Aircraft equipment problem transponder. Loss of radar targets (coasting and ghosting).

Attributes
ACN	196780
Time
Date	199112
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ord
State Reference	IL
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 8
ASRS Report	196780
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	faa : investigated
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

It has been determined that certain aircraft do not send out a reliable transponder reply and subsequently, our radar cannot track these planes. The medium large transport and the large transport operated by X airlines for the most part do not have reliable transponders or else there is something unique about them that does not allow them to 'communicate' with our radar. The problem exists in all phases of flight including straight and level, turns, climbs and dscnts. Air carrier X and Y avionics have looked into the problem, but there has been no indications that they can find the problem.

Original NASA ASRS Text

Title: ACFT EQUIP PROBLEM TRANSPONDER. LOSS OF RADAR TARGETS (COASTING AND GHOSTING).

Narrative: IT HAS BEEN DETERMINED THAT CERTAIN ACFT DO NOT SEND OUT A RELIABLE TRANSPONDER REPLY AND SUBSEQUENTLY, OUR RADAR CANNOT TRACK THESE PLANES. THE MLG AND THE LGT OPERATED BY X AIRLINES FOR THE MOST PART DO NOT HAVE RELIABLE TRANSPONDERS OR ELSE THERE IS SOMETHING UNIQUE ABOUT THEM THAT DOES NOT ALLOW THEM TO 'COMMUNICATE' WITH OUR RADAR. THE PROBLEM EXISTS IN ALL PHASES OF FLT INCLUDING STRAIGHT AND LEVEL, TURNS, CLBS AND DSCNTS. ACR X AND Y AVIONICS HAVE LOOKED INTO THE PROBLEM, BUT THERE HAS BEEN NO INDICATIONS THAT THEY CAN FIND THE PROBLEM.

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.