Unknown or undetermined: Robinson R44 Raven II, N323TT, fatal accident occurred on June 19, 2024, near near Bluestem, Washington

• Location: Bluestem, Washington 
• Accident Number: WPR24FA200 
• Date & Time: June 19, 2024, 16:20 Local 
• Registration: N323TT 
• Aircraft: ROBINSON HELICOPTER COMPANY R44 II 
• Aircraft Damage: Destroyed 
• Defining Event: Unknown or undetermined 
• Injuries: 2 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal 

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194501/pdf

https://data.ntsb.gov/Docket?ProjectID=194501

On June 19, 2024, about 1620 Pacific daylight time, a Robinson Helicopters R-44 II, N323TT, was destroyed when it was involved in an accident near Bluestem, Washington. The pilot and pilot-rated passenger were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot and pilot-rated passenger were returning the helicopter to its home airport after it had undergone routine maintenance, which included the installation of a fuel flow transducer. While in day visual meteorological conditions (VMC), in cruise flight, and about 745 ft above ground level (agl), the helicopter entered a descent. During the descent, the main rotor blades impacted the tailcone, severing the empennage, while about the same time the main rotor’s pitch horns and control rod ends fractured and separated. The lack of tail rotor and main rotor components resulted in a total loss of helicopter control. The helicopter impacted terrain at a high descent rate in a nose-high attitude as evidenced by the flattening and upward bending of the tailcone and the fracturing of the engine case. A postaccident fire destroyed most of the wreckage. 

Examination of the wreckage revealed evidence of a total loss of engine power as indicated by the lack of rotational scoring on the upper sheave and the undamaged section of the engine cooling fan. Main rotor blade impact with the tailcone and damage to the main rotor system were indicative of main rotor blade blow back and stall due to low rotor rpm. Examination of the freewheeling unit (sprag clutch) revealed normal operation. Multiple B-nuts on the fuel lines associated with the transducer and fuel servo were found loose; however, due to the thermal exposure, it could not be determined if the loss of torque to the B-nuts was due to heat damage or other factors.

The pilot was a highly experienced airplane pilot but had only accumulated about 350 hours of flight experience in helicopters. Based on the helicopter’s altitude and the wreckage signatures, after the loss of total power the pilot likely did not reflexively and simultaneously lower the collective, apply aft cyclic, and trim the helicopter to enter an autorotation while in cruise flight, and/or improperly managed the rotor rpm during the remainder of the autorotation. The lack of timely action allowed the main rotor rpm to reduce to an unrecoverable speed and likely resulted in the main rotor blades stalling, as detailed in the manufacturer’s Safety Notices and FAA guidance documents. The reason for the pilot’s failure to manage rotor rpm during an autorotation could not be determined. According to a Safety Notice published by the manufacturer, pilots with many hours of flight experience in airplanes and fewer hours experience in helicopters may instinctively make flight control inputs that are inappropriate for helicopters, which can result in catastrophic consequences.

- Probable Cause: The pilot’s failure to manage main rotor rpm during an autorotation, which resulted in a loss of helicopter control. Contributing to the accident was a loss of power for reasons that could not be determined.

Fuel exhaustion: Ayres S-2R-G10 Turbo Thrush, N40261, fatal accident occurred on April 9, 2024, near Derner, California

• Location: Derner, California 
• Accident Number: WPR24FA123 
• Date & Time: April 9, 2024, 14:44 Local 
• Registration: N40261 
• Aircraft: AYRES CORPORATION S2R-G10 
• Aircraft Damage: Substantial 
• Defining Event: Fuel exhaustion 
• Injuries: 1 Fatal 
• Flight Conducted Under: Part 137: Agricultural 

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194065/pdf

https://data.ntsb.gov/Docket?ProjectID=194065

On April 9, 2024, at 1444 Pacific daylight time, an Ayres Corporation S2R-G10 airplane, N40261, was substantially damaged when it was involved in an accident near Derner, California. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.

