A commercial pilot on the situation RNAV (GPS) runway 11 approach reported a TCAS RA from an unknown...

Attributes
ACN	957733
Time
Date	201107
Local Time Of Day	0601-1200
Place
Locale Reference	SIT.Airport
State Reference	AK
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Plan	None
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Conflict Airborne Conflict Deviation - Procedural FAR

Narrative:

Descending into situation and cleared for a RNAV (GPS) runway 11 approach; TCAS traffic appeared on my ehsi in front of me that appeared to be on an opposing course and climbing rapidly. Shortly there after zan issued a traffic alert; as did the TCAS; followed by a TCAS resolution instruction to climb; which was followed. After the conflict was resolved; the approach was resumed and the subsequent landing at situation was non-eventful. The scary part of this event was the other aircraft involved was flying in the clouds without any clearance and not communicating with any ATC facilities. In my opinion; the other aircraft involved could not have been in VFR conditions! Given my instruments; it's impossible to know exactly how close this came to being a tragic event.

Original NASA ASRS Text

Title: A commercial pilot on the SIT RNAV (GPS) Runway 11 approach reported a TCAS RA from an unknown aircraft outbound near the localizer in IMC; but not talking with ATC.

Narrative: Descending into SIT and cleared for a RNAV (GPS) Runway 11 approach; TCAS traffic appeared on my EHSI in front of me that appeared to be on an opposing course and climbing rapidly. Shortly there after ZAN issued a traffic alert; as did the TCAS; followed by a TCAS resolution instruction to climb; which was followed. After the conflict was resolved; the approach was resumed and the subsequent landing at SIT was non-eventful. The scary part of this event was the other aircraft involved was flying in the clouds without any clearance and not communicating with any ATC facilities. In my opinion; the other aircraft involved could not have been in VFR conditions! Given my instruments; it's impossible to know exactly how close this came to being a tragic event.

Data retrieved from NASA's ASRS site as of April 2012 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.

A commercial pilot on the situation RNAV (GPS) runway 11 approach reported a TCAS RA from an unknown aircraft outbound near the localizer in IMC; but not talking with ATC.