Lebanon, TN, USA
N508AH
EROS 1600
The private pilot conducted a 20-minute local flight in the experimental, amateur-built airplane after installing a new ignition coil on the two-stroke, two-cylinder engine. He then returned to the departure airport, where he landed the airplane, back-taxied on the runway, and initiated a second takeoff. Witnesses reported that, shortly after takeoff, the airplane experienced a total loss of engine power. The airplane entered a left turn back toward the runway, then subsequently turned "sharply" left and descended to ground contact. Examination of the airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Examination of the engine revealed that the front spark plug was burnt white, consistent with exposure to high temperatures or an excessively lean carburetor calibration. Although both front and aft carburetor adaptors exhibited degradation, the front cylinder adaptor exhibited significantly more damage and cracking compared to that of the aft cylinder. This likely resulted in additional air being ingested by the front carburetor, which subsequently resulted in a leaner fuel/air mixture in that cylinder. In addition, the front cylinder piston exhibited a hole about 1 centimeter in diameter, consistent with detonation/preignition. Records located in the pilot's hangar indicated that the pilot was servicing the engine with a fuel/oil ratio of 40:1, rather than the manufacturer-recommended ratio of 50:1. It is likely that the use of an improper fuel/oil ratio resulted in carbon deposits in the front cylinder. Combined with the effects of the lean fuel/air mixture as a result of the degraded carburetor adaptors, the engine was susceptible to the development of detonation and/or preignition, which subsequently resulted in the development of a hole in the front cylinder piston head. As a result, the engine experienced a total loss of power, to which the pilot responded by attempting to turn back to the airport at low altitude. During the turn, the pilot allowed the airplane's airspeed to decay and exceeded its critical angle of attack, which resulted in an aerodynamic stall and collision with terrain.
HISTORY OF FLIGHTOn January 7, 2016, about 1540 central standard time, an experimental amateur-built Eros 1600 airplane, N508AH, collided with terrain following a total loss of engine power near Lebanon, Tennessee. The private pilot was fatally injured, and the airplane was substantially damaged. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed in the area, and no flight plan was filed for the local flight, which departed from Lebanon Municipal Airport (M54). GPS data indicated that the airplane departed M54 at 1515 and conducted an approximate 20-minute local flight. The airplane then returned to the airport, landed, and initiated a second takeoff. One witness, who was a pilot, stated the airplane conducted a normal takeoff, then began a right turn at low altitude. The airplane then "abruptly" turned left about 100 ft above ground level (agl) "as if it was trying to return to the airport." The airplane subsequently rotated "sharply" to the left and descended to ground contact as it disappeared from his view. Several witnesses reported hearing the airplane "circle" at low altitude, followed by a loss of engine power. A friend of the pilot stated that the pilot had been performing maintenance on the engine because it was "intermittently missing." The pilot had installed a new ignition coil onto the engine, and on the day of the accident, the pilot reinstalled the engine onto the airplane. The accident flight was a test flight to determine if the engine problem had been resolved. PERSONNEL INFORMATIONAccording to Federal Aviation Administration (FAA) records, the pilot held a private pilot certificate with a rating for airplane single-engine land. In addition, the pilot held a repairman experimental aircraft builder certificate that was issued on May 15, 2014. He was issued a third-class FAA medical certificate on August 24, 2006, with no limitations. The pilot's logbooks indicated that he had about 259 total hours of flight time, of which 8.9 hours were in the accident airplane. His most recent flight review was completed on May 27, 2014. AIRCRAFT INFORMATIONAccording to FAA records, the experimental amateur-built airplane was owned by the pilot and issued an airworthiness certificate on May 15, 2014. It was equipped with a two-cylinder Rotax 532, 64-horsepower (hp) engine, which was installed on October 7, 2015. According to maintenance logbooks, the airplane had a total time of about 14 hours. The airplane's most recent condition inspection was completed by the pilot on October 7, 2015, at a total time of 1.6 hours. A white board in the pilot's hangar noted that he serviced the engine with a fuel/oil ratio of 40:1. According to the pilot's son, the engine was previously installed on a snowmobile. According to the airplane operating handbook, the airplane was designed to be equipped with a 41-hp, Rotax 447 engine. With this engine installed, the airplane's flaps-up stall speed was 34 mph, and its flaps-extended stall speed was 29 mph. The emergency procedures section stated, "About the only failure you