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An A320 on short final approach in IMC for ILS runway 27L receives an erratic ILS signal due to a widebody transport aircraft crossing the runway. The reporter continued approach and land, but believes that the widebody transport should not have been cleared across the runway.
| Attributes | |
| ACN | 356260 |
| Time | |
| Date | 199612 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : ord |
| State Reference | IL |
| Altitude | agl bound lower : 700 agl bound upper : 700 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : ord |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent : approach |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Navigation In Use | Other |
| Flight Phase | ground other : taxi |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 9000 flight time type : 100 |
| ASRS Report | 356260 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | other |
Narrative:
On final ILS runway 27L ord, had ground contact, but runway was not in sight due to a developing and passing snow shower. Tower cleared a large aircraft (B747 or DC10) to cross the approach end of runway 27L from north to south to join taxiway south. Shortly thereafter our ILS signal became very erratic for several seconds while the large aircraft taxied in front of the ILS transmitter. Realizing the reason the signal was erratic, and with the approach lights coming into view, we continued the approach to an uneventful landing. The aircraft should never have been cleared to taxi between us and the ILS transmitter in these WX conditions. Had the aircraft been coupled, I can only imagine the potential results of chasing an erratic signal. Ord is the last place I'd expect this to happen.
Original NASA ASRS Text
Title: AN A320 ON SHORT FINAL APCH IN IMC FOR ILS RWY 27L RECEIVES AN ERRATIC ILS SIGNAL DUE TO A WDB ACFT XING THE RWY. THE RPTR CONTINUED APCH AND LAND, BUT BELIEVES THAT THE WDB SHOULD NOT HAVE BEEN CLRED ACROSS THE RWY.
Narrative: ON FINAL ILS RWY 27L ORD, HAD GND CONTACT, BUT RWY WAS NOT IN SIGHT DUE TO A DEVELOPING AND PASSING SNOW SHOWER. TWR CLRED A LARGE ACFT (B747 OR DC10) TO CROSS THE APCH END OF RWY 27L FROM N TO S TO JOIN TXWY S. SHORTLY THEREAFTER OUR ILS SIGNAL BECAME VERY ERRATIC FOR SEVERAL SECONDS WHILE THE LARGE ACFT TAXIED IN FRONT OF THE ILS XMITTER. REALIZING THE REASON THE SIGNAL WAS ERRATIC, AND WITH THE APCH LIGHTS COMING INTO VIEW, WE CONTINUED THE APCH TO AN UNEVENTFUL LNDG. THE ACFT SHOULD NEVER HAVE BEEN CLRED TO TAXI BTWN US AND THE ILS XMITTER IN THESE WX CONDITIONS. HAD THE ACFT BEEN COUPLED, I CAN ONLY IMAGINE THE POTENTIAL RESULTS OF CHASING AN ERRATIC SIGNAL. ORD IS THE LAST PLACE I'D EXPECT THIS TO HAPPEN.
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.