NTSB Identification: ANC06FA020.
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Accident occurred Wednesday, February 22, 2006 in Scottsdale, AZ
Probable Cause Approval Date: 05/29/2007
Aircraft: Robinson R22, registration: N7512G
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The certificated helicopter flight instructor was conducting an introductory flight instruction lesson under Title 14, CFR part 91 with a prospective student. A witness, about 1 mile south of the accident site, estimated that the helicopter was about 1,000 feet above the ground as it passed over him. Shortly afterwards, he heard a "pop", and the helicopter started a shallow, controlled turn to the left, followed by two or three more popping sounds. The helicopter then began to descend rapidly, and started spinning counter-clockwise. As the helicopter's descent rate increased, the main rotor blades stopped turning, and the helicopter entered a vertical descent. The witness said he could no longer hear any engine sounds during the accident helicopter's vertical descent. The helicopter crashed in a residential area, and came to rest between two houses. The helicopter sustained damage consistent with a high speed, fuselage level, vertical impact. Postaccident inspection of the engine core and airframe disclosed no evidence of any preimpact anomalies. Impact damage prevented testing of the engine's carburetor and ignition wiring harness assemblies. A review of the accident pilot's historical training records revealed a series of failed check rides and overall substandard performance. The NTSB IIC interviewed both previous and prospective employers, which disclosed that the accident pilot had either been dismissed or not hired due to his lack of academic and/or flight skills. The FAA approved flight manual for the accident helicopter, emergency procedures section, states that at the first indication of an engine failure, the pilot's required emergency action is, in part: 1) Lower collective immediately to maintain rotor rpm, and enter a normal autorotation. 2) Establish a steady glide at approximately 65 knots. The helicopter manufacturer published a safety notice, which addressed the dangers of a low rotor rpm conditions, stating in part: "A primary cause of fatal accidents in light helicopters is the [pilots] failure to maintain rotor rpm. To avoid this, every pilot must have his reflexes conditioned so he will instantly add throttle and lower the collective to maintain rpm in any emergency." Additionally, the safety notice states, in part: "If the pilot not only fails to lower the collective, but instead pulls up on the collective to keep the ship [helicopter] from going down, the rotor will stall almost immediately. When it stalls, the blades will either "blow back" and cut off the tail cone or it will just stop flying, allowing the helicopter to fall at an extreme rate. In either case, the resulting crash is likely to be fatal. No matter what causes the low rotor rpm, the pilot must first roll on the throttle and lower the collective simultaneously to recover rpm BEFORE investigating the problem. It must be a conditioned reflex. In forward flight, applying aft cyclic to bleed off airspeed will also help recover lost [rotor] rpm."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A loss of engine power during cruise flight for an undetermined reason, and the pilot's failure to maintain rotor rpm, which resulted in an uncontrolled descent and collision with terrain. Full narrative available
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