Narrative:

After doing several touch and go's with my student we performed a full-stop landing due to a long flare that did not leave enough room for a safe takeoff. The fire fighting tankers called ready for takeoff on the intersecting runway. As soon as we cleared our runway I called 'clear of the runway;' so the tankers could depart. As we were taxing back to our runway a tanker took off on the intersecting runway. As we taxied I watched the second tanker at the hold short of the intersecting runway. We were approaching the hold short of their runway and the second tanker called 'taking off.' I could see the second tanker had not even taxied onto the runway yet and we were a few feet from the hold short at about 10 mph. Knowing the second tanker would not be lined up with the runway heading (i.e. Ready for takeoff) before we were across the runway I radioed that my aircraft was taxiing across his runway. He radioed that he was taking off as I watched him power up to start to taxi onto the runway. I could clearly see this tanker was not going to be on the runway before I was across the runway. I radioed we would be clear of the runway; not to interfere. I could see this plane and he was just taxiing onto the runway about half a mile from our position. As we crossed onto the runway I saw the plane on takeoff roll; I had been looking at the third tanker at the hold short and never the second tanker until I was on the runway in front of him. He radioed 'watch it watch it watch it'; but the only thing I could do to get out of his way at that point was apply full throttle to get to the other side of the runway (we were already well onto the runway). He lifted off about 250 ft in front of us. Being in a high wing aircraft I have no idea of how high he was above us. Neither the student nor I heard any radio calls from tanker two other than the call to takeoff as we were approaching the runway. Because of the short interval of time between takeoff he must have taxied into position while the lead was on the roll. Not a big deal; but the timing between lead takeoff and number two's call lead me to believe the second aircraft was still taking the runway; not on the roll. This was an assumption; and clearly not correct. While the second tanker might have helped situational awareness by making a call of taxiing onto the runway the bottom line is; I thought I was looking at the correct aircraft (you don't know what you are not seeing) and crossed a hold short when I knew the runway was in use. Whether it was about to be in use (as I thought); or actually in use does not matter; I should have stopped and waited. I don't have any corrective actions other than not taxiing onto an 'active' runway even if you can see the plan using the runway won't be ready for a while. You may not be looking at the correct plane. I discussed this with my student thoroughly. A good lesson was learned; but not a lesson worth risking 3 lives.

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Original NASA ASRS Text

Title: An Instructor and Student crossed the runway at the end just as an air tanker was taking off. The reporter did not see the second of three aircraft until it was lifting off and thought the previous radio calls were from a third tanker at the other end.

Narrative: After doing several touch and go's with my student we performed a full-stop landing due to a long flare that did not leave enough room for a safe takeoff. The fire fighting tankers called ready for takeoff on the intersecting runway. As soon as we cleared our runway I called 'clear of the runway;' so the tankers could depart. As we were taxing back to our runway a tanker took off on the intersecting runway. As we taxied I watched the second tanker at the hold short of the intersecting runway. We were approaching the hold short of their runway and the second tanker called 'taking off.' I could see the second tanker had not even taxied onto the runway yet and we were a few feet from the hold short at about 10 MPH. Knowing the second tanker would not be lined up with the runway heading (i.e. ready for takeoff) before we were across the runway I radioed that my aircraft was taxiing across his runway. He radioed that he was taking off as I watched him power up to start to taxi onto the runway. I could clearly see this tanker was not going to be on the runway before I was across the runway. I radioed we would be clear of the runway; not to interfere. I could see this plane and he was just taxiing onto the runway about half a mile from our position. As we crossed onto the runway I saw the plane on takeoff roll; I had been looking at the third tanker at the hold short and never the second tanker until I was on the runway in front of him. He radioed 'Watch it watch it watch it'; but the only thing I could do to get out of his way at that point was apply full throttle to get to the other side of the runway (we were already well onto the runway). He lifted off about 250 FT in front of us. Being in a high wing aircraft I have no idea of how high he was above us. Neither the student nor I heard any radio calls from tanker two other than the call to takeoff as we were approaching the runway. Because of the short interval of time between takeoff he must have taxied into position while the lead was on the roll. Not a big deal; but the timing between lead takeoff and number two's call lead me to believe the second aircraft was still taking the runway; not on the roll. This was an assumption; and clearly not correct. While the second tanker might have helped situational awareness by making a call of taxiing onto the runway the bottom line is; I thought I was looking at the correct aircraft (you don't know what you are not seeing) and crossed a hold short when I knew the runway was in use. Whether it was about to be in use (as I thought); or actually in use does not matter; I should have stopped and waited. I don't have any corrective actions other than not taxiing onto an 'active' runway even if you can see the plan using the runway won't be ready for a while. You may not be looking at the correct plane. I discussed this with my student thoroughly. A good lesson was learned; but not a lesson worth risking 3 lives.

Data retrieved from NASA's ASRS site as of April 2012 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.