On the morning of the accident, the pilot departed from the operator’s base and flew the airplane about 174 miles northeast, to an airstrip near a rice farm. About 1230, after performing multiple flights to drop wild rice in the paddies near the airstrip, the pilot asked the fuel truck operators to fuel the airplane until the tanks were 3/4 full and subsequently departed the airstrip to continue spreading rice. When the pilot returned to the airstrip about 1400, he said he was not feeling well and was going to apply one last load of rice before leaving work. The pilot declined to have more fuel added to the fuel tanks. The pilot was seen with his safety harnesses fastened when he last departed.

About 1444, witnesses near the rice farm heard the airplane crash and saw it inverted and partially submerged in the rice paddy. When they opened the airplane’s canopy, they found the pilot unbuckled from the safety harness, unresponsive. 

Examination of the airplane revealed an unusable amount of fuel (less than 2 gallons) in the fuel system, and no fuel sheen was observed in the water. No preaccident mechanical failures or malfunctions that would have precluded normal operation were found. The propeller blade damage signatures at the accident site were consistent with low rotational energy at impact. 

The airplane’s fuel system was intact, and there was no evidence of fuel leakage. After the pilot departed the operator’s facility, he had texted the mechanic stating the airplane’s fuel gauge was inoperative and that the airplane’s fuel gauge was slower to respond to fuel quantity changes than other airplanes. The mechanic explained that the gauge did not read fuel quantities greater than 82 gallons per tank; additionally, the cockpit fuel gauge noted that fuel quantities above 82 gallons were “ungageable.” Postaccident testing of the airplane’s fuel gauge and level senders indicated that they were operating to the manufacturer’s specifications. Fuel consumption calculations indicate that, with the reported fuel load, the airplane would have had an endurance of 2.1 to 2.9 hours. 

Although the airplane sustained substantial damage, the accident appeared to be survivable.  

The pilot’s autopsy identified no obvious fatal traumatic injuries, and the cause of death was determined to be hypertensive and atherosclerotic cardiovascular disease. However, the accident circumstances provide no clear evidence of in-flight pilot incapacitation, and it is unlikely that the pilot’s cardiovascular disease contributed to the accident. Additionally, severe acute mental or physical stress may be a trigger for cardiac events in individuals with underlying heart disease. It is possible that the airplane’s impact with the water of the rice paddy, followed by it becoming partially submerged and inverted, could have resulted in such a cardiac event in the setting of the pilot’s preexisting heart disease.

The lack of fuel at the accident site and onboard the airplane during postaccident examination is consistent with fuel exhaustion, which resulted in the airplane’s impact with terrain. Though the pilot reported he was feeling unwell in the hours before the accident, available evidence is insufficient to determine what specific symptoms he was experiencing, or whether his symptoms contributed to the accident.

- Probable Cause: The pilot’s failure to adequately monitor his fuel supply, resulting in fuel exhaustion, a total loss of engine power, and the airplane’s impact with terrain.

Loss of control in flight: Champion 7GCBC Citabria, N3464D, fatal accident occurred on July 6, 2024, near Swanson Airport (2W3), Eatonville, Washington

• Location: Eatonville, Washington 
• Accident Number: WPR24FA226 
• Date & Time: July 6, 2024, 21:22 Local 
• Registration: N3464D 
• Aircraft: Champion 7GCBC 
• Aircraft Damage: Substantial 
• Defining Event: Loss of control in flight 
• Injuries: 2 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194619/pdf

https://data.ntsb.gov/Docket?ProjectID=194619

On July 6, 2024, at about 2122 Pacific daylight time, a Champion 7GCBC airplane, N3464D, was substantially damaged when it was involved in an accident near Swanson Airport (2W3), Eatonville, Washington. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot planned to depart on his fourth flight of the day. Witnesses reported that the engine run-up, departure, and climbout were normal. When the airplane reached about 500 ft above ground level and was about 0.5 nautical miles (nm) south of the runway, the airplane entered an abrupt left bank, which was immediately followed by a spin before it impacted the ground in a nose-low attitude.

Postaccident examination of the engine and flight controls did not reveal any preimpact mechanical anomalies. Witness reports indicated that the engine power was smooth and continuous and then ceased just before the airplane impacted trees. As the propeller damage signatures showed limited to no rotation at the time of impact, the pilot likely reduced the throttle during the descent. In addition, the gascolator sump valve was found in the open position. However, a witness did not observe any fuel leaking from the airplane during taxi or takeoff; thus, the sump valve position was likely a result of the impact.

