Altitude deviation altitude excursion on TCASII RA. Possible phantom event.

Attributes
ACN	285320
Time
Date	199410
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : iso
State Reference	NC
Altitude	msl bound lower : 27000 msl bound upper : 28000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc tower : ord
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	285320
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	285321
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation 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
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

While cruising at FL280, about 15 mi northeast of the iso VOR on J121 a TA alert showed up on the TCASII followed quickly by a RA alert. We were in the clouds. The TCASII showed traffic at our 12:30-1 O'clock position at our altitude. We followed the TCASII instructions to descend at 2000 FPM. At this time we advised ATC that we were descending because of an RA. Between 27500 and 27000 ft we were given the clear of conflict by the TCASII and initiated a climb back to FL280. During this period we repeated our deviation and the reason for the deviation when we thought ATC did not hear us when we were approaching FL280 -- ATC asked us to confirm our altitude. We once again explained we had an RA on the TCASII, again ATC did not respond. We called ATC again to make it clear that we were responding to an RA. We were told to stand by. About 5 mins later he came back to us, we explained once again, he told us there was no traffic in the area. This was 10 mins after the RA. I don't know if he meant now or then. We were in the clouds with zero visibility. We had no other option. I don't know if it was an anomaly of the TCASII. I don't know if there really was a conflict or not. I do know that after leaving my altitude and trying to explain to ATC that we had an RA that they didn't quite understand the situation or weren't aware of what a RA is. The lack of understanding or communication was the most disconcerting about the RA.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION ON TCASII RA. POSSIBLE PHANTOM EVENT.

Narrative: WHILE CRUISING AT FL280, ABOUT 15 MI NE OF THE ISO VOR ON J121 A TA ALERT SHOWED UP ON THE TCASII FOLLOWED QUICKLY BY A RA ALERT. WE WERE IN THE CLOUDS. THE TCASII SHOWED TFC AT OUR 12:30-1 O'CLOCK POS AT OUR ALT. WE FOLLOWED THE TCASII INSTRUCTIONS TO DSND AT 2000 FPM. AT THIS TIME WE ADVISED ATC THAT WE WERE DSNDING BECAUSE OF AN RA. BTWN 27500 AND 27000 FT WE WERE GIVEN THE CLR OF CONFLICT BY THE TCASII AND INITIATED A CLB BACK TO FL280. DURING THIS PERIOD WE REPEATED OUR DEV AND THE REASON FOR THE DEV WHEN WE THOUGHT ATC DID NOT HEAR US WHEN WE WERE APCHING FL280 -- ATC ASKED US TO CONFIRM OUR ALT. WE ONCE AGAIN EXPLAINED WE HAD AN RA ON THE TCASII, AGAIN ATC DID NOT RESPOND. WE CALLED ATC AGAIN TO MAKE IT CLR THAT WE WERE RESPONDING TO AN RA. WE WERE TOLD TO STAND BY. ABOUT 5 MINS LATER HE CAME BACK TO US, WE EXPLAINED ONCE AGAIN, HE TOLD US THERE WAS NO TFC IN THE AREA. THIS WAS 10 MINS AFTER THE RA. I DON'T KNOW IF HE MEANT NOW OR THEN. WE WERE IN THE CLOUDS WITH ZERO VISIBILITY. WE HAD NO OTHER OPTION. I DON'T KNOW IF IT WAS AN ANOMALY OF THE TCASII. I DON'T KNOW IF THERE REALLY WAS A CONFLICT OR NOT. I DO KNOW THAT AFTER LEAVING MY ALT AND TRYING TO EXPLAIN TO ATC THAT WE HAD AN RA THAT THEY DIDN'T QUITE UNDERSTAND THE SIT OR WEREN'T AWARE OF WHAT A RA IS. THE LACK OF UNDERSTANDING OR COM WAS THE MOST DISCONCERTING ABOUT THE RA.

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.