ATR 42-500 pilot crew reported the #1 DME was malfunctioning and receiving a cftt alert.

Attributes
ACN	1741444
Time
Date	202005
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	ATR 42
Operating Under FAR Part	Part 121
Flight Phase	Final Approach Initial Approach
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	ILS/VOR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Private Flight Crew Multiengine Flight Crew Instrument Flight Crew Commercial
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Undershoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Narrative:

On VOR-a approach just short of the VOR passage at a 2800; VOR 1 DME became erroneous. This distracted us for a moment and PIC switched his screen to VOR/ILS system 2 to read correct DME. VOR2 DME seemed to be working. Because we were so close to station passage and the next step down altitude was after VOR passage; we descended to the next step down altitude too soon. When we left 2800 ft. The airport was in sight and was VMC. We were then aware that we descended early by a mile or two prior to the VOR and received a cautionary taws (terrain avoidance and warning system) once but at that point we arrested the descent and adjusted the flight path and the alert had gone away and by then we had crossed the VOR and were at the altitude we were supposed to be at. The circle approach and landing were normal.10 minutes after landing DME 1 corrected itself and we contacted maintenance control to let them know about DME 1and they informed us nothing was wrong with the plane.

Original NASA ASRS Text

Title: ATR 42-500 pilot crew reported the #1 DME was malfunctioning and receiving a CFTT alert.

Narrative: On VOR-A approach just short of the VOR passage at a 2800; VOR 1 DME became erroneous. This distracted us for a moment and PIC switched his screen to VOR/ILS system 2 to read correct DME. VOR2 DME seemed to be working. Because we were so close to station passage and the next step down altitude was after VOR passage; we descended to the next step down altitude too soon. When we left 2800 ft. the airport was in sight and was VMC. We were then aware that we descended early by a mile or two prior to the VOR and received a cautionary TAWS (Terrain Avoidance and Warning System) once but at that point we arrested the descent and adjusted the flight path and the alert had gone away and by then we had crossed the VOR and were at the altitude we were supposed to be at. The circle approach and landing were normal.10 minutes after landing DME 1 corrected itself and we contacted Maintenance control to let them know about DME 1and they informed us nothing was wrong with the plane.

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.