Reporter misguided first officer into believing he was cleared to 3000 ft from 4000 ft.

Attributes
ACN	293180
Time
Date	199501
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : lga
State Reference	NY
Altitude	msl bound lower : 3500 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 235 flight time total : 3900 flight time type : 260
ASRS Report	293180
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At 15 NM northeast of lga, ATC said 'air carrier X, you're 5 mi from yoman, cleared ILS 22 to lga.' we were currently assigned 4000 ft and the first officer (flying) asked me if it was ok to descend to 3000 ft. Thinking that ATC had said cross yoman at 3000 ft, cleared the approach, I said yes. Passing 3500 ft, 2 mi from yoman, I realized ATC had not cleared us to 3000 ft and that we should not have let down without asking ATC on passing yoman. Nothing was said to us by ATC. No conflict arose and we crossed yoman at 3500 ft. I realized my error and hope this goes no further.

Original NASA ASRS Text

Title: RPTR MISGUIDED FO INTO BELIEVING HE WAS CLRED TO 3000 FT FROM 4000 FT.

Narrative: AT 15 NM NE OF LGA, ATC SAID 'ACR X, YOU'RE 5 MI FROM YOMAN, CLRED ILS 22 TO LGA.' WE WERE CURRENTLY ASSIGNED 4000 FT AND THE FO (FLYING) ASKED ME IF IT WAS OK TO DSND TO 3000 FT. THINKING THAT ATC HAD SAID CROSS YOMAN AT 3000 FT, CLRED THE APCH, I SAID YES. PASSING 3500 FT, 2 MI FROM YOMAN, I REALIZED ATC HAD NOT CLRED US TO 3000 FT AND THAT WE SHOULD NOT HAVE LET DOWN WITHOUT ASKING ATC ON PASSING YOMAN. NOTHING WAS SAID TO US BY ATC. NO CONFLICT AROSE AND WE CROSSED YOMAN AT 3500 FT. I REALIZED MY ERROR AND HOPE THIS GOES NO FURTHER.

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.