can have in planes as simple as the MAX is an engine failure, and since you are flying an uncertified engine, that occurrence is not too unlikely. Unless the failure is a result of inadvertently switching off the magneto, a restart is unlikely, therefore, begin planning immediately for a forced landing. Establish a glide at minimum airspeed at least 45 [calibrated airspeed]. If you are climbing, immediately lower the nose to the glide attitude. Pick a landing spot (you should already have one in mind). The MAX glides at about 6/1 angle, but any turbulence will strongly effect this. Also, keep in mind wind shear (gradient) as you approach the ground, and keep your airspeed up in a strong wind. Perform a normal power off landing (you should have practiced this many times). Minimum airspeed as you begin your flare should be approximately 40 mph. Any lower airspeed and you may not have enough energy to arrest your sink rate." METEOROLOGICAL INFORMATIONThe 1553 recorded weather observation at Smyrna Airport (MQY), Smyrna, Tennessee, located about 14 nautical miles southwest of the accident location, included wind from 120° at 4 knots, visibility 10 statute miles, broken cloud layers at 3,500 ft agl and 4,400 ft agl, temperature 13°C, dew point 8°C, and an altimeter setting of 30.02 inches of mercury. AIRPORT INFORMATIONAccording to FAA records, the experimental amateur-built airplane was owned by the pilot and issued an airworthiness certificate on May 15, 2014. It was equipped with a two-cylinder Rotax 532, 64-horsepower (hp) engine, which was installed on October 7, 2015. According to maintenance logbooks, the airplane had a total time of about 14 hours. The airplane's most recent condition inspection was completed by the pilot on October 7, 2015, at a total time of 1.6 hours. A white board in the pilot's hangar noted that he serviced the engine with a fuel/oil ratio of 40:1. According to the pilot's son, the engine was previously installed on a snowmobile. According to the airplane operating handbook, the airplane was designed to be equipped with a 41-hp, Rotax 447 engine. With this engine installed, the airplane's flaps-up stall speed was 34 mph, and its flaps-extended stall speed was 29 mph. The emergency procedures section stated, "About the only failure you can have in planes as simple as the MAX is an engine failure, and since you are flying an uncertified engine, that occurrence is not too unlikely. Unless the failure is a result of inadvertently switching off the magneto, a restart is unlikely, therefore, begin planning immediately for a forced landing. Establish a glide at minimum airspeed at least 45 [calibrated airspeed]. If you are climbing, immediately lower the nose to the glide attitude. Pick a landing spot (you should already have one in mind). The MAX glides at about 6/1 angle, but any turbulence will strongly effect this. Also, keep in mind wind shear (gradient) as you approach the ground, and keep your airspeed up in a strong wind. Perform a normal power off landing (you should have practiced this many times). Minimum airspeed as you begin your flare should be approximately 40 mph. Any lower airspeed and you may not have enough energy to arrest your sink rate." WRECKAGE AND IMPACT INFORMATIONThe airplane impacted terrain and came to rest inverted on a westerly heading, next to a residence located about 850 ft from the departure end of runway 04. All components of the airplane were located near the wreckage. Flight control continuity was established from the flight controls in the cockpit to all flight control surfaces. The propeller was rotated by hand and engine continuity was confirmed from the propeller flange to the back of the engine. The two spark plugs were removed; the aft cylinder spark plug was dark grey in color and exhibited normal wear. The front spark plug was white in color. Thumb compression was obtained on the aft cylinder, however, no compression was observed on the front cylinder. The top section of the engine case was removed to facilitate further examination, and a hole was found in the front cylinder piston. The hole was approximately 1 centimeter in diameter located in the center of the piston. The aft cylinder exhibited carbon deposits and oil residue on the top of the cylinder. The connecting rod bearings were loose in both the front and aft cylinders. The exhaust y-pipe was removed and carbon deposits were noted in the aft exhaust pipe. The front cylinder exhaust gas temperature probe was white in color, and the aft cylinder exhaust gas temperature probe was grey in color. Each of the engine's two carburetors were impact separated but remained attached to the engine through cables. Disassembly of both carburetors revealed that the respective jet needles were on the third clip from the top and were under the white retaining cup, and both the main jet and the pilot jet were free of debris. The front and aft carburetor rubber adaptors contained cracks and evidence consistent with material degradation. The front carburetor adaptor was also partially fractured in several places around the boot. The rotary valve plate cover was removed to examine the timing of the rotary valve. It was timed so that