B350 taxiing for departure at mdw crossed runway without ATC clearance.

Attributes
ACN	581031
Time
Date	200305
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	other
Make Model Name	Super King Air 350
Operating Under FAR Part	Part 91
Flight Phase	ground : taxi
Flight Plan	IFR
Person 1
Affiliation	government other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 90 flight time total : 15000 flight time type : 9000
ASRS Report	581031
Person 2
Affiliation	government other
Function	flight crew : first officer
Events
Anomaly	conflict : ground less severe incursion : runway non adherence : clearance non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to taxi to runway 22L and told to hold short of runway 31L. When we arrived at runway 31L, we cleared to the left and had traffic in position to the right. The traffic (cessna single) was holding in position. We referred to our notes and mistook runway 31L for runway 31C. We crossed the left and held short of the center. Normally, we are cleared to cross the left (small runway seldom used) and are told to hold short of center. On our notes, the runway 31L looked like runway 31C. Also, a large aircraft was landing on runway 31C and the small single was holding on runway 31L. We should have confirmed with ATC before crossing, but thought we knew (notes showed runway 31C) and normally that is how it is done. The 'left' and 'C' looked the same on our notes and past operating practice actually led us astray. Since I was in doubt, we should have checked with ATC, not our notes. The good thing was our clearing procedure did keep it safe.

Original NASA ASRS Text

Title: B350 TAXIING FOR DEP AT MDW CROSSED RWY WITHOUT ATC CLRNC.

Narrative: WE WERE CLRED TO TAXI TO RWY 22L AND TOLD TO HOLD SHORT OF RWY 31L. WHEN WE ARRIVED AT RWY 31L, WE CLRED TO THE L AND HAD TFC IN POS TO THE R. THE TFC (CESSNA SINGLE) WAS HOLDING IN POS. WE REFERRED TO OUR NOTES AND MISTOOK RWY 31L FOR RWY 31C. WE CROSSED THE L AND HELD SHORT OF THE CTR. NORMALLY, WE ARE CLRED TO CROSS THE L (SMALL RWY SELDOM USED) AND ARE TOLD TO HOLD SHORT OF CTR. ON OUR NOTES, THE RWY 31L LOOKED LIKE RWY 31C. ALSO, A LARGE ACFT WAS LNDG ON RWY 31C AND THE SMALL SINGLE WAS HOLDING ON RWY 31L. WE SHOULD HAVE CONFIRMED WITH ATC BEFORE XING, BUT THOUGHT WE KNEW (NOTES SHOWED RWY 31C) AND NORMALLY THAT IS HOW IT IS DONE. THE 'L' AND 'C' LOOKED THE SAME ON OUR NOTES AND PAST OPERATING PRACTICE ACTUALLY LED US ASTRAY. SINCE I WAS IN DOUBT, WE SHOULD HAVE CHKED WITH ATC, NOT OUR NOTES. THE GOOD THING WAS OUR CLRING PROC DID KEEP IT SAFE.

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.