Task distraction contributes to an altitude overshoot in descent.

Attributes
ACN	462370
Time
Date	199911
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : msp.vortac
State Reference	MN
Altitude	msl bound lower : 7700 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : m98.tracon
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : m98.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 70 flight time total : 3500 flight time type : 70
ASRS Report	462370
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment : altitude alert aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude
Supplementary
Problem Areas	Weather Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The flight was assigned a descent to 8000 ft. The altitude was properly set in the altitude reminder window and called out 1000 ft prior to leveloff. We were IMC and the WX radar was on. Passing approximately 8200-8300 ft we received a TCASII TA. Both of us looked at the screen to identify the traffic. The screen was on too large a scale and was cluttered with the WX radar. As a fairly new first officer with the company, I had only seen the radar on twice before and had never found it on or off myself. I adjusted the scale and then fumbled with the switches to turn off the radar in order to identify the traffic. After what could only have been 5 seconds, the captain reached over and turned off the radar himself. As we inspected the screen we received a TCASII RA 'reduce descent.' the captain then noted that we had descended through our assigned altitude. I don't recall seeing any lower than 7700 ft. As we leveled off at 8000 ft msp approach asked us to confirm 8000 ft assigned. We then confirmed that we were level at 8000 ft and the matter seemed closed. Contributing factors: a cluttered screen, first officer unfamiliar with switches on the other side of the cockpit (radar), captain distracted by TCASII and first officer. If I had been more familiar with the radar switches then the incident may have been avoided. Perhaps this should be added to simulator/classroom instruction. If the captain had concentrated on flying the aircraft first then the incident would have been avoided.

Original NASA ASRS Text

Title: TASK DISTR CONTRIBUTES TO AN ALT OVERSHOOT IN DSCNT.

Narrative: THE FLT WAS ASSIGNED A DSCNT TO 8000 FT. THE ALT WAS PROPERLY SET IN THE ALT REMINDER WINDOW AND CALLED OUT 1000 FT PRIOR TO LEVELOFF. WE WERE IMC AND THE WX RADAR WAS ON. PASSING APPROX 8200-8300 FT WE RECEIVED A TCASII TA. BOTH OF US LOOKED AT THE SCREEN TO IDENT THE TFC. THE SCREEN WAS ON TOO LARGE A SCALE AND WAS CLUTTERED WITH THE WX RADAR. AS A FAIRLY NEW FO WITH THE COMPANY, I HAD ONLY SEEN THE RADAR ON TWICE BEFORE AND HAD NEVER FOUND IT ON OR OFF MYSELF. I ADJUSTED THE SCALE AND THEN FUMBLED WITH THE SWITCHES TO TURN OFF THE RADAR IN ORDER TO IDENT THE TFC. AFTER WHAT COULD ONLY HAVE BEEN 5 SECONDS, THE CAPT REACHED OVER AND TURNED OFF THE RADAR HIMSELF. AS WE INSPECTED THE SCREEN WE RECEIVED A TCASII RA 'REDUCE DSCNT.' THE CAPT THEN NOTED THAT WE HAD DSNDED THROUGH OUR ASSIGNED ALT. I DON'T RECALL SEEING ANY LOWER THAN 7700 FT. AS WE LEVELED OFF AT 8000 FT MSP APCH ASKED US TO CONFIRM 8000 FT ASSIGNED. WE THEN CONFIRMED THAT WE WERE LEVEL AT 8000 FT AND THE MATTER SEEMED CLOSED. CONTRIBUTING FACTORS: A CLUTTERED SCREEN, FO UNFAMILIAR WITH SWITCHES ON THE OTHER SIDE OF THE COCKPIT (RADAR), CAPT DISTRACTED BY TCASII AND FO. IF I HAD BEEN MORE FAMILIAR WITH THE RADAR SWITCHES THEN THE INCIDENT MAY HAVE BEEN AVOIDED. PERHAPS THIS SHOULD BE ADDED TO SIMULATOR/CLASSROOM INSTRUCTION. IF THE CAPT HAD CONCENTRATED ON FLYING THE ACFT FIRST THEN THE INCIDENT WOULD HAVE BEEN AVOIDED.

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.