DEN00TA160
DEN00TA160

On August 31, 2000, at 1055 mountain daylight time, a Bell 212 helicopter, N8224V, sustained substantial damage when control was lost as it was standing with the rotors turning near Jackson, Wyoming. The commercial pilot received minor injuries. Visual meteorological conditions prevailed for this United States Forest Service (USFS) contract public use flight being conducted under Title 14 CFR Part 91 and no flight plan was filed.

According to the pilot, and verified by the (USFS), the helicopter rotor system was turning at flight rpm and passengers were preparing to board for a firefighting operation. The helicopter tipped back and to the right causing the tail rotor to strike the ground. Subsequently, the helicopter became airborne in a nose low attitude, spun several times, and impacted the ground damaging the skids and tail boom.

A witness, who was located 50 to 60 yards from the aircraft, said he saw the aircraft land and the passengers were approaching from the front of the helicopter. The witness said he looked away and looked back to the helicopter due to a change in power sound. The helicopter was airborne moving backwards. According to the witness, the helicopter stopped its rearward movement when it was "standing on the stinger and tail cone. At this time the tail rotor blades were in dirt and the right horizontal stabilizer was in contact with the ground. There was a bang and the tail rotor assembly became non-rotating."

In his submission, the operator, Houston Helicopters, said the pilot failed to reduce the power to flight idle after landing, as required, and that he did not engage the force trim, also a requirement. The operator contnded that the pilot momentarily released the stick allowing the rotor blades to dip toward the approaching passengers. A representative of the owner said he found the force trim in the off position when he inspected the aircraft following the accident.

A review of procedures in the Bell 212 Flight Manual requires the force trim to be engaged during engine shutdown and also requires the pilot to reduce the power to flight idle for 1 minute prior to shutdown of the engine. No procedures were found requiring a reduction in power to flight idle prior to boarding passengers with the rotor turning, nor were any procedures found requiring the force trim to be engaged except during engine shut down. According to Forest Service Flight Management, boarding and deplaning with the rotor stopped or at flight rpm is preferred over the rotor turning at idle due to the possibility of more pronounced blade flapping at idle rpm.

On September 27, 2000, two cyclic servos, two hydraulic pumps, and two hydraulic modules from the accident helicopter were tested at the Bell Helicopter facilities in Fort Worth, Texas. One servo exhibited a slight difference in the null between the upper and lower rods, and one pump was approximately 100 pounds low on output pressure. According to systems information provided by Bell, neither discrepancy would have contributed to the accident.

The landing gear cross tubes and skids were examined at the facilities of Aeronautical Accessories, Inc., Bristol, Tennessee. Personnel from the Forest Service, Office of Aviation Management, monitored the examination. The following findings resulted from the examination.

1. Aeronautical Accessories did not manufacture the cross tube saddles.

2. At some point in time, the rear cross tube had been replaced to the existing skid landing gear assembly. The rear cross tube was an Aeronautical Accessories cross tube.

3. Both cross tube assemblies and clamps were loose on the aft cross tubes.

4. All four cross tube saddles showed evidence of working rivets and bolt hole elongation.

5. Cross tube support assemblies were not installed to factory specifications.

6. Paint and metal etching witness marks on the right rear cross tube showed the right aft support assembly had moved down across the cross tube to approximately 4.5 inches above the top portion of the cross tube saddle.

7. The right skid tube, forward of the cross tube saddle, was dented.

8. No evidence was found of inspection of the aft cross tube every 300 hours as prescribed by Aeronautical Accessories inspection and maintenance instruction number AA-97601.

9. The u-bolts, part numbers 604-025-013 and 015, were not torqued to 80-100 inch pounds as prescribed in the maintenance manual. They displayed metal wear on the support assemblies and the clamps had walked laterally on the support assembly.

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