Transponder ghosting contributing to near midair collision occurrences.

Attributes
ACN	287756
Time
Date	199409
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 2200 msl bound upper : 2200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord tower : saf
Operator	general aviation : personal
Make Model Name	BAe 146 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach landing other
Flight Plan	VFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 17500 flight time type : 6500
ASRS Report	287756
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : exited penetrated airspace
Consequence	Other
Miss Distance	horizontal : 0 vertical : 500
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During the past yr we have had 3 'TCASII -- TA' alerts without 'ATC' having any radar contact with the intruding aircraft (no primary or code 1200 target). Enclosed you will find an article from the 'professional pilot's magazine (dated apr/xx/94). Each of our problems relates to a stealth aircraft on 'mode-south' radar! 2 of our TA alerts did not have altitude encode capabilities. Why has the FAA not issued an airworthy directive? (Avionics, xponders.)

Original NASA ASRS Text

Title: XPONDER GHOSTING CONTRIBUTING TO NMAC OCCURRENCES.

Narrative: DURING THE PAST YR WE HAVE HAD 3 'TCASII -- TA' ALERTS WITHOUT 'ATC' HAVING ANY RADAR CONTACT WITH THE INTRUDING ACFT (NO PRIMARY OR CODE 1200 TARGET). ENCLOSED YOU WILL FIND AN ARTICLE FROM THE 'PROFESSIONAL PLT'S MAGAZINE (DATED APR/XX/94). EACH OF OUR PROBS RELATES TO A STEALTH ACFT ON 'MODE-S' RADAR! 2 OF OUR TA ALERTS DID NOT HAVE ALT ENCODE CAPABILITIES. WHY HAS THE FAA NOT ISSUED AN AIRWORTHY DIRECTIVE? (AVIONICS, XPONDERS.)

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.