Air carrier has altitude deviation while looking for traffic. Similar call sign confusion as well.

Attributes
ACN	183653
Time
Date	199107
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lga
State Reference	NY
Altitude	msl bound lower : 6500 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Route In Use	arrival star : star enroute airway : n90
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 7000
ASRS Report	183653
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 250 flight time total : 20000
ASRS Report	183522
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descent was given to 7000 ft. Automatic functions of medium large transport dropped out the altitude and failed to capture. We were looking for reported traffic at 7200 ft altitude at 12 to 2 O'clock, the distance was 2 mi. We could not see the traffic. In the meantime the medium large transport continued through 7000 ft to 6600 ft on copilot's altimeter and 6500 ft on captain's. We immediately recovered and leveled at 7000 ft. As we were looking out for the traffic we were also given a vector to avoid the traffic. We never saw the traffic. TCAS warned us of the traffic but due to the haze it was impossible to see. Supplemental information from acn 183522: at the time of this incident we had just received a clearance we were unsure of due to similar call signs on frequency ('was that for us, better check with approach'). Of late, it seems there are many similar call signs, both within our own company and other carriers. Air carrier X, def: air carrier Y, def: air carrier Z, edf this makes for many 'was that for us's', much confusion and late compliance with issued clrncs. I do not think there is an answer to this problem, we'll just have to live with it!

Original NASA ASRS Text

Title: ACR HAS ALT DEV WHILE LOOKING FOR TFC. SIMILAR CALL SIGN CONFUSION AS WELL.

Narrative: DSCNT WAS GIVEN TO 7000 FT. AUTO FUNCTIONS OF MLG DROPPED OUT THE ALT AND FAILED TO CAPTURE. WE WERE LOOKING FOR RPTED TFC AT 7200 FT ALT AT 12 TO 2 O'CLOCK, THE DISTANCE WAS 2 MI. WE COULD NOT SEE THE TFC. IN THE MEANTIME THE MLG CONTINUED THROUGH 7000 FT TO 6600 FT ON COPLT'S ALTIMETER AND 6500 FT ON CAPT'S. WE IMMEDIATELY RECOVERED AND LEVELED AT 7000 FT. AS WE WERE LOOKING OUT FOR THE TFC WE WERE ALSO GIVEN A VECTOR TO AVOID THE TFC. WE NEVER SAW THE TFC. TCAS WARNED US OF THE TFC BUT DUE TO THE HAZE IT WAS IMPOSSIBLE TO SEE. SUPPLEMENTAL INFO FROM ACN 183522: AT THE TIME OF THIS INCIDENT WE HAD JUST RECEIVED A CLRNC WE WERE UNSURE OF DUE TO SIMILAR CALL SIGNS ON FREQ ('WAS THAT FOR US, BETTER CHK WITH APCH'). OF LATE, IT SEEMS THERE ARE MANY SIMILAR CALL SIGNS, BOTH WITHIN OUR OWN COMPANY AND OTHER CARRIERS. ACR X, DEF: ACR Y, DEF: ACR Z, EDF THIS MAKES FOR MANY 'WAS THAT FOR US'S', MUCH CONFUSION AND LATE COMPLIANCE WITH ISSUED CLRNCS. I DO NOT THINK THERE IS AN ANSWER TO THIS PROBLEM, WE'LL JUST HAVE TO LIVE WITH IT!

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.