Narrative:

I have assisted in the execution of the procedures contained in [approved engine manufacturer procedures] in its several iterations; now version F; by operating the aircraft engine a dozen or more times without incidence in this aircraft since I purchased it. The procedure entails multiple engine runs with minor adjustments to fuel pressure and/or idle mixture between runs. The procedure calls for a range of power settings ranging from idling at 600 rpms to applying full throttle.the airplane must be firmly secured to assure that it cannot move during the engine runs. Large wooden chocks were placed firmly against the main wheels and checked before each engine run to assure that they had not moved during the prior run. The last several engine runs involves setting fuel pressure at full throttle; so extra care is taken to assure that the aircraft is firmly chocked and; to further assure maximum braking; the brakes are released and re-locked prior to each engine start. The test has proven so trouble-free over the years that I must have grown complacent; fully expecting the preparations to assure that the aircraft could not move under any of the test conditions. A series of eight or more runs had been made prior to the event in question with minor adjustments made to fuel pressure or idle mixture between each run. On what was intended to be the final run to simply confirm that idle fuel pressure; idle mixture and full-throttle fuel pressure settings were in the specified range; the aircraft moved unexpectedly while at full power. At the time I applied full power; my attention was focused inside the cockpit in in order to record maximum rpms and fuel flow. By the time I picked up motion in my peripheral vision; the aircraft was moving rather briskly and turning toward a hangar and parked vehicle. Rather than reducing power as I should have done; I concentrated on changing the direction of motion; only shutting down the engine after the left wing contacted the hangar and vehicle.the main wheels had apparently rocked up on the triangular shocks as the nose dipped under full power conditions. That reduced the weight on the ground directly under the wheels; transferring the weight partially to the wooden chocks. The coefficient of friction of the wood against the tarmac was less than the coefficient of friction of the rubber tires against the same surface and the chocks were simply pushed along wedged firmly under the locked wheels. Light skid marks and tire scuffs confirmed that the wheels had remained locked; and the paint was scraped completely off the bottom of the two chocks.damage to the aircraft is relatively minor and damage to the hangar is even more minor. The greatest damage is to my pride because an aircraft under my control was harmed for the first; and hopefully the last time. The seriousness of this event stems from what might have happened; rather than what actually happened and points to the necessity of having an escape plan in place covering all adverse possibilities at all times. In addition to simply having a plan in mind; the plan should be mentally; if not physically; practiced in advance. Had I not been so confident that the technique for securing the aircraft would be as successful during this procedure as it had been on all prior occasions; it is likely that I would have planned for; discussed and practiced reducing power instantly upon detection of motion. Had I done that; all of the damage could have been avoided. This is a lesson that; hopefully; will serve me well in the future. Always plan for the worst and hope for the best.

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Original NASA ASRS Text

Title: The Pilot of a Beechcraft Bonanza lost control of their aircraft during routine high power engine runs when the wheel chocks did not adequately prevent movement.

Narrative: I have assisted in the execution of the procedures contained in [approved engine manufacturer procedures] in its several iterations; now version F; by operating the aircraft engine a dozen or more times without incidence in this aircraft since I purchased it. The procedure entails multiple engine runs with minor adjustments to fuel pressure and/or idle mixture between runs. The procedure calls for a range of power settings ranging from idling at 600 rpms to applying full throttle.The airplane must be firmly secured to assure that it cannot move during the engine runs. Large wooden chocks were placed firmly against the main wheels and checked before each engine run to assure that they had not moved during the prior run. The last several engine runs involves setting fuel pressure at full throttle; so extra care is taken to assure that the aircraft is firmly chocked and; to further assure maximum braking; the brakes are released and re-locked prior to each engine start. The test has proven so trouble-free over the years that I must have grown complacent; fully expecting the preparations to assure that the aircraft could not move under any of the test conditions. A series of eight or more runs had been made prior to the event in question with minor adjustments made to fuel pressure or idle mixture between each run. On what was intended to be the final run to simply confirm that idle fuel pressure; idle mixture and full-throttle fuel pressure settings were in the specified range; the aircraft moved unexpectedly while at full power. At the time I applied full power; my attention was focused inside the cockpit in in order to record maximum rpms and fuel flow. By the time I picked up motion in my peripheral vision; the aircraft was moving rather briskly and turning toward a hangar and parked vehicle. Rather than reducing power as I should have done; I concentrated on changing the direction of motion; only shutting down the engine after the left wing contacted the hangar and vehicle.The main wheels had apparently rocked up on the triangular shocks as the nose dipped under full power conditions. That reduced the weight on the ground directly under the wheels; transferring the weight partially to the wooden chocks. The coefficient of friction of the wood against the tarmac was less than the coefficient of friction of the rubber tires against the same surface and the chocks were simply pushed along wedged firmly under the locked wheels. Light skid marks and tire scuffs confirmed that the wheels had remained locked; and the paint was scraped completely off the bottom of the two chocks.Damage to the aircraft is relatively minor and damage to the hangar is even more minor. The greatest damage is to my pride because an aircraft under my control was harmed for the first; and hopefully the last time. The seriousness of this event stems from what might have happened; rather than what actually happened and points to the necessity of having an escape plan in place covering all adverse possibilities at all times. In addition to simply having a plan in mind; the plan should be mentally; if not physically; practiced in advance. Had I not been so confident that the technique for securing the aircraft would be as successful during this procedure as it had been on all prior occasions; it is likely that I would have planned for; discussed and practiced reducing power instantly upon detection of motion. Had I done that; all of the damage could have been avoided. This is a lesson that; hopefully; will serve me well in the future. Always plan for the worst and hope for the best.

Data retrieved from NASA's ASRS site 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.