N1088YBell Helicopter Textron Canada 505 · 2018

On September 22, 2011, about 1540 Pacific daylight time, a Hughes 269C helicopter, N1088Y, was substantially damaged following a loss of power and a hard landing about five miles north of Ramona, California. The helicopter was registered to Civic Helicopters Inc., of Carlsbad, California. The certified flight instructor (CFI) and the student pilot were not injured. Visual meteorological conditions prevailed for the local instructional flight, which was being operated in accordance with Title 14 Code of Federal Regulations (CFR) Part 91, and a flight plan was not filed. The flight departed the McClellan-Palomar Airport (CRQ), about 1405.

In a statement submitted to the National Transportation Safety Board investigator-in-charge (IIC), the CFI reported that he had demonstrated three straight-in autorotations for the student and what to expect if an actual engine failure occurred. The CFI stated that after the third autorotation the aircraft ascended to about 600 to 700 feet above ground level (agl); the plan was to demonstrate a simulated engine failure, enter the glide and recover by 200 feet agl. The CFI added that he had control of the helicopter with the student on the controls [following along], and that all engine indications were normal. The CFI reported that he then rolled the throttle to split the needles, verified that the needles were split and that the engine revolutions per minute (RPM) was bouncing between 1,500 and 2,000 RPM; he said that this was normal for this helicopter before [the needles] settled down. The CFI further stated that at about 300 feet agl when it came time to recover, he began to add throttle to join the needles but noticed that the engine RPM was at zero and that the engine would not respond to throttle input. He then instructed the student to remove his hands from the controls and told him that they had actually experienced an engine failure. The CFI reported that when he was about 100 feet agl his speed was 40 knots and rotor RPM was on the low side of green arc. As a result, he was unable to slow the descent and unable to build enough rotor RPM for a landing, which resulted in the helicopter landing hard and spreading the skids. The helicopter subsequently slid forward and rolled onto its right side.

In a statement provided to the IIC, the chief pilot reported that while conducting an instructor proficiency check on the accident CFI shortly after being hired, the CFI initiated a practice autorotation in flight with a throttle chop and proceeded by lowering the collective. The chief pilot stated that when he detected the throttle rolling he immediately stopped the throttle from rolling off, returned the rotor RPM back to normal, and brought the collective back to straight and level flight. When the chief pilot asked the CFI what he was doing the CFI replied, “I am demonstrating an engine failure by rolling off the throttle then entering the autorotation. How else should I demonstrate the engine failure autorotation?” The chief pilot stated to the CFI that this is not how it is done at Civic. The chief pilot reported that after reviewing the procedures that the flight school used, he worked with the CFI for several autorotations in an effort to show him the proper way to conduct the maneuver. The chief pilot added that he advised the CFI to refer to the flight manual, which notes “Avoid rolling the throttle off in flight.”

At the request of the IIC and under the supervision of a Federal Aviation Administration (FAA) airworthiness inspector assigned to the San Diego Flight Standards District Office, San Diego, California, an examination of the accident helicopter’s engine was performed on November 21, 2011. The inspector reported that all spark plugs were removed, each of which showed no visible damage or defects, and that each appeared normal. The inspector further reported that all cylinders exhibited [proper] compression; #1 cylinder exhibited compression but was leaking due to impact damage. The inspector revealed that a check of the magnetos was performed and that both magnetos tested normally. The inspector also revealed that the engine did rotate except for some binding of sheet metal, which had been bent due to the impact sequence. No attempt was made to operate (run) the engine due to the damage to the engine components as a result of the impact damage. The inspector concluded that with the exception of the damage received to the engine during the crash sequence, the engine was operating at the normal operating range prior to impact.

On January 12, 2012, the FAA issued Special Airworthiness Information Bulletin (SAIB) SW-12-12, entitled “Conducting Engine Failure Simulation in Helicopters with Reciprocating Engines.” SAIB SW-12-12 specifically referenced owners and operators of Schweizer 269C and 269C-1 aircraft, which noted that Schweizer had updated the instructions and warnings in the approved Pilot Flight Manual (PFM) to avoid throttle chops to full idle, in order to minimize the possibility of engine stoppage. The FAA recommended that pilots and operators follow the updated PFM revision #18, which was approved on June 28, 2011, which clarified warnings for pilots that “rapid throttle reductions to full idle shall not be conducted.”

On January 17, 2012, the Sikorsky Aircraft Corporation Lead Accident Investigator for light helicopters reported to the IIC that changes to their flight manual had been issued to address this issue. The investigator stated that most piston engine helicopters that have airplane piston engines installed don’t have the propeller associated rotational momentum it provides. As such, when the engine is rolled back rapidly from power on to idle [power] there is an acceleration of the RPM in a downward direction that can reduce RPM below the idle setting. This may result in the engine to unwind below idle and quit, or it may struggle along at idle and then quit when the throttle is rolled back on.

As a direct result of the accident and in post accident conversations with the IIC, Civic Helicopters initiated remedial training for all qualified company certified flight instructors in accident make and model helicopter to verify that proper techniques are being followed relative to the demonstration of practice autorotations. Additionally, autorotation training was restricted to the company Chief Pilot and Assistant Chief Pilot until the remaining staff of flight instructors had accumulated 500 hours of instruction time given prior to being able to provide autorotation training, and only after the approval of the company Chief Flight Instructor.