Large transport cargo flight has altitude deviation while looking for traffic.

Attributes
ACN	316780
Time
Date	199509
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mem
State Reference	TN
Altitude	msl bound lower : 3700 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mem
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : commercial pilot : instrument
Experience	flight time last 90 days : 70 flight time total : 2500 flight time type : 70
ASRS Report	316780
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
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:

While being vectored east of mem for a visual approach to runway 27 we descended 300 ft below our assigned altitude of 4000 ft MSL. The first officer was flying the aircraft and at the time all 3 of us (crew members) were trying to spot traffic that was called out to us by mem approach control. We were instructed to follow the traffic into mem. While we were searching, our aircraft descended to 3700 ft MSL (aircraft was already in a descent from 6000 ft MSL). We noticed the deviation shortly after spotting our traffic to follow. The first officer corrected back to 4000 ft MSL immediately. I believe the contributing factor was that our attention was diverted from flying the aircraft to looking for traffic. ZME (approach control) did not say anything to us about the deviation.

Original NASA ASRS Text

Title: LGT CARGO FLT HAS ALTDEV WHILE LOOKING FOR TFC.

Narrative: WHILE BEING VECTORED E OF MEM FOR A VISUAL APCH TO RWY 27 WE DSNDED 300 FT BELOW OUR ASSIGNED ALT OF 4000 FT MSL. THE FO WAS FLYING THE ACFT AND AT THE TIME ALL 3 OF US (CREW MEMBERS) WERE TRYING TO SPOT TFC THAT WAS CALLED OUT TO US BY MEM APCH CTL. WE WERE INSTRUCTED TO FOLLOW THE TFC INTO MEM. WHILE WE WERE SEARCHING, OUR ACFT DSNDED TO 3700 FT MSL (ACFT WAS ALREADY IN A DSCNT FROM 6000 FT MSL). WE NOTICED THE DEV SHORTLY AFTER SPOTTING OUR TFC TO FOLLOW. THE FO CORRECTED BACK TO 4000 FT MSL IMMEDIATELY. I BELIEVE THE CONTRIBUTING FACTOR WAS THAT OUR ATTN WAS DIVERTED FROM FLYING THE ACFT TO LOOKING FOR TFC. ZME (APCH CTL) DID NOT SAY ANYTHING TO US ABOUT THE DEV.

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.