Lincoln, IL, USA
N157SF
Cessna 172
The pilot was conducting an aerial survey flight with two ecologists onboard. Flight track data showed that after departure from the airport, the airplane continued a southwest path toward the destination. According to flight track data, while circling a heavily wooded area near the destination, the airplane entered a right descending turn during which its altitude and groundspeed decreased. The last portion of track data indicated the airplane was traveling to the southwest at an estimated altitude of 1,075 ft mean sea level (msl) and an estimated groundspeed of 50 knots. A witness reported observing the left wing of the airplane suddenly drop, and another witness reported observing the airplane perform 2.5 rotations while it descended vertically. The airplane impacted a highway and a postimpact fire ensued, which destroyed the airplane. Postaccident examination of the wreckage revealed no preimpact mechanical malfunctions or failures with the airframe and engine that would have precluded normal operation. A flight instructor from the operator flew to the accident site shortly after the accident occurred and reported there was “light chop” throughout the flight. A weather model sounding that was created for the accident site near the time of the accident indicated the possibility of light low-level wind shear between the surface and 3,000 ft msl. Based on the flight track data and witness statements, it is likely the pilot experienced an in-flight loss of control while circling at low altitude near the destination. The pilot likely allowed the airplane’s airspeed to decrease to facilitate the ecologists’ view of the destination site or due to distraction associated with low altitude aerial work. The reduced airspeed and the likely presence of low-level windshear in the area resulted in the pilot exceeding the airplane's critical angle of attack, an aerodynamic stall, and a loss of control at an altitude too low to recover.
HISTORY OF FLIGHTOn March 3, 2020, about 0847 central standard time, a Cessna 172S airplane, N157SF, was destroyed when it was involved in an accident near Lincoln, Illinois. The pilot and two passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 aerial survey flight. According to the owner of the airplane, the purpose of the flight was to conduct an aerial survey of a bald eagle nest near Lincoln. Shoener Environmental contacted Synergy Flight Center to use its airplanes for several aerial survey flights, with two of their ecologists as passengers. Prior to the flight, the pilot requested the airplane to be “topped off” with fuel. At 0759, Synergy Flight Center completed fueling the airplane with 27.8 gallons of 100 low lead fuel. A review of L3Harris Technologies OpsVue flight track data showed that, after departing at 0804, the airplane traveled south near Le Roy, Illinois, before traveling southwest near Heyworth, Illinois. The airplane continued a southwest path toward Lincoln. Northwest of Lincoln, the airplane entered a right descending turn, circling a heavily wooded area that is intersected by Kickapoo Creek and Interstate 55 (I-55). The flight track data showed that the airplane’s altitude and groundspeed decreased during the turn. The last several segments of flight track data, which ended at 0846, showed the airplane at an altitude of about 1,150 ft above mean sea level (msl) and an estimated groundspeed of 80 knots, which gradually decreased. The last data point indicated the airplane was traveling to the southwest at an altitude of about 1,075 ft msl and estimated groundspeed of 50 knots. A witness reported observing the left wing of the airplane suddenly drop and another witness reported observing the airplane perform 2.5 rotations while it descended vertically. The airplane impacted the southbound lanes of the I-55 and state routes 10 and 121 interchange. A postimpact fire ensued. There were no injuries to any personnel on the ground. PERSONNEL INFORMATIONThe pilot’s training records and flight times from his employer, along with his personal logbook, were not recovered during the investigation. AIRCRAFT INFORMATIONThe airplane was equipped with a Garmin GFC 700 digital autopilot system, a stall warning system, and onboard weather capability. The Cessna 172S Pilot’s Operating Handbook states that the stall speed (power off) for the flaps up position is 53 kts calibrated airspeed (KCAS) and for the flaps down position is 48 kts KCAS. This document further discusses stalls and states in part: The stall characteristics are conventional and aural warning is provided by a stall warning horn which sounds between 5 and 10 kts above the stall in all configurations. A review of the airplane's maintenance records revealed no evidence of any uncorrected mechanical discrepancies with the airframe and engine. METEOROLOGICAL INFORMATIONThe accident pilot did not request nor receive a weather briefing from Leidos or ForeFlight. A flight instructor from Synergy Flight Center who flew to the accident site shortly