior notice, therefore, ord controller felt that something occurred suddenly that caused the abnormal use of the spare frequency. Controller further stated that the spare frequencys are not published anywhere available to flcs.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC IS GIVEN A TWR FREQ TO BE USED FOR DEP THAT IS NOT PUBLISHED.

Narrative: ON TAXI OUT WE WERE #3 OR #4 IN LINE FOR RWY 32L FROM INTXN T10 WHEN WE SWITCHED TO N TWR FREQ OF 126.9. WE NOTICED THAT WE DID NOT HEAR THE TKOF CLRNC FOR DEPARTING ACFT. SWITCHED TO S TWR FREQ AND STILL HEARD NOTHING. RETURNED TO N TWR FREQ AND THEY TOLD US, AS WE WERE APCHING THE #1 POS, TO CONTACT TWR 132.7. THIS FREQ IS NOT PUBLISHED ON THE ARPT DIAGRAM CHART, 10-9. WE PROBABLY COULD HAVE WAITED TO CHANGE FROM GND CTL TO TWR, BUT THE XMISSION VOLUME IS SO LARGE AT ORD, WE ASSUMED THE N TWR FREQ WAS THE CORRECT ONE AND THAT THE TIMING WAS RIGHT FOR THE FREQ CHANGE. LAST CLRNC RECEIVED WAS 'TAXI TO RWY 32L, INTXN T10.' THE 132.7 FREQ IS NEW TO ME AS I'VE NEVER SEEN IT ON A CHART OR BEEN GIVEN IT BEFORE. CALLBACK CONVERSATION WITH ORD TWR AND ORD TRACON REVEALED THE FOLLOWING INFO: CALLBACK WAS MADE TO ORD TWR AND ORD TRACON. TRACON STATED THAT THE FREQ THE FLC WAS TOLD TO USE IS A #3 SPARE FREQ. THERE ARE 3 FREQS THAT ARE TO BE USED WHENEVER THE MAIN FREQ IS BLOCKED BY AN EMER, MAINT WORK, OR ACFT BOMB THREAT. THE FREQ ASSIGNED (132.7) WAS USED WITH NO PRIOR NOTICE, THEREFORE, ORD CTLR FELT THAT SOMETHING OCCURRED SUDDENLY THAT CAUSED THE ABNORMAL USE OF THE SPARE FREQ. CTLR FURTHER STATED THAT THE SPARE FREQS ARE NOT PUBLISHED ANYWHERE AVAILABLE TO FLCS.

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.