R44 Ditched After Loss of TGB & TR: Improper Maintenance (N1241W, Air Adventures Helicopters, Key West)
On 17 June 2019 Robinson R44 N1241W of Air Adventures Helicopters was ditched off Key West, Florida following the in-flight loss of its Tail Gear Box (TGB) and tail rotor during a Part 91 revenue sightseeing flight. The three occupants were all uninjured.
Robinson R44 N1241W of Air Adventures Helicopters Ditching off Key West, FL (Credit: Unknown)
History of the Flight
The US National Transportation Safety Board (NTSB) safety investigation report explains that:
As the helicopter climbed through 300 ft AGL, the pilot [aged 29, 1430 flying hours total, 1274 on type] detected “rapid tail vibrations.” The pilot radioed tower and requested a return to the airport. He proceeded back to the airport when he heard a loud pop and felt a “hard” right yaw. Attempts to regain control of the helicopter with the anti-torque pedals were ineffective.
He initiated an autorotation, and the helicopter began to yaw to the left. Again, attempts to regain control of the helicopter were ineffective. As the helicopter descended toward the water, the pilot deployed the floats, and landed the helicopter upright on the water without further incident.
Safety Investigation
Examination of the helicopter revealed that the tail rotor assembly had separated from the tail boom…
As well as losing the means of yaw control this will have also resulted in a significant forward shift in centre of gravity, adding to the challenges the pilot faced.
[E]xamination of the mounting hardware between the TGB input cartridge and the tail boom mating flange found that two of the four bolts were missing; both missing bolts came from the right side of the connection. The left side bolts remained secured in place. The missing bolts’ holes in the input cartridge were deformed and were out of round. All of the 4 bolt holes on the input cartridge displayed imprints from the bolt threads, with the deepest imprints on the right sides of the holes, consistent with movement between the lug holes and the bolt shanks. All tail boom flange bolt holes were examined and found that the threading was present, not stripped, and locking inserts present.
The NTSB reveal that c60 flying hours and 5 weeks earlier the tail boom assembly had been removed and replaced.
As part of this maintenance, the tail rotor input cartridge and gearbox would have been removed from the old tailboom and placed on the new tailboom. It is likely that, during this procedure, the right-side mounting bolts were not completely secured to the tail boom casting locking inserts and properly torqued [the the required 240 in-lbs], which resulted in the failure of the right side mounting bolts.
The NTSB report unfortunately contains no further detail on the conduct of this maintenance.
Following the replacement of the tail boom, the pilot reported rapid tail rotor vibrations which required multiple attempts to successfully balance the tail rotor as part of the post maintenance checks.
NTSB Probable Cause
The failure of maintenance personnel to properly secure the right-side tail boom mounting bolts which resulted in the failure of the bolts and an inflight separation of the tail rotor.
Safety Resources
The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest:
- Compressive Creep and the Loss of a UH-1H’s Tail Rotor
- Prompt Emergency Landing Saves Powerline Survey Crew After MGB Pinion Failure
- Fatal $16 Million Maintenance Errors
- Dramatic Malaysian S-76C 2013 Ditching Video
- NTSB Report on Bizarre 2012 US S-76B Ditching
- Insecure Pitch Link Fatal R44 Accident
- R44 Force Lands After Improper Repair
- Incomplete Maintenance Leads to Fatal Collective Control Loss on B407
- Torched Tennessee Tour Trip (B206L N16760)
- Fatal EC130B4 Water Impact in the Tennessee River after “Entry to VRS” Say NTSB
- EC130 Door Loss Damaged Main Rotor Blades
- Hawaiian Air Tour EC130T2 Hard Landing after Power Loss (Part 1)
- Hawaiian Air Tour EC130T2 Hard Landing after Power Loss (Part 2 – Survivability)
- R44 Unanticipated Yaw Accident During Tailwind Take Off Caught on Video
- A Try and See Catastrophe: R44 Accident in Norway in Bad Weather
- Fatal Wisconsin Wire Strike When Robinson R44 Repositions to Refuel
- Fatal R44 Loss of Control Accident: Overweight and Out of Balance
- Latent Engine Defect Downs R44: NR Dropped to Zero During Autorotation
- Helicopter Destroyed in Hover Taxi Accident
- EC130B4 Accident: Incorrect TRDS Bearing Installation
- Air Ambulance Leaps into Air: Misrigged Flying Controls
- Prior Engine Mount Damage Lead to Fatal Aerial Saw Crash
- Loose Engine B-Nut Triggers Fatal Forced Landing
- Ungreased Japanese AS332L Tail Rotor Fatally Failed
- SAR AS365N3 Flying Control Disconnect: BFU Investigation
- For Rotors Grease is the Word
- AAR Bell 214ST Accident in Afghanistan in 2012: NTSB Report
- Maintenance Misdiagnosis Precursor to EC135T2 Tail Rotor Control Failure
- Misassembled Anti-Torque Pedals Cause EC135 Accident
- Insecure Pitch Link Fatal R44 Accident
- EC135 Main Rotor Actuator Tie-Bar Failure
- Bell 429 TR Pitch Change Link Bearing Failure
- S-61N Damaged During Take Off When Swashplate Seized Due to Corrosion
- Tail Rotor Pitch Control Loss During Hoisting
- UPDATE 16 July 2022: Distracted Dynamic Rollover
- UPDATE 30 July 2022: B212 LOC-I: Windshear Encounter in the Lee of Mountain Ridge
Plus:
- Airworthiness Matters: Next Generation Maintenance Human Factors
- Aircraft Maintenance: Going for Gold?
- B1900D Emergency Landing: Maintenance Standards & Practices
Aerossurance worked with the Flight Safety Foundation (FSF) to create a Maintenance Observation Program (MOP) requirement for their contractible BARSOHO offshore helicopter Safety Performance Requirements to help learning about routine maintenance and then to initiate safety improvements:
Aerossurance can provide practice guidance and specialist support to successfully implement a MOP.
Aerossurance’s Andy Evans was recently interviewed about safety investigations, the perils of WYLFIWYF (What-You-Look-For-Is-What-You-Find) and some other ‘stuff’ by with Sam Lee of Integra Aerospace:
Recent Comments