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An S80 flight crew experiences scalloping of their glide slope indicator while on approach to ord runway 27L. This was their third occurrence in 2 weeks. Ord, il.
| Attributes | |
| ACN | 452663 |
| Time | |
| Date | 199910 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| State Reference | IL |
| Altitude | msl single value : 3000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : ord.tower |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Super 80 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 27l |
| Flight Phase | descent : vacating altitude descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 452663 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe |
| Independent Detector | aircraft equipment other aircraft equipment : ils receiver other flight crewa |
| Resolutory Action | flight crew : overrode automation none taken : anomaly accepted |
| Consequence | faa : reviewed incident with flight crew other |
| Supplementary | |
| Problem Areas | Navigational Facility Airspace Structure Airport |
| Primary Problem | Navigational Facility |
Narrative:
At about 9.0 DME on the ILS runway 27L ord we experienced a glide path deviation on the approach. The glide slope first dropped to full scale deflection down followed by a slow movement to full scale up indication, then a glide slope fail indication. It came back normally in several seconds and the approach was continued visually while monitoring the glide path for the remainder of the approach. Several other aircraft verified our indications when we notified ord tower and ground control. This is the third time in three lndgs on the runway that this has occurred in some degree or another on the same runway and ILS. I reported this apparent malfunction to ord tower on oct/xa/99 and oct/xb/99 just after midnight. One aircraft said his glide path deviated when a wide-body departed runway 22L underneath him. On today's incident I did see a B747 departure, but it was before the symptoms occurred by about a minute, I believe. This needs to be checked and even flight checked by FAA people soon.
Original NASA ASRS Text
Title: AN S80 FLC EXPERIENCES SCALLOPING OF THEIR GLIDE SLOPE INDICATOR WHILE ON APCH TO ORD RWY 27L. THIS WAS THEIR THIRD OCCURRENCE IN 2 WEEKS. ORD, IL.
Narrative: AT ABOUT 9.0 DME ON THE ILS RWY 27L ORD WE EXPERIENCED A GLIDE PATH DEV ON THE APCH. THE GLIDE SLOPE FIRST DROPPED TO FULL SCALE DEFLECTION DOWN FOLLOWED BY A SLOW MOVEMENT TO FULL SCALE UP INDICATION, THEN A GLIDE SLOPE FAIL INDICATION. IT CAME BACK NORMALLY IN SEVERAL SECONDS AND THE APCH WAS CONTINUED VISUALLY WHILE MONITORING THE GLIDE PATH FOR THE REMAINDER OF THE APCH. SEVERAL OTHER ACFT VERIFIED OUR INDICATIONS WHEN WE NOTIFIED ORD TWR AND GND CTL. THIS IS THE THIRD TIME IN THREE LNDGS ON THE RWY THAT THIS HAS OCCURRED IN SOME DEGREE OR ANOTHER ON THE SAME RWY AND ILS. I RPTED THIS APPARENT MALFUNCTION TO ORD TWR ON OCT/XA/99 AND OCT/XB/99 JUST AFTER MIDNIGHT. ONE ACFT SAID HIS GLIDE PATH DEVIATED WHEN A WIDE-BODY DEPARTED RWY 22L UNDERNEATH HIM. ON TODAY'S INCIDENT I DID SEE A B747 DEP, BUT IT WAS BEFORE THE SYMPTOMS OCCURRED BY ABOUT A MINUTE, I BELIEVE. THIS NEEDS TO BE CHECKED AND EVEN FLT CHECKED BY FAA PEOPLE SOON.
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.