Medium large transport on approach has TCASII TA, then RA. Descends.

Attributes
ACN	247523
Time
Date	199307
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dsm
State Reference	IA
Altitude	msl bound lower : 4500 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dsm
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 110 flight time total : 9200 flight time type : 670
ASRS Report	247523
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 4000 flight time type : 180
ASRS Report	247937
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	vertical : 300
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flight ord to dsm was given headings by dsm approach and assigned 5000 ft. Dsm radar was out. There was another aircraft at 5500 ft in our area. As we were told to intercept kdsm 31R localizer our TCASII alerted us to traffic (TA). The TCASII painted traffic at our 11 O'clock at plus 300 ft. We were then given an RA to descend. We went from 5000 ft to 4500 and got a clear of traffic. We never saw the other traffic. I spoke with mr X at dsm tower. Mr X said that the traffic was off his altitude.

Original NASA ASRS Text

Title: MLG ON APCH HAS TCASII TA, THEN RA. DSNDS.

Narrative: FLT ORD TO DSM WAS GIVEN HDGS BY DSM APCH AND ASSIGNED 5000 FT. DSM RADAR WAS OUT. THERE WAS ANOTHER ACFT AT 5500 FT IN OUR AREA. AS WE WERE TOLD TO INTERCEPT KDSM 31R LOC OUR TCASII ALERTED US TO TFC (TA). THE TCASII PAINTED TFC AT OUR 11 O'CLOCK AT PLUS 300 FT. WE WERE THEN GIVEN AN RA TO DSND. WE WENT FROM 5000 FT TO 4500 AND GOT A CLR OF TFC. WE NEVER SAW THE OTHER TFC. I SPOKE WITH MR X AT DSM TWR. MR X SAID THAT THE TFC WAS OFF HIS ALT.

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.