Mode C failure discovered after departure. Requested waiver for return trip.

Attributes
ACN	190529
Time
Date	199110
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ocn
State Reference	CA
Altitude	msl bound lower : 5500 msl bound upper : 5500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sna tracon : san
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 25 flight time total : 205 flight time type : 10
ASRS Report	190529
Person 2
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

This flight from santa ana to montgomery field. Takeoff was normal. During climb out, coast departure asked our altitude, which was given. We were informed that our mode C was off by several thousand ft, and asked to recycle, which did not improve or correct the altitude squawk. Coast asked us to stop the mode C and continue. I asked coast well outside the 30 NM mode C veil if they could work a handoff, and was told they were in the process of doing so. I assumed that coast had informed san diego approach that we had an inoperative mode C and was surprised when, after passing oceanside VOR, well inside the 30 NM veil, I was asked to squawk 1200, frequency change approved. San diego gave us a squawk code and had no idea that our mode C was in error. The controller cleared us through and admonished me to 'get that thing fixed' before leaving. Since we needed to return that night, and no repair facility was open, and the owner of the airplane (it was rented) wanted us to bring it to home base (sna) for repairs, we called san diego and got a mode C waiver and returned without further problem. I feel first that pilots need to be aware that ATC may or may not inform each controller in succession of an equipment failure. In our case, we would have turned around had I thought that san diego didn't know about our malfunctioning mode C. Second, being aware of this, pilots need to ask what the controller is doing when something isn't firmly established. I am aware of the importance of mode C in helping controllers keep everyone apart and had no intention of causing a problem. I did learn how tough it is when a controller must ask for your altitude before he can issue instructions to other aircraft. Finally, I wonder if there is any way to verify transponder operation on the ground. In this case, the transponder test setting indicated normal operation even as I was told it wasn't functioning and gave the same indications on the ground before the return flight. This was extremely frustrating! In fact, on being cleared into san diego's TCA, I was told that our mode C was agreeing with our altimeter, then told moments later that it wasn't, then it was, etc. Only the controller can monitor this.

Original NASA ASRS Text

Title: MODE C FAILURE DISCOVERED AFTER DEP. REQUESTED WAIVER FOR RETURN TRIP.

Narrative: THIS FLT FROM SANTA ANA TO MONTGOMERY FIELD. TKOF WAS NORMAL. DURING CLBOUT, COAST DEP ASKED OUR ALT, WHICH WAS GIVEN. WE WERE INFORMED THAT OUR MODE C WAS OFF BY SEVERAL THOUSAND FT, AND ASKED TO RECYCLE, WHICH DID NOT IMPROVE OR CORRECT THE ALT SQUAWK. COAST ASKED US TO STOP THE MODE C AND CONTINUE. I ASKED COAST WELL OUTSIDE THE 30 NM MODE C VEIL IF THEY COULD WORK A HDOF, AND WAS TOLD THEY WERE IN THE PROCESS OF DOING SO. I ASSUMED THAT COAST HAD INFORMED SAN DIEGO APCH THAT WE HAD AN INOP MODE C AND WAS SURPRISED WHEN, AFTER PASSING OCEANSIDE VOR, WELL INSIDE THE 30 NM VEIL, I WAS ASKED TO SQUAWK 1200, FREQ CHANGE APPROVED. SAN DIEGO GAVE US A SQUAWK CODE AND HAD NO IDEA THAT OUR MODE C WAS IN ERROR. THE CTLR CLRED US THROUGH AND ADMONISHED ME TO 'GET THAT THING FIXED' BEFORE LEAVING. SINCE WE NEEDED TO RETURN THAT NIGHT, AND NO REPAIR FACILITY WAS OPEN, AND THE OWNER OF THE AIRPLANE (IT WAS RENTED) WANTED US TO BRING IT TO HOME BASE (SNA) FOR REPAIRS, WE CALLED SAN DIEGO AND GOT A MODE C WAIVER AND RETURNED WITHOUT FURTHER PROBLEM. I FEEL FIRST THAT PLTS NEED TO BE AWARE THAT ATC MAY OR MAY NOT INFORM EACH CTLR IN SUCCESSION OF AN EQUIP FAILURE. IN OUR CASE, WE WOULD HAVE TURNED AROUND HAD I THOUGHT THAT SAN DIEGO DIDN'T KNOW ABOUT OUR MALFUNCTIONING MODE C. SECOND, BEING AWARE OF THIS, PLTS NEED TO ASK WHAT THE CTLR IS DOING WHEN SOMETHING ISN'T FIRMLY ESTABLISHED. I AM AWARE OF THE IMPORTANCE OF MODE C IN HELPING CTLRS KEEP EVERYONE APART AND HAD NO INTENTION OF CAUSING A PROBLEM. I DID LEARN HOW TOUGH IT IS WHEN A CTLR MUST ASK FOR YOUR ALT BEFORE HE CAN ISSUE INSTRUCTIONS TO OTHER ACFT. FINALLY, I WONDER IF THERE IS ANY WAY TO VERIFY TRANSPONDER OP ON THE GND. IN THIS CASE, THE TRANSPONDER TEST SETTING INDICATED NORMAL OP EVEN AS I WAS TOLD IT WASN'T FUNCTIONING AND GAVE THE SAME INDICATIONS ON THE GND BEFORE THE RETURN FLT. THIS WAS EXTREMELY FRUSTRATING! IN FACT, ON BEING CLRED INTO SAN DIEGO'S TCA, I WAS TOLD THAT OUR MODE C WAS AGREEING WITH OUR ALTIMETER, THEN TOLD MOMENTS LATER THAT IT WASN'T, THEN IT WAS, ETC. ONLY THE CTLR CAN MONITOR THIS.

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.