<< >> NASA ASRS Report 169410, February 1991

Controller released small aircraft C in front of small aircraft B which resulted in less than standard separation. Controller had less than 3000' between the two aircraft. He needed 3000'.

Attributes
ACN	169410
Time
Date	199102
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : baf
State Reference	MA
Altitude	agl bound lower : 50 agl bound upper : 50
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : baf tower : mdw
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	landing other
Flight Plan	VFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	landing other
Route In Use	approach : straight in arrival other
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
ASRS Report	169410
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 2500 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working local. I had small aircraft a and small aircraft B sequenced #1 and #2 for landing about a mi and a half apart. The small aircraft C called ready on the same runway for departure. When the small aircraft a xed the threshold I told the small aircraft C to taxi into position and hold and to be prepared for an immediate. The small aircraft a was told to taxi west/O delay to the first turnoff and the small aircraft B was told that small aircraft C would depart prior to his arrival. The small aircraft a taxied slower than expected and the small aircraft B progressed faster than anticipated. When the small aircraft a was clear, I cleared the small aircraft C for an immediate takeoff. Although the small aircraft C was airborne before the small aircraft B xed the threshold, I did not have 3000' sep. I deemed it would be safer to let the small aircraft B land than to send him around short final.

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Original NASA ASRS Text

Title: CTLR RELEASED SMA C IN FRONT OF SMA B WHICH RESULTED IN LESS THAN STANDARD SEPARATION. CTLR HAD LESS THAN 3000' BETWEEN THE TWO ACFT. HE NEEDED 3000'.

Narrative: I WAS WORKING LCL. I HAD SMA A AND SMA B SEQUENCED #1 AND #2 FOR LNDG ABOUT A MI AND A HALF APART. THE SMA C CALLED READY ON THE SAME RWY FOR DEP. WHEN THE SMA A XED THE THRESHOLD I TOLD THE SMA C TO TAXI INTO POS AND HOLD AND TO BE PREPARED FOR AN IMMEDIATE. THE SMA A WAS TOLD TO TAXI W/O DELAY TO THE FIRST TURNOFF AND THE SMA B WAS TOLD THAT SMA C WOULD DEPART PRIOR TO HIS ARR. THE SMA A TAXIED SLOWER THAN EXPECTED AND THE SMA B PROGRESSED FASTER THAN ANTICIPATED. WHEN THE SMA A WAS CLR, I CLRED THE SMA C FOR AN IMMEDIATE TKOF. ALTHOUGH THE SMA C WAS AIRBORNE BEFORE THE SMA B XED THE THRESHOLD, I DID NOT HAVE 3000' SEP. I DEEMED IT WOULD BE SAFER TO LET THE SMA B LAND THAN TO SEND HIM AROUND SHORT FINAL.

Data retrieved from NASA's ASRS site as of July 2007 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.