Narrative:

On the afternoon of the planned trip, the winds aloft over the sierras were from 260-280 KTS at 30-40 KTS, resulting in light to occasional moderate turbulence and strong up and downdrafts in the vicinity of the mountains (ie, practically the entire route between las vegas and fresno). I was returning to pao from santa flight engineer, via las vegas. Except for the winds, the WX was perfect--unlimited ceiling and visibility. I was receiving VFR flight following from edw approach and had been battling the headwinds for ages (sometimes down to 70 KTS ground speed) along the north ends of the MOA's all along the route. I advised edw that I was having trouble maintaining altitude due to strong up and downdrafts. The friendly approach controller indicated that the altitude variations were not a problem (a non-binding observation; not a clearance, of course). My cruising altitude was nominally 16500', but really more like 16000-17000' in updrafts and downdrafts. I climbed to 17500' in preparation for the inevitable downdraft I would encounter when I approached the east side of the sierras north of lone pine, east of king's canyon and well north of mount whitney and its pointy companions. There the surrounding terrain is around 14000'. The downdraft was followed by a strong updraft (greater than 2500 FPM), which briefly (about 30 seconds?) drove me to FL185 (oops, positive controled airspace violation) while I was maintaining maneuvering speed due to turbulence. The strength of the drafts and turbulence decreased as I proceeded westward from the first sierra ridge, and I was better able to maintain altitude and didn't subsequently exceed 17500'. The flying itself was safe enough, but the far's didn't provide for the situation. In retrospect: I knew my altimeter setting was current; I wanted reasonable terrain sep (100 FPM is the best I could hope for at that altitude in calm air--certainly not enough to climb through a 2500 FPM downdraft); I wasn't willing to go much beyond maneuvering speed; and an IFR clearance into positive controled airspace would have had an altitude (which I would have been unable to maintain) attached to it. To prevent recurrence, allow a controller to authorize VFR entry into positive controled airspace with a maximum altitude restriction--FL200 would be a reasonable maximum.

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Original NASA ASRS Text

Title: SMA CRUISING OVER HIGH MOUNTAIN PASS AT NEAR TOP OF ALT RANGE ENCOUNTERS VERTICAL TURBULENCE AND PENETRATES PCA.

Narrative: ON THE AFTERNOON OF THE PLANNED TRIP, THE WINDS ALOFT OVER THE SIERRAS WERE FROM 260-280 KTS AT 30-40 KTS, RESULTING IN LIGHT TO OCCASIONAL MODERATE TURB AND STRONG UP AND DOWNDRAFTS IN THE VICINITY OF THE MOUNTAINS (IE, PRACTICALLY THE ENTIRE ROUTE BTWN LAS VEGAS AND FRESNO). I WAS RETURNING TO PAO FROM SANTA FE, VIA LAS VEGAS. EXCEPT FOR THE WINDS, THE WX WAS PERFECT--UNLIMITED CEILING AND VISIBILITY. I WAS RECEIVING VFR FLT FOLLOWING FROM EDW APCH AND HAD BEEN BATTLING THE HEADWINDS FOR AGES (SOMETIMES DOWN TO 70 KTS GND SPD) ALONG THE N ENDS OF THE MOA'S ALL ALONG THE ROUTE. I ADVISED EDW THAT I WAS HAVING TROUBLE MAINTAINING ALT DUE TO STRONG UP AND DOWNDRAFTS. THE FRIENDLY APCH CTLR INDICATED THAT THE ALT VARIATIONS WERE NOT A PROB (A NON-BINDING OBSERVATION; NOT A CLRNC, OF COURSE). MY CRUISING ALT WAS NOMINALLY 16500', BUT REALLY MORE LIKE 16000-17000' IN UPDRAFTS AND DOWNDRAFTS. I CLBED TO 17500' IN PREPARATION FOR THE INEVITABLE DOWNDRAFT I WOULD ENCOUNTER WHEN I APCHED THE E SIDE OF THE SIERRAS N OF LONE PINE, E OF KING'S CANYON AND WELL N OF MOUNT WHITNEY AND ITS POINTY COMPANIONS. THERE THE SURROUNDING TERRAIN IS AROUND 14000'. THE DOWNDRAFT WAS FOLLOWED BY A STRONG UPDRAFT (GREATER THAN 2500 FPM), WHICH BRIEFLY (ABOUT 30 SECS?) DROVE ME TO FL185 (OOPS, POSITIVE CTLED AIRSPACE VIOLATION) WHILE I WAS MAINTAINING MANEUVERING SPD DUE TO TURB. THE STRENGTH OF THE DRAFTS AND TURB DECREASED AS I PROCEEDED WESTWARD FROM THE FIRST SIERRA RIDGE, AND I WAS BETTER ABLE TO MAINTAIN ALT AND DIDN'T SUBSEQUENTLY EXCEED 17500'. THE FLYING ITSELF WAS SAFE ENOUGH, BUT THE FAR'S DIDN'T PROVIDE FOR THE SITUATION. IN RETROSPECT: I KNEW MY ALTIMETER SETTING WAS CURRENT; I WANTED REASONABLE TERRAIN SEP (100 FPM IS THE BEST I COULD HOPE FOR AT THAT ALT IN CALM AIR--CERTAINLY NOT ENOUGH TO CLB THROUGH A 2500 FPM DOWNDRAFT); I WASN'T WILLING TO GO MUCH BEYOND MANEUVERING SPD; AND AN IFR CLRNC INTO POSITIVE CTLED AIRSPACE WOULD HAVE HAD AN ALT (WHICH I WOULD HAVE BEEN UNABLE TO MAINTAIN) ATTACHED TO IT. TO PREVENT RECURRENCE, ALLOW A CTLR TO AUTHORIZE VFR ENTRY INTO POSITIVE CTLED AIRSPACE WITH A MAX ALT RESTRICTION--FL200 WOULD BE A REASONABLE MAX.

Data retrieved from NASA's ASRS site as of August 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.