Turbojet aircraft descends below cleared altitude after misinterping clearance in phl airspace.

Attributes
ACN	421810
Time
Date	199812
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ttn
State Reference	NJ
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Navigation In Use	Other
Flight Phase	cruise other descent other
Route In Use	approach : visual arrival other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 120 flight time total : 6000 flight time type : 380
ASRS Report	421810
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

Flight was a cpr passenger flight from teb to ttn. Phl approach cleared the aircraft for a visual approach to ttn airport and then canceled the clearance. Captain did not hear the visual approach cancellation so he started out of assigned altitude of 3000 ft. Approach called, 'traffic at 10 O'clock, 5 mi, and until we call traffic in sight we are not cleared for visual approach, maintain assigned altitude of 3000 ft.' we had the traffic on TCASII but not visual until approximately 45 seconds later, at which time we were cleared for the visual approach to ttn. Because we were now less than 1 mi from the field at 3000 ft, I told the controller that we would fly over the top of the field and enter a downwind. She responded with a suggestion that we ask permission to do a maneuver instead of telling her what we had planned. Normal approach and landing were made. Contributing factors: short flight in congested airspace. New york approach did not hand us over to phl until we were about 5 mi from field. Congested approach frequency, leading the captain to not hear the visual approach clearance cancellation. I was busy and did not see captain leave assigned altitude. Time of day was at XA40 and we were looking into the sun the entire flight which caused reduced in-flight visibility.

Original NASA ASRS Text

Title: TURBOJET ACFT DSNDS BELOW CLRED ALT AFTER MISINTERPING CLRNC IN PHL AIRSPACE.

Narrative: FLT WAS A CPR PAX FLT FROM TEB TO TTN. PHL APCH CLRED THE ACFT FOR A VISUAL APCH TO TTN ARPT AND THEN CANCELED THE CLRNC. CAPT DID NOT HEAR THE VISUAL APCH CANCELLATION SO HE STARTED OUT OF ASSIGNED ALT OF 3000 FT. APCH CALLED, 'TFC AT 10 O'CLOCK, 5 MI, AND UNTIL WE CALL TFC IN SIGHT WE ARE NOT CLRED FOR VISUAL APCH, MAINTAIN ASSIGNED ALT OF 3000 FT.' WE HAD THE TFC ON TCASII BUT NOT VISUAL UNTIL APPROX 45 SECONDS LATER, AT WHICH TIME WE WERE CLRED FOR THE VISUAL APCH TO TTN. BECAUSE WE WERE NOW LESS THAN 1 MI FROM THE FIELD AT 3000 FT, I TOLD THE CTLR THAT WE WOULD FLY OVER THE TOP OF THE FIELD AND ENTER A DOWNWIND. SHE RESPONDED WITH A SUGGESTION THAT WE ASK PERMISSION TO DO A MANEUVER INSTEAD OF TELLING HER WHAT WE HAD PLANNED. NORMAL APCH AND LNDG WERE MADE. CONTRIBUTING FACTORS: SHORT FLT IN CONGESTED AIRSPACE. NEW YORK APCH DID NOT HAND US OVER TO PHL UNTIL WE WERE ABOUT 5 MI FROM FIELD. CONGESTED APCH FREQ, LEADING THE CAPT TO NOT HEAR THE VISUAL APCH CLRNC CANCELLATION. I WAS BUSY AND DID NOT SEE CAPT LEAVE ASSIGNED ALT. TIME OF DAY WAS AT XA40 AND WE WERE LOOKING INTO THE SUN THE ENTIRE FLT WHICH CAUSED REDUCED INFLT VISIBILITY.

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.