Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1.3
Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Separated Traffic; Air Traffic Control Issued New Clearance
Aircraft; Manuals; Procedure
The SOP allows Tower to launch successive departures utilizing pilot provided visual separation. The ATCT must modify the secondary scratchpad in the STARS data-tag to advise the TRACON that pilot provided visual separation is being used. However; in this case the first aircraft is an [Airbus] and that type of aircraft is notorious for climbing out much slower than most other aircraft. According to the FALCON replay the trailing B738 is 1.55 miles behind the [Airbus] with a 60 knot overtake. I restricted the B738 to 230 knots and requested the [Airbus] increase to 250 knots as soon as possible. Despite those efforts the situation continued to compress. While I was aware pilot provided visual separation was being utilized; in my judgment the situation had become unsafe and I decided to break our noise abatement procedures and initiate an early eastbound turn for the B738. After initiating the turn I made the supervisor aware of the situation. Both aircraft subsequently continued their departures without further incident.This is a common problem that we experience with [this type of Airbus departure]. I do not know why this specific aircraft type climbs out so differently; but it is common knowledge at the TRACON. I would propose that this situation could be corrected by changing the Letter of Agreement to exclude [this Airbus aircraft type departure] from the provision allowing the use of pilot provided visual separation between successive departures. If Tower had utilized the standard 3-5 mile in-trail spacing that would have been required during IMC; this event would have been completely avoided.
S46 TRACON Controller stated Airbus type departing aircraft routinely climb at much slower airspeeds than similar size type aircraft.