Narrative:

I was receiving dual instruction as part of my training for a commercial certificate. My instructor suggested that we fly from oak to C83 to practice short and soft field takeoffs and lndgs. When we first approached byron airport, the AWOS was reporting winds of 240 degrees at 15 KTS gusting to 20 KTS, and the winds were increasing through the afternoon (AWOS reported winds of 240 degrees at 22 KTS gusting to 32 KTS by the time we departed the airport 2 hours later). The airport lies at the base of the east bay hills, and on this day the winds were flowing directly perpendicular to the hills (which are dotted with windmills). We had already made 4 takeoffs and lndgs to a full stop on runway 23 at byron when the incident took place. Our previous departure was a soft field takeoff made without incident, although with some drift to the left while in ground effect. At my instructor's request, I configured the aircraft for another soft field takeoff, with approach flaps, and began my takeoff roll with the yoke all the way back, full power and propeller pitch, and the necessary right rudder to maintain the centerline of the runway. As soon as the main wheels left the ground, I lowered the nose to gain airspeed and applied increased right rudder to maintain centerline. The aircraft flew momentarily in ground effect, and then went into an uncommanded 30 degree left bank despite the application of full right rudder. The aircraft continued to turn left and would not climb. The instructor reports that just prior to the bank he observed 80 KTS on the airspeed indicator, the ball centered, and the correct pitch attitude. It appears that my aircraft had flown into a strong rotor caused by the winds flowing over the nearby hills that prevented the aircraft from climbing or maintaining runway heading. I was able to level the wings just as the aircraft (apparently either the right main or the left horizontal stabilizer) hit the top line of a barbed wire fence running parallel with the runway. The wire lodged between the stabilizer and the elevator, and the aircraft from that point on, remained tethered to the ground. The aircraft, on its tether and now back on the ground, arced back through the fence, this time catching the barbed wire on the right tip tank. We rolled to a stop in the field alongside the runway. The aircraft damage was caused by running into the barbed wire fence twice. The fence posts appear to have hit both wings, the right stabilizer, the right gear door, and the propeller. The barbed wire scraped the belly and the underside of the wings. The gear did not collapse, although the right main tire was punctured. There were no injuries. While the primary cause of the incident was an unseen rotor and downdraft caused by the strong winds coming over the nearby hills, in hindsight, it would probably have been more prudent to have avoided practicing this maneuver, which requires flight at minimum airspeed during which the aircraft is more susceptible to rotors, in the strong winds at the time.

Related reports:

Google
 

Original NASA ASRS Text

Title: BE36 STUDENT PLT AND INSTRUCTOR PLT ENCOUNTER XWIND WHILE CONDUCTING A SOFT FIELD TKOF AND DRIFT OFF RWY.

Narrative: I WAS RECEIVING DUAL INSTRUCTION AS PART OF MY TRAINING FOR A COMMERCIAL CERTIFICATE. MY INSTRUCTOR SUGGESTED THAT WE FLY FROM OAK TO C83 TO PRACTICE SHORT AND SOFT FIELD TKOFS AND LNDGS. WHEN WE FIRST APCHED BYRON ARPT, THE AWOS WAS RPTING WINDS OF 240 DEGS AT 15 KTS GUSTING TO 20 KTS, AND THE WINDS WERE INCREASING THROUGH THE AFTERNOON (AWOS RPTED WINDS OF 240 DEGS AT 22 KTS GUSTING TO 32 KTS BY THE TIME WE DEPARTED THE ARPT 2 HRS LATER). THE ARPT LIES AT THE BASE OF THE EAST BAY HILLS, AND ON THIS DAY THE WINDS WERE FLOWING DIRECTLY PERPENDICULAR TO THE HILLS (WHICH ARE DOTTED WITH WINDMILLS). WE HAD ALREADY MADE 4 TKOFS AND LNDGS TO A FULL STOP ON RWY 23 AT BYRON WHEN THE INCIDENT TOOK PLACE. OUR PREVIOUS DEP WAS A SOFT FIELD TKOF MADE WITHOUT INCIDENT, ALTHOUGH WITH SOME DRIFT TO THE L WHILE IN GND EFFECT. AT MY INSTRUCTOR'S REQUEST, I CONFIGURED THE ACFT FOR ANOTHER SOFT FIELD TKOF, WITH APCH FLAPS, AND BEGAN MY TKOF ROLL WITH THE YOKE ALL THE WAY BACK, FULL PWR AND PROP PITCH, AND THE NECESSARY R RUDDER TO MAINTAIN THE CTRLINE OF THE RWY. AS SOON AS THE MAIN WHEELS LEFT THE GND, I LOWERED THE NOSE TO GAIN AIRSPD AND APPLIED INCREASED R RUDDER TO MAINTAIN CTRLINE. THE ACFT FLEW MOMENTARILY IN GND EFFECT, AND THEN WENT INTO AN UNCOMMANDED 30 DEG L BANK DESPITE THE APPLICATION OF FULL R RUDDER. THE ACFT CONTINUED TO TURN L AND WOULD NOT CLB. THE INSTRUCTOR RPTS THAT JUST PRIOR TO THE BANK HE OBSERVED 80 KTS ON THE AIRSPD INDICATOR, THE BALL CTRED, AND THE CORRECT PITCH ATTITUDE. IT APPEARS THAT MY ACFT HAD FLOWN INTO A STRONG ROTOR CAUSED BY THE WINDS FLOWING OVER THE NEARBY HILLS THAT PREVENTED THE ACFT FROM CLBING OR MAINTAINING RWY HDG. I WAS ABLE TO LEVEL THE WINGS JUST AS THE ACFT (APPARENTLY EITHER THE R MAIN OR THE L HORIZ STABILIZER) HIT THE TOP LINE OF A BARBED WIRE FENCE RUNNING PARALLEL WITH THE RWY. THE WIRE LODGED BTWN THE STABILIZER AND THE ELEVATOR, AND THE ACFT FROM THAT POINT ON, REMAINED TETHERED TO THE GND. THE ACFT, ON ITS TETHER AND NOW BACK ON THE GND, ARCED BACK THROUGH THE FENCE, THIS TIME CATCHING THE BARBED WIRE ON THE R TIP TANK. WE ROLLED TO A STOP IN THE FIELD ALONGSIDE THE RWY. THE ACFT DAMAGE WAS CAUSED BY RUNNING INTO THE BARBED WIRE FENCE TWICE. THE FENCE POSTS APPEAR TO HAVE HIT BOTH WINGS, THE R STABILIZER, THE R GEAR DOOR, AND THE PROP. THE BARBED WIRE SCRAPED THE BELLY AND THE UNDERSIDE OF THE WINGS. THE GEAR DID NOT COLLAPSE, ALTHOUGH THE R MAIN TIRE WAS PUNCTURED. THERE WERE NO INJURIES. WHILE THE PRIMARY CAUSE OF THE INCIDENT WAS AN UNSEEN ROTOR AND DOWNDRAFT CAUSED BY THE STRONG WINDS COMING OVER THE NEARBY HILLS, IN HINDSIGHT, IT WOULD PROBABLY HAVE BEEN MORE PRUDENT TO HAVE AVOIDED PRACTICING THIS MANEUVER, WHICH REQUIRES FLT AT MINIMUM AIRSPD DURING WHICH THE ACFT IS MORE SUSCEPTIBLE TO ROTORS, IN THE STRONG WINDS AT THE TIME.

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.