Mast bumping: Robinson R44 Raven II, N144KW, fatal accident occurred on July 11, 2024, near Kekaha, Hawaii

 

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194676/pdf

https://data.ntsb.gov/Docket?ProjectID=194676

https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=N144KW

Aloha Helicopter Tours LLC dba Ali’i Air Tours

• Location: Kekaha, Hawaii 
• Accident Number: ANC24FA063 
• Date & Time: July 11, 2024, 13:05 Local 
• Registration: N144KW 
• Aircraft: ROBINSON HELICOPTER R44 
• Aircraft Damage: Substantial 
• Defining Event: Mast bumping 
• Injuries: 3 Fatal 
• Flight Conducted Under: Part 91: General aviation - Aerial observation

On July 11, 2024, about 1305 Hawaii-Aleutian standard time, a Robinson R44 helicopter, N144KW, sustained substantial damage when it was involved in an accident near Kekaha, Hawaii. The pilot and two passengers were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 sightseeing flight.

The helicopter was on a local air tour when the accident occurred. Witnesses reported strong, gusting wind and that a “huge” and sudden gust of wind blew over them, which was followed by a very loud “bang” noise. As their attention was drawn to the source of the loud noise, they saw the helicopter wreckage freefalling into the ocean in two sections: a main fuselage section and the tail boom section.

Examination of the wreckage revealed no evidence of any preexisting anomalies that would have precluded normal operation of the helicopter. There was evidence that a mast bumping event had occurred and that the main rotor blades had contacted the airframe, which resulted in an in-flight breakup. There was no recorded information available that could be used to determine the helicopter's airspeed, altitude, or the pilot's control inputs.

A weather study indicated that conditions were conducive to the development of strong downdraft winds. It is likely that the helicopter encountered turbulence due to downdrafts, which resulted in mast bumping and a subsequent in-flight breakup.

Robinson Safety Notice SN-32 discusses flight in high winds and turbulence and explains how improper application of control inputs in response to turbulence can increase the likelihood of a mast bumping accident. It recommends that pilots reduce airspeed below normal cruise speed to 60 to 70 knots for flight in significant turbulence. It suggests techniques to avoid overcontrol of the helicopter and says to avoid flying on the downwind side of hills and ridges.

- Probable Cause: An encounter with turbulence due to downdraft winds that resulted in mast bumping and an in-flight breakup.

Loss of engine power (total): Aeromarine Merlin Lite, N622PC, fatal accident occurred on April 2, 2024, at South Lakeland Airport (X49), Lakeland, Florida:

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194019/pdf

https://data.ntsb.gov/Docket?ProjectID=194019

https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=N622PC

• Location: Mulberry, Florida 
• Accident Number: ERA24FA160 
• Date & Time: April 2, 2024, 10:38 Local 
• Registration: N622PC 
• Aircraft: ARTHUR B CANNING MERLIN LITE 
• Aircraft Damage: Substantial 
• Defining Event: Loss of engine power (total) 
• Injuries: 1 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal

On April 2, 2024, at 1038 eastern daylight time, an experimental amateur-built Merlin Lite motorglider, N622PC, was substantially damaged when it was involved in an accident at the South Lakeland Airport (X49), Mulberry, Florida. The private pilot sustained fatal injuries. The motorglider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The kit manufacturer manager reported that the accident flight was the pilot/builder’s second flight in the motorglider, the first of which was two days before the accident. A witness at the airport reported seeing the pilot taxi for takeoff and that the engine sounded “a bit rough,” but due to the nature of the small two-stroke engine he was not concerned. The witness reported that the motorglider took off and, when it reached about 100 ft to 150 ft above ground level (agl), the engine sputtered then went silent. Video footage showed that when the motorglider was about midfield, it turned right, then left, then pitched up before the left wing dropped and the motorglider began a near-vertical left rotating descent to ground impact consistent with a low-altitude stall and spin.

