Altitude deviation on TCASII RA.

Attributes
ACN	206663
Time
Date	199203
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : phl
State Reference	PA
Altitude	msl bound lower : 3700 msl bound upper : 4000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phl
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 97 flight time total : 13000 flight time type : 97
ASRS Report	206662
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 7000 flight time type : 1500
ASRS Report	206663
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude 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	horizontal : 15000 vertical : 300
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Got command from TCASII to descend immediately (target appeared suddenly as 'red' with no prior warning or advisory). We started a descent and notified ATC. ATC stated that he showed no traffic above us and that there was traffic at 3000 ft. The TCASII warning ceased and we quickly climbed back to 4000 ft. Total loss of altitude was approximately 300 ft. The warning was apparently false. No further problems occurred. Supplemental information from acn 206662: the TCASII was showing the conflict on our altitude at the 12 O'clock position and 3 mi. We deviated from assigned altitude for about 30 seconds.

Original NASA ASRS Text

Title: ALTDEV ON TCASII RA.

Narrative: GOT COMMAND FROM TCASII TO DSND IMMEDIATELY (TARGET APPEARED SUDDENLY AS 'RED' WITH NO PRIOR WARNING OR ADVISORY). WE STARTED A DSCNT AND NOTIFIED ATC. ATC STATED THAT HE SHOWED NO TFC ABOVE US AND THAT THERE WAS TFC AT 3000 FT. THE TCASII WARNING CEASED AND WE QUICKLY CLBED BACK TO 4000 FT. TOTAL LOSS OF ALT WAS APPROX 300 FT. THE WARNING WAS APPARENTLY FALSE. NO FURTHER PROBLEMS OCCURRED. SUPPLEMENTAL INFO FROM ACN 206662: THE TCASII WAS SHOWING THE CONFLICT ON OUR ALT AT THE 12 O'CLOCK POS AND 3 MI. WE DEVIATED FROM ASSIGNED ALT FOR ABOUT 30 SECONDS.

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.