Cessna 140 N76075 accident near Wayne, Nebraska

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack on final approach while conducting traditional short takeoff and landing operations in gusting wind conditions, which resulted in an aerodynamic stall and spin from which the pilot could not recover. Contributing to the accident was the competitive environment, which likely influenced the pilot’s approach speed and the subsequent loss of control.

NTSB analysis

The accident pilot had planned to participate in an aviation event that involved a form of air racing called short takeoff and landing drag racing (STOL Drag). On the day of the accident, in the afternoon, the aviation event was supposed to begin with STOL Drag qualification racing; however, the air racing was postponed to the following day due to gusting wind conditions that were oriented in an unfavorable direction relative to the orientation of the racecourse.

After the postponement decision was made, several of the competing pilots expressed a desire to perform traditional STOL (without any drag racing component) on a grass runway where a more favorable, but gusty, headwind prevailed. A safety briefing was held with representatives of the event organizer, Federal Aviation Administration (FAA) inspectors who were on site to supervise the STOL Drag event, and pilots who planned to fly in the traditional STOL. A representative of the STOL Drag event organizer informed the pilots that the flying was optional, and it was not a part of the formal air race competition. To limit traffic pattern congestion, multiple groups of 5 airplanes were organized.

According to witnesses and video/photographic evidence, the accident airplane was the last airplane within a group of 5, and all 5 airplanes had each performed two landings without incident. During the third approach, while the accident airplane was on final approach following a slower airplane ahead also on final approach, the accident airplane descended and appeared to be lower than the airplane ahead of it. Subsequently, the accident airplane’s pitch attitude increased, it rolled to the right, completed a 3/4-turn right spin, and impacted terrain in a near-vertical attitude. Postaccident examination of the airframe and engine found no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Based on this information, it is likely that the accident pilot allowed the airplane to exceed its critical angle of attack while on final approach and the airplane entered an aerodynamic stall and spin at too low an altitude to successfully recover. The strong, gusting wind conditions increased the likelihood of a sudden increase in angle of attack as the pilot approached the runway at a slow speed, already operating near the airplane’s critical angle of attack.

The evidence further showed that the accident pilot turned onto final approach early and, as a result, may have been altering his approach path and speed to maintain spacing behind the slower airplane ahead. If the pilot observed his airspeed decaying, given the lack of spacing ahead, adding engine power and/or increasing airspeed would only exacerbate the already close spacing with the airplane ahead. In this case, the only alternative would have been for the pilot to execute a go-around. Additionally, review of high-resolution photographs showed no evidence that the airplane’s flaps had been extended on final approach, despite having used flaps for the prior landings. Data from the airplane’s operations manual showed that extending the flaps would result in the airplane’s stall speed being about 5 mph slower, all other factors being equal. It could not be determined whether the pilot inadvertently forgot to extend the flaps during the landing attempt or had chosen not to extend them due to the gusting wind conditions.

The pilot’s loss of control occurred during non-traditional traffic pattern operations, and other factors may also have contributed to the pilot’s loss of control in flight. The pilot was flying an approach in which his touchdown and landing distance would be measured and judged by spectators and fellow pilots. Regardless of whether the STOL activity being conducted at the time of the accident was part of an official competition, it is likely that the pilot’s approach was influenced by the competitive environment. The gusting wind should have resulted in the pilot increasing the airplane’s speed on final approach; however, doing so would conflict with the desire to perform a competitive STOL landing. Additionally, while the accident pilot had completed STOL Drag training and was certified to compete in STOL Drag racing, no training was required of the pilots participating in the impromptu traditional STOL operations, which was a characteristically different flight activity as compared to STOL Drag racing in which airplanes do not exit ground effect.

An FAA-issued a Certificate of Waiver (CoW), outlined several exceptions to aviation regulations that were required in order to conduct the STOL Drag event. The CoW, in addition to a National Air Race Accreditation Letter and associated policies and procedures, incorporated risk mitigations that included a variety of elements, such as requirements for pilot training and certification, as well as operational wind limitations; however, these risk management controls were not present for the impromptu traditional STOL operations in which the accident pilot was participating. Had risk mitigations like those that were planned for the STOL Drag event been in place and adhered to by the event organizers and the FAA personnel present, it is possible that the accident could have been avoided.

Text from the NTSB. Open the NTSB docket for ERA22FA233 for the full record.