B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 195
Human-Machine Interface; Training / Qualification
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Chart Or Publication; Human Factors; Procedure
PDC clearance was BWI CONLE1 COLIN V213 HPW ...  The FMC was omitting the DIXXE fix between CONLE and COLIN.  First Officer tried three times to load and finally entered DIXIE (not DIXXE) between CONLE and COLIN.  I was informed of this and asked to check carefully.  I checked it twice and missed the difference.  We also briefed the departure standard (pilot flying reading SID and pilot monitoring (PM) verifying FMC). The FMC was programmed incorrectly for DIXIE instead of DIXXE.  On departure off Runway 28; we were cleared the SID and around STABL at 11;000' were given direct DIXXE.  Brought up DIXIE; concur; EXC.  Aircraft started turn to northeast.  We both noticed error immediately and PM was trying to work out error.  ATC queried; and gave heading to the south.  Found error and corrected to DIXXE.  Was able to tell ATC error and he said no conflict and asked where/spelling of the other DIXIE was.  He wanted to know because this was a new departure and it was new to everyone.I felt that this SID was cumbersome and hard to brief due to the CONLE1 COLIN part being similar as well as there being a chance that DIXXE could be DIXIE if exact spelling was not checked.  I have learned that the SID should have been rejected and not even a simple modification should have been entered.  The First Officer and I discussed that if we would have stepped through the plan view on the FMC; it would have clearly stopped this error.  We don't phonetically spell the fixes.  Similar sounding fixes should NOT be within several hundred miles of each other.
B737NG Captain experiences a track deviation during the CONLE1 departure COLIN transition when the First Officer cannot get the DIXXE fix to load automatically and DIXIE is entered manually. He believes that CONLE and COLIN and the two Dixie's make this a difficult departure to brief and enter correctly in the FMC.