A B757 crew reported capturing a false sju runway 8 glide slope twice; first at about 2;700 ft prior...

Narrative:

Intercepted 2 false glide slopes. Cleared by center to wesen intersection for ILS 8 in sju down to 3;000 ft. On sju approach control cleared to wesen intersection for ILS 8 and down to 2;500 ft. Armed approach (app) on left autopilot. Glide slope appeared and intercepted as normal on localizer and began to descend. After 300 ft or so I realized that the glide slope was wrong. I turned off app/autopilot and it went away. We were VFR with no traffic so I just maintained my altitude and re-engaged. Glide slope again came into play and once more intercepted. I followed down to about 1;800 ft realizing again this was a false glide slope. I disengaged and leveled off. I asked tower if they had any low level alerts for me and if any thing abnormal was happening. I was told no. I re-engaged at about 1;800 ft with what appeared to be the real glide slope that finally made sense. But now the localizer was way off with correct heading in the head. This was all very confusing and we got a little behind but it was all drawn back into an acceptable environment and never unsafe for the conditions. But could have been a real problem in weather. This problem demanded 2 heads and first officer was great back up.

Original NASA ASRS Text

Title: A B757 crew reported capturing a false SJU Runway 8 glide slope twice; first at about 2;700 FT prior to WESEN and again at about 2;500 FT prior to PATTY. The approach was completed VMC on the VASI and the correct glide slope but the localizer indicated an incorrect course.

Narrative: Intercepted 2 false glide slopes. Cleared by Center to WESEN Intersection for ILS 8 in SJU down to 3;000 FT. On SJU Approach Control cleared to WESEN Intersection for ILS 8 and down to 2;500 FT. Armed APPROACH (APP) on left autopilot. Glide slope appeared and intercepted as normal on localizer and began to descend. After 300 FT or so I realized that the glide slope was wrong. I turned off APP/autopilot and it went away. We were VFR with no traffic so I just maintained my altitude and re-engaged. Glide slope again came into play and once more intercepted. I followed down to about 1;800 FT realizing again this was a false glide slope. I disengaged and leveled off. I asked Tower if they had any low level alerts for me and if any thing abnormal was happening. I was told NO. I re-engaged at about 1;800 FT with what appeared to be the real glide slope that finally made sense. But now the localizer was way off with correct heading in the head. This was all very confusing and we got a little behind but it was all drawn back into an acceptable environment and never unsafe for the conditions. But could have been a real problem in weather. This problem demanded 2 heads and First Officer was great back up.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	915577
Time
Date	201010
Local Time Of Day	1801-2400
Place
Locale Reference	SJU.Airport
State Reference	PR
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

A B757 crew reported capturing a false sju runway 8 glide slope twice; first at about 2;700 ft prior to wesen and again at about 2;500 ft prior to patty. The approach was completed VMC on the VASI and the correct glide slope but the localizer indicated an incorrect course.