B737-700
Air Traffic Control Fully Certified
Confusion; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
I was working the midnight shift with all of the Phoenix Terminal Area (PTA) sectors combined to one position; Navajo Sector. Traffic at the time was very light and I was talking to about 5 airplanes; two of which were the aircraft involved in the LoSS (Lack of Standard Separation): Aircraft X and Aircraft Y. Sky Harbor Airport (PHX) was on East Flow; which normally arrive [on] Runway 8 and 7R [and] depart [on] Runway 7L.Unusual for this time; but a common situation for the midnight shift is that the City of Phoenix will close a runway to do maintenance. In this case; Runway 7R; normally used for arrivals with Runway 8; was closed. Because of the closure of Runway 7R; arrivals to Runway 8 and 7L were required to maintain approved separation until established on an angle no greater than 30 degrees. Knowing that rule and taking advantage of the greater visibility to see aircraft at night; I issued traffic to Aircraft X and Aircraft Y hoping that one aircraft would see the other. Aircraft X was able to see Aircraft Y. Aircraft Y was already established on final for Runway 7L and had been cleared for the visual approach. I issued a visual separation clearance to Aircraft X and informed him that Aircraft Y was landing the middle runway; Runway 7L. I then turned Aircraft X on a base leg in so that he would still keep the aircraft; Aircraft Y; in sight and cleared Aircraft X for the visual approach to Runway 8. My thinking at the time was that Aircraft X had visual separation with Aircraft Y. Since approved separation; more than 3 miles; was maintained before the approach clearance; Aircraft X would continue to maintain visual separation; which allowed visual to become approved separation; with Aircraft Y until completing the intercept with the 30 degrees to the runway final approach course. Then; discontinue the visual separation use and resume the 7110.65 para 7-4-4c2a1; satisfying the after visual separation requirement to allow visual separation clearance. 7110.65 para 7-4-4c2c says: 'Provided aircraft flight paths do not intersect; and when the provisions of subparas (a) and (b) are met; it is not necessary to apply any other type of separation with aircraft on the adjacent final approach course.' Because I was not meeting the requirements of suparas (a) and (b); I utilized 7-2-1 paragraph a2 in order to maintain approved separation until the aircraft turned within 30 degrees of the final approach course.I was informed of the RAE (Risk Analysis Event) in association with the LoSS. I was also handed a Letter of Interpretation in a memo format. In this Letter of interpretation; it states that visual separation is not an approved separation to satisfy 7-4-4c2a. The memo states: 'References to 'approved separation' do not include visual separation. Although visual separation can be employed by ATC under certain conditions; it does not meet the definition of 'approved separation;' which can be found in FAA JO Order 7110.65; subparagraph 1-2-1; WORD MEANINGS.' In looking at the definition of 'approved separation' in 1-2-1; I found the following: 'Approved separation' means separation in accordance with the applicable minima in this order.' So I looked at the applicable minima in 5-5-4; and found the lateral separation minima to be 3 miles. I then looked at 7-2-1 to find out how to go below the 5-5-4 minima which allows the use of visual separation before and after the application of approved separation. So I asked myself; is visual separation not approved separation? To find out the answer; I had to make an inference from a note in 5-5-4 and found that the suggestion in 5-5-4 Minima in a note for when an ISR message is received; that the Controller should take steps to regain 5 NM separation or use another form of approved separation. It recommends the use of visual or vertical separation as another method of approved separation: 'NOTE: In the event of an unexpected ISR on one or more aircraft; the ATCs working that aircraft must transition from 3-mile to 5-mile separation; or establish some other form of approved separation; visual or vertical; as soon as feasible...'So my point to this is; to prevent another Loss due to confusion with 7110.65 para 7-4-4; the 7110.65 needs to be updated to explicitly disallow the use of visual separation in conjunction with a visual approach clearance. I take pride in my job and knowing the rules to follow; but being handed a Letter of Interpretation stating why I can't conduct the visual approach in the manner that I did absolutely confused me. This letter was issued before I was certified on the finals sector; so how are future CPCs supposed to find out the interpretation before another Loss occurs? There are other references in the 7110.65 which disallow visual separation usage; for example aircraft behind a super or with opposite direction operations.
Phoenix TRACON Controller reported an after the fact loss of separation between two aircraft and confusion over the regulation.