A departure controller reported an A321 departing climbed at a much slower speed than a trailing B73...

Narrative:

Aircraft X departed and was climbing on the SID. Aircraft Y subsequently departed on the same SID. When aircraft Y's tag acquired they were 2.8 miles behind and only 10 knots slower over the ground than aircraft X. Having encountered this scenario numerous times before; I immediately utilized the shoutline to the local east controller and assigned 3;000 feet to aircraft Y. Since aircraft X had already vacated 3;000 feet; I knew I would at least retain vertical separation. Within 10-15 seconds aircraft Y had accelerated to and exceeded aircraft X's ground speed. Within one minute of aircraft Y's departure they were showing 30 to 40 knots faster than their preceding traffic. Aircraft Y was subsequently vectored and climbed appropriately in-trail of aircraft X and both left our airspace without further incident.this is a common problem that we experience with A321 departures. I do not know why this specific aircraft type climbs out so differently; but it is common knowledge at the TRACON. Tower does not seem to consistently take into account the performance of A321s on departure. Without my anticipation of the problem and action to retain vertical separation; there would have been a loss of separation.the letter of agreement (LOA) with tower should be changed to exclude the use of pilot provided visual separation and require the provision of additional spacing to account for the lackluster performance characteristics of A321s' on departure. I would recommend a provision of 4 to 5 miles between an A321 and subsequent departures.

Original NASA ASRS Text

Title: A Departure Controller reported an A321 departing climbed at a much slower speed than a trailing B737 requiring them to vector the B737 away to maintain separation.

Narrative: Aircraft X departed and was climbing on the SID. Aircraft Y subsequently departed on the same SID. When Aircraft Y's tag acquired they were 2.8 miles behind and only 10 knots slower over the ground than Aircraft X. Having encountered this scenario numerous times before; I immediately utilized the shoutline to the Local East controller and assigned 3;000 feet to Aircraft Y. Since Aircraft X had already vacated 3;000 feet; I knew I would at least retain vertical separation. Within 10-15 seconds Aircraft Y had accelerated to and exceeded Aircraft X's ground speed. Within one minute of Aircraft Y's departure they were showing 30 to 40 knots faster than their preceding traffic. Aircraft Y was subsequently vectored and climbed appropriately in-trail of Aircraft X and both left our airspace without further incident.This is a common problem that we experience with A321 departures. I do not know why this specific aircraft type climbs out so differently; but it is common knowledge at the TRACON. Tower does not seem to consistently take into account the performance of A321s on departure. Without my anticipation of the problem and action to retain vertical separation; there would have been a loss of separation.The Letter of Agreement (LOA) with Tower should be changed to exclude the use of pilot provided visual separation and require the provision of additional spacing to account for the lackluster performance characteristics of A321s' on departure. I would recommend a provision of 4 to 5 miles between an A321 and subsequent departures.

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	1478078
Time
Date	201709
Local Time Of Day	1801-2400
Place
Locale Reference	S46.TRACON
State Reference	WA
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	SID SUMMA
Flight Plan	IFR
Aircraft 2
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	SID SUMMA
Flight Plan	IFR
Person 1
Function	Departure
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 2.7
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy Deviation - Speed All Types

A departure controller reported an A321 departing climbed at a much slower speed than a trailing B737 requiring them to vector the B737 away to maintain separation.