Instructor pilot misinterps clearance instructions and flies to south boundary instead of north boun...

Attributes
ACN	366670
Time
Date	199704
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sea
State Reference	WA
Altitude	msl bound lower : 1500 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sea
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	None
Aircraft 2
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Person 1
Affiliation	Other
Function	instruction : instructor
Qualification	pilot : commercial pilot : instrument pilot : cfi
Experience	flight time last 90 days : 74 flight time total : 1972 flight time type : 1329
ASRS Report	366670
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : student
Events
Anomaly	non adherence : clearance non adherence : far other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : became reoriented other
Consequence	Other
Miss Distance	horizontal : 8000 vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was on a VFR training flight with a student from rnt to tiw via the VFR transition wbound across sea. The traffic flow was to the south at both rnt and sea and our clearance was 'cleared to enter the sea class B airspace at or below 2000 ft, cross at the north field boundary.' I was handling communications and read back the clearance, and here I'm not sure what happened. I think I read it back including, 'south field boundary,' and if I did, I can't imagine why, but this is where I directed my student to cross, ie, at 1500 ft across the numbers of runway 34R. We flew southeast then lined up on a 250 degree heading to cross sea. About 1 - 1 1/4 mi from the runway, I saw a B737 departing runway 16R and immediately turned northbound to cross at the north field boundary. Abeam midfield, sea tower cleared us to cross midfield with no further comment. I don't know how I made this mistake. The traffic flow was to the south, my student questioned my directions (I assured him we'd been cleared for the south field boundary), and when we departed rnt we were given an early frequency change to sea which would expedite crossing at the north field boundary. All I can think of is that I misheard the controller because my attention was on the student, and there was a lull in arrs and departures at sea, ie, no visual cues. I am absolutely mortified that this happened! (And damned lucky this is a state of mind and not a physical one.)

Original NASA ASRS Text

Title: INSTRUCTOR PLT MISINTERPS CLRNC INSTRUCTIONS AND FLIES TO S BOUNDARY INSTEAD OF N BOUNDARY OF SEA ARPT TO CROSS OVER RWYS. HE SEES HIS ERROR AND IS TURNING TO CORRECT WHEN ATC ISSUES NEW CLRNC.

Narrative: I WAS ON A VFR TRAINING FLT WITH A STUDENT FROM RNT TO TIW VIA THE VFR TRANSITION WBOUND ACROSS SEA. THE TFC FLOW WAS TO THE S AT BOTH RNT AND SEA AND OUR CLRNC WAS 'CLRED TO ENTER THE SEA CLASS B AIRSPACE AT OR BELOW 2000 FT, CROSS AT THE N FIELD BOUNDARY.' I WAS HANDLING COMS AND READ BACK THE CLRNC, AND HERE I'M NOT SURE WHAT HAPPENED. I THINK I READ IT BACK INCLUDING, 'S FIELD BOUNDARY,' AND IF I DID, I CAN'T IMAGINE WHY, BUT THIS IS WHERE I DIRECTED MY STUDENT TO CROSS, IE, AT 1500 FT ACROSS THE NUMBERS OF RWY 34R. WE FLEW SE THEN LINED UP ON A 250 DEG HDG TO CROSS SEA. ABOUT 1 - 1 1/4 MI FROM THE RWY, I SAW A B737 DEPARTING RWY 16R AND IMMEDIATELY TURNED NBOUND TO CROSS AT THE N FIELD BOUNDARY. ABEAM MIDFIELD, SEA TWR CLRED US TO CROSS MIDFIELD WITH NO FURTHER COMMENT. I DON'T KNOW HOW I MADE THIS MISTAKE. THE TFC FLOW WAS TO THE S, MY STUDENT QUESTIONED MY DIRECTIONS (I ASSURED HIM WE'D BEEN CLRED FOR THE S FIELD BOUNDARY), AND WHEN WE DEPARTED RNT WE WERE GIVEN AN EARLY FREQ CHANGE TO SEA WHICH WOULD EXPEDITE XING AT THE N FIELD BOUNDARY. ALL I CAN THINK OF IS THAT I MISHEARD THE CTLR BECAUSE MY ATTN WAS ON THE STUDENT, AND THERE WAS A LULL IN ARRS AND DEPS AT SEA, IE, NO VISUAL CUES. I AM ABSOLUTELY MORTIFIED THAT THIS HAPPENED! (AND DAMNED LUCKY THIS IS A STATE OF MIND AND NOT A PHYSICAL ONE.)

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.

Instructor pilot misinterps clearance instructions and flies to south boundary instead of north boundary of sea airport to cross over runways. He sees his error and is turning to correct when ATC issues new clearance.