14 CFR Part 91: General Aviation
Accident occurred Thursday, March 14, 2013 in Eagle Nest, NM
Probable Cause Approval Date: 06/24/2013
Aircraft: ROBINSON HELICOPTER COMPANY R44 II, registration: N392GP
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The flight instructor and student pilot were cruising about 800 feet above ground level when they heard a loud “bang,” followed immediately by the low rotor rpm horn, a warning light illumination, and a rapid decrease in rotor rpm indication. In response, the instructor initiated an autorotation by lowering the collective, and the engine immediately lost power. The helicopter touched down and then rocked forward due to soft and downward-sloping terrain. The instructor applied slight aft cyclic to prevent the main rotor blades from contacting the ground; however, the main rotor blades struck and severed the tail boom.
The engine was functionally tested, and it operated normally. However, one of the magnets used to provide rotor rpm indications was missing from the rotating transmission yoke and was found affixed to a bolt just aft of the yoke. It likely had become loose in flight, and its movement was the bang heard by the pilots. Scarring was found on one of the sensors opposite the magnet, indicating that the magnet had contacted the sensor. The separation of the magnet caused the rotor rpm indication to drop and the low rotor rpm warning horn and light to activate. Due to the control linkage between the collective and the throttle, when the instructor lowered the collective, the throttle closed rapidly. According to Robinson Helicopters, rapid throttle changes can result in a fuel-air ratio becoming too rich or too lean to sustain engine operation and result in an engine failure.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A total loss of engine power due to a rapid throttle change during autorotation, which the flight instructor initiated in response to a low rotor rpm warning, which resulted from the separation of one of the magnets used to provide rotor rpm indications from the rotating transmission yoke. Contributing to the accident was the flight instructor's aft cyclic input upon landing.
On March 14, 2013, about 1445 mountain daylight time, the flight instructor of a Robinson R-44, N392GP, was forced to make an autorotation to an open field after the engine lost power near Eagle Nest, New Mexico. The flight instructor and second pilot were not injured. The helicopter was substantially damaged. The helicopter was registered to Global Positioning Services, Inc., Anchorage, Alaska, and operated by Leading Edge Aviation, Inc., Bend, Oregon, under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed at the time of the accident, and a visual flight rules flight plan had been filed but not activated. The flight originated from Dalhart, Texas, and was en route to Monte Vista, Colorado.
According to the instructor’s accident report, he and his student were cruising at 800 feet above the ground when they heard a loud “bang,” followed immediately by the low rotor RPM horn, warning light illumination, and a rapid decrease in rotor RPM. The instructor initiated an autorotation to an open field. The helicopter touched down and rocked forward due to the soft and downward sloping terrain. The pilot applied slight aft cyclic to prevent the main rotor blades from contacting the ground. The main rotor blades struck and severed the tail boom.
The helicopter was later transported to the operator’s facility in Bend, Oregon, where the engine was functionally tested. The engine was started and ran normally, and all parameters where within normal limits.
During the examination, it was discovered that one of the magnets used to provide rotor RPM indications was missing from the transmission yoke. There was scaring on one of the sensors opposite this magnet, indicating it had made contact with the magnet while the yoke was rotating. According to Robinson Helicopters, if one of the magnets or sensors opens, rotor RPM will drop and the low rotor RPM warning horn will activate. The magnet was later found affixed to a bolt just aft of the yoke, and a small dent was found on the horizontal firewall.
According to Robinson Helicopter, rapid throttle changes in the R44 can result in the fuel-air ratio becoming too rich or too lean to sustain engine operation and result in an engine failure, particularly at higher density altitudes.
14 CFR Part 91: General Aviation
Accident occurred Thursday, March 14, 2013 in Eagle Nest, NM
Aircraft: ROBINSON HELICOPTER COMPANY R44 II, registration: N392GP
Injuries: 2 Uninjured.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
On March 14, 2013, about 1430 mountain daylight time, the pilot of a Robinson R-44, N392GP, was forced to autorotate to an open field after the engine lost power near Eagle Nest, New Mexico. The certificated flight instructor and student pilot were not injured. The helicopter was substantially damaged. The helicopter was registered to Global Positioning Services, Inc., Anchorage, Alaska, and was operated by Leading Edge Aviation, Inc., Bend, Oregon, under the provisions of 14 Code of Federal Regulations Part 91 as a instructional flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The flight originated at Fort Smith, Arkansas, with an en route stop at Dalhart, Texas, and was en route to Moab, Utah, and Bend, Oregon.
Preliminary information indicates the engine lost power while the helicopter was in cruise flight. The flight instructor autorotated the helicopter to an open field. The tail boom was severed by the main rotor blades when the helicopter struck the ground.
The tail of a helicopter broke off during a hard landing at about 2:30 p.m. Thursday (March 14) in a field near Eagle Nest.
Assistant Moreno Valley Fire Department Chief Craig Sime said that neither one of the two people onboard the aircraft were injured in the accident, which occurred near the village boundary northeast of Therma Way and Iron Queen Drive.
Village of Eagle Nest employee Amarante Tafoya said he was checking a road in the area when the helicopter came down.
“It just sounded like an engine cut out, and it just smoothly came down and hit the ground,” he said.
Tafoya estimated that the helicopter fell about 10 feet, and he said the tail broke off while it was still in the air.
“They were kind of sputtering, and then they got to their lowest point and they just cut out and landed right there,” he said.
The New Mexico State Police took control of the scene at about 4 p.m. Thursday.
The helicopter is registered to Global Positioning Services, Inc. of Anchorage, Alaska, according to a search of the aircraft’s N number on the Federal Aviation Administration website.
The helicopter accident came less than two weeks after four people died in a single-engine airplane crash March 3 in Angel Fire, which is about 10 miles south of Eagle Nest.
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