B737-800 first officer reported ATC issued a low altitude alert due to descent on a false glide slop...

Attributes
ACN	1532294
Time
Date	201804
Local Time Of Day	0601-1200
Place
Locale Reference	BOS.Airport
State Reference	MA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Narrative:

On visual approach to runway 27 at bos. Normal approach up until the point I selected approach mode. It showed us high on the glideslope just outside the final approach fix. I dropped the gear and flaps early to try to descend. Unfortunately; it ended up being a false glideslope. The aircraft would intercept the glideslope; but then either level off or climb. Very confusing. When we checked in with the tower inside the FAF; they said they had an altitude warning on us. We were never below 1;200 feet and over the water the whole time. There was no GPWS warning and we weren't in danger. I disconnected the autopilot; acquired the papis; and once established on the correct glideslope; we continued the approach uneventfully. Suggestions: please make others aware of this possibility on [runway] 27 at bos.

Original NASA ASRS Text

Title: B737-800 First Officer reported ATC issued a low altitude alert due to descent on a false glide slope for BOS Runway 27.

Narrative: On visual approach to Runway 27 at BOS. Normal approach up until the point I selected approach mode. It showed us high on the glideslope just outside the final approach fix. I dropped the gear and flaps early to try to descend. Unfortunately; it ended up being a false glideslope. The aircraft would intercept the glideslope; but then either level off or climb. Very confusing. When we checked in with the Tower inside the FAF; they said they had an altitude warning on us. We were never below 1;200 feet and over the water the whole time. There was no GPWS warning and we weren't in danger. I disconnected the autopilot; acquired the PAPIs; and once established on the correct glideslope; we continued the approach uneventfully. Suggestions: Please make others aware of this possibility on [Runway] 27 at BOS.

Data retrieved from NASA's ASRS site 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.

B737-800 first officer reported ATC issued a low altitude alert due to descent on a false glide slope for bos runway 27.