B737-300 crew has a runway incursion at mmun.

Attributes
ACN	583233
Time
Date	200305
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mmun.airport
State Reference	FO
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	ground : taxi
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 450 flight time total : 10000 flight time type : 950
ASRS Report	583233
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	incursion : runway non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At XA25Z pushback commenced, called ground for taxi, taxied down taxiway a, ground control calls, runway in use is now runway 12, take taxiway C back contact tower. First officer read back 'taxi C, down the runway contact tower.' I looked left, clear, first officer looked right, clear. Entered runway for taxi back, called tower. Tower says not cleared, take first exit right. Did so, no danger to aircraft or passenger. Terminology and verbal context led to the misunderstanding. The perception of being cleared for taxi back was no hold short was heard nor was it in the read back. Never was aircraft in any immediate danger.

Original NASA ASRS Text

Title: B737-300 CREW HAS A RWY INCURSION AT MMUN.

Narrative: AT XA25Z PUSHBACK COMMENCED, CALLED GND FOR TAXI, TAXIED DOWN TXWY A, GND CTL CALLS, RWY IN USE IS NOW RWY 12, TAKE TXWY C BACK CONTACT TWR. FO READ BACK 'TAXI C, DOWN THE RWY CONTACT TWR.' I LOOKED L, CLR, FO LOOKED R, CLR. ENTERED RWY FOR TAXI BACK, CALLED TWR. TWR SAYS NOT CLRED, TAKE FIRST EXIT R. DID SO, NO DANGER TO ACFT OR PAX. TERMINOLOGY AND VERBAL CONTEXT LED TO THE MISUNDERSTANDING. THE PERCEPTION OF BEING CLRED FOR TAXI BACK WAS NO HOLD SHORT WAS HEARD NOR WAS IT IN THE READ BACK. NEVER WAS ACFT IN ANY IMMEDIATE DANGER.

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.