While in a holding pattern at bos, flight crew received a TCASII RA to descend.

Attributes
ACN	405874
Time
Date	199806
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bos
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent other other
Route In Use	approach : straight in
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	405874
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Holding at nabbo for ILS runway 4R CAT III. Boston approach had us holding at nabbo at 6000 ft. Approaching nabbo, the TCASII gave us an RA to descend, descend. The TCASII screen alerted us to an aircraft about 2 mi away about 200 ft above our 6000 ft. We immediately complied with RA procedures, and the other aircraft appeared to begin a climb on TCASII. I asked the controller if the airline was at the proper altitude at 6000 ft. He confirmed we were correct, but to descend and maintain 5000 ft. The flight continued without further problems. Boston ATC supervisor and I spoke about 30 mins later. He said he would be conducting a look into the matter. Also advised boston chief pilot.

Original NASA ASRS Text

Title: WHILE IN A HOLDING PATTERN AT BOS, FLC RECEIVED A TCASII RA TO DSND.

Narrative: HOLDING AT NABBO FOR ILS RWY 4R CAT III. BOSTON APCH HAD US HOLDING AT NABBO AT 6000 FT. APCHING NABBO, THE TCASII GAVE US AN RA TO DSND, DSND. THE TCASII SCREEN ALERTED US TO AN ACFT ABOUT 2 MI AWAY ABOUT 200 FT ABOVE OUR 6000 FT. WE IMMEDIATELY COMPLIED WITH RA PROCS, AND THE OTHER ACFT APPEARED TO BEGIN A CLB ON TCASII. I ASKED THE CTLR IF THE AIRLINE WAS AT THE PROPER ALT AT 6000 FT. HE CONFIRMED WE WERE CORRECT, BUT TO DSND AND MAINTAIN 5000 FT. THE FLT CONTINUED WITHOUT FURTHER PROBS. BOSTON ATC SUPVR AND I SPOKE ABOUT 30 MINS LATER. HE SAID HE WOULD BE CONDUCTING A LOOK INTO THE MATTER. ALSO ADVISED BOSTON CHIEF PLT.

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.