Narrative:

A B737 was departing runway 8R and assigned the RNAV 'off-the-ground' of hrshl. The clearance was issued and readback correctly. On departure the aircraft appeared to dip his/her left wing indicating that a left turn had begun; as is normal for this RNAV (approximately 020 degree left turn from centerline). For whatever reason; the aircraft ceased the turn and continued straight out. At the same time (which is common at the world's busiest airport) there was another aircraft simultaneously departing runway 9L with an RNAV (approx 095 heading or 'runway heading'). The aircraft almost [merged] off the departure end of the runways.this has been happening in alarming amounts off our runways; in a both west operation and an east operation. We; as controllers; have gone to great lengths to mitigate these occurrences to no avail. The best solution to this is to eliminate RNAV off-the-ground and go back to issuing headings all the time. We are confusing the pilots. Sometimes we issue headings; sometimes rnavs; and it is too busy of a facility to babysit every aircraft. Rnavs were tauted as the best thing to come to aviation since the transponder. The workload is all on the computer in the aircraft; easier for pilots and controllers alike. It is not turning out to be as reliable as once thought. I fear that there will be a midair resulting from this if we don't eliminate it!we have multiple errors and pilot deviations from this every week. That is the ones that we don't catch and prevent. Unfortunately; reverting back to headings would; in some managers' minds; be a step backwards in progress. Nextgen is coming and we are trying to automate more and more things. I am telling you now that if this isn't addressed and fixed there will be a terrible situation that occurs. All of us can see it coming; please help us prevent it before it happens.

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Original NASA ASRS Text

Title: ATL Tower Controller reported a B737 departure did not fly the assigned RNAV route; resulting in a loss of separation with a departure off another runway. Aircraft proximity was approximately 1 mile.

Narrative: A B737 was departing Runway 8R and assigned the RNAV 'off-the-ground' of HRSHL. The clearance was issued and readback correctly. On departure the aircraft appeared to dip his/her left wing indicating that a left turn had begun; as is normal for this RNAV (approximately 020 degree left turn from centerline). For whatever reason; the aircraft ceased the turn and continued straight out. At the same time (which is common at the World's Busiest Airport) there was another aircraft simultaneously departing Runway 9L with an RNAV (approx 095 heading or 'runway heading'). The aircraft almost [merged] off the departure end of the runways.This has been happening in alarming amounts off our runways; in a both west operation and an east operation. We; as controllers; have gone to great lengths to mitigate these occurrences to no avail. The best solution to this is to eliminate RNAV Off-The-Ground and go back to issuing headings ALL THE TIME. We are confusing the pilots. Sometimes we issue headings; sometimes RNAVs; and it is too busy of a facility to babysit every aircraft. RNAVs were tauted as the best thing to come to aviation since the transponder. The workload is all on the computer in the aircraft; easier for pilots and controllers alike. It is not turning out to be as reliable as once thought. I fear that there will be a midair resulting from this if we don't eliminate it!We have multiple errors and pilot deviations from this every week. That is the ones that we don't catch and prevent. Unfortunately; reverting back to headings would; in some Managers' minds; be a step backwards in progress. Nextgen is coming and we are trying to automate more and more things. I am telling you now that if this isn't addressed and fixed there WILL BE a terrible situation that occurs. All of us can see it coming; please help us prevent it BEFORE IT HAPPENS.

Data retrieved from NASA's ASRS site as of April 2012 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.