Narrative:

Formation departure from porterville; ca; runway 30. I was #3 in a flight of 3. On takeoff I encountered stronger than usual wake turbulence from the aircraft ahead of me who were airborne prior to my departure roll. There was also significant orographic turbulence through the entire wkend. Perhaps it was a dust devil; but I didn't see the normal patterns of a dust devil. At initial encounter of turbulence I turned 30 degrees right to clear the winds as there was remote control aircraft activity to the west all wkend. My attention then focused on the people and aircraft parked on the ramp I unintentionally flew close to and turned back towards the runway centerline and began a steep climb to escape further wake encounters. Upon reacquiring the runway centerline; the wake turbulence or possibly it was a dust devil or the orographic (hangars) turbulence; caused my aircraft to roll sharply to the right and nearly inverted before I was able to get back to level and resume a climb. It happened in an instant and far stronger than any I have ever encountered before. This is the exact reason I do not make formation (element) takeoffs and lndgs. Contributing factor was the left quartering headwind that pushed the wake from the preceding aircraft that were departing to the west back onto the centerline. In the future; I will pay more attention to avoidance of wake by monitoring wind conditions.

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Original NASA ASRS Text

Title: YAK 50 PLT ENCOUNTERED TURBULENCE ON TKOF DURING FORMATION DEP WITH UNCOMMANDED RAPID ROLL TO NEARLY INVERTED. PILOT RECOVERED AND RESUMED CLIMB.

Narrative: FORMATION DEP FROM PORTERVILLE; CA; RWY 30. I WAS #3 IN A FLT OF 3. ON TKOF I ENCOUNTERED STRONGER THAN USUAL WAKE TURB FROM THE ACFT AHEAD OF ME WHO WERE AIRBORNE PRIOR TO MY DEP ROLL. THERE WAS ALSO SIGNIFICANT OROGRAPHIC TURB THROUGH THE ENTIRE WKEND. PERHAPS IT WAS A DUST DEVIL; BUT I DIDN'T SEE THE NORMAL PATTERNS OF A DUST DEVIL. AT INITIAL ENCOUNTER OF TURB I TURNED 30 DEGS R TO CLR THE WINDS AS THERE WAS REMOTE CTL ACFT ACTIVITY TO THE W ALL WKEND. MY ATTN THEN FOCUSED ON THE PEOPLE AND ACFT PARKED ON THE RAMP I UNINTENTIONALLY FLEW CLOSE TO AND TURNED BACK TOWARDS THE RWY CTRLINE AND BEGAN A STEEP CLB TO ESCAPE FURTHER WAKE ENCOUNTERS. UPON REACQUIRING THE RWY CTRLINE; THE WAKE TURB OR POSSIBLY IT WAS A DUST DEVIL OR THE OROGRAPHIC (HANGARS) TURB; CAUSED MY ACFT TO ROLL SHARPLY TO THE R AND NEARLY INVERTED BEFORE I WAS ABLE TO GET BACK TO LEVEL AND RESUME A CLB. IT HAPPENED IN AN INSTANT AND FAR STRONGER THAN ANY I HAVE EVER ENCOUNTERED BEFORE. THIS IS THE EXACT REASON I DO NOT MAKE FORMATION (ELEMENT) TKOFS AND LNDGS. CONTRIBUTING FACTOR WAS THE L QUARTERING HEADWIND THAT PUSHED THE WAKE FROM THE PRECEDING ACFT THAT WERE DEPARTING TO THE W BACK ONTO THE CTRLINE. IN THE FUTURE; I WILL PAY MORE ATTN TO AVOIDANCE OF WAKE BY MONITORING WIND CONDITIONS.

Data retrieved from NASA's ASRS site as of January 2009 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.