Byron, CA, USA
N507RV
GRAVES BRYON S VANS RV-7A
Shortly after takeoff, the private pilot began a series of aerobatic maneuvers in the experimental, amateur-built airplane. After executing two rolls, the engine began to run rough, and an instrument panel annunciator indicated that the ignition system had reverted to backup mode. Unable to maintain altitude, the pilot performed a forced landing to a field, where the airplane nosed over and sustained substantial damage. The airplane's engine was equipped with a composite propeller and an FAA-certified ignition system, which used traditional magnetos combined with an electronic control module. The design was such that, should the electronic system fail or malfunction, the ignition system would revert to "backup" mode, operating on the traditional magnetos. Postaccident examination revealed that the steel magneto drive gear for the left magneto had broken off and fallen into the engine accessory case. Based on the damage signatures to the gear teeth and its shaft, it is most likely that a foreign object within the engine crankcase or accessory case moved into the path of the gear drivetrain during inverted flight, imparting a heavy side load on the gear and separating it from the magneto. The system was designed to tolerate such a failure and revert to backup mode on the remaining magneto with only a minimal loss of engine power. However, postaccident examination revealed that the right magneto's internal contact point timing ("E" gap) was offset by about 16 degrees. This was likely the result of an improper adjustment during overhaul of the magneto, which was completed at a repair facility about 20 flight hours prior to the accident. This internal error would not have been visible to the pilot (builder), who followed the correct procedures to reinstall the magneto and synchronize it to the engine. Under this condition, the engine-to-magneto timing would have been correct, but the magneto's internal timing was wrong, resulting in a reduction of energy available for the spark plugs. This error would not have been a factor under normal operation, because the electronic ignition system did not use the magneto timing points. The error should have been noticeable during the pre-takeoff engine magneto check, because the system reverted to backup mode as the ignition was switched from BOTH to either the LEFT or RIGHT magneto position. However, it is possible that engine and environmental variables, or operating conditions at the departure airport's elevation, were sufficient to mask the lower spark energy during ground run-up, but not in the more demanding environment of powered flight.
HISTORY OF FLIGHTOn September 20, 2015, about 1706 Pacific daylight time, an experimental amateur-built Bryon S Graves (Vans Aircraft) RV-7A, N507RV, nosed over during an off-airport landing following a loss of engine power near Byron Airport, Byron, California. The airplane was registered to the pilot/builder and operated by him under the provisions of 14 Code of Federal Regulations Part 91. The private pilot and passenger were not injured. The airplane sustained substantial damage to the vertical stabilizer, right wing and lower airframe structure during the accident sequence. The local flight departed Byron about 1650. Visual meteorological conditions prevailed and no flight plan had been filed. The pilot stated that after an uneventful preflight inspection and engine run-up, which included a magneto check, his intention was to fly to a practice area north of the airport and perform aerobatic maneuvers. He departed, and after executing two rolls and leveling off at 4,500 ft mean sea level (msl), the engine began to "sputter", and the airplane's Vertical Power VP-200 display indicated that the ignition system had reverted to backup mode. The pilot turned the magneto switch from left to right, and then back to both, and also switched the fuel selector valve to the opposite fuel tank, with no noticeable change in engine operation. He initiated a return to the airport, and stated that having descended to about 3,500 ft msl the engine lost all power. The pilot declared an emergency on the airport's common traffic advisory frequency, and performed a forced landing into an alfalfa field about 2 miles northeast of the airport. During the landing flare he maintained full airplane nose-up elevator input in an effort to keep the nosewheel from touching the ground. The airplane began to fishtail on the main landing gear. Once the airspeed reached about 30 knots the nose dropped, the nosewheel made contact with the soil, and the airplane immediately nosed over. Both the pilot and passenger released their harnesses and repositioned themselves within the inverted cabin. The airplane was equipped with a sliding canopy, which had become impinged against the soil, and unable to open; the pilot began to kick at its Plexiglas sides. About 20 to 25 minutes after the accident he was able to open a hole large enough to exit, and emergency response personnel reached the site about 10 minutes later. AIRCRAFT INFORMATIONThe airplane was equipped with a four-cylinder normally aspirated, fuel injected experimental engine, constructed utilizing Superior Air Parts components. It was built by Eagle Engines, and marketed as an Xtreem 360, model number IO-360-B1BC3, serial number 6D081429. The engine was equipped with an FAA certified Champion Aerospace LASAR electronic ignition system, and a Whirlwind two-blade constant-speed composite propeller. The airplane was completed in 2009, and first flown in March of that year. At the time of the accident, the airplanes tachometer indicated a total time of 311.6 hours. AIRPORT INFORMATIONThe airplane was equipped with a four-cylinder normally aspirated, fuel injected experimental engine, constructed utilizing Superior Air Parts components. It was built by Eagle Engines, and marketed as an Xtreem 360, model number IO-360-B1BC3, serial number 6D081429. The engine was equipped with an FAA certified Champion Aerospace LASAR electronic ignition system, and a Whirlwind two-blade constant-speed composite propeller. The airplane was completed in 2009, and first flown in March of that year. At the time of the accident, the airplanes tachometer indicated a total time of 311.6 hours. ADDITIONAL INFORMATIONThe airplane was equipped with an Advanced Flight