On September 23, 2017, about 1415 Pacific daylight time, an experimental SC Aerostar SA, Yak-52W airplane, N52KF, sustained substantial damage while taxiing at Gillespie Field Airport (SEE), El Cajon, California. The airline transport pilot and the passenger were not injured. The airplane was registered to an individual and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot did not submit an NTSB Pilot/Operator Aircraft Accident/Incident Report Form 6120.1, however, his legal counsel provided an email statement which described the sequence of events.

The pilot reported that he conducted a normal preflight inspection, completed the starting engine checklist, and attempted to start the engine, but was unable to do so due to low pressure in the pneumatic system. An individual arrived with a tank of air to pressurize the system, while the pilot remained in the airplane. The pilot shut off the compressed air supply valve, as required during a pneumatic system recharge. The individual with the tank of air realized that they had accidentally brought the wrong adapter for the airplane, and left to find the correct adapter. A second individual arrived and offered to assist to start the engine by manually turning the propeller. The pilot accepted the offer, and the engine was subsequently started.

The pilot completed the post-start checklist, and started to taxi. Shortly thereafter, he experienced a loss of braking performance which affected the airplane's steering capabilities (the steering is accomplished through differential braking, and the brake system requires pneumatic pressure to operate). The pilot realized that the compressed air supply valve was still shut off, and attempted to turn it back on while turning the engine off and maintaining steering control. Due to the size constraints of the cockpit, he could not reach the supply valve without unstrapping his seat belt and turning around. The airplane impacted a fence before he was able to do so, and sustained substantial damage to the left wing.

Further investigation revealed that the Yak-52 checklist does not require the pilot to check air pressure or the valve position during the preflight, engine start or before takeoff phases.

There was no noted preimpact mechanical malfunction that would have precluded normal operations.