Light transport captain reported flying the GPS glideslope instead of the ILS glideslope.

Attributes
ACN	1544033
Time
Date	201805
Local Time Of Day	0601-1200
Place
Locale Reference	LZU.Airport
State Reference	GA
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 30 Flight Crew Total 9500 Flight Crew Type 3400
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy

Narrative:

Cleared for the ILS 25 approach at lzu. Sic (second in command) armed the appr (approach) mode on the proline 21 avionics. The localizer needle centered and started to receive a glideslope indication. Upon reaching 2;500 feet we determined that we were receiving a GPS glideslope and not the glideslope for the ILS. We climbed back to 3;000 feet and continued the approach without incident.the error that we made was that we did not backup the information with the DME which would have informed us that the glideslope intercept was closer to the airport.

Original NASA ASRS Text

Title: Light Transport Captain reported flying the GPS glideslope instead of the ILS glideslope.

Narrative: Cleared for the ILS 25 approach at LZU. SIC (Second in Command) armed the APPR (Approach) mode on the Proline 21 avionics. The localizer needle centered and started to receive a glideslope indication. Upon reaching 2;500 feet we determined that we were receiving a GPS glideslope and not the glideslope for the ILS. We climbed back to 3;000 feet and continued the approach without incident.The error that we made was that we did not backup the information with the DME which would have informed us that the glideslope intercept was closer to the airport.

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.