CHI04FA177

The loss of control due to the student pilot's failure to maintain rotor RPM and the flight instructor's inadequate supervision.

A helicopter piloted by a student pilot and a flight instructor was destroyed when it impacted terrain during a landing approach. A witness reported that the helicopter appeared to be making a normal approach toward the helicopter pad. He reported the helicopter was about 100 feet above the ground and going about 30 knots. When he looked at the helicopter again, he saw it "bobble" twice (yawing motion). Within 2-3 seconds, the helicopter rolled, "fell out of the sky" and impacted the ground. The flight instructor reported he could not remember much about the accident. He reported that the student pilot was at the controls and they were flying a right downwind approach to the helicopter pad. He reported that he did not think there was anything mechanically wrong with the helicopter, and did not remember anything being out of the ordinary. The inspection of the helicopter revealed that here were no ground impact marks other than the ground scars immediately below the main wreckage of the helicopter. The helicopter came to rest on its right side in a nose down attitude. The main rotor blades had severed the tailcone. The tail rotor drive shaft was found in one piece about 150 feet from the main wreckage with a 90-degree bend in it. The post accident inspection of the helicopter's airframe and engine revealed no preexisting anomalies that could be associated with a pre-impact condition. The Robinson Helicopter Company issued Safety Notice SN-24 in September 1986 with a revision in June 1994. The safety notice stated the following warning: LOW RPM ROTOR STALL CAN BE FATAL. The safety notice stated, "Rotor stall … can occur at any airspeed and when it does, the rotor stops producing the lift required to support the helicopter and the aircraft literally falls out of the sky." The safety notice explained, "As with the airplane wing, the blade airfoil will stall at a critical angle, resulting in a sudden loss of lift and a large increase in drag. The increased drag on the blades acts like a huge rotor brake causing the rotor RPM to rapidly decrease, further increasing the rotor stall. As the helicopter begins to fall, the upward rushing air continues to increase the angle-of-attack on the slowly rotating blades, making recovery virtually impossible, even with down collective."

