Narrative:

Enroute from kcma to kpoc between northwest of ksmo headed east I encountered turbulence and windshear and downdraft's across the santa monica mountains making altitude control difficult. I received a FAA weather briefing prior to flight and there was no mention of the potential for turbulence. My plan was to cross the ridge at 3000 feet MSL. The air was warm and smooth as I departed kcma and as such gave no indication of the encounter soon to come. Due to the warm temperatures; I kept the climb gradual; with the mixture rich; and the power less than full to keep the cylinder head temperatures down (there are no cowl flaps). This plan; I reasoned; would be more suitable than a direct climb to 3000 after after takeoff. As I got closer to the ridge crossing; I encountered significant turbulence and windshear suddenly with the aircraft departing its even trajectory and disrupting my plan. I focused on attitude control while trying not to lose orientation between the class B; C; and D airspace in the adjacent area. The combination of focusing on aircraft attitude control and maintaining orientation of the the aircraft relative to the nearby class B; C; and D airspace; led to lower than planned flight across the ridge. I had planned to climb; however; was not able to execute the climb. Contributing factors 1. Flight path was near highly congested areas which includes class; B; C; and D airspace all in close proximity. 2. The cessna 152 is an aircraft with limited performance. 3. Assumption that smooth air would continue throughout flight regardless of localized terrain topography. 4. A relaxed composure prior to the rough air encounter. 5. The turbulence and windshear was most likely generated by onshore winds crossing the steep ridge line and uneven terrain heating. This placed my flight path on the leeside of the ridge. Human performance: in retrospect; perception that 'everything' is going to 'plan' and relaxed composure led to poor future projections (in terms of situational awareness). A perception of the upcoming rough terrain with the likelihood of onshore winds should have led me to comprehend the potential of leeside turbulence; this should have have lead to a decision to climb much earlier than plan. The quality of the decisions made were based on my preconceived mind-set. That is: the route was chosen; the air was smooth; keep the cylinder temps under control; watch out for airspace and other aircraft; and enjoy a beautiful day for flying. This was a brimstone path. It is imperative that a pilot constantly remain engaged in the situational awareness process; constantly engaged in perceiving (rough terrain ahead!); comprehending (where's the wind?); and projecting (how will this possibly impact the flight?). The limitations of human performance may be limited by expectations. I expected a smooth and trouble-free flight on this flight - it's not what I encountered. I have flown in conditions substantially worse without concern or incident. The difference is that I was prepared for those conditions prior to flight. In this case; situational awareness suffered. Corrective actions. 1. Climb to crossing altitude should have been accomplished earlier in flight; or; 2. Upon reaching the turbulence; a turn could have been made to the north through west to remove the aircraft from the environment. 3. Never being 'perfectly' relaxed on a flight. Always asking questions and coming up with alternate plans. The edge of the seat may be the place to fly from. Never forget that a situational awareness breakdown can get any pilot of any experience level. 4. Improve my knowledge of human performance.

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Original NASA ASRS Text

Title: VFR general aviation aircraft described lower than planned ridge altitude crossing event when wind conditions and complex airspace concerns prevented execution.

Narrative: Enroute from KCMA to KPOC between northwest of KSMO headed east I encountered turbulence and windshear and downdraft's across the Santa Monica mountains making altitude control difficult. I received a FAA weather briefing prior to flight and there was no mention of the potential for turbulence. My plan was to cross the ridge at 3000 feet MSL. The air was warm and smooth as I departed KCMA and as such gave no indication of the encounter soon to come. Due to the warm temperatures; I kept the climb gradual; with the mixture rich; and the power less than full to keep the cylinder head temperatures down (there are no cowl flaps). This plan; I reasoned; would be more suitable than a direct climb to 3000 after after takeoff. As I got closer to the ridge crossing; I encountered significant turbulence and windshear suddenly with the aircraft departing its even trajectory and disrupting my plan. I focused on attitude control while trying not to lose orientation between the Class B; C; and D airspace in the adjacent area. The combination of focusing on aircraft attitude control and maintaining orientation of the the aircraft relative to the nearby Class B; C; and D airspace; led to lower than planned flight across the ridge. I had planned to climb; however; was not able to execute the climb. Contributing Factors 1. Flight path was near highly congested areas which includes Class; B; C; and D airspace all in close proximity. 2. The Cessna 152 is an aircraft with limited performance. 3. Assumption that smooth air would continue throughout flight regardless of localized terrain topography. 4. A relaxed composure prior to the rough air encounter. 5. The turbulence and windshear was most likely generated by onshore winds crossing the steep ridge line and uneven terrain heating. This placed my flight path on the leeside of the ridge. Human Performance: In retrospect; perception that 'everything' is going to 'plan' and relaxed composure led to poor future projections (in terms of situational awareness). A perception of the upcoming rough terrain with the likelihood of onshore winds should have led me to comprehend the potential of leeside turbulence; this should have have lead to a decision to climb much earlier than plan. The quality of the decisions made were based on my preconceived mind-set. That is: the route was chosen; the air was smooth; keep the cylinder temps under control; watch out for airspace and other aircraft; and enjoy a beautiful day for flying. This was a brimstone path. It is imperative that a pilot constantly remain engaged in the situational awareness process; constantly engaged in perceiving (rough terrain ahead!); comprehending (where's the wind?); and projecting (how will this possibly impact the flight?). The limitations of human performance may be limited by expectations. I expected a smooth and trouble-free flight on this flight - it's not what I encountered. I have flown in conditions substantially worse without concern or incident. The difference is that I was prepared for those conditions prior to flight. In this case; situational awareness suffered. Corrective Actions. 1. Climb to crossing altitude should have been accomplished earlier in flight; or; 2. Upon reaching the turbulence; a turn could have been made to the north through west to remove the aircraft from the environment. 3. Never being 'perfectly' relaxed on a flight. Always asking questions and coming up with alternate plans. The edge of the seat may be the place to fly from. Never forget that a situational awareness breakdown can get any pilot of any experience level. 4. Improve my knowledge of human performance.

Data retrieved from NASA's ASRS site as of April 2012 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.