A-319 crew descended early after a false GS capture was indicated.

Attributes
ACN	603544
Time
Date	200312
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : buf.airport
State Reference	NY
Altitude	msl bound lower : 1700 msl bound upper : 2200
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : buf.tracon
Operator	common carrier : air carrier
Make Model Name	A319
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 23
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : commercial pilot : instrument pilot : atp
ASRS Report	603544
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
ASRS Report	6033551
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : published procedure non adherence : far non adherence : company policies
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude
Consequence	other
Supplementary
Problem Areas	Weather Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Captain PF. WX MVFR with ground contact. Buffalo approach vectored flight directly to FAF ILS runway 23 at buffalo to maintain 2200 ft until established. ILS was positively idented. Captain was concerned about the tight approach and was configuring and slowing aircraft when ILS GS captured. Captain, hand flying, followed GS knowing that localizer capture was imminent. Crew realized that the GS was a false capture just as buffalo approach queried about departing the intercept altitude early. Captain immediately climbed back to intercept altitude. Total deviation was approximately 500 ft. The rest of the approach and landing was uneventful. Crew received no GPWS warnings during deviation.

Original NASA ASRS Text

Title: A-319 CREW DSNDED EARLY AFTER A FALSE GS CAPTURE WAS INDICATED.

Narrative: CAPT PF. WX MVFR WITH GND CONTACT. BUFFALO APCH VECTORED FLT DIRECTLY TO FAF ILS RWY 23 AT BUFFALO TO MAINTAIN 2200 FT UNTIL ESTABLISHED. ILS WAS POSITIVELY IDENTED. CAPT WAS CONCERNED ABOUT THE TIGHT APCH AND WAS CONFIGURING AND SLOWING ACFT WHEN ILS GS CAPTURED. CAPT, HAND FLYING, FOLLOWED GS KNOWING THAT LOC CAPTURE WAS IMMINENT. CREW REALIZED THAT THE GS WAS A FALSE CAPTURE JUST AS BUFFALO APCH QUERIED ABOUT DEPARTING THE INTERCEPT ALT EARLY. CAPT IMMEDIATELY CLBED BACK TO INTERCEPT ALT. TOTAL DEV WAS APPROX 500 FT. THE REST OF THE APCH AND LNDG WAS UNEVENTFUL. CREW RECEIVED NO GPWS WARNINGS DURING DEV.

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.