Tucson, AZ, USA
N7059S
Robinson R22 Beta
The pilot and his passenger, an aerial photographer, departed and headed for a mountain pass. With the available engine power on the hot day, and the pilot's close proximity to the rising terrain, the helicopter did not have adequate climb performance to traverse the first mountain pass route selected. The second available route was 500 feet lower, but it also exceeded the performance capability of the helicopter. As the helicopter climbed, its clearance above the rising mountainous terrain decreased to 300 feet, at which time the pilot reversed course to head toward lower elevation terrain. The pilot failed to maintain adequate main rotor rpm to sustain flight, and impacted the 6,400-foot mean sea level mountainside in an uncontrolled descent. The approximate density altitude was about 8,600 feet. The helicopter was 41 pounds over its maximum certificated gross weight at takeoff, and about 18 pounds below its maximum certificated gross weight at the time of the accident.
HISTORY OF FLIGHT On August 10, 2006, about 0930 mountain standard time, a Robinson R22 Beta, N7059S, descended into high mountainous terrain about 19 miles north of Tucson, Arizona. The helicopter was operated by Air Photo, Inc., Everett, Washington, during the aerial photography flight, and it was substantially damaged. The commercial pilot was seriously injured, and the passenger (photographer) was killed. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and it originated from Tucson (TUS) about 0820. The pilot reported to the National Transportation Safety Board investigator that after takeoff from the Tucson International Airport, elevation 2,643 feet mean sea level (msl), he proceeded on his aerial photography assignment in the direction specified by his passenger, a company photographer. As the pilot was proceeding in a northerly direction he approached rising mountainous terrain and he "started looking for a way through [the mountains]." The pilot reported "the first route [he] chose didn't work. Halfway up [he] determined that with the power [he was] using that [he] had to go another way." The pilot indicated that the second route he chose was 500 feet lower at the peak, and there were 2 valleys oriented up to the face of the mountain. The helicopter was 1,000 feet above ground level (agl), but that clearance decreased to 500 feet agl, and then to 300 feet agl. At this time the rpms "started to sag," so he performed a "low rpm recovery and aborted the approach." The pilot reversed course to the left and headed back down the valley toward lower elevation terrain. Upon completing the course reversal turn the helicopter descended and the low rotor rpm warning horn sounded. Despite his recovery efforts, the helicopter rapidly descended until impacting the underlying mountainous terrain. Regarding the meteorological conditions in the general area, the pilot reported observing a developing thunderstorm between 10 and 15 miles northeast of his location. The sky was clear along his flight route. The pilot stated that he recalled the outside air temperature gauge indicated it was 21 degrees Celsius. The pilot reported to the Federal Aviation Administration (FAA) coordinator that during the accident flight he had not experienced any mechanical malfunction with the helicopter. The helicopter came to rest in a ravine, located in the Pusch Ridge Wilderness area of the Coronado National Forest. The accident site is about 19 nautical miles north (017 degrees, magnetic) of TUS. The estimated elevation of the site is 6,400 feet msl. The elevation of terrain within approximately 0.2 miles northwest through east of the site rises to over 6,700 feet msl. ROTORCRAFT INFORMATION Weight. Information regarding the helicopter and baggage weight was received from the FAA coordinator, the Robertson Helicopter Company, the operator, the helicopter's registered owner, helicopter recovery personnel and the pilot. In summary, the pilot reported that the helicopter's tanks were completely full of fuel at takeoff, for a total weight of 174 pounds. The helicopter's empty weight was 872.25 pounds. The pilot and passenger weighed a total of approximately 349 pounds. Extra baggage/cargo that was on board during the accident flight consisted of the following items: cameras and related equipment, film, batteries, charts, a spark plug socket, wrench, 1 quart bottle of aircraft oil, 2 hand held GPS receivers, ear plugs and suntan lotion. The approximate total weight of these items is 16 pounds. The helicopter's maximum certificated gross weight was 1,370 pounds. Its estimated weight at takeoff from TUS was about 1,411 pounds. Based upon an estimated 9 gallons per hour fuel burn off rate for 1.1 hours, the weight of the burned off fuel was about 59 pounds. At the time of the accident, the estimated helicopter weight was 1,411 pounds minus 59 pounds, or 1,352 pounds. ADDITIONAL INFORMATION The pilot reported on his completed "Aircraft Accident Report" that he began the accident flight at 0810, and he crashed at 0915. Also, the outside air temperature was 21 degrees Celsius, which computed to an 8,000-foot density altitude. However, during an interview with the Safety Board investigator, the pilot reported that the flight began at 0820, and he crashed at 0930. The Safety Board investigator computed the density altitude as being at least 8,600 feet.
The pilot's failure to maintain adequate rotor rpm and adequate terrain clearance while maneuvering to reverse direction. Contributing factors were the high density altitude, that exceeded the helicopter's performance capability, and the rising mountainous terrain.
Source: NTSB Aviation Accident Database
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