after the accident occurred reported “very light chop experienced throughout the flight” and “when operating at around 1,300 ft msl, chop intensity increased, but was still considered light chop.” An Airmen’s Meteorological Information (AIRMET) advisory Tango was issued at 0845 for turbulence. This AIRMET was valid for the accident site at the accident time and warned of moderate turbulence below 8,000 ft msl.A High-Resolution Rapid Refresh (HRRR) model sounding was created for the accident site for 0900 central standard time. The HRRR sounding wind profile indicated a surface wind from 244° at 14 kts with a southwesterly wind through 1,000 ft msl and a westerly wind from 1,000 ft msl through 10,000 ft msl. The wind increased in speed to 20 kts by 500 ft above ground level (agl) with a 30 kt wind by about 1,500 ft agl. The Universal RAwinsonde OBservation Program (RAOB) indicated the possibility of light low-level wind shear between the surface and 3,000 ft msl. The RAOB indicated a possibility of light to moderate clear-air turbulence between the surface and 10,000 ft msl. AIRPORT INFORMATIONThe airplane was equipped with a Garmin GFC 700 digital autopilot system, a stall warning system, and onboard weather capability. The Cessna 172S Pilot’s Operating Handbook states that the stall speed (power off) for the flaps up position is 53 kts calibrated airspeed (KCAS) and for the flaps down position is 48 kts KCAS. This document further discusses stalls and states in part: The stall characteristics are conventional and aural warning is provided by a stall warning horn which sounds between 5 and 10 kts above the stall in all configurations. A review of the airplane's maintenance records revealed no evidence of any uncorrected mechanical discrepancies with the airframe and engine. WRECKAGE AND IMPACT INFORMATIONThe accident site consisted of an asphalt highway and the airplane came to rest on a heading of about 280° (magnetic). The accident site elevation was about 566 ft above mean sea level. No obstacles in the vicinity of the accident site appeared to be struck the airplane. The airplane impacted the asphalt in a nose-down attitude. All structural components of the airplane were located at the accident site. An examination found no preimpact mechanical malfunctions or failures with the airframe and engine that would have precluded normal operation. No evidence of a bird strike were observed in the wreckage. ADDITIONAL INFORMATIONThe Aircraft Owners and Pilots Association Air Safety Foundation has published Safety Advisor (Operations and Proficiency Number 8) Maneuvering Flight – Hazardous to your Health? This document discusses aerial work, which includes aerial surveys, and states in part: Aerial work includes photography, pipeline patrol, banner towing, and crop dusting. These activities require a significant division-of-attention at low altitudes. Pilots performing aerial work are generally highly qualified and use excellent judgment. But, if something goes wrong, there is little time to recover. The FAA has published the Airplane Flying Handbook (FAA-H-8083-3B). This document discusses what a loss of control in flight is, and states: A pilot’s fundamental responsibility is to prevent a loss of control (LOC). Loss of control in-flight (LOC-I) is the leading cause of fatal general aviation accidents in the U.S. and commercial aviation worldwide. LOC-I is defined as a significant deviation of an aircraft from the intended flightpath and it often results from an airplane upset. Maneuvering is the most common phase of flight for general aviation LOC-I accidents to occur; however, LOC-I accidents occur in all phases of flight. To prevent LOC-I accidents, it is important for pilots to recognize and maintain a heightened awareness of situations that increase the risk of loss of control. Those situations include: uncoordinated flight, equipment malfunctions, pilot complacency, distraction, turbulence, and poor risk management. The FAA's Airplane Flying Handbook, discusses about stall awareness, and states: The key to stall awareness is the pilot's ability to visualize the wing's angle of attack in any particular circumstance, and thereby be able to estimate his/her margin of safety above stall. This is a learned skill that must be acquired early in-flight training and carried through the pilot's entire flying career. The pilot must understand and appreciate factors such as airspeed, pitch attitude, load factor, relative wind, power setting, and airplane configuration in order to develop a reasonably accurate mental picture of the wing's angle of attack at any particular time. It is essential to flight safety that a pilot take into consideration this visualization of the wing's angle of attack prior to entering any flight maneuver.
The pilot's exceedance of the airplane's critical angle of attack during an aerial survey, which resulted in an aerodynamic stall at an altitude too low to recover.
Source: NTSB Aviation Accident Database
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