Hawker 800XP flight crew has an altitude deviation during the ILS 6 teb.

Attributes
ACN	699483
Time
Date	200606
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : teb.airport
State Reference	NJ
Altitude	msl single value : 2000
Environment
Flight Conditions	Mixed
Weather Elements	Rain
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	general aviation : corporate
Make Model Name	Hawker Horizon (Raytheon)
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 15000 flight time type : 5000
ASRS Report	699483
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : overrode automation flight crew : overcame equipment problem flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

The aircraft was on radar vectors at 2000 ft MSL for the ILS approach to runway 6 at teb. The autoplt was engaged in FMS and altitude hold modes with the approach tuned. When cleared to intercept the localizer; I armed the approach mode. We were then cleared to cross a fix on the localizer course at 1500 ft. I started a descent in the vertical speed mode and the autoplt captured the approach almost simultaneously. From several mi out we had been getting erratic GS indications; but at this point it was steady and indicating that we were below the GS. When the autoplt captured the ILS; the aircraft began to pitch up to intercept the glide path. I disconnected the autoplt at 2240 ft indicated and started back down to the assigned 1500 ft. ATC immediately requested verification of altitude and stated our mode C indications all the way down to 1500 ft where we continued the approach manually to landing. My mistake was arming the approach prematurely. Since I had armed it with the altitude hold captured at 2000 ft and then subsequently descended toward 1500 ft; the autoplt initiated a fly-up command to intercept the glide path. I usually do not arm approach until 'cleared for the approach' but did so this time because I had the airport in sight. Both crew members were scanning visually for other traffic and; therefore; did not stop the climb initiated by the autoplt sooner. I trusted the automation too much.

Original NASA ASRS Text

Title: HAWKER 800XP FLT CREW HAS AN ALT DEV DURING THE ILS 6 TEB.

Narrative: THE ACFT WAS ON RADAR VECTORS AT 2000 FT MSL FOR THE ILS APCH TO RWY 6 AT TEB. THE AUTOPLT WAS ENGAGED IN FMS AND ALT HOLD MODES WITH THE APCH TUNED. WHEN CLRED TO INTERCEPT THE LOC; I ARMED THE APCH MODE. WE WERE THEN CLRED TO CROSS A FIX ON THE LOC COURSE AT 1500 FT. I STARTED A DSCNT IN THE VERT SPD MODE AND THE AUTOPLT CAPTURED THE APCH ALMOST SIMULTANEOUSLY. FROM SEVERAL MI OUT WE HAD BEEN GETTING ERRATIC GS INDICATIONS; BUT AT THIS POINT IT WAS STEADY AND INDICATING THAT WE WERE BELOW THE GS. WHEN THE AUTOPLT CAPTURED THE ILS; THE ACFT BEGAN TO PITCH UP TO INTERCEPT THE GLIDE PATH. I DISCONNECTED THE AUTOPLT AT 2240 FT INDICATED AND STARTED BACK DOWN TO THE ASSIGNED 1500 FT. ATC IMMEDIATELY REQUESTED VERIFICATION OF ALT AND STATED OUR MODE C INDICATIONS ALL THE WAY DOWN TO 1500 FT WHERE WE CONTINUED THE APCH MANUALLY TO LNDG. MY MISTAKE WAS ARMING THE APCH PREMATURELY. SINCE I HAD ARMED IT WITH THE ALT HOLD CAPTURED AT 2000 FT AND THEN SUBSEQUENTLY DSNDED TOWARD 1500 FT; THE AUTOPLT INITIATED A FLY-UP COMMAND TO INTERCEPT THE GLIDE PATH. I USUALLY DO NOT ARM APCH UNTIL 'CLRED FOR THE APCH' BUT DID SO THIS TIME BECAUSE I HAD THE ARPT IN SIGHT. BOTH CREW MEMBERS WERE SCANNING VISUALLY FOR OTHER TFC AND; THEREFORE; DID NOT STOP THE CLB INITIATED BY THE AUTOPLT SOONER. I TRUSTED THE AUTOMATION TOO MUCH.

Data retrieved from NASA's ASRS site as of January 2009 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.