the intake port on the cylinder was fully open when the respective piston was at the top dead center position. The ignition coil remained attached to the engine; however, a wire was separated. The coil was rigged and was tested. Ignition continuity was confirmed from the flywheel to the spark plugs during propeller rotation. ADDITIONAL INFORMATIONEngine Operator's Manual According to the engine operator's manual, the proper mixing ratio of fuel to oil was 50:1. The manual stated, "Too much oil will cause carbon deposits on the spark plug, on the piston, in the cylinder ports and in the muffler and will cause problems." The manual stated that white spark plug electrodes indicated a low heat range (hot plug) or excessively lean carburetor calibration. Engine Repair Manual The engine repair manual stated that the carburetor must be checked and adjusted after every 25 hours of operation. The carburetor adaptor should be checked thoroughly for "tightness, cracks, cuts or other physical damage." The manual stated that, at "the slightest signs of damage" the carburetor adaptor should be exchanged, "Otherwise pressure conditions in carburetor will be changed, additional air will be taken in, possibly leading to engine damage." Pilot's Handbook of Aeronautical Knowledge – Aircraft Systems According to the Pilot's Handbook of Aeronautical Knowledge, "Detonation is an uncontrolled, explosive ignition of the fuel/air mixture within the cylinder's combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to failure of the piston, cylinder, or valves. Detonation is characterized by high cylinder head temperatures and most likely occur when operating at high power settings. Common operational causes of detonation are: - Use of a lower fuel grade than that specified by the aircraft manufacturer. - Operation of the engine with extremely high manifold pressures in conjunction with low rpm. - Operation of the engine at high power settings with an excessively lean mixture. - Maintaining extended ground operations or steep climbs in which cylinder cooling is reduced. Preignition occurs when the fuel/air mixture ignites prior to the engine's normal ignition event. Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug, a cracked spark plug insulator, or other damage in the cylinder that causes a part to heat sufficiently to ignite the fuel/air charge… Detonation and preignition often occur simultaneously and one may cause the other." According to an engine manufacturer presentation on piston failure analysis, the damage noted on the front piston was consistent with piston dome detonation, which can be a result of "pre-ignition, leading to detonation." A pamphlet published by the FAA Safety Team entitled, "Aircraft Control After Engine Failure on Takeoff" stated, "Studies have shown that startle responses during unexpected situations such as a powerplant failure during takeoff or initial climb have contributed to loss of control of aircraft…Research indicates a higher probability of survival if you continue straight ahead following an engine failure after takeoff. Turning back actually requires a turn of greater than 180 degrees after taking into account the turning radius. Making a turn at low altitudes and airspeeds could create a scenario for a stall/spin accident." MEDICAL AND PATHOLOGICAL INFORMATIONThe Office of the Medical Examiner, Nashville, Tennessee, performed an autopsy on the pilot. The autopsy report indicated that the pilot died as a result of multiple blunt force injuries. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of the pilot. Fluid and tissue specimens from the pilot tested negative for carbon monoxide and ethanol. Sitagliptin, an oral prescription medication for the treatment of Type 2 diabetes, was detected in the liver and blood. The pilot's diabetes and his treatment were not likely to be impairing at the time of the accident. TESTS AND RESEARCHA Garmin Aera 500 GPS navigation device was recovered from the wreckage and sent to the NTSB Recorders laboratory for download. The retrieved data indicated that the airplane began its taxi at 1509 and departed runway 01 about 1515. The airplane maneuvered in the area, returned to the airport, and landed on runway 04 about 1537. It back-taxied on the runway and began another takeoff at 1538:08. At 1539:02, the airplane reached a maximum of 853 ft GPS altitude at a ground speed of 41 knots, and then began a descending left turn. The airplane continued descending, completed a 360° left turn, and the last data point recorded was at 1539:49, at 620 ft GPS altitude. During the last minute of recorded data, the airplane's ground speed peaked at 46 knots and decreased to 2 knots through the turn.
A failure of the front cylinder piston due to the pilot's improper maintenance, which resulted in a total loss of engine power after takeoff. Contributing to the accident was the pilot's decision to return to the runway at low altitude following the loss of engine power, and his failure to maintain adequate airspeed during the turn, which resulted in the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall.
Source: NTSB Aviation Accident Database
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