Xponders of some types reported as unreadable by some ATC radar and TCASII receivers.

Attributes
ACN	448617
Time
Date	199909
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : cmh.airport
State Reference	OH
Altitude	agl single value : 0
Person 1
Affiliation	government : faa
Function	other personnel other
ASRS Report	448617
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other other : 1
Resolutory Action	other
Supplementary
Problem Areas	ATC Facility Aircraft
Primary Problem	Ambiguous

Narrative:

In sum: reporter submitted a letter and an article that has been sent to almost everyone in the industry that might be interested referring to the problem of xponders of at least 2 makes that are not received by surveillance radar and TCASII. He concludes that it may be a major problem in the GA area and seems to be somewhat connected with the upgrade of system at some ATC locations. He states in conclusion: 'I feel it is important to bring this to our attention because it attests to the possibility of a more widespread problem in the fleet of GA xponders than may be realized or reported. This concerns me a great deal, as proper operation of xponders is the backbone of the ATC radar beacon and TCASII system. It is disconcerting to realize that possibly 1 in 5 xponders are likely to be invisible to TCASII equipped aircraft!'

Original NASA ASRS Text

Title: XPONDERS OF SOME TYPES RPTED AS UNREADABLE BY SOME ATC RADAR AND TCASII RECEIVERS.

Narrative: IN SUM: RPTR SUBMITTED A LETTER AND AN ARTICLE THAT HAS BEEN SENT TO ALMOST EVERYONE IN THE INDUSTRY THAT MIGHT BE INTERESTED REFERRING TO THE PROB OF XPONDERS OF AT LEAST 2 MAKES THAT ARE NOT RECEIVED BY SURVEILLANCE RADAR AND TCASII. HE CONCLUDES THAT IT MAY BE A MAJOR PROB IN THE GA AREA AND SEEMS TO BE SOMEWHAT CONNECTED WITH THE UPGRADE OF SYS AT SOME ATC LOCATIONS. HE STATES IN CONCLUSION: 'I FEEL IT IS IMPORTANT TO BRING THIS TO OUR ATTN BECAUSE IT ATTESTS TO THE POSSIBILITY OF A MORE WIDESPREAD PROB IN THE FLEET OF GA XPONDERS THAN MAY BE REALIZED OR RPTED. THIS CONCERNS ME A GREAT DEAL, AS PROPER OP OF XPONDERS IS THE BACKBONE OF THE ATC RADAR BEACON AND TCASII SYS. IT IS DISCONCERTING TO REALIZE THAT POSSIBLY 1 IN 5 XPONDERS ARE LIKELY TO BE INVISIBLE TO TCASII EQUIPPED ACFT!'

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.