Flight crew changes frequency prematurely in response to similar call sign.

Attributes
ACN	318830
Time
Date	199510
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : phx
State Reference	AZ
Altitude	msl bound lower : 2300 msl bound upper : 2300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phx tower : mso
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Navigation In Use	Other
Flight Phase	climbout : initial
Route In Use	departure other
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 : 280 flight time total : 8800
ASRS Report	318830
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 270 flight time total : 8900 flight time type : 6200
ASRS Report	318923
Events
Anomaly	non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Air Traffic Incident	other

Narrative:

We were cleared for takeoff on runway 8L at phx on the drake 6 departure and told to expect a turn. SID calls for a slight turn to the right to join the phx VOR 075 degree radial. Normally when we are told to expect a turn we are assigned runway heading. This is normally done to keep from conflicting with traffic off the south (parallel) runway. We are normally given the turn out of 2300 ft from runway heading but this was not the case in this occurrence. We inadvertently answered a frequency change for a preceding company flight with a similar call sign and we did not receive a clearance to turn until we were with departure control. This may conflict with traffic off of the south parallel runway in the event of lost communication, stuck microphone, etc. I would recommend that traffic departing north runway 8L be given runway heading when deviating from the SID and this would remove the possibility of a conflict with traffic off the south runway.

Original NASA ASRS Text

Title: FLC CHANGES FREQ PREMATURELY IN RESPONSE TO SIMILAR CALL SIGN.

Narrative: WE WERE CLRED FOR TKOF ON RWY 8L AT PHX ON THE DRAKE 6 DEP AND TOLD TO EXPECT A TURN. SID CALLS FOR A SLIGHT TURN TO THE R TO JOIN THE PHX VOR 075 DEG RADIAL. NORMALLY WHEN WE ARE TOLD TO EXPECT A TURN WE ARE ASSIGNED RWY HDG. THIS IS NORMALLY DONE TO KEEP FROM CONFLICTING WITH TFC OFF THE S (PARALLEL) RWY. WE ARE NORMALLY GIVEN THE TURN OUT OF 2300 FT FROM RWY HDG BUT THIS WAS NOT THE CASE IN THIS OCCURRENCE. WE INADVERTENTLY ANSWERED A FREQ CHANGE FOR A PRECEDING COMPANY FLT WITH A SIMILAR CALL SIGN AND WE DID NOT RECEIVE A CLRNC TO TURN UNTIL WE WERE WITH DEP CTL. THIS MAY CONFLICT WITH TFC OFF OF THE S PARALLEL RWY IN THE EVENT OF LOST COM, STUCK MIKE, ETC. I WOULD RECOMMEND THAT TFC DEPARTING N RWY 8L BE GIVEN RWY HDG WHEN DEVIATING FROM THE SID AND THIS WOULD REMOVE THE POSSIBILITY OF A CONFLICT WITH TFC OFF THE S RWY.

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.