GPWS terrain warning received and followed during descent on approach transition when above cleared ...

Attributes
ACN	439901
Time
Date	199906
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : vny.vor
State Reference	CA
Altitude	msl single value : 3500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : charter
Make Model Name	Medium Transport
Operating Under FAR Part	Part 91
Navigation In Use	ils localizer & glide slope : 08 other
Flight Phase	descent : approach
Route In Use	approach other
Flight Plan	VFR
Person 1
Affiliation	company : charter
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : multi engine
Experience	flight time last 90 days : 250 flight time total : 3100 flight time type : 250
ASRS Report	439901
Person 2
Affiliation	company : charter
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Events
Anomaly	other anomaly other
Independent Detector	aircraft equipment : gpws
Resolutory Action	flight crew : took precautionary avoidance action
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

I was PF. Approach control cleared us to intercept localizer and cleared for the approach. Altitude restr was 3000 ft crossing vny. During the descent (between 3500-3300 ft) GPWS sounded. I immediately took proper action and warning silenced within 2 seconds. In reviewing the incident, both pilots agreed that we were within all restrs shown on the approach plate. We also agreed that we never saw a terrain picture shown on either navigation display (multi function display) even though both were set to terrain display. The only conclusion drawn was that the rate of descent versus the terrain caused the warning to activate. Because it was night, we will unfortunately not ever know just how close we came, and it was VFR.

Original NASA ASRS Text

Title: GPWS TERRAIN WARNING RECEIVED AND FOLLOWED DURING DSCNT ON APCH TRANSITION WHEN ABOVE CLRED ALT.

Narrative: I WAS PF. APCH CTL CLRED US TO INTERCEPT LOC AND CLRED FOR THE APCH. ALT RESTR WAS 3000 FT XING VNY. DURING THE DSCNT (BTWN 3500-3300 FT) GPWS SOUNDED. I IMMEDIATELY TOOK PROPER ACTION AND WARNING SILENCED WITHIN 2 SECONDS. IN REVIEWING THE INCIDENT, BOTH PLTS AGREED THAT WE WERE WITHIN ALL RESTRS SHOWN ON THE APCH PLATE. WE ALSO AGREED THAT WE NEVER SAW A TERRAIN PICTURE SHOWN ON EITHER NAV DISPLAY (MULTI FUNCTION DISPLAY) EVEN THOUGH BOTH WERE SET TO TERRAIN DISPLAY. THE ONLY CONCLUSION DRAWN WAS THAT THE RATE OF DSCNT VERSUS THE TERRAIN CAUSED THE WARNING TO ACTIVATE. BECAUSE IT WAS NIGHT, WE WILL UNFORTUNATELY NOT EVER KNOW JUST HOW CLOSE WE CAME, AND IT WAS VFR.

Data retrieved from NASA's ASRS site as of July 2007 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.

GPWS terrain warning received and followed during descent on approach transition when above cleared altitude.