Tower controller described a separation loss with two successive arrival aircraft; the first not cle...

Narrative:

A B737 checked in on a right base for a visual approach to runway 21. East radar (er) advised me that the B737 did not see the king air. I told er I would provide visual. The B737 slowed and turned back in to the runway and the spacing was fine. Then a B757 checked in on a visual approach just over a mile in trail and about 600 ft above the B737. I could tell from the BRITE the sequence was getting messy; but I still could not believe the B757 turned it in that close behind the B737. I was not sure how this was going to work; and at that time I heard er in my ear 'you can give the B757 a 360 if you need' and that was it. The B737 and the B757 were complaining on my frequency about the sequence. I cut in and told the B757 'you're following the B737 ahead; I'm sorry; I may have to have you make a 360.' the B757 said he was slowed all the way but he would see what he could do. It was clear the pilot was frustrated and did not want to go around or make a 360. As the B737 landed and rolled out I thought this was actually going to work so I cleared the B757 to land. The B737 turned right at taxiway C 6;850 ft down the runway. He slowed down considerably after he turned but he was still taxiing off. Half of the B737 was off the runway but the tail was not clear when the B757 crossed the landing threshold. I thought it was going to work; it was so close. The B737 was completely clear while the B757 was still within the first 1;000 ft of the runway. The sequence was a mess; the pilots were frustrated; and it was so close. This one was tough; but 'so close' is not the same as having approved separation. I should have canceled landing clearance and gave the B757 a go around when I was not positive it was going to work. The aim 4-3-20 b. Says the aircraft is clear when all parts of the aircraft are clear of the runway edge. Not when 'most' of the aircraft is clear. I also should not let it get personal. I wanted it to work because I thought the aircraft had received bad service; I knew they were upset; and I did not want anyone to have to go around or make a 360; making it even worse. Especially when they were as far apart on the runway as they were in the air. It did not feel unsafe. But; letting it go so far was the wrong call; I let myself get lead down a path. I cannot do that; even if it means someone has to go around.

Original NASA ASRS Text

Title: Tower Controller described a separation loss with two successive arrival aircraft; the first not clearing the runway prior to second crossing the runway threshold.

Narrative: A B737 checked in on a right base for a visual approach to Runway 21. East RADAR (ER) advised me that the B737 did not see the King Air. I told ER I would provide Visual. The B737 slowed and turned back in to the runway and the spacing was fine. Then a B757 checked in on a visual approach just over a mile in trail and about 600 FT above the B737. I could tell from the BRITE the sequence was getting messy; but I still could not believe the B757 turned it in that close behind the B737. I was not sure how this was going to work; and at that time I heard ER in my ear 'you can give the B757 a 360 if you need' and that was it. The B737 and the B757 were complaining on my frequency about the sequence. I cut in and told the B757 'you're following the B737 ahead; I'm sorry; I may have to have you make a 360.' The B757 said he was slowed all the way but he would see what he could do. It was clear the pilot was frustrated and did not want to go around or make a 360. As the B737 landed and rolled out I thought this was actually going to work so I cleared the B757 to land. The B737 turned right at Taxiway C 6;850 FT down the runway. He slowed down considerably after he turned but he was still taxiing off. Half of the B737 was off the runway but the tail was not clear when the B757 crossed the landing threshold. I thought it was going to work; it was so close. The B737 was completely clear while the B757 was still within the first 1;000 FT of the runway. The sequence was a mess; the pilots were frustrated; and it was so close. This one was tough; but 'so close' is not the same as having approved separation. I should have canceled landing clearance and gave the B757 a go around when I was not positive it was going to work. The AIM 4-3-20 b. says the aircraft is clear when all parts of the aircraft are clear of the runway edge. Not when 'most' of the aircraft is clear. I also should not let it get personal. I wanted it to work because I thought the aircraft had received bad service; I knew they were upset; and I did not want anyone to have to go around or make a 360; making it even worse. Especially when they were as far apart on the runway as they were in the air. It did not feel unsafe. But; letting it go so far was the wrong call; I let myself get lead down a path. I cannot do that; even if it means someone has to go around.

Data retrieved from NASA's ASRS site as of July 2013 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	1111642
Time
Date	201308
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Landing
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Landing
Route In Use	Visual Approach
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Tower controller described a separation loss with two successive arrival aircraft; the first not clearing the runway prior to second crossing the runway threshold.