N480FX

HISTORY OF FLIGHT

On August 5, 2005, about 1100 central daylight time, an Enstrom 480, N480FX, sustained substantial damage after landing at Goshen Municipal Airport (KGSH), near Goshen, Indiana. The training flight was operating under 14 CFR Part 91. Day visual meteorological conditions prevailed at the time of the accident. No flight plan was filed. The student pilot sustained serious injuries and was hospitalized. The certified flight instructor (CFI) and rear seat passenger sustained minor injuries. The flight originated from Warsaw Airport, to Goshen Airport to pick up a passenger, then a flight to Grand Rapids to pick up the owner/pilot in training, and then back to Goshen Airport.

The CFI stated that upon landing at Goshen Airport:

"The winds were light and variable from the north. He [student pilot] set up with a right hand downwind for grass Runway 36. He made the appropriate radio calls and a nice normal approach to the center of the runway. He then stopped, cleared the tail and made 180 degree turn to the south. He then proceeded to hover taxi back to the ramp. [The student pilot] then made a radio call prior to crossing Runway 9-27 and also when he was cleared on the other side. He then proceeded to the ramp area. His hover taxi was very slow and controlled. On the ramp, [the student pilot] made two right hand turns to point back to the helipad, both times clearing the tail before turning the aircraft. [The student pilot] then moved the aircraft forward to the helipad. He then smoothly lowered the collective and set the aircraft on the ground as he was rolling off the throttle. The aircraft started to bounce. I reached down to make sure the collective was down and the throttle was off. Then the aircraft started shaking violently and ripped itself apart."

The student pilot stated that he does not recall the accident.

WITNESS STATEMENTS

The rear seat passenger stated:

"[The student pilot] piloted the helicopter all the way to Goshen, making all of the appropriate calls along the way. When we arrived at Goshen, the winds were light out of the North. [The student pilot] decided to use Runway 36. He had a very good approach and came to a hover over Runway 36. [The student pilot] began to hover taxi to the ramp crossing runway 9-27 and making the proper radio calls as he crossed. He hovered to the ramp and cleared his tail before each turn. [The student pilot] came to a hover over the helipad facing into the wind. He slowly and carefully lowered the collective and set the helicopter down on the helipad with the collective full down and [the student pilot] rolling off throttle the rest of the way the helicopter began to shutter and bounce. Then a split second later the helicopter started to shake very violently. I looked forward at [the CFI] and [the student pilot] and the both of them had their hands on the collective to hold it full down and I could see that [the CFI's] wrist was completely turned at a ninety degree angle like a backward 'L', throttle was completely rolled off.The aircraft began ripping itself apart."

Another witness who was at the fuel pumps at the time of the accident stated:

"I was actually close to the scene. I was out by the fuel pumps at the time of the accident. I took time to watch as the helicopter landed. It appeared to be a good, normal landing. The next thing I knew was that the helicopter began to shake back and forth. From the time the shaking started the intensity increased. As this happened the helicopter rose about 2 feet off the ground. It appeared as if the people in the helicopter were trying to shut it down. As quickly as this took place I saw that the helicopter tail broke off from the body of the helicopter. As soon as that took place the helicopter rose off the ground-about 30 feet."

PERSONNEL INFORMATION

The CFI, who was seated in the right seat. held a commercial single engine land certificate, a flight instructor helicopter certificate and an instrument helicopter rating. The CFI's last medical examination was completed May 4, 2005. He held a second class medical certificate with a limitation to wear corrective lenses.

According to the CFI's logbook, he had 2,107 hours aircraft total time, 1,965 hours rotorcraft total time. He had 92 hours total in the Enstrom 480. He had flown 84 hours in the last 90 days, 29 hours in the last 30 days, and 5 hours in the last 24 hours in the make and model.

The student pilot's flight times were not received by the National Transportation Safety Board (NTSB).

AIRCRAFT INFORMATION

N480FX, an Enstrom 480, powered by a turbo shaft, 285 horsepower Allison engine, model number 250-C20W, was a normal category helicopter with skid type landing gear. The helicopter was owned by the student pilot.

The aircraft's last annual was done May 23, 2005, with an aircraft total time of 1454.0 hours. Damper Kit P/N 4230030-1 was installed during this annual inspection.

The aircraft had a total time of 1545.0 hours at the time of the accident.

