Flight crew of commuter airline misread their clearance. Deviated from assigned heading.

Attributes
ACN	140214
Time
Date	199003
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sli
State Reference	CA
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : sna
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 2800 flight time type : 800
ASRS Report	140214
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On our flight from sna to lax I (copilot) was talking to company with our departure and arrival times, etc. Captain was flying and talking to ATC. ATC clearance him to sli, then heading 330 degrees. I was talking to company and was bleeding through onto the other radio. All he heard was heading 330 degrees. He acknowledged this, 'heading 330, XXX.' nothing was returned from ATC. 5 mins later ATC told us we were cleared, 'sli, then 330,' and gave a new heading to us for sli. The problem was caused by poor intercom system on the aircraft commuter airplane. Many calls are missed or have to be repeated. Due to this problem. Perhaps a check to assure radios don't bleed through onto each other could be performed periodically. Normally this is not a problem, but on shirt, high workload legs it can be.

Original NASA ASRS Text

Title: FLT CREW OF COMMUTER AIRLINE MISREAD THEIR CLRNC. DEVIATED FROM ASSIGNED HEADING.

Narrative: ON OUR FLT FROM SNA TO LAX I (COPLT) WAS TALKING TO COMPANY WITH OUR DEP AND ARR TIMES, ETC. CAPT WAS FLYING AND TALKING TO ATC. ATC CLRNC HIM TO SLI, THEN HDG 330 DEGS. I WAS TALKING TO COMPANY AND WAS BLEEDING THROUGH ONTO THE OTHER RADIO. ALL HE HEARD WAS HDG 330 DEGS. HE ACKNOWLEDGED THIS, 'HDG 330, XXX.' NOTHING WAS RETURNED FROM ATC. 5 MINS LATER ATC TOLD US WE WERE CLRED, 'SLI, THEN 330,' AND GAVE A NEW HDG TO US FOR SLI. THE PROB WAS CAUSED BY POOR INTERCOM SYS ON THE ACFT COMMUTER AIRPLANE. MANY CALLS ARE MISSED OR HAVE TO BE REPEATED. DUE TO THIS PROB. PERHAPS A CHK TO ASSURE RADIOS DON'T BLEED THROUGH ONTO EACH OTHER COULD BE PERFORMED PERIODICALLY. NORMALLY THIS IS NOT A PROB, BUT ON SHIRT, HIGH WORKLOAD LEGS IT CAN BE.

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.