Narrative:

The initial taxi instructions from gate area from ord from ground control were to 'taxi to runway 4L, left turn on txwys B, J, and west.' once on taxiway H with our aircraft heading 270 degrees and approaching the area of txwys a and B, ground said 'the aircraft on taxiway right will give way to you.' I told the captain that I would be off the radio getting the passenger count and weights for takeoff. While I was off the radio, I could tell the captain and the ground controller were talking. We then continued straight ahead on taxiway H and crossed runway 4L. There was no traffic on the runway or the approach or runway 4L runup area. After crossing runway 2L, on taxiway H, I returned to monitor the ground frequency where the captain and the ground controller were discussing the taxi route. Ground asked what we were doing. The captain said we were 'taxiing straight ahead to runway 4L per your last instructions.' since this was different than our original clearance to taxi, I assumed that while I was off the radio that the ground controller had changed our taxi route and that the captain was complying with his instructions. When I asked what was going on, the captain explained that he was following ground instructions to taxi straight ahead, and that the aircraft on taxiway right facing southeast would be holding for us. The captain taxied down taxiway H, made a left turn on taxiway J and a left turn on taxiway west, holding short of runway 4L. Contributing factors: an engine problem caused us to return to the gate for maintenance. Upon our taxi out, the chief purser told the captain some of the passenger had deplaned, but did not give us a count. This caused us to isolate the radios, call for a count, advise load control of the change. A short taxi, with poor ATC language 'taxi straight ahead' when a 45 degree turn was required to get to taxiway B from taxiway H, was also confusing. Language such as 'continue taxi to runway 4L as cleared' or 'continue, left on taxiway G, right on taxiway J, right on taxiway west' would have eliminated any confusion on the part of the captain. A procedure to isolate the radios for cabin communication and load control could be put in place to only do this while the aircraft is stopped. But this is not practical. Better ATC adherence to standard phraseology as well as repeating full clrncs when the initial clrncs have changes in parts of the initial clearance.

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Original NASA ASRS Text

Title: A TAXIING B747-400 CROSSES RWY 4L WITHOUT CLRNC FROM GND CTLR AT ORD, IL.

Narrative: THE INITIAL TAXI INSTRUCTIONS FROM GATE AREA FROM ORD FROM GND CTL WERE TO 'TAXI TO RWY 4L, L TURN ON TXWYS B, J, AND W.' ONCE ON TXWY H WITH OUR ACFT HDG 270 DEGS AND APCHING THE AREA OF TXWYS A AND B, GND SAID 'THE ACFT ON TXWY R WILL GIVE WAY TO YOU.' I TOLD THE CAPT THAT I WOULD BE OFF THE RADIO GETTING THE PAX COUNT AND WTS FOR TKOF. WHILE I WAS OFF THE RADIO, I COULD TELL THE CAPT AND THE GND CTLR WERE TALKING. WE THEN CONTINUED STRAIGHT AHEAD ON TXWY H AND CROSSED RWY 4L. THERE WAS NO TFC ON THE RWY OR THE APCH OR RWY 4L RUNUP AREA. AFTER XING RWY 2L, ON TXWY H, I RETURNED TO MONITOR THE GND FREQ WHERE THE CAPT AND THE GND CTLR WERE DISCUSSING THE TAXI RTE. GND ASKED WHAT WE WERE DOING. THE CAPT SAID WE WERE 'TAXIING STRAIGHT AHEAD TO RWY 4L PER YOUR LAST INSTRUCTIONS.' SINCE THIS WAS DIFFERENT THAN OUR ORIGINAL CLRNC TO TAXI, I ASSUMED THAT WHILE I WAS OFF THE RADIO THAT THE GND CTLR HAD CHANGED OUR TAXI RTE AND THAT THE CAPT WAS COMPLYING WITH HIS INSTRUCTIONS. WHEN I ASKED WHAT WAS GOING ON, THE CAPT EXPLAINED THAT HE WAS FOLLOWING GND INSTRUCTIONS TO TAXI STRAIGHT AHEAD, AND THAT THE ACFT ON TXWY R FACING SE WOULD BE HOLDING FOR US. THE CAPT TAXIED DOWN TXWY H, MADE A L TURN ON TXWY J AND A L TURN ON TXWY W, HOLDING SHORT OF RWY 4L. CONTRIBUTING FACTORS: AN ENG PROB CAUSED US TO RETURN TO THE GATE FOR MAINT. UPON OUR TAXI OUT, THE CHIEF PURSER TOLD THE CAPT SOME OF THE PAX HAD DEPLANED, BUT DID NOT GIVE US A COUNT. THIS CAUSED US TO ISOLATE THE RADIOS, CALL FOR A COUNT, ADVISE LOAD CTL OF THE CHANGE. A SHORT TAXI, WITH POOR ATC LANGUAGE 'TAXI STRAIGHT AHEAD' WHEN A 45 DEG TURN WAS REQUIRED TO GET TO TXWY B FROM TXWY H, WAS ALSO CONFUSING. LANGUAGE SUCH AS 'CONTINUE TAXI TO RWY 4L AS CLRED' OR 'CONTINUE, L ON TXWY G, R ON TXWY J, R ON TXWY W' WOULD HAVE ELIMINATED ANY CONFUSION ON THE PART OF THE CAPT. A PROC TO ISOLATE THE RADIOS FOR CABIN COM AND LOAD CTL COULD BE PUT IN PLACE TO ONLY DO THIS WHILE THE ACFT IS STOPPED. BUT THIS IS NOT PRACTICAL. BETTER ATC ADHERENCE TO STANDARD PHRASEOLOGY AS WELL AS REPEATING FULL CLRNCS WHEN THE INITIAL CLRNCS HAVE CHANGES IN PARTS OF THE INITIAL CLRNC.

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.