On ILS approach to runway 27L at atl, after autoplt had engaged the glide slope, glide slope went off scale up. Autoplt followed and altitude excursion resulted before flight crew could take aircraft off automatic.

Home

Browse by month

Random

Latest

About

Contact

Attributes
ACN	136649
Time
Date	199002
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 3500 msl bound upper : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl tower : atl
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach descent other descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 600
ASRS Report	136649
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Airport	procedure or policy : unspecified
Navigational Aid	Unspecified

Narrative:

Cleared to 3500' and cleared for visual approach. At 3500' and outside the OM for 27L the autoplt captured the glide slope and localizer. Apparently a false glide slope because the glide slope went off scale high and the aircraft immediately climbed 700' to recapture the glide slope. We disconnected and hand flew the approach. This is the second time this has happened to me in atl on 27L and the second ASRS form I have submitted for this. Last time the aircraft followed the false glide slope to the floor of the TCA and we could see we were low and disconnected. This is the only false glide slope below the real glide slope I know of and could be a potential hazard. Callback conversation with reporter revealed the following: I mentioned the erratic glide slope to other pilots and one or two agreed they had observed erroneous indications. I have no idea what is causing the erratic glide slope indication. I did not query the tower to see if the monitor was indicating any problem.

Original NASA ASRS Text

Title: ON ILS APCH TO RWY 27L AT ATL, AFTER AUTOPLT HAD ENGAGED THE GLIDE SLOPE, GLIDE SLOPE WENT OFF SCALE UP. AUTOPLT FOLLOWED AND ALT EXCURSION RESULTED BEFORE FLT CREW COULD TAKE ACFT OFF AUTO.

Narrative: CLRED TO 3500' AND CLRED FOR VISUAL APCH. AT 3500' AND OUTSIDE THE OM FOR 27L THE AUTOPLT CAPTURED THE GLIDE SLOPE AND LOC. APPARENTLY A FALSE GLIDE SLOPE BECAUSE THE GLIDE SLOPE WENT OFF SCALE HIGH AND THE ACFT IMMEDIATELY CLIMBED 700' TO RECAPTURE THE GLIDE SLOPE. WE DISCONNECTED AND HAND FLEW THE APCH. THIS IS THE SECOND TIME THIS HAS HAPPENED TO ME IN ATL ON 27L AND THE SECOND ASRS FORM I HAVE SUBMITTED FOR THIS. LAST TIME THE ACFT FOLLOWED THE FALSE GLIDE SLOPE TO THE FLOOR OF THE TCA AND WE COULD SEE WE WERE LOW AND DISCONNECTED. THIS IS THE ONLY FALSE GLIDE SLOPE BELOW THE REAL GLIDE SLOPE I KNOW OF AND COULD BE A POTENTIAL HAZARD. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: I MENTIONED THE ERRATIC GLIDE SLOPE TO OTHER PLTS AND ONE OR TWO AGREED THEY HAD OBSERVED ERRONEOUS INDICATIONS. I HAVE NO IDEA WHAT IS CAUSING THE ERRATIC GLIDE SLOPE INDICATION. I DID NOT QUERY THE TWR TO SEE IF THE MONITOR WAS INDICATING ANY PROBLEM.

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.