VFR C172 is concerned with entering sfo mode C veil without functioning transponder.

Attributes
ACN	594727
Time
Date	200308
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : evgen
State Reference	CA
Altitude	msl single value : 9500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc tracon : nct.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	None
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 60 flight time total : 200 flight time type : 180
ASRS Report	594727
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	airspace violation : entry non adherence : far non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	flight crew : took precautionary avoidance action
Supplementary
Problem Areas	Airspace Structure Flight Crew Human Performance Aircraft ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flew from F70 santa ynez (iza), with flight following, completely without incident. After refueling, took off heading for haf, with sql as my alternate. Shortly after leaving iza, was informed that mode C inoperative/intermittent, but had good primary target. At request of ATC, recycled it numerous times. Unable to get consistent mode C operation, and was told to report altitude changes. Was informed by ATC that would not be able to enter class B airspace. I acknowledged this, but asked if I could enter the mode C veil, and fly below class B. He admitted he didn't know ('a good question' was the actual reply), but that he didn't deal with that area of airspace, and that norcal would make that decision. Shortly after, contacted norcal approach, who restated no entry into class B airspace without mode C transponder. Asked about entering the mode C veil below class B, and was told 'squawk 1200, radar services terminated.' I circled down to 3500 ft MSL, above eugen, and proceeded to haf, which was IFR conditions. So headed to sql at same altitude, landing without incident, and without further communication with norcal. On aug/sun/03, I left sql, and followed the haywood departure (think this is correct name) at 3500 ft MSL, remaining outside class B at all time., on reaching eugen, climbed to 7500 ft MSL. Obtained flight following -- again, mode C was intermittent, with good primary target. Refueled at iza, and shortly after, obtained flight following, this time with perfect mode C response, which lasted all through the los angeles basin, back through march gca, and to F70. From the response of norcal, I believe that this is a known problem with the mode C. It is too much of a coincidence that the mode C stopped working at iza, and then started working at exactly the same place on the return journey. I flew the aircraft, 2 days later, and the mode C worked perfectly. Spoke with other pilots, who informed me that they have also had problems in that area. I feel that the problem lies with ATC radar system between iza and the general area of san francisco. This problem needs to be addressed.

Original NASA ASRS Text

Title: VFR C172 IS CONCERNED WITH ENTERING SFO MODE C VEIL WITHOUT FUNCTIONING XPONDER.

Narrative: FLEW FROM F70 SANTA YNEZ (IZA), WITH FLT FOLLOWING, COMPLETELY WITHOUT INCIDENT. AFTER REFUELING, TOOK OFF HEADING FOR HAF, WITH SQL AS MY ALTERNATE. SHORTLY AFTER LEAVING IZA, WAS INFORMED THAT MODE C INOP/INTERMITTENT, BUT HAD GOOD PRIMARY TARGET. AT REQUEST OF ATC, RECYCLED IT NUMEROUS TIMES. UNABLE TO GET CONSISTENT MODE C OP, AND WAS TOLD TO RPT ALT CHANGES. WAS INFORMED BY ATC THAT WOULD NOT BE ABLE TO ENTER CLASS B AIRSPACE. I ACKNOWLEDGED THIS, BUT ASKED IF I COULD ENTER THE MODE C VEIL, AND FLY BELOW CLASS B. HE ADMITTED HE DIDN'T KNOW ('A GOOD QUESTION' WAS THE ACTUAL REPLY), BUT THAT HE DIDN'T DEAL WITH THAT AREA OF AIRSPACE, AND THAT NORCAL WOULD MAKE THAT DECISION. SHORTLY AFTER, CONTACTED NORCAL APCH, WHO RESTATED NO ENTRY INTO CLASS B AIRSPACE WITHOUT MODE C XPONDER. ASKED ABOUT ENTERING THE MODE C VEIL BELOW CLASS B, AND WAS TOLD 'SQUAWK 1200, RADAR SVCS TERMINATED.' I CIRCLED DOWN TO 3500 FT MSL, ABOVE EUGEN, AND PROCEEDED TO HAF, WHICH WAS IFR CONDITIONS. SO HEADED TO SQL AT SAME ALT, LNDG WITHOUT INCIDENT, AND WITHOUT FURTHER COM WITH NORCAL. ON AUG/SUN/03, I LEFT SQL, AND FOLLOWED THE HAYWOOD DEP (THINK THIS IS CORRECT NAME) AT 3500 FT MSL, REMAINING OUTSIDE CLASS B AT ALL TIME., ON REACHING EUGEN, CLBED TO 7500 FT MSL. OBTAINED FLT FOLLOWING -- AGAIN, MODE C WAS INTERMITTENT, WITH GOOD PRIMARY TARGET. REFUELED AT IZA, AND SHORTLY AFTER, OBTAINED FLT FOLLOWING, THIS TIME WITH PERFECT MODE C RESPONSE, WHICH LASTED ALL THROUGH THE LOS ANGELES BASIN, BACK THROUGH MARCH GCA, AND TO F70. FROM THE RESPONSE OF NORCAL, I BELIEVE THAT THIS IS A KNOWN PROB WITH THE MODE C. IT IS TOO MUCH OF A COINCIDENCE THAT THE MODE C STOPPED WORKING AT IZA, AND THEN STARTED WORKING AT EXACTLY THE SAME PLACE ON THE RETURN JOURNEY. I FLEW THE ACFT, 2 DAYS LATER, AND THE MODE C WORKED PERFECTLY. SPOKE WITH OTHER PLTS, WHO INFORMED ME THAT THEY HAVE ALSO HAD PROBS IN THAT AREA. I FEEL THAT THE PROB LIES WITH ATC RADAR SYS BTWN IZA AND THE GENERAL AREA OF SAN FRANCISCO. THIS PROB NEEDS TO BE ADDRESSED.

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.