Flight crew of a B757 descended in response to a TCASII RA and then subsequently when returning to assigned cruise altitude, overshot altitude.

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Attributes
ACN	477537
Time
Date	200006
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : lmn.vor
State Reference	IA
Altitude	msl bound lower : 24500 msl bound upper : 26500
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Flight Phase	climbout : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : private pilot : multi engine pilot : instrument pilot : atp pilot : commercial
Experience	flight time last 90 days : 160 flight time total : 10000 flight time type : 1200
ASRS Report	477537
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa
Resolutory Action	controller : issued advisory flight crew : took precautionary avoidance action
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

In cruise at FL260, got TCASII TA then RA symbol with aural 'descend, descend' appeared at 12 O'clock position at FL260. Followed RA maneuver guidance to approximately FL245. First officer notified ATC ZMP 118.82. ATC said other traffic was climbing to F;250 at our 2 O'clock approximately 4-8 mi. So I (captain/PF) climbed back up to FL260 to avoid traffic. Overshot to FL265. At FL265 got another RA symbol. At FL265 (12 O'clock position) with TCASII aural maneuver guidance 'climb, climb, climb.' so I climbed and leveled at FL270. Now we realized these were both false RA's (bad TCASII unit). ATC got alarms for real traffic that was climbing to FL250. ATC showed no traffic at FL260 or FL265. We had no choice but to follow RA commands since we were IMC and could not be sure of traffic. Aircraft tail number had a history of TCASII problems in previous 30 days. ATC controller got alarms but was not considered an near midair collision.

Original NASA ASRS Text

Title: FLC OF A B757 DSNDED IN RESPONSE TO A TCASII RA AND THEN SUBSEQUENTLY WHEN RETURNING TO ASSIGNED CRUISE ALT, OVERSHOT ALT.

Narrative: IN CRUISE AT FL260, GOT TCASII TA THEN RA SYMBOL WITH AURAL 'DSND, DSND' APPEARED AT 12 O'CLOCK POS AT FL260. FOLLOWED RA MANEUVER GUIDANCE TO APPROX FL245. FO NOTIFIED ATC ZMP 118.82. ATC SAID OTHER TFC WAS CLBING TO F;250 AT OUR 2 O'CLOCK APPROX 4-8 MI. SO I (CAPT/PF) CLBED BACK UP TO FL260 TO AVOID TFC. OVERSHOT TO FL265. AT FL265 GOT ANOTHER RA SYMBOL. AT FL265 (12 O'CLOCK POS) WITH TCASII AURAL MANEUVER GUIDANCE 'CLB, CLB, CLB.' SO I CLBED AND LEVELED AT FL270. NOW WE REALIZED THESE WERE BOTH FALSE RA'S (BAD TCASII UNIT). ATC GOT ALARMS FOR REAL TFC THAT WAS CLBING TO FL250. ATC SHOWED NO TFC AT FL260 OR FL265. WE HAD NO CHOICE BUT TO FOLLOW RA COMMANDS SINCE WE WERE IMC AND COULD NOT BE SURE OF TFC. ACFT TAIL NUMBER HAD A HISTORY OF TCASII PROBS IN PREVIOUS 30 DAYS. ATC CTLR GOT ALARMS BUT WAS NOT CONSIDERED AN NMAC.

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.