Ringgold, VA, USA
N17HA
Bell BH-206-B
The pilot/owner prepared to land on an estimated 7 degree slope with the right/uphill skid first. When the right skid made contact with the ground, the helicopter began to rock back and forth longitudinally. The pilot then lifted the helicopter back up into the air, but it nosed forward. To counteract the nose down attitude, the pilot applied aft cyclic, but it did not arrest the situation. The pilot was then concerned about striking trees that were directly in front of him, so he "dropped" the collective to set the helicopter down again. However, the helicopter landed on the front part of the skids, and rolled over onto its nose, and came to rest on its left side. According to Advisory Circular 90-87-Helicopter Dynamic Rollover, "During normal or slope take-offs and landings with the same degree of bank angle or side drift with one skid on the ground, the bank angle or side drift can place the helicopter in a situation where it is pivoting (rolling) about a skid, which is still in contact with the ground. When the uphill slope skid hits the ground, the dynamics of the motion can cause the helicopter to bounce off the upslope skid, and the inertia can cause the helicopter to roll about the downslope ground contact point and over onto its side. The collective should not be pulled suddenly to get airborne, as a large and abrupt rolling moment in the opposite direction will result. This movement can be uncontrollable. If the helicopter develops a roll rate with one skid on the ground, the helicopter can roll over on its side." The pilot reported that there were no mechanical deficiencies.
On April 8, 2001, at 0945 eastern daylight time, a Bell 206B, N17HA, was substantially damaged when it rolled over during landing on private property in Ringgold, Virginia. The certificated commercial pilot/owner and passenger sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. In a telephone interview, the pilot said he had flown into Danville Municipal Airport (DAN), Danville, Virginia, on the morning of the accident with three passengers. When he arrived in Danville, he dropped off his passengers and prepared to take his friend on a local flight. The pilot and new passenger departed DAN, and flew to another friend's home where the pilot planned to land in his friend's backyard. The pilot stated he had landed in his friend's backyard on several occasions when he owned a Hughes 269B helicopter. The pilot approached his friend's property at a slow hover about 300 feet away from his friend's house, and taxied upslope into the backyard. He made a 90 degree left pedal turn over the landing area, so he was parallel to the slope. The pilot then set the right (uphill) skid down first. When the right skid made contact with the ground, the helicopter began to longitudinally rock back and forth. The pilot stated that the rocking motion startled him, and he lifted the helicopter back into the air. When he did this, the helicopter nosed forward. To counteract the nose down attitude, the pilot applied aft cyclic, but it did not arrest the situation. According to the pilot, there were trees directly in front of him and he was concerned about hitting them. To avoid striking the trees, he "dropped" the collective to set the helicopter down again, which resulted in the helicopter landing on the front part of the skids. The helicopter then rolled forward onto its nose, and came to rest on its left side. The pilot also reported that the slope was about 4-5 degrees. In a written statement, a witness said: "April 8 about 9:45 am, [the pilot] approached from the backside of the house approx. 300 feet from house, hovered, then moved slowly to landing area. Hovered again appx. 30 seconds, slowly began to land helicopter. The helicopter appeared to tip forward, rotor touched the ground and fell to left side." Two Federal Aviation Administration (FAA) inspectors performed and on-scene examination. According to an inspector, the helicopter's main rotor mast sheared, the main struts were damaged, the fuselage and tail boom were damaged, and the main rotor blades were fractured. In a written statement, the inspector stated: "On April 8, 2001, at 0945 LT, a Bell BHT-206B, attempted to land in a private yard, one mile North of Danville, VA Airport (DAN). The pilot conducted a normal approach to an area approximately 350 feet to the West of the desired landing site. He then hovered upslope (slope 7 degrees) East and turned the aircraft to the North, and attempted to conduct a slope landing. There were trees in front of and to the right side of the aircraft in close proximity. The aircraft was drifting to the left/West as the skids touched down. The left skid dug into the soft turf and the aircraft rolled onto its left side. The main rotor made ground contact and broke into several pieces, the mast sheered, a portion of the main rotor blade was thrown approximately 871 feet from the impact site. The helicopter was substantially damaged." According to the inspector, the trees were located directly in front of and to the right side of the helicopter, about 10-15 feet away from the main rotor blades. According to Advisory Circular 90-87-Helicopter Dynamic Rollover, "During normal or slope take-offs and landings with the same degree of bank angle or side drift with one skid/wheel on the ground, the bank angle or side drift can place the helicopter in a situation where it is pivoting (rolling) about a skid/wheel, which is still in contact with the ground.' "When this happens, lateral cyclic control response becomes more sluggish and less effective than for a free hovering helicopter. Consequently, if a roll rate is permitted to develop, a critical bank angle (the angle between the helicopter and horizon) may be reached where a roll cannot be corrected, even with full lateral cyclic, and the helicopter will roll over on to its side. As the roll rate increases, the angle at which recovery is still possible is significantly reduced. The critical rollover angle is also reduced. The critical rollover angle is further reduced under the following conditions: right side skid down condition, crosswinds, lateral center of gravity offset, main rotor thrust almost equal to helicopter weight, and left yaw inputs.' "When the uphill slope skid/wheel hits the ground, the dynamics of the motion can cause the helicopter to bounce off the upslope skid/wheel, and the inertia can cause the helicopter to roll about the downslope ground contact point and over onto its side. The collective should not be pulled suddenly to get airborne, as a large and abrupt rolling moment in the opposite direction will result . This movement can be uncontrollable. If the helicopter develops a roll rate with one skid/wheel on the ground, the helicopter can roll over on its side." The winds at DAN, about 3 miles from the accident site, were reported from 200 degrees at 5 knots. The pilot reported a total of 1,851 flight hours; 446 hours in helicopters, of which 27 hours were in make and model. The pilot also reported that there were no mechanical deficiencies.
pilot's failure to properly control the helicopter during a slope landing, which resulted in a dynamic rollover.
Source: NTSB Aviation Accident Database
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