A srq tower local controller reported an air carrier did not fly the RNAV SID as expected and toward...

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1654260
Time
Date	201906
Local Time Of Day	1801-2400
Place
Locale Reference	SRQ.Airport
State Reference	FL
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	SID SRKUS4
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 0
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Deviation - Track / Heading All Types

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.