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Small transport given an assigned altitude in ARTCC computer showed up 2000' lower when handed off to adjacent ARTCC.
| Attributes | |
| ACN | 86398 |
| Time | |
| Date | 198804 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : ukn |
| State Reference | IA |
| Altitude | msl bound lower : 21000 msl bound upper : 23000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zau artcc : zmp |
| Operator | general aviation : personal |
| Make Model Name | Small Transport, Low Wing, 2 Recip Eng |
| Flight Phase | cruise other |
| Route In Use | enroute airway : zau |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 4 |
| ASRS Report | 86398 |
| Person 2 | |
| Function | controller : radar |
| Qualification | controller : radar |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude other anomaly other |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Deviation |
| Situations | |
| ATC Facility | other physical facility |
Narrative:
Small transport anw mcw etc was handed off to ZAU lnr low sector. Data block showed '230A' in altitude field. Strip showed computer printed altitude of 230 with a check mark. I had been at sector for about a minute. ZAU called to verify the altitude because they showed 210 in the mode C. The pilot stated to them that he had been issued FL210 at some point and was at FL210. There were no conflicts with aircraft in our sector or in ZAU lnr sector. There were 2 other ZMP sectors and perhaps one ZDV sector that could have been involved. Once a controller enters a manually reported altitude, further mode C reports from that aircraft are ignored by the computer, if they differ from the manually entered altitude by a certain amount. Perhaps a message should be generated alerting the controller when a constant mode C is received that differs from a manually entered altitude, and that mode C remains constant for some period of time.
Original NASA ASRS Text
Title: SMT GIVEN AN ASSIGNED ALT IN ARTCC COMPUTER SHOWED UP 2000' LOWER WHEN HANDED OFF TO ADJACENT ARTCC.
Narrative: SMT ANW MCW ETC WAS HANDED OFF TO ZAU LNR LOW SECTOR. DATA BLOCK SHOWED '230A' IN ALT FIELD. STRIP SHOWED COMPUTER PRINTED ALT OF 230 WITH A CHECK MARK. I HAD BEEN AT SECTOR FOR ABOUT A MINUTE. ZAU CALLED TO VERIFY THE ALT BECAUSE THEY SHOWED 210 IN THE MODE C. THE PLT STATED TO THEM THAT HE HAD BEEN ISSUED FL210 AT SOME POINT AND WAS AT FL210. THERE WERE NO CONFLICTS WITH ACFT IN OUR SECTOR OR IN ZAU LNR SECTOR. THERE WERE 2 OTHER ZMP SECTORS AND PERHAPS ONE ZDV SECTOR THAT COULD HAVE BEEN INVOLVED. ONCE A CTLR ENTERS A MANUALLY REPORTED ALT, FURTHER MODE C REPORTS FROM THAT ACFT ARE IGNORED BY THE COMPUTER, IF THEY DIFFER FROM THE MANUALLY ENTERED ALT BY A CERTAIN AMOUNT. PERHAPS A MESSAGE SHOULD BE GENERATED ALERTING THE CTLR WHEN A CONSTANT MODE C IS RECEIVED THAT DIFFERS FROM A MANUALLY ENTERED ALT, AND THAT MODE C REMAINS CONSTANT FOR SOME PERIOD OF TIME.
Data retrieved from NASA's ASRS site as of August 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.