Spanish Fork, UT, USA
N7480F
HUGHES 269C
The pilot receiving instruction was preparing for his upcoming checkride for a rotorcraft certificate. About 50 minutes into the flight, the flight instructor announced a simulated engine failure, and the pilot receiving instruction reduced throttle, lowered collective, and entered an autorotation. When the helicopter approached 500 ft above ground level (agl) and the instructor advised the pilot to recover, they realized that the engine had stopped producing power. The instructor took control of the helicopter about 200 ft agl and started to flare about 30 ft agl. He raised collective to cushion the landing, but the helicopter still had forward airspeed when it touched down on the soft ground, which resulted in a noseover. Postaccident examination of the helicopter did not reveal any preimpact mechanical anomalies with the airframe or the engine. An engine run showed that with the throttle at the idle detent, the engine cut out intermittently, and the engine idle speed was about 500 rpm lower than the minimum idle speed given in the Pilot’s Operating Manual (POH) for the helicopter. However, the engine power could be advanced from idle to higher speeds, and the engine never lost power as occurred during the accident flight. The flight instructor reported that the pilot receiving instruction would rapidly reduce throttle for practice autorotations, and the POH warned against rapid throttle reduction as it could result in a sudden stoppage of the engine; however, given that the pilot receiving instruction had been following this practice throughout the flight and during previous flights without issue, it is unlikely his rapid throttle reduction led to the loss of power. The investigation was unable to determine the reason for the loss of engine power. The pilot receiving instruction had started his recovery from about 500 ft agl, which required the instructor to re-establish the autorotation following the loss of power. Although the instructor was successful in re-establishing autorotation, he was unable to fully arrest the helicopter’s forward motion before touchdown.
On January 13, 2020, about 1350 mountain standard time, a Hughes 269C helicopter, N7480F, was substantially damaged when it was involved in an accident near Spanish Fork, Utah. The instructor and the pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The pilot receiving instruction stated that he was preparing for his rotorcraft certificate and was practicing for his upcoming checkride when the accident occurred. According to the flight instructor, they performed an uneventful preflight inspection and started the helicopter. The pilot receiving instruction reported that during the engine run-up, which was performed at 2,500 rpm, he reduced engine power to idle and observed normal rotor and engine rpm separation. The instructor stated that after departure, they entered the airport traffic pattern and performed several landings and three autorotative maneuvers. They subsequently departed the airport traffic pattern and flew to a nearby practice area west of the airport. After performing two recoveries from settling with power, they elected to return to the airport. During cruise flight at 6,500 ft mean sea level, about 1,500 ft above ground level (agl), the instructor announced a simulated engine failure, and the pilot receiving instruction decreased power to idle and lowered collective to enter an autorotation. As the helicopter descended to 500 ft agl, the instructor advised the pilot receiving instruction to recover; however, they realized that the engine had stopped producing power. According to the pilot receiving instruction, the instructor took control of the helicopter about 200 ft agl during an estimated 1,600 ft per minute rate of descent. The instructor stated that he started a flare as the helicopter passed below 30 ft agl to reduce airspeed and rate of descent. The instructor then raised the collective to cushion their landing and further reduce the rate of descent. The helicopter had about 7 mph of forward movement as it contacted the soft ground. The helicopter nosed over, and the main rotor blades contacted the tailboom, which separated from the helicopter. The front right skid tube broke, and the helicopter rolled onto its right side before it came to rest. The checklist that was found on board the helicopter contained a section titled “ENGINE WARMUP AND GROUND CHECK” that included a condensed procedure from the Pilot’s Operating Handbook (POH). The section began with “set engine to 2500 rpm” and continued with several steps including a control check before ending with the following steps: Raise collective (14” [manifold pressure] MP at 2500 rpm). Perform magneto check, (maximum drop in 5 sec). Stabilize engine at 2500 rpm. Position collective full down. Close throttle, observe engine and rotor needles separation. Stabilize engine at 2500 rpm. Boost pump “ON”. The onboard checklist also included a section titled “ENGINE COOLING AND SHUTDOWN PROCEDURE” that was condensed from the POH. Following steps for an engine cooldown, the section continued with the following steps: Set engine at 1400 rpm. Set clutch control switch to “RELEASE”. Wait for rotor rpm to drop below 100 rpm. Radios “OFF”. Mixture IDLE CUT OFF”. The section ended with several more steps for turning switches off and closing the fuel valve. The helicopter POH stated that a check of idle speed was required at the end of the last flight of each day before engine shut down. The purpose of the check was to determine whether the engine idle speeds were within required limits. This was accomplished with two individual checks; tThe first check (throttle into full override) should produce an idle speed of no less than 1400 rpm; and the second (throttle at normal idle stop) should produce an idle speed no greater than 1600 rpm. The procedure stated that the pilot should notify maintenance personnel if the idle speeds were not within required limits. The POH section that discussed the procedure for a practice autorotation included the following warning: To reduce the chance of engine stoppage when initiating practice autorotations or simulated forced landing training the throttle shall not be abruptly retarded to the idle position. The pilot receiving instruction, who was a co-owner of the helicopter, stated that he performed an engine check before each flight by running the engine up to 1,800 rpm and observing the gauges, oil pressure, and fuel pressure. After performing a magneto check, he would then reduce throttle and observe the rotor and engine rpm split. He stated that he would never reduce throttle below 1,200 rpm even during simulated engine failures. According to the pilot receiving instruction, he did not rapidly reduce throttle during any of the practice autorotations. The instructor stated that the pilot receiving instruction typically reduced power within 1 second during simulated engine failures. The pilot receiving instruction stated that he was not familiar with the POH procedure for a check of engine idle speed at the end of the last flight of the day. The flight instructor reported that they followed the shutdown procedure from the onboard checklist after each flight. During postaccident examination, continuity was confirmed from the anti-torque pedals to the tail rotor through the bellcrank and push-pull tube. Cyclic control continuity was confirmed from the cockpit to the swashplate. The throttle control was moved through its full range from idle to full, and the throttle cable linkage to the carburetor moved accordingly. The mixture control was manipulated from full lean to rich with no discrepancies. Manipulation of the engine drive pulleys turned the main rotor and the tail rotor drive shaft. The drive belts were cut so that the engine could be run without movement of the main and tail rotor drives. A postaccident engine run showed that the engine idled at 500 to 750 rpm at which setting it would run rough and cut out periodically. According to the POH, the engine should idle between 1,200 and 1,600 rpm. A magneto check at 1,800 rpm showed a drop of about 300 rpm when the ignition was switched to the left and right magnetos individually. The engine ran smoothly when engine power was increased to 2,500 rpm.
The loss of engine power during a practice autorotation for an undetermined reason.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
