Commercial Fixed Wing
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 0
Situational Awareness; Confusion
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Procedure; Human Factors; Chart Or Publication; Company Policy
I cleared Aircraft Y for takeoff and as he was established in his climbing right turn heading 180 to 1;600 feet I switched the aircraft to Departure Control. Then I cleared Aircraft X for takeoff on the RNAV Departure. As the aircraft climbed off the departure end; I noticed the wing dip and the aircraft begin a right turn toward the previously departed Aircraft Y. I instructed the pilot of Aircraft X that they should be Runway Heading and the pilot replied; 'No sir'. I immediately went to issue traffic to Aircraft X but mid-transmission; noticed he was turning faster than expected and gave 'traffic alert' on the Aircraft Y that was now less than a mile at his 1 o'clock. I advised Aircraft Y of traffic just in case they were on my frequency but did not receive a response. The RNAV departure procedure should have the aircraft climbing to 3;000 feet on runway heading before any turns are made. This is not the first time this issue has occurred in my short time here. I have been in the tower cab for three of these occurrences and each time has resulted in a close call. The wording of the climb-out instructions for this RNAV SID are on a separate page and can be confusing for pilots as compared to many other RNAV departures I have seen and read. The wording must be changed to alleviate further confusion.
Reporter stated Local Controller is supposed to state Fly Runway heading with takeoff clearance and the facility is working to clear up the confusing verbiage on the SID.
A SRQ Tower Local Controller reported an Air Carrier did not fly the RNAV SID as expected and towards a confliction with previous departing traffic and that this is a recurring issue using this RNAV SID.