A controller supervising a developmental and an instructor pilot report the student pilot delayed th...

Attributes
ACN	1291921
Time
Date	201508
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Tower
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	SR22
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	VFR
Aircraft 2
Make Model Name	PA-46 Malibu/Malibu Mirage/Malibu Matrix
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	VFR
Person 1
Function	Local Instructor
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 5
Person 2
Function	Instructor
Qualification	Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Commercial
Experience	Flight Crew Last 90 Days 37 Flight Crew Total 283 Flight Crew Type 27
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance
Miss Distance	Horizontal 1000 Vertical 50

Narrative:

I was training a 100 hour developmental on the local position which was combined with ground at the time. After sitting for 45 minutes with no traffic; traffic built quickly and we immediately had 3 arrivals from radar. The cirrus was on a downwind and the malibu was on a 4 mile final. The cirrus was cleared touch and go and number one and the malibu was cleared to land number two behind the cirrus. When the cirrus took his base out a little further than expected; I told the developmental to tell the cirrus to cross final and rejoin the opposite down wind. The cirrus was not in a good spot to be in front of the malibu and I was taken by surprise by this. I am not sure if the cirrus actually extended his downwind slightly; or made a dogleg base; and ended up much closer to the malibu than I thought they would be. It is possible that when I told the cirrus to cross final he maneuvered off the normal base because he did not understand what I needed him to do. Just prior to the conflict alert (ca/ca) going off; I got them both in sight in the haze and realized they were not where I thought they were initially.as the ca/ca went off; I told the cirrus to fly eastbound immediately; and the pilot complied as he was already turning to avoid the malibu on 2 mile final.well; honestly; the only recommendation I can make is that I should not let a developmental go as far as I did. This is a pretty common recommendation; from the [safety] briefings I have read; and it looks like I got caught in the classic trap.

Original NASA ASRS Text

Title: A Controller supervising a Developmental and an Instructor Pilot report the Student Pilot delayed the base turn which caused a conflict with another aircraft on final. The Developmental Controller was slow to resolve the conflict so the Supervisory Controller interceded.

Narrative: I was training a 100 hour Developmental on the Local position which was combined with ground at the time. After sitting for 45 minutes with no traffic; traffic built quickly and we immediately had 3 arrivals from radar. The Cirrus was on a downwind and the Malibu was on a 4 mile final. The Cirrus was cleared touch and go and number one and the Malibu was cleared to land number two behind the Cirrus. When the Cirrus took his base out a little further than expected; I told the developmental to tell the Cirrus to cross final and rejoin the opposite down wind. The Cirrus was not in a good spot to be in front of the Malibu and I was taken by surprise by this. I am not sure if the Cirrus actually extended his downwind slightly; or made a dogleg base; and ended up much closer to the Malibu than I thought they would be. It is possible that when I told the Cirrus to cross final he maneuvered off the normal base because he did not understand what I needed him to do. Just prior to the conflict alert (CA/CA) going off; I got them both in sight in the haze and realized they were not where I thought they were initially.As the CA/CA went off; I told the Cirrus to fly eastbound immediately; and the pilot complied as he was already turning to avoid the Malibu on 2 mile final.Well; honestly; the only recommendation I can make is that I should not let a developmental go as far as I did. This is a pretty common recommendation; from the [Safety] Briefings I have read; and it looks like I got caught in the classic trap.

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.

A controller supervising a developmental and an instructor pilot report the student pilot delayed the base turn which caused a conflict with another aircraft on final. The developmental controller was slow to resolve the conflict so the supervisory controller interceded.