An examination of the engine controls revealed that the mixture control cable had separated at the carburetor. A metallurgical examination did not yield sufficient evidence, on its own, to determine whether the separation occurred prior to the accident. While there was evidence that the mixture cable attachment was worn and may have been slipping before the accident flight, the fracture surfaces showed overstress fracture features that could have occurred during the accident. If the fracture had occurred before the accident, it likely would have required at least one instance of aggressive use of the controls to cause the initial buckling of the control cable. However, evidence showed the pilot was able to adjust engine power during the descent, which suggests the cable failure likely occurred during the impact, and not before.

The airplane’s precise fuel quantity at the time of the accident could not be determined, as the pilot also used a personal fuel trailer that did not contain any fuel records. Fuel receipts indicated that the pilot had most recently refueled the airplane at a nearby airport three months prior to the accident. Fuel performance computations showed that he likely filled the tanks to their total capacity during his last refueling, which would have left him with about 18 gallons of fuel on the day of the accident. This was sufficient to complete the estimated 30-minute scenic flight but would have placed the airplane about 40 lbs over its gross weight.

The airplane was in a nose-high attitude about 10 ft above trees and approaching rising terrain when it stalled. The airplane impacted the ground after the pilot attempted to avoid the trees by entering a rapid left bank and a pitch attitude that exceeded the airplane’s critical angle of attack, which resulted in an aerodynamic stall and a loss of control.  

- Probable Cause: The pilot’s exceedance of the airplane’s critical angle of attack while maneuvering to avoid trees, which resulted in an aerodynamic stall.

Loss of control in flight: Lancair Super ES, N18BG, fatal accident occurred on July 22, 2024, near Oshkosh Regional Airport (OSH/KOSH), Oshkosh, Wisconsin

• Location: Oshkosh, Wisconsin 
• Accident Number: CEN24FA277 
• Date & Time: July 22, 2024, 12:13 Local 
• Registration: N18BG Aircraft: Lancair ES 
• Aircraft Damage: Destroyed 
• Defining Event: Loss of control in flight 
• Injuries: 2 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194740/pdf

https://data.ntsb.gov/Docket?ProjectID=194740 

On July 22, 2024, about 1213 central daylight time a Lancair ES, N18BG, was destroyed when it was involved in an accident near Oshkosh, Wisconsin. The pilot and pilot-rated passenger were fatally injured. The airplane was operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight.

The pilot was flying the airplane on an arrival route when the air traffic controller instructed the pilot to widen the turn to allow for two warbird airplanes to land in front of him. The pilot acknowledged the transmission and stated that he had the two airplanes in sight. Wind was recorded as variable at 4 kts. According to ADS-B data, the airplane turned south, consistent with a modified downwind, then back to the east, and then toward the north, consistent with a base-to-final turn. The airplane was about 975 ft mean sea level (msl) and 84 kts ground speed when it started a turn to the north toward the airport. The last data point recorded from the airplane was about 975 ft msl and 70 kts ground speed, 1.5 miles from the approach end of the runway. According to the airframe pilot operating handbook, the stall speed varies from 59 to 74 kts indicated airspeed at zero degrees of bank. 

The airplane impacted a soybean field upright and was destroyed by a postimpact fire. An examination of the airplane, engine, and flight control system revealed no mechanical anomalies or failures that would have precluded normal operations. 

Further review of the ADS-B data from the warbird flight showed that the landing Aero L-39 airplane passed well to the east and above the flight path of the accident airplane. A review of the wake vortices generated by the L-39 revealed that the accident airplane would not have encountered the wake of the L-39 before impact. 

It is most likely that the pilot did not maintain adequate airspeed while maneuvering to ensure spacing from the L-39 that landed ahead while completing his turn toward final. This resulted in an inadvertent stall and subsequent impact with terrain.

- Probable Cause: The pilot’s failure to maintain adequate airspeed which resulted in an exceedance of the airplane’s critical angle of attack and an aerodynamic stall while maneuvering for traffic spacing.