Narrative:

During certain time periods, daily tmu restrictions require ZTL controllers to provide ZID with at least 15 mi (sometimes 20-30) in trail sep for aircraft landing ord and mdw. This spacing is required regardless of aircraft type or altitude, and traffic on J89 and J99 must be treated as 1 arwy. Problems occur because of traffic vol and a wide range of aircraft speeds. ZTL controllers are constantly asked to provide in trail spacing between widebody transport and medium large transport type aircraft. Because some widebody transport aircraft cannot operate at speeds as slow as medium large transport aircraft, and there is no alternate route or altitude available, controllers are left with only radar vectors and/or 360 degree turns as options. This creates a chaotic and frequently hazardous situation because it puts these aircraft on conflicting and/or converging courses with other aircraft in the sector. This makes the potential for an unsafe situation even greater. While tmu monitors this traffic and has an edct program in effect for atl departures, the burden on ensuring that the restrictions are met routinely fall on the crossville (37) and altdona (36) sectors. During this time, these sectors are extremely busy with other traffic. Controllers have voiced their concerns about these problems to their supervisors who share their concern. This information has been forwarded through proper channels, but to date no solutions have been offered. In my opinion, possible solutions to this problem are: 1) change the restriction to read 'per stratum,' instead of 'regardless of altitude.' this would allow controllers to assign lower altitudes to slower aircraft. 2) change the restriction to allow an alternate route to be used. Example: atl-bvt. 3) reinstate '30 KT rule.' this is an agency approved rule, but has been suspended by ZID.

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Original NASA ASRS Text

Title: CTLR REPORTER COMPLAINS ABOUT IN TRAIL FLOW CONTROL AND DIFFICULTY IN ACHIEVING MANDATORY SPACING.

Narrative: DURING CERTAIN TIME PERIODS, DAILY TMU RESTRICTIONS REQUIRE ZTL CTLRS TO PROVIDE ZID WITH AT LEAST 15 MI (SOMETIMES 20-30) IN TRAIL SEP FOR ACFT LNDG ORD AND MDW. THIS SPACING IS REQUIRED REGARDLESS OF ACFT TYPE OR ALT, AND TFC ON J89 AND J99 MUST BE TREATED AS 1 ARWY. PROBS OCCUR BECAUSE OF TFC VOL AND A WIDE RANGE OF ACFT SPDS. ZTL CTLRS ARE CONSTANTLY ASKED TO PROVIDE IN TRAIL SPACING BTWN WDB AND MLG TYPE ACFT. BECAUSE SOME WDB ACFT CANNOT OPERATE AT SPDS AS SLOW AS MLG ACFT, AND THERE IS NO ALTERNATE RTE OR ALT AVAILABLE, CTLRS ARE LEFT WITH ONLY RADAR VECTORS AND/OR 360 DEG TURNS AS OPTIONS. THIS CREATES A CHAOTIC AND FREQUENTLY HAZARDOUS SITUATION BECAUSE IT PUTS THESE ACFT ON CONFLICTING AND/OR CONVERGING COURSES WITH OTHER ACFT IN THE SECTOR. THIS MAKES THE POTENTIAL FOR AN UNSAFE SITUATION EVEN GREATER. WHILE TMU MONITORS THIS TFC AND HAS AN EDCT PROGRAM IN EFFECT FOR ATL DEPS, THE BURDEN ON ENSURING THAT THE RESTRICTIONS ARE MET ROUTINELY FALL ON THE CROSSVILLE (37) AND ALTDONA (36) SECTORS. DURING THIS TIME, THESE SECTORS ARE EXTREMELY BUSY WITH OTHER TFC. CTLRS HAVE VOICED THEIR CONCERNS ABOUT THESE PROBS TO THEIR SUPVRS WHO SHARE THEIR CONCERN. THIS INFO HAS BEEN FORWARDED THROUGH PROPER CHANNELS, BUT TO DATE NO SOLUTIONS HAVE BEEN OFFERED. IN MY OPINION, POSSIBLE SOLUTIONS TO THIS PROB ARE: 1) CHANGE THE RESTRICTION TO READ 'PER STRATUM,' INSTEAD OF 'REGARDLESS OF ALT.' THIS WOULD ALLOW CTLRS TO ASSIGN LOWER ALTS TO SLOWER ACFT. 2) CHANGE THE RESTRICTION TO ALLOW AN ALTERNATE RTE TO BE USED. EXAMPLE: ATL-BVT. 3) REINSTATE '30 KT RULE.' THIS IS AN AGENCY APPROVED RULE, BUT HAS BEEN SUSPENDED BY ZID.

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.