Overview
On September 30, 2022, at approximately 1310 mountain daylight time, a Robinson R44 Cadet, registration N297SU, sustained substantial damage in an accident near Cedar City, Utah. The flight instructor and student pilot, who were on a Title 14 Code of Federal Regulations Part 91 instructional flight, were not injured.
Sequence of Events
The instructor and student had just completed practice maneuvers and decided to practice off-airport landings at a location previously used by the instructor. After performing reconnaissance orbits, low passes, and power checks, with the helicopter operating normally, the instructor proceeded with landing.
The student began maneuvering for landing but moved to a sloped area. The instructor asked the student to pull into a hover of about 7 ft. While hovering, the manifold pressure gauge indicated between 20.8 and 21.1 inches of mercury. They initiated a departure when the “full throttle” light illuminated. The manifold pressure gauge then indicated 22.5 inches of mercury, and the instructor lowered the collective control, extinguishing the light. The helicopter descended to about 3 ft. Concerned about surrounding trees, the instructor asked the student to pull into a 5 ft hover, taxi forward to clear the tail, and perform a pedal turn to face a clearing for climb-out.
As the student pushed forward on the cyclic to depart, a jolt was felt, and the helicopter yawed left. The instructor, suspecting a tree strike, took the controls. Due to the confined area and forward motion, he continued applying forward cyclic. The helicopter vibrated and yawed aggressively left, with an accompanying reduction in engine speed. The helicopter descended, and the engine speed gauge needle dropped below main rotor speed. The instructor lowered the collective and rolled on the throttle, but the engine did not respond. With the low rotor rpm warning sounding, he initiated an autorotation.
During the landing flare, the helicopter contacted trees. The pilot applied aft cyclic to prevent tipping forward down the hill. The main rotor blades cut through the tail as the helicopter came to rest. The instructor reported the engine was still running after impact, but at sporadic speeds.
Environmental and Operational Factors
The instructor reported using carburetor heat due to atmospheric conditions, with the control pulled out about 1/4 of its limit. The accident site was surrounded by low-lying cedar trees in rolling hills at an elevation of 6,385 ft mean sea level. According to the instructor, this location was commonly used for stage checks.
Post-Accident Examination
The helicopter was recovered and examined by a Federal Aviation Administration inspector, who noted no anomalies. The engine had accrued 2,386.7 hours since overhaul, and both engine and airframe were scheduled for overhaul in the following weeks. The helicopter was shipped to the overhaul facility for assessment. During engine disassembly, the facility reported that the No. 1 cylinder intake valve head appeared discolored, and a notch was found in both the valve head and its corresponding seat. The facility could not provide further details or photographic evidence.
Performance Calculations
The instructor provided performance calculations for the accident flight. Based on helicopter weight, environmental conditions, carburetor heat use, and the flight school’s standard operating procedure including a 500 ft buffer, he calculated the out-of-ground-effect hover ceiling as 6,400 ft. The calculations appeared consistent with the helicopter’s Pilot’s Operating Handbook performance data.