Narrative:

Small transport descending out of 33000' with a clearance to cross 35 mi southeast of springfield, mo, VOR at 15000'. Reported light/moderate turbulence to ATC out of 21000' as we let down through a wide area of rain showers associated with a front. Copilot was on #2 communication getting customers a cabin attendant and picking up ATIS. Captain was flying and talking to ATC. Traffic was issued for our 2 O'clock position at 14000'. Visibility in the local area was good at the time, better than 5 mi. No contact was made with the traffic, (copilot's window). The copilot was told of the traffic by the captain when he got off the radio and crew was looking for it. Altitude alerter chimed, crew checked altimeter and saw 14600'. Captain pushed power levers up to stop descent and climbed back to 15000' as ATC called us to say they showed an altitude deviation and reissued the traffic. A phone number for kansas city ATC was copied by the crew and then the flight was turned over to springfield approach control. No further incident occurred. Other factors involved in this incident were the altitude alerter which had been functioning erratically the whole leg of the flight. The unit had been a replacement for a similar unit which had also been malfunctioning and was sent out for maintenance by our base mechanics. Sometimes the unit chimed 200' + low to 400' high or sometimes did not chime at all. Crew had been flying all afternoon. It was the fifth leg of the day with one more to follow, of a 3 day trip. This was day 2. Temperatures were 90 degree on the ramps prior to this leg and the a/C had lost all its freon charge. The fatigue associated with the warm temperatures had an effect on the crew. Also the diversion of duties, as we hurried to make a crossing restriction in areas of sometimes moderate turbulence, with an emphasis on arriving at springfield as close to schedule as possible in addition to being issued traffic increased cockpit workload greatly. Further note: #2 communication push-to-talk switch cuts out #1 communication audio when both radios are in use. Makes it very difficult to use more than one radio at a time.

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Original NASA ASRS Text

Title: SMT ON DESCENT WITH MALFUNCTIONING ALT ALERT HAS ALT DEVIATION.

Narrative: SMT DSNDING OUT OF 33000' WITH A CLRNC TO CROSS 35 MI SE OF SPRINGFIELD, MO, VOR AT 15000'. RPTED LIGHT/MODERATE TURB TO ATC OUT OF 21000' AS WE LET DOWN THROUGH A WIDE AREA OF RAIN SHOWERS ASSOCIATED WITH A FRONT. COPLT WAS ON #2 COM GETTING CUSTOMERS A CAB AND PICKING UP ATIS. CAPT WAS FLYING AND TALKING TO ATC. TFC WAS ISSUED FOR OUR 2 O'CLOCK POS AT 14000'. VISIBILITY IN THE LCL AREA WAS GOOD AT THE TIME, BETTER THAN 5 MI. NO CONTACT WAS MADE WITH THE TFC, (COPLT'S WINDOW). THE COPLT WAS TOLD OF THE TFC BY THE CAPT WHEN HE GOT OFF THE RADIO AND CREW WAS LOOKING FOR IT. ALT ALERTER CHIMED, CREW CHKED ALTIMETER AND SAW 14600'. CAPT PUSHED PWR LEVERS UP TO STOP DSNT AND CLBED BACK TO 15000' AS ATC CALLED US TO SAY THEY SHOWED AN ALT DEV AND REISSUED THE TFC. A PHONE NUMBER FOR KANSAS CITY ATC WAS COPIED BY THE CREW AND THEN THE FLT WAS TURNED OVER TO SPRINGFIELD APCH CTL. NO FURTHER INCIDENT OCCURRED. OTHER FACTORS INVOLVED IN THIS INCIDENT WERE THE ALT ALERTER WHICH HAD BEEN FUNCTIONING ERRATICALLY THE WHOLE LEG OF THE FLT. THE UNIT HAD BEEN A REPLACEMENT FOR A SIMILAR UNIT WHICH HAD ALSO BEEN MALFUNCTIONING AND WAS SENT OUT FOR MAINT BY OUR BASE MECHS. SOMETIMES THE UNIT CHIMED 200' + LOW TO 400' HIGH OR SOMETIMES DID NOT CHIME AT ALL. CREW HAD BEEN FLYING ALL AFTERNOON. IT WAS THE FIFTH LEG OF THE DAY WITH ONE MORE TO FOLLOW, OF A 3 DAY TRIP. THIS WAS DAY 2. TEMPS WERE 90 DEG ON THE RAMPS PRIOR TO THIS LEG AND THE A/C HAD LOST ALL ITS FREON CHARGE. THE FATIGUE ASSOCIATED WITH THE WARM TEMPS HAD AN EFFECT ON THE CREW. ALSO THE DIVERSION OF DUTIES, AS WE HURRIED TO MAKE A XING RESTRICTION IN AREAS OF SOMETIMES MODERATE TURB, WITH AN EMPHASIS ON ARRIVING AT SPRINGFIELD AS CLOSE TO SCHEDULE AS POSSIBLE IN ADDITION TO BEING ISSUED TFC INCREASED COCKPIT WORKLOAD GREATLY. FURTHER NOTE: #2 COM PUSH-TO-TALK SWITCH CUTS OUT #1 COM AUDIO WHEN BOTH RADIOS ARE IN USE. MAKES IT VERY DIFFICULT TO USE MORE THAN ONE RADIO AT A TIME.

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.