METEOROLOGICAL INFORMATION

The weather at the time of accident was clear, with calm winds, no visibility restrictions and no turbulence.

WRECKAGE AND IMPACT INFORMATION

The helicopter's tail was sheared from the body of the helicopter and came to rest about 30 feet away across the ramp area. The front seats were found about 10 feet away. The instrument panel was separated from the fuselage and lay in pieces near the fuselage.

A piece of the engine's transmission mount pylon tube was found broken and sent to the NTSB Materials Laboratory for inspection.

Inspection of the flight controls and engine did not reveal any evidence of preimpact failure or malfunction.

The new design dampers, that were installed during the latest annual inspection, were retained for further investigation.

TESTS AND RESEARCH

Inspection of the broken transmission mount pylon tube at the NTSB Metallurgical Laboratory determined that the break was an overstress fracture with no evidence of a preexisting crack or fatigue.

The three Elastomeric Dampers were tested at the manufacturer's facility in Erie, Pennsylvania on October 25, 2005, under the supervision of the National Transportation Safety Board. Damper numbers LK0053, LK0058, AND LK0088 were inspected for damage and conformity to manufacturer's specifications. The following was noted during the inspections:

LK0053 Elastomer:

-No evidence of damage or failure in the form of bond separation except for very slight edge bond separation at the point of most severe center plate deformation. No elastomer cracks are observed, slight ozone checks are visible, but not out of the ordinary.

Metal components:

-Bronze bushing cracks were observed in flange (approx 12 & 6 o'clock positions on both ends) on inboard end of damper.

-Clamping bolts on inboard end are in good condition and torque stripe is in-line.

-Evidence of impact in outer plate lead-lag pin window. Damage is observed toward the ends and along one side of the oval window.

-Both outer metals are deformed

-Evidence of impact on bottom outer plate (near name plate)

-Center plate deformed along its length and also has an indentation on the edge of the plate approximately 0.90" from outboard end of plate.

-Evidence of center plate impact on outer member at each end (more pronounced at outboard end).

-Outer members separated at outboard end (measured gap=0.107" fwd blade side end and 0.227" at other end). Bolt sheared near "nut side" on outboard end of damper.

-Spherical bearing has noticeable axial and radial "play" by hand feel (see measurement below) some dirt & dust noted. Staking markings are intact and staking joint appears to be in good condition.

-Rotational break away torque measured 0.14-0.22 in-Lbs

-Axial play measured 0.007"

-Scrapes and wear observed on outboard end of outer member plates, surface nearest grip.

-Witness mark noted on edge of center plate adjacent to the Spherical bearing.

LK0058 Elastomer:

-No evidence of damage or failure in the form of bond separation except for very slight edge bond separation at point of most severe plate deformation. No elastomer cracks observed, slight ozone checks are visible, but not out of the ordinary.

Metal components:

-Bronze bushing crack observed in flange (approx 6 o'clock position on lower, 12 o'clock on upper, both ends) on inboard end of damper.

-Clamping bolts on inboard end in good condition and torque stripe is in-line.

-Evidence of impact in outer plate lead-lag pin window. Damage observed toward the ends and along one side of the oval window.

-Outer member upper plate deformed/bowed slightly at center. Lower plate has little/no visual evidence of deformation.

-Center plate deformed along its length and also has an indentation on the edge of the plate approximately 0.90" from outboard end of plate, also slight mark on opposite end (same edge)

-Evidence of center plate impact on outer member at each end (more pronounced at outboard end).

-Outer members separated at outboard end (measured gap=0.008" fwd blade side end and 0.043" at other end). Bolt appears to be intact, head and nut in place, nut torque stripe is aligned.

-Spherical bearing has noticeable axial and radial "play" by hand feel (see measurement below), some dirt & dust noted. Staking markings are intact and staking joint appears to be in good condition.

-Rotational break-away torque measured 0.12-0.22 in-Lbs

-Axial play measured 0.005"

-Scrapes and wear observed on outboard end of outer member plates, surface nearest grip.

LK0088 Elastomer:

-No evidence of damage or failure in the form of bond separation. Slight surface crack (approx 3/8" length) observed on inboard edge of upper outboard pad cracks, slight ozone checks are visible, but not out of ordinary.

Metal components:

-Bronze bushing cracks observed in flange (approx 12 & 6 o'clock positions on both ends) on inboard end of damper.

-Clamping bolts on inboard end in good c...