A DA20 flight crew received a GPWS terrain warning when they descended based on a clearance intended...

Narrative:

The conditions were: IFR with turbulence; rain and icing. The report at teb was for + or - 20 KTS on final with moderate turbulence from 2000 ft to the surface. We had diverted from hpn because it was closed due to a report of severe turbulence there. The frequency was congested; with a lot of pilots asking for condition reports and weather information. We were being vectored to the ILS 19 at teb; going direct to unvil (a fix on the approach) at 3000 ft; when I heard 'descend to 2000 ft' so I set the altitude alerter to 2000 and started descending. Just after we leveled off at 2000 ft; we had a momentary ground proximity warning with a single 'terrain' call. I immediately brought the power up and started a climb. I then paused because it went away; and thought it was in error. Then ATC told us to climb back up to 3000 ft. We did. The rest of the approach and landing was normal. We were not asked to make a phone call after landing. I believe the root cause of the event was my being distracted by the continuous moderate turbulence; and mistakenly accepted a clearance given to the aircraft ahead of us. I was anticipating the 2000 ft clearance; and thought it was for us. If I had more closely listened to the ATC instructions; we would not have descended; and the incident would not have happened. I should have asked for clarification. I will in the future.

Original NASA ASRS Text

Title: A DA20 flight crew received a GPWS TERRAIN warning when they descended based on a clearance intended for another aircraft.

Narrative: The conditions were: IFR with turbulence; rain and icing. The report at TEB was for + or - 20 KTS on final with moderate turbulence from 2000 FT to the surface. We had diverted from HPN because it was closed due to a report of severe turbulence there. The frequency was congested; with a lot of pilots asking for condition reports and weather information. We were being vectored to the ILS 19 at TEB; going direct to UNVIL (a fix on the approach) at 3000 FT; when I heard 'Descend to 2000 FT' So I set the altitude alerter to 2000 and started descending. Just after we leveled off at 2000 FT; we had a momentary ground proximity warning with a single 'Terrain' call. I immediately brought the power up and started a climb. I then paused because it went away; and thought it was in error. Then ATC told us to climb back up to 3000 FT. We did. The rest of the approach and landing was normal. We were not asked to make a phone call after landing. I believe the root cause of the event was my being distracted by the continuous moderate turbulence; and mistakenly accepted a clearance given to the aircraft ahead of us. I was anticipating the 2000 FT clearance; and thought it was for us. If I had more closely listened to the ATC instructions; we would not have descended; and the incident would not have happened. I should have asked for clarification. I will in the future.

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	871276
Time
Date	201001
Local Time Of Day	1201-1800
Place
Locale Reference	TEB.Airport
State Reference	NJ
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Falcon 2000
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT Inflight Event / Encounter Weather / Turbulence

A DA20 flight crew received a GPWS terrain warning when they descended based on a clearance intended for another aircraft.