CHI01LA152

The experimental amateur-built helicopter impacted muddy terrain and rolled over when its skids became stuck in the mud during an emergency autorotation following a total loss of engine power. The pilot reported that after the number one electronic control unit (ECU) had failed followed by the number two ECU failing while returning to the departure point at an airspeed of 40 mph and at an altitude of 100 feet agl. An operation at 40 mph and at 100 feet agl was within the shaded region of the height velocity envelope for the helicopter. A postaccident engine run was performed while operating on the primary and secondary fully automated digital electronic control systems. Inspection of the number one electronic control unit revealed two resistors damaged within its circuit board. The number one ECU was found to be inoperative during testing and the number two ECU did not communicate with the number one ECU.

On June 3, 2001, at 1015 central daylight time, an experimental amateur-built Allen Rotorway 162F, N242KA, sustained substantial damage on impact with terrain following a loss of engine power after takeoff from a farm field near Jerseyville, Illinois. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The private pilot reported no injuries. The local flight was originating at the time of the accident.

In a written statement, the pilot reported "After preflight and startup I allowed the engine to warm up to green arc (mandatory to prevent over pressurization of cooling system). After warmup, all systems in the green I lifted to a hover did a 360 [degree] clearing turn and departed to the south. Approx. 200' AGL 65 mph I noticed the split tach had failed. Almost [immediately] I got a red light indicating No. 1 ECU had failed. I made a 180 [degree] turn back to the pad. At about 100' 40 mph No. 2 ECU failed cutting the engine. Autorotated, [flared] a little late striking tail rotor. Still having forward motion the skids stuck in the mud and the aircraft rolled on to its right side. Shut off all switches and fuel and departed the A/C."

According to the Rotorway 162F pilot operating handbook, a red instrument light annunciation of the electronic control unit (ECU) 1 indicates that the primary ECU is off. Also, flight at 100 feet agl and 40 mph operation is within the shaded area of the height velocity envelope. Referring to the Rotorcraft Flying Handbook (FAA-H-8083-21), the height/velocity (H/V) diagram depicts the critical combination of airspeed and altitude should an engine failure occur. Operating within the shaded area of the H/V diagram may not allow enough time for the critical transition from powered flight to autorotation.

Postaccident examination of the engine by the Federal Aviation Administration (FAA) revealed that the helicopter was fueled with 91-octane automotive fuel. Both electric fuel pumps were operated and fuel was available at the injector ports. The oil screen was checked and reported to be normal. The engine was run at idle and accelerated to 2,600 rpm. After a short period of time, the primary fully automated digital electronic control (FADEC) system was turned off and the secondary FADEC system took control of the engine and it ran normally, but slightly rougher. Both FADEC computer systems were then removed and shipped to Rotorway International, Chandler, Arizona, for inspection and testing.

Inspection and testing of the ECU's, under the supervision of the FAA, revealed that the number one ECU was inoperative and the number two ECU was operational, but it would not communicate with number one ECU. Inspection of the number one ECU's circuit board revealed that the "L1" and "L3" resistors were damaged.