Narrative:

I was returning from redlands airport to brackett airport at 3250 ft MSL along the base of the san gabriel mountains outside of ontario's class C airspace. I had begun the day just about 45 mins earlier departing brackett for redlands. The terrain is generally at 1500 ft to 2000 ft MSL along this route. The airspace is class east. The visibility was good at 5 mi east of cable airport (uncontrolled) since I could easily spot cable airport from this position. Temperature was very hot and the mechanical/convective turbulence was producing updrafts and downdrafts. While monitoring cable's frequency. I also picked up the brackett ATIS and learned that bracket was reporting 2 mi visibility. Departing brackett earlier, the WX was 3 mi -- I had expected WX to improve. Brackett is located just a few mi west of cable and can have significantly lower localizer WX due to a nearby lake. There were aircraft operating at cable, and as a result, it's very important to keep an eye out for traffic as cable's traffic typically departs to the north toward the base of the san gabriel mountains. This is a high density traffic environment. I requested special VFR from brackett and was given an appropriate clearance ito brackett's class D airspace. The clearance included the following '...maintain at or below 2500 ft ...' normally, I stay above 3000 ft MSL until just west of cable airport to maintain proper minimum altitudes, and then start a descent for landing. Unfortunately, this time, I started my descent, for the purpose of landing, too early and descended lower than was necessary for the operation. I began my descent too early to meet the 2500 foot limitation. I believe that the problem was compounded by low visibilities at brackett airport, the 'awareness' of the high traffic environment, monitoring of multiple communication sources, trying to stay clear of ontario's class C airspace, and the mountains. In hindsight, it would have been best to start the day with better than 3 mi to provide adequate margins for VFR flight. As a result, I will increase my personal VFR minimums to 5 mi. The workload was quite high and situational awareness was negatively effected.

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Original NASA ASRS Text

Title: A C152 PLT WAS CONCERNED THAT HE DSNDED TOO EARLY ON APCH TO POC, EVEN THOUGH HE FOLLOWED THE INSTRUCTIONS GIVEN.

Narrative: I WAS RETURNING FROM REDLANDS ARPT TO BRACKETT ARPT AT 3250 FT MSL ALONG THE BASE OF THE SAN GABRIEL MOUNTAINS OUTSIDE OF ONTARIO'S CLASS C AIRSPACE. I HAD BEGUN THE DAY JUST ABOUT 45 MINS EARLIER DEPARTING BRACKETT FOR REDLANDS. THE TERRAIN IS GENERALLY AT 1500 FT TO 2000 FT MSL ALONG THIS RTE. THE AIRSPACE IS CLASS E. THE VISIBILITY WAS GOOD AT 5 MI E OF CABLE ARPT (UNCTLED) SINCE I COULD EASILY SPOT CABLE ARPT FROM THIS POS. TEMP WAS VERY HOT AND THE MECHANICAL/CONVECTIVE TURB WAS PRODUCING UPDRAFTS AND DOWNDRAFTS. WHILE MONITORING CABLE'S FREQ. I ALSO PICKED UP THE BRACKETT ATIS AND LEARNED THAT BRACKET WAS REPORTING 2 MI VISIBILITY. DEPARTING BRACKETT EARLIER, THE WX WAS 3 MI -- I HAD EXPECTED WX TO IMPROVE. BRACKETT IS LOCATED JUST A FEW MI W OF CABLE AND CAN HAVE SIGNIFICANTLY LOWER LOC WX DUE TO A NEARBY LAKE. THERE WERE ACFT OPERATING AT CABLE, AND AS A RESULT, IT'S VERY IMPORTANT TO KEEP AN EYE OUT FOR TFC AS CABLE'S TFC TYPICALLY DEPARTS TO THE N TOWARD THE BASE OF THE SAN GABRIEL MOUNTAINS. THIS IS A HIGH DENSITY TFC ENVIRONMENT. I REQUESTED SPECIAL VFR FROM BRACKETT AND WAS GIVEN AN APPROPRIATE CLRNC ITO BRACKETT'S CLASS D AIRSPACE. THE CLRNC INCLUDED THE FOLLOWING '...MAINTAIN AT OR BELOW 2500 FT ...' NORMALLY, I STAY ABOVE 3000 FT MSL UNTIL JUST W OF CABLE ARPT TO MAINTAIN PROPER MINIMUM ALTS, AND THEN START A DSCNT FOR LNDG. UNFORTUNATELY, THIS TIME, I STARTED MY DSCNT, FOR THE PURPOSE OF LNDG, TOO EARLY AND DSNDED LOWER THAN WAS NECESSARY FOR THE OP. I BEGAN MY DSCNT TOO EARLY TO MEET THE 2500 FOOT LIMITATION. I BELIEVE THAT THE PROB WAS COMPOUNDED BY LOW VISIBILITIES AT BRACKETT ARPT, THE 'AWARENESS' OF THE HIGH TFC ENVIRONMENT, MONITORING OF MULTIPLE COM SOURCES, TRYING TO STAY CLR OF ONTARIO'S CLASS C AIRSPACE, AND THE MOUNTAINS. IN HINDSIGHT, IT WOULD HAVE BEEN BEST TO START THE DAY WITH BETTER THAN 3 MI TO PROVIDE ADEQUATE MARGINS FOR VFR FLT. AS A RESULT, I WILL INCREASE MY PERSONAL VFR MINIMUMS TO 5 MI. THE WORKLOAD WAS QUITE HIGH AND SITUATIONAL AWARENESS WAS NEGATIVELY EFFECTED.

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.