HISTORY OF FLIGHT On July 8, 2004, at 1218 central daylight time, a Robinson R-22 Beta helicopter, N8118L, piloted by a student pilot and a flight instructor, was destroyed when it impacted terrain near Rochester, Minnesota. The student pilot was fatally injured and the flight instructor received serious injuries. The 14 CFR Part 91 cross-country instructional flight was operating in visual meteorological conditions without a flight plan. The last leg of the flight departed from the Austin Municipal Airport (AUM), Austin, Minnesota, about 1155. The cross-country flight originated from a helicopter pad in front of the helicopter's hangar at a farmstead located about 5 nautical miles northeast of the Rochester International Airport (RST), Rochester, Minnesota. The first leg of the cross-country flight was from the helicopter pad to Fillmore County Airport (FKA), Preston, Minnesota, located about 20 miles to the southeast. The second leg of the flight was from FKA to AUM, located about 33 nautical miles to the west. A witness reported that the helicopter was shut down when it arrived at AUM. The witness reported that the pilots started the helicopter in order to depart, but soon shut the helicopter down again in order to put on additional fuel. At 1146, a total of 4.8 gallons of fuel was added at AUM. The witness, who had flown about 98 hours in a Robinson R-22, reported that he fueled the left main tank. He reported the helicopter sounded fine, and that there were no indications that anything was wrong with the helicopter. The flight departed AUM on its final leg of the cross-country flight, and was en route to the helicopter pad located about 29 miles to the northeast of AUM. The navigation log found in the helicopter after the accident indicated that the estimated time en route to the helicopter pad was 23 minutes. The navigation log indicated that the estimated fuel burn was 9 gallons per hour, and that the aircraft would burn about 3.5 gallons of fuel en route from AUM to the helicopter pad. The owner of the helicopter witnessed the accident. He reported that he was in the process of starting a Robinson R-44 helicopter that was positioned in the grass southeast of the helicopter pad, and about 300-400 feet east of the accident site. He reported that he had started the R-44's engine and had engaged the rotor blades when he first observed the R-22 approaching from the southwest. The R-22 was about 300 feet above ground level (agl) and over flying a machine shed. He reported that the helicopter appeared to be making a normal approach toward the helicopter pad. He reported the helicopter was about 100 feet in altitude and going about 30 knots. When he looked at the helicopter again, he saw it "bobble" twice (yawing motion). Within 2-3 seconds, the helicopter rolled, "fell out of the sky" and impacted the ground. He shut down the R-44 and went to the downed helicopter to provide assistance. He turned off the R-22's ignition key and master switch. The flight instructor reported he could not remember much about the accident. He reported that the student pilot was at the controls and they were flying a right downwind approach to the helicopter pad. On the downwind leg they observed that the R-44 was being started and that it was positioned near the hangar. The flight instructor reported that they were going to land in the field and let the R-44 helicopter depart, and then they would reposition to the helicopter pad. He stated, "I think that was our plan." He reported that he did not think there was anything mechanically wrong with the helicopter, and did not remember anything being out of the ordinary. The helicopter impacted the terrain in a pasture about 350 feet west of the helicopter pad. The local fire department and paramedics responded to the accident and assisted with the recovery of the flight instructor. There was no post impact fire. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with single-engine land, single-engine sea, multi-engine land, helicopter, and airplane instrument ratings. He was a certified flight instructor (CFI) with airplane single-engine land, multi-engine land, helicopter, and airplane instrument instructor ratings. He held a second class medical certificate. He had a total of about 6,300 flight hours. He had logged about 275 hours in a Robinson R-22 helicopter and about 25 hours in a Robinson R-44 helicopter. The student pilot held a third class medical certificate. He had logged about 30 hours in Robinson R-22 helicopters. The student pilot had a non-fatal helicopter accident on April 27, 2004, when he was the pilot-in-command of a Robinson R-22, N40725, during a solo instructional flight. The National Transportation Safety Board accident number for that occurrence was CHI04CA111. AIRCRAFT INFORMATION The helicopter was a single-engine Robinson R-22 Beta, serial number 2409. The helicopter seated two and had a maximum gross weight of 1,370 pounds. The engine was a 160-horsepower Lycoming O-320-B2C engine, serial number L-17880-39A. The last annual inspection was conducted on March 3, 2004. The last 100-hour inspection was conducted on April 16, 2004. The helicopter had a total of 2,424 hours at the time of the accident, and had accumulated 56 hours since the last 100-hour inspection. METEOROLOGICAL INFORMATION At 1233, the weather conditions reported at RST were: Winds 050 at 6 knots; sky clear; visibility 10 statute miles; temperature 22 degrees C, dew point 11 degrees C, altimeter 29.99 inches of mercury. WRECKAGE AND IMPACT INFORMATION The helicopter impacted the terrain at coordinates 43 degrees 57.466 minutes north, 092 degrees 24.923 minutes west. The nose of the helicopter was oriented on a 160 magnetic heading. There were no ground impact marks other than the ground scars below the main wreckage of the helicopter. The cockpit, cabin, fuselage, landing gear, engine, main transmission, main rotor mast, main rotor hub, main rotor blades, and the forward two bays of the tailcone made up the helicopter's main wreckage. The distribution of wreckage parts consisted of parts associated with the tailcone, empennage, tail rotor gearbox and tail rotor of the helicopter. The helicopter came to rest on its right side in a nose down attitude with the aft end of the fuselage being held up by the two forward bays of the tailcone, which were bent 60-70 degrees to the right. The lower right side and nose of the cabin received crush damage. The windshields were broken out. The windshield bow and the two forward door posts were disconnected from the roof and the left door post was also disconnected from the chin. The aft door jam and bulkhead around the upper seat belt mount on the left side were collapsed inward. The lower left frame was bent inward at the battery box mount. The lower right frame was broken at the landing gear attachment point and bent in several places. The right skid tube of the landing gear was broken fore and aft of the forward strut attachment. The right aft strut attachment was partially separated from the skid tube. Both struts on the right side were angled aft. The left skid tube and struts were undamaged. The forward crosstube was bent aft, and the aft crosstube was straight. The inspection of the cockpit revealed that the mixture was in the full rich position and the mixture guard was in place. The throttle was about two-thirds open. The governor switch was in the "ON" position. The carburetor heat was in the full up (on) position and the carburetor heat valve was found in the open position. The fuel valve was in the open position. All circuit breakers were found down or in. The warning lights were inspected and no light bulb coils were found stretched. The inspection of the fuel system revealed that the main fuel tank and the auxiliary fuel tank we