A B737 flight crew has to break suddenly at sna, as a low wing small aircraft cuts in front of them.

Attributes
ACN	587460
Time
Date	200307
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sna.airport
State Reference	CA
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	ground : taxi
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : sna.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	ground : taxi
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	587460
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	conflict : ground less severe incursion : taxiway non adherence : far non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : took precautionary avoidance action
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

During taxi out at sna, a runway change was made. We followed an air carrier X and air carrier Y south on taxiway B and directed to hold short of taxiway D. While holding at this position, under the control of sna tower, we were directed to allow a cessna to precede us to the runway for takeoff. After this cessna taxied into position, I started to taxi forward. After releasing brakes, a low wing aircraft cut directly across the taxiway less than 50 ft in front of our aircraft and proceeded into a clear area for their engine run-up! I had to heavily brake to avoid contact with this light aircraft. According to sna tower, the aircraft was under ground control and was told to hold short of the active taxiway. Tower could not see the event because of their position and the relationship of our aircraft to the event.

Original NASA ASRS Text

Title: A B737 FLT CREW HAS TO BREAK SUDDENLY AT SNA, AS A LOW WING SMALL ACFT CUTS IN FRONT OF THEM.

Narrative: DURING TAXI OUT AT SNA, A RWY CHANGE WAS MADE. WE FOLLOWED AN ACR X AND ACR Y S ON TXWY B AND DIRECTED TO HOLD SHORT OF TXWY D. WHILE HOLDING AT THIS POS, UNDER THE CTL OF SNA TWR, WE WERE DIRECTED TO ALLOW A CESSNA TO PRECEDE US TO THE RWY FOR TKOF. AFTER THIS CESSNA TAXIED INTO POS, I STARTED TO TAXI FORWARD. AFTER RELEASING BRAKES, A LOW WING ACFT CUT DIRECTLY ACROSS THE TXWY LESS THAN 50 FT IN FRONT OF OUR ACFT AND PROCEEDED INTO A CLR AREA FOR THEIR ENG RUN-UP! I HAD TO HEAVILY BRAKE TO AVOID CONTACT WITH THIS LIGHT ACFT. ACCORDING TO SNA TWR, THE ACFT WAS UNDER GND CTL AND WAS TOLD TO HOLD SHORT OF THE ACTIVE TXWY. TWR COULD NOT SEE THE EVENT BECAUSE OF THEIR POS AND THE RELATIONSHIP OF OUR ACFT TO THE EVENT.

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.