Postaccident examination of the motorglider revealed no evidence of any preimpact mechanical malfunctions or failures of the flight controls or airframe that would have precluded normal operation. Examination of the engine revealed that the original airbox had been replaced with an unrestricted cone-type air filter. The main carburetor jet had also been replaced with a smaller jet, which would have resulted in the engine running slightly lean (the builder had reported that he thought the engine had been running too rich). Additionally, a hole was noted in the center of the engine’s single piston. A metallurgical examination of the piston revealed light gray deposits covering portions of the crown surface around the hole. The piston crown had features consistent with pre-ignition damage. This damage was likely the result of an excessively lean mixture due to the unrestricted air intake and smaller main jet. The hole in the piston would have resulted in a total loss of engine power.

The distance from the accident site to the end of the available grass area was about 1,300 ft. The kit manufacturer reported that the motorglider’s typical landing roll was about 200 ft or less. Had the pilot aggressively lowered the nose of the motorglider to maintain airspeed following the loss of engine power, it is likely that he could have avoided the low altitude aerodynamic stall/spin and landed within the remaining available runway.

- Probable Cause: The pilot/builder’s modifications of the motorglider’s engine, which resulted in an excessively lean fuel air mixture, preignition, piston failure, and a subsequent total loss of engine power during the initial climb. Contributing to the outcome was the pilot’s failure to maintain airspeed and his exceedance of the motorglider’s critical angle of attack following the loss of engine power, which resulted in an aerodynamic stall/spin at an altitude too low to recover.

Loss of engine power (total): Mooney M20R Ovation, N13LV, fatal accident occurred on June 25, 2023, near Oak Island-Cape Fear Regional Jetport (SUT/KSUT), Southport, North Carolina

• Location: Southport, North Carolina 
• Accident Number: ERA23FA273 
• Date & Time: June 25, 2023, 16:20 Local 
• Registration: N13LV Aircraft: Mooney M20R 
• Aircraft Damage: Destroyed 
• Defining Event: Loss of engine power (total) 
• Injuries: 1 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal 

On June 25, 2023, about 1620 eastern daylight time, a Mooney M20R, N13LV, was destroyed when it was involved in an accident near Southport, North Carolina. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot was picking up his airplane following unfinished maintenance. Witnesses reported excessive white exhaust smoke and oil leaking from the airplane onto the ground as the pilot taxied it from the mechanic’s hangar to the runway for takeoff. Shortly after takeoff, the pilot reported an engine failure on the common traffic advisory frequency and that he was returning to the runway; however, the airplane impacted a residential area about 1/2-mile before the runway threshold and a postimpact fire ensued.

The airplane had been in for maintenance for 8 months. The private pilot/owner had requested that the mechanic troubleshoot interior lighting, service the brakes, attach a standby vacuum hose, and repair an exhaust leak. The mechanic could not complete the work as he could not start and run up the engine due to dead batteries. When he inspected the batteries, he realized that they were unairworthy. Specifically, the airplane was designed with a 24-volt electrical system that utilized two 24-volt batteries; however, the mechanic found four 12-volt batteries installed. When the mechanic contacted the pilot about the discrepancy, the pilot instructed him to reinstall the four 12-volt batteries. The mechanic refused, as it would have been an unapproved and unairworthy installation. The pilot then stated that he wanted his airplane back. The mechanic told him that the airplane was unairworthy, as he had not completed repairs on it; he also noted that it was unairworthy on the invoice.

The wreckage came to rest on its right side and oil streaks were noted on the underside of the empennage. The engine came to rest inverted, and the propeller remained attached to the engine. An oil sump accessory port plug was observed loose, with oily blue stained baffling material resting below it. Additionally, the No. 4 connecting rod had protruded through the top of the engine case. A check of the oil dipstick revealed no measurable oil in the engine. The engine likely failed due to oil starvation as the oil leaked from a loose oil sump accessory port plug as a result of uncompleted maintenance work.

- Probable Cause: The pilot’s improper decision to fly a known unairworthy airplane, which resulted in a total loss of engine power due to oil starvation.

https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=N13LV

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192440/pdf

https://data.ntsb.gov/Docket?ProjectID=192440