Narrative:

I completely misunderstood information given to me as a clearance to follow another aircraft and cross runway 31R at mdw. This caused a light twin to go around. When I reflect on the radio transmission from ground to us, I can't imagine why I thought I received a clearance. Phraseology played a part in the misunderstanding on my part. At all times phraseology should be short to the point and stated or issued to 1 aircraft at a time. Callback conversation with reporter revealed the following information: the reporter stated he was captain of a DC9- 30. He said he saw an airplane landing on runway 04 about the time the controller cleared them to taxi to runway 22L. His 'mindset' locked on to taxi to runway 04L. As he was going on the runway 31R the first officer called attention to the light twin going around at the approach end of runway 31R. The captain was told he had crossed an active runway without a clearance and to continue to runway 31C. The captain continued to runway 31C and flew an uneventful flight to stl. At stl the captain called midway tower to apologize and was told by midway tower supervisor they saw what was happening and sent the light twin around. The supervisor further stated the tower phraseology was not as clear as it should have been and no further action would be taken by the tower and thanks for calling. Supplemental information from acn 328162: our clearance was to wait for an air carrier B727 to pass, then to follow it to runway 31C, holding short of runway 31R. During the wait several aircraft were cleared to runway 22L prompting the captain to ask me to concur that we were going to runway 31C. I concurred and we began the taxi. As we approached runway 31R ground cleared us to 'taxi to runway 22L.' still rolling toward runway 31R, I looked left and saw an aircraft landing light. Due to the distortion of the sliding window I could not tell which runway it was aligned with or how far out it was. The captain was adding power to cross when I pointed it out. The aircraft was on final for runway 31R and was issued a go around. Ground then informed us we had crossed an active without clearance. I became confused as to our clearance when I saw the aircraft on final approach. When I pointed the traffic out to the captain, my expectation was that he would stop even though we might still have intruded on the runway. In retrospect, my perception that something was amiss should have resulted in a challenge to his decision to cross. Callback conversation with reporter of acn 328162 revealed the following information: the reporter stated he was first officer on a DC9- 30. He said the controller could have alerted the crew to a change of plans by saying 'disregard clearance to runway 31C, make a 110 degree turn to your right and cleared to runway 22L.' landing at their destination the captain called midway tower. After reviewing the tapes the tower said there was a lot of confusion and they were not going to pursue the issue.

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Original NASA ASRS Text

Title: THE FLC TAXIES ACROSS THE ACTIVE RWY WITHOUT A CLRNC.

Narrative: I COMPLETELY MISUNDERSTOOD INFO GIVEN TO ME AS A CLRNC TO FOLLOW ANOTHER ACFT AND CROSS RWY 31R AT MDW. THIS CAUSED A LIGHT TWIN TO GAR. WHEN I REFLECT ON THE RADIO XMISSION FROM GND TO US, I CAN'T IMAGINE WHY I THOUGHT I RECEIVED A CLRNC. PHRASEOLOGY PLAYED A PART IN THE MISUNDERSTANDING ON MY PART. AT ALL TIMES PHRASEOLOGY SHOULD BE SHORT TO THE POINT AND STATED OR ISSUED TO 1 ACFT AT A TIME. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS CAPT OF A DC9- 30. HE SAID HE SAW AN AIRPLANE LNDG ON RWY 04 ABOUT THE TIME THE CTLR CLRED THEM TO TAXI TO RWY 22L. HIS 'MINDSET' LOCKED ON TO TAXI TO RWY 04L. AS HE WAS GOING ON THE RWY 31R THE FO CALLED ATTN TO THE LIGHT TWIN GOING AROUND AT THE APCH END OF RWY 31R. THE CAPT WAS TOLD HE HAD CROSSED AN ACTIVE RWY WITHOUT A CLRNC AND TO CONTINUE TO RWY 31C. THE CAPT CONTINUED TO RWY 31C AND FLEW AN UNEVENTFUL FLT TO STL. AT STL THE CAPT CALLED MIDWAY TWR TO APOLOGIZE AND WAS TOLD BY MIDWAY TWR SUPVR THEY SAW WHAT WAS HAPPENING AND SENT THE LIGHT TWIN AROUND. THE SUPVR FURTHER STATED THE TWR PHRASEOLOGY WAS NOT AS CLR AS IT SHOULD HAVE BEEN AND NO FURTHER ACTION WOULD BE TAKEN BY THE TWR AND THANKS FOR CALLING. SUPPLEMENTAL INFO FROM ACN 328162: OUR CLRNC WAS TO WAIT FOR AN ACR B727 TO PASS, THEN TO FOLLOW IT TO RWY 31C, HOLDING SHORT OF RWY 31R. DURING THE WAIT SEVERAL ACFT WERE CLRED TO RWY 22L PROMPTING THE CAPT TO ASK ME TO CONCUR THAT WE WERE GOING TO RWY 31C. I CONCURRED AND WE BEGAN THE TAXI. AS WE APCHED RWY 31R GND CLRED US TO 'TAXI TO RWY 22L.' STILL ROLLING TOWARD RWY 31R, I LOOKED L AND SAW AN ACFT LNDG LIGHT. DUE TO THE DISTORTION OF THE SLIDING WINDOW I COULD NOT TELL WHICH RWY IT WAS ALIGNED WITH OR HOW FAR OUT IT WAS. THE CAPT WAS ADDING PWR TO CROSS WHEN I POINTED IT OUT. THE ACFT WAS ON FINAL FOR RWY 31R AND WAS ISSUED A GAR. GND THEN INFORMED US WE HAD CROSSED AN ACTIVE WITHOUT CLRNC. I BECAME CONFUSED AS TO OUR CLRNC WHEN I SAW THE ACFT ON FINAL APCH. WHEN I POINTED THE TFC OUT TO THE CAPT, MY EXPECTATION WAS THAT HE WOULD STOP EVEN THOUGH WE MIGHT STILL HAVE INTRUDED ON THE RWY. IN RETROSPECT, MY PERCEPTION THAT SOMETHING WAS AMISS SHOULD HAVE RESULTED IN A CHALLENGE TO HIS DECISION TO CROSS. CALLBACK CONVERSATION WITH RPTR OF ACN 328162 REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FO ON A DC9- 30. HE SAID THE CTLR COULD HAVE ALERTED THE CREW TO A CHANGE OF PLANS BY SAYING 'DISREGARD CLRNC TO RWY 31C, MAKE A 110 DEG TURN TO YOUR R AND CLRED TO RWY 22L.' LNDG AT THEIR DEST THE CAPT CALLED MIDWAY TWR. AFTER REVIEWING THE TAPES THE TWR SAID THERE WAS A LOT OF CONFUSION AND THEY WERE NOT GOING TO PURSUE THE ISSUE.

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.