Small aircraft on IFR flight plan told ATC unable to pick up mode C.

Attributes
ACN	190086
Time
Date	199109
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : msn
State Reference	WI
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mke tracon : msn
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 40 flight time total : 3700 flight time type : 3100
ASRS Report	190086
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

IFR racine to madison and return. Mke departure picked up mode C. Transferred to madison approach. Madison said they weren't receiving mode C. This has happened before, about a yr ago and eventually madison picked it up. Continued approach and landed. Departed madison about xx pm. Madison still didn't pick up mode C. Mke said they didn't either but I don't believe flight path took me through or above mke arsa. Checked connections to encoder after landing but could find nothing wrong. Flight checked airplane on 9/ab/91 and mke approach reported encoder was working properly. IFR flight to madison 9/ad/91. Verified encoder operation after takeoff with mke. Madison made no comment so presumably they were picking it up. Took off a few hours later and madison said they couldn't pick up my mode C. Verified this just before switching to mke approach. Mke was picking up my mode C loud and clear. Callback conversation with reporter revealed the following information: reporter states unable to determine problem. Has transponder in for maintenance check again. Really hopes something can be found to resolve this trouble. Will let us know if this occurs. Feels his equipment is the problem since msn had not commented reference other complaints.

Original NASA ASRS Text

Title: SMA ON IFR FLT PLAN TOLD ATC UNABLE TO PICK UP MODE C.

Narrative: IFR RACINE TO MADISON AND RETURN. MKE DEP PICKED UP MODE C. TRANSFERRED TO MADISON APCH. MADISON SAID THEY WEREN'T RECEIVING MODE C. THIS HAS HAPPENED BEFORE, ABOUT A YR AGO AND EVENTUALLY MADISON PICKED IT UP. CONTINUED APCH AND LANDED. DEPARTED MADISON ABOUT XX PM. MADISON STILL DIDN'T PICK UP MODE C. MKE SAID THEY DIDN'T EITHER BUT I DON'T BELIEVE FLT PATH TOOK ME THROUGH OR ABOVE MKE ARSA. CHKED CONNECTIONS TO ENCODER AFTER LNDG BUT COULD FIND NOTHING WRONG. FLT CHKED AIRPLANE ON 9/AB/91 AND MKE APCH RPTED ENCODER WAS WORKING PROPERLY. IFR FLT TO MADISON 9/AD/91. VERIFIED ENCODER OP AFTER TKOF WITH MKE. MADISON MADE NO COMMENT SO PRESUMABLY THEY WERE PICKING IT UP. TOOK OFF A FEW HRS LATER AND MADISON SAID THEY COULDN'T PICK UP MY MODE C. VERIFIED THIS JUST BEFORE SWITCHING TO MKE APCH. MKE WAS PICKING UP MY MODE C LOUD AND CLR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES UNABLE TO DETERMINE PROBLEM. HAS TRANSPONDER IN FOR MAINT CHK AGAIN. REALLY HOPES SOMETHING CAN BE FOUND TO RESOLVE THIS TROUBLE. WILL LET US KNOW IF THIS OCCURS. FEELS HIS EQUIP IS THE PROBLEM SINCE MSN HAD NOT COMMENTED REF OTHER COMPLAINTS.

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.