PADUCAH, KY, USA
N9398F
Hughes 269B
The flight instructor and student pilot had departed from a confined area and were climbing through about 200 feet AGL, at 60 knots, when the engine lost power. The flight instructor took control of the helicopter and performed an autorotation to an open field. Both pilots reported the touchdown was harder than expected during which the right skid collapsed. The flight instructor had performed autorotations to a power recovery, but could not remember the last time he had performed a touchdown autorotation. The manufacturer reported that the blades had flapping damage, and indicated no significant rotation at impact. Examination of the helicopter revealed that the lower fuselage fairing had separated from the fuselage. After separation, the wire inside of the intake hose that supplied air to the fuel control unit pulled out and the intake hose collapsed into the engine air intake, and blocked it. The attachment holes on the lower fuselage fairing were found to be elongated.
On July 14, 1997, about 1800 eastern daylight time, a Hughes 269B, N9398F, was substantially damaged during a forced landing near Farrington Airpark, Paducah, Kentucky. The certificated flight instructor and commercial pilot/owner received minor injuries. Visual meteorological conditions prevailed for the dual instructional flight which originated from Farrington Airpark, about 1715. No flight plan had been filed for the flight which was conducted under 14 CFR Part 91. During the flight, the flight instructor occupied the left seat, and the owner occupied the right seat. In the NTSB Pilot/Operator Aircraft Accident Report, the flight instructor stated: "...after practicing in a confined area, we took off from the spot and started a normal climb (60 miles/h) over the woods, my student was on [the] controls. At about 200 feet AGL, I heard the engine quit suddenly. Instinctively, I entered in autorotation, the rotor RPM was a needle [width] below the green arc and the engine RPM close to zero - I said to my student, 'I have control.' I had to pull slightly the stick back to put the rotor RPM back on the green arc and stabilized my glide - (only about 10 seconds between the beginning of the autorotation and the touchdown) - Everything was looking good, I flare and pull up the collective to cushion the touchdown. At this point I believe we got into ground resonance, the rotor hit the tail boom, the ship collapsed on the right side and the blades hit the ground...." Interviews were conducted with both pilots by an inspector from the Federal Aviation Administration (FAA), who stated: "...[the flight instructor] noted the airspeed was at about 60 mph when he began a deceleration at about 35 feet, followed by initial collective pitch application at about 8 to 10 feet height, then leveling the aircraft and cushioning the landing with remaining collective pitch. They both recalled that everything appeared and felt normal for an autorotation up to the point of touchdown." "Upon touchdown, which they both said was harder than they expected, directional control was lost as the aircraft yawed left about 45 degrees and rolled right about 25 degrees. They also became aware of parts leaving the aircraft at this point, as the windshield and canopy departed to the right front, and the floor and instrument column rotated down and forward...In the last several days of their training, they had practiced straight in and 180 degree autorotations, all of them terminating with power...[the flight instructor] could not recall the last time he had practiced a touchdown autorotation. All that he could offer is that had been quite a while...." The helicopter was examined by an FAA airworthiness inspector who stated: "...No major work had been accomplished to the aircraft since the annual. No work which would require the removal of the lower fuselage fairing was done to the aircraft. The log books were reviewed for indications of any such work. The attachment points for the forward lower fuselage fairing were all in poor shape, the holes were elongated. The attaching hardware was still in place on the aircraft side. When the lower forward fuselage fairing departed the aircraft, the flexible air intake hose between the fairing and the fuel/air servo started to stretch. The fabric covering broke away from the fairing side first and the internal support wire remained attached to the fairing. The wire stretched to the breaking point and allowed the fabric to collapse." "When the fabric blocked the airflow to the fuel/air servo the fuel flow reduced due to no air flow and the engine shut down...." Additionally, the helicopter was examined by a representative of Boeing (Mesa), the manufacturer, who reported that the main rotor blades indicated no significant rotation at impact, and "...All 3 main rotor blades exhibit high flapping angles evidenced by pitch case impacts on the main rotor driveshaft retaining bolts and droop stop ring...."
The failure of maintenance personnel to identify and correct the worn holes on the lower fuselage fairing and the failure of the flight instructor to maintain main rotor RPM during the autorotative landing. A contributing factor was the flight instructor's lack of recent experience in performing autorotations to a landing.
Source: NTSB Aviation Accident Database
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