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After handoff from a C90 controller on 2 in trail aircraft climbing, action taken by ZAU controller causes trailing aircraft to overtake the lead aircraft resulting in a loss of separation.
| Attributes | |
| ACN | 571801 |
| Time | |
| Date | 200101 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : ord.airport |
| State Reference | IL |
| Altitude | msl single value : 17000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : c90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | tracon : c90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar pilot : instrument |
| Experience | controller radar : 12 flight time total : 250 |
| ASRS Report | 571801 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation non adherence : published procedure |
| Independent Detector | atc equipment : conflict alert |
| Resolutory Action | controller : issued new clearance |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 27600 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
B737-300 was lead aircraft climbing to 17000 ft without a speed assignment. B757-200 was trailing aircraft assigned 250 KIAS. At around 11500 ft, lead aircraft was switched to ZAU. 1 min later, trailing aircraft was 6 NM behind, 30 KTS slower, and 200 ft lower and climbing to FL230. Trailing aircraft was told to 'resume normal speed' and given a heading diverging by 10 degrees, and switched to ZAU. ZAU controller apparently turned trailing aircraft back toward lead aircraft. Lead aircraft accelerated only 20 KTS between 13000 ft and 17000 ft. Trailing aircraft, which was performing similarly to lead aircraft prior to 13000 ft, accelerated by 120 KTS between 13000 ft and 17000 ft. Separation was apparently lost when lead aircraft leveled at 17000 ft and trailing aircraft was climbing through 17000 ft, only 4 1/2 NM behind.
Original NASA ASRS Text
Title: AFTER HDOF FROM A C90 CTLR ON 2 IN TRAIL ACFT CLBING, ACTION TAKEN BY ZAU CTLR CAUSES TRAILING ACFT TO OVERTAKE THE LEAD ACFT RESULTING IN A LOSS OF SEPARATION.
Narrative: B737-300 WAS LEAD ACFT CLBING TO 17000 FT WITHOUT A SPD ASSIGNMENT. B757-200 WAS TRAILING ACFT ASSIGNED 250 KIAS. AT AROUND 11500 FT, LEAD ACFT WAS SWITCHED TO ZAU. 1 MIN LATER, TRAILING ACFT WAS 6 NM BEHIND, 30 KTS SLOWER, AND 200 FT LOWER AND CLBING TO FL230. TRAILING ACFT WAS TOLD TO 'RESUME NORMAL SPD' AND GIVEN A HDG DIVERGING BY 10 DEGS, AND SWITCHED TO ZAU. ZAU CTLR APPARENTLY TURNED TRAILING ACFT BACK TOWARD LEAD ACFT. LEAD ACFT ACCELERATED ONLY 20 KTS BTWN 13000 FT AND 17000 FT. TRAILING ACFT, WHICH WAS PERFORMING SIMILARLY TO LEAD ACFT PRIOR TO 13000 FT, ACCELERATED BY 120 KTS BTWN 13000 FT AND 17000 FT. SEPARATION WAS APPARENTLY LOST WHEN LEAD ACFT LEVELED AT 17000 FT AND TRAILING ACFT WAS CLBING THROUGH 17000 FT, ONLY 4 1/2 NM BEHIND.
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.