Air carrier descended below assigned crossing altitude resulting in a conflict with another aircraft...

Attributes
ACN	129660
Time
Date	198911
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : oak
State Reference	CA
Altitude	msl bound lower : 1350 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : oak tower : hwd
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach descent other
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 4800 flight time type : 200
ASRS Report	129660
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : ground less severe non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 0 vertical : 600
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approach control cleared us for a visibility to runway 29 at oak to cross 6 DME above 2000'. From 6000' through 2000', we were given 3 traffic advisories and I flew the G/south while helping the captain look for targets. Abeam hayward or approximately 6 DME, I noticed the altimeter abeam hwd, reading 1400'. After landing ramp operations told the captain hwd tower wanted him to call the tower told the captain we crossed his airport at 1350'. I disagree and believe the tower was exaggerating, because I personally witnessed 1900' abeam hwd. The tower was concerned about a possible conflict between us and a departure from hwd wbound.

Original NASA ASRS Text

Title: ACR DESCENDED BELOW ASSIGNED CROSSING ALT RESULTING IN A CONFLICT WITH ANOTHER ACFT.

Narrative: APCH CTL CLRED US FOR A VIS TO RWY 29 AT OAK TO CROSS 6 DME ABOVE 2000'. FROM 6000' THROUGH 2000', WE WERE GIVEN 3 TFC ADVISORIES AND I FLEW THE G/S WHILE HELPING THE CAPT LOOK FOR TARGETS. ABEAM HAYWARD OR APPROX 6 DME, I NOTICED THE ALTIMETER ABEAM HWD, READING 1400'. AFTER LNDG RAMP OPS TOLD THE CAPT HWD TWR WANTED HIM TO CALL THE TWR TOLD THE CAPT WE CROSSED HIS ARPT AT 1350'. I DISAGREE AND BELIEVE THE TWR WAS EXAGGERATING, BECAUSE I PERSONALLY WITNESSED 1900' ABEAM HWD. THE TWR WAS CONCERNED ABOUT A POSSIBLE CONFLICT BTWN US AND A DEP FROM HWD WBOUND.

Data retrieved from NASA's ASRS site as of August 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.