<< >> NASA ASRS Report 443843, July 1999

An SF340 flight crew received a TCASII RA 'descend' message which would have placed them at the altitude of observed traffic.

Attributes
ACN	443843
Time
Date	199907
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : bdl.vortac
State Reference	CT
Altitude	msl bound lower : 9500 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	SF 340B
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute airway : v419.airway
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zbw.artcc
Operator	general aviation : personal
Make Model Name	Cessna Twin Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute airway : v419.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial
Experience	flight time last 90 days : 220 flight time total : 9000 flight time type : 6000
ASRS Report	443843
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude flight crew : took precautionary avoidance action
Miss Distance	horizontal : 8000 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

Twin cessna approaching from 10 O'clock position at 9000 ft has us visually. At 2-3 mi, an RA appeared on TCASII level at +10000 ft. TCASII commanded descent, 'descend now.' first officer, the PF, began a descent. I had him level at 9500 ft to avoid conflict with twin cessna at 9000 ft. At 9500 ft, 10000 ft RA aircraft disappeared. TCASII triggered 9000 ft twin cessna as an RA, 'climb, climb now.' we returned to 10000 ft. We believe the 10000 ft aircraft was a false target. ATC reported they would report a loss of IFR altitude separation. We leveled at 9500 ft.

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Original NASA ASRS Text

Title: AN SF340 FLC RECEIVED A TCASII RA 'DSND' MESSAGE WHICH WOULD HAVE PLACED THEM AT THE ALT OF OBSERVED TFC.

Narrative: TWIN CESSNA APCHING FROM 10 O'CLOCK POS AT 9000 FT HAS US VISUALLY. AT 2-3 MI, AN RA APPEARED ON TCASII LEVEL AT +10000 FT. TCASII COMMANDED DSCNT, 'DSND NOW.' FO, THE PF, BEGAN A DSCNT. I HAD HIM LEVEL AT 9500 FT TO AVOID CONFLICT WITH TWIN CESSNA AT 9000 FT. AT 9500 FT, 10000 FT RA ACFT DISAPPEARED. TCASII TRIGGERED 9000 FT TWIN CESSNA AS AN RA, 'CLB, CLB NOW.' WE RETURNED TO 10000 FT. WE BELIEVE THE 10000 FT ACFT WAS A FALSE TARGET. ATC RPTED THEY WOULD RPT A LOSS OF IFR ALT SEPARATION. WE LEVELED AT 9500 FT.

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.