Systems combination electronic flight instrument and engine monitor. The unit was capable of storing engine and flight parameters in non-volatile memory, at 5 second intervals. The data for the accident flight was downloaded and reviewed, and revealed an increase in engine speed to about 1,800 RPM approximately 4 minutes after engine start, with a corresponding increase in fuel flow and manifold pressure. The rise was consistent with the pilot performing a magneto check, and lasted about 30 seconds; however, the data resolution prevented an accurate determination of the exact engine speed drops during the check. About 11 minutes and 30 seconds after takeoff, having reached a GPS altitude of almost 5,000 ft, the manifold pressure dropped from 25 to 15 inches of mercury (inHg) and the fuel flow dropped from 12 to 7 gallons per hour. For the next 90 seconds the airplane began to descend. During that period the engine speed remained at 2,400 RPM as the exhaust gas temperatures rose about 200 degrees F, accompanied by a reduction in cylinder head temperatures of about 75 degrees F. With the airplane now at 2,000 ft, the engine speed dropped to 1,400 RPM, as the manifold pressure increased to 28 inHg. The descent continued as both the exhaust gas and cylinder head temperatures decreased, until the recording ended 2 minutes later. Oil temperature and pressure remained relatively constant throughout the flight. TESTS AND RESEARCHEngine Examination Post-accident examination revealed no evidence of catastrophic engine failure, and the engine crankshaft could be manually rotated smoothly by the propeller hub. All fuel lines were intact, and remained attached at their respective fittings. All spark plugs were of the aviation-grade, massive electrode type, were free of mechanical damage, and exhibited light-grey and brown deposits, and normal wear signatures consistent with a short service life. Ignition switch operation and electrical continuity was confirmed through to the wiring harness forward of the firewall. The magneto-to-engine timing was checked utilizing a Champion Aerospace T-300 SyncroLASAR timing system. The right magneto appeared set to the correct timing, however during engine rotation, the left magneto top dead center (TDC) light remained illuminated on the T-300, and the BKR/PT light did not turn on. According to the LASAR system maintenance manual, such a condition indicated a failure of the left magneto. The left magneto was then removed from the engine, revealing that its steel drive gear had become detached, and was found loose within the accessory case. Examination of the gear revealed that it remained attached to the rotor shaft end, but the shaft had fractured at the main magneto bearing. The fracture surfaces revealed a generally cup-shaped curvature, with uniform granular features, and no indication of "beachmarks" or propagation lines typically associated with fatigue. The engine's accessory drive gear teeth all remained intact, and one tooth on the separated magneto gear exhibited a 3-mm-long gouge to its top land surface. Ignition System Operation The LASAR Ignition system was developed and manufactured by Slick Aircraft Products/Unison Industries until September 2008, when the product line was purchased by Champion Aerospace. The model installed was certified for use in a Lycoming 180 horsepower IO-360 engine. The system utilizes an electronic controller interfaced to a set of traditional magnetos, and operates in either "automatic" or "backup" modes. In automatic mode, when the ignition switch "BOTH" position is selected, the controller receives engine parameter inputs including manifold pressure and crankshaft speed, and adjusts the ignition timing, spark duration, and spark energy based on an internal software map. In this mode, a series of relays are energized within the magnetos, electrically isolating their contact points from the ignition coils. One "sensor" magneto (left in the accident airplane) contains a Hall Effect switch, which provides timing and speed reference to the controller. The system switches to traditional magneto ignition (backup) mode when the controller detects a fault, or when the ignition switch is moved to the "LEFT" or "RIGHT" position. Under these circumstances, the internal relays de-energize, and the magneto reverts to the fixed ignition timing angle utilizing its contact points and ignition coil. The controller also switches an annunciator output, which in the accident airplane was connected to the VP-200 display and configured to present a "backup mode" indicator. During preflight magneto checks, as the ignition switch is moved between BOTH and either the RIGHT or LEFT position, the system reverts to backup mode, with RPM drops equal to that observed in a traditional magneto system. In order to check and adjust the magneto timing following maintenance, the specialized T-300 SyncroLASAR timing system is required. Magneto Maintenance The pilot reported that about 20 flight hours prior to the accident, he had been experiencing uneven engine operation when in backup mode, with symptoms including high RPM drops of about 180-200 rpm during magneto checks. After conferring with technical support at Champion Aerospace, he sent the magnetos to a repair facility for a 500-hour inspection and maintenance. Records revealed that the repair shop performed the inspection in accordance with the L-1503E overhaul manual, which was appropriate for the LASAR ignition system. As part of the maintenance, the contact and cam assemblies were replaced in both magnetos and the coil was replaced in the right magneto. Once complete, the pilot reinstalled the magnetos and performed the engine-to-magneto timing adjustments utilizing the T-300. He reported that the engine roughness had now been resolved, and that all preflight magneto checks for the remaining flights leading up to the accident resulted in normal engine RPM drops. Magneto Examination Both magnetos, along with the LASAR control unit, and ignition and control harnesses were examined by the NTSB investigator-in-charge and technical representatives from Champion Aerospace at the Champion facility in Liberty, South Carolina. A complete examination report is contained within the public docket. Left: Slick Model 4771 Due to the separation of the drive gear, a dynamic test of the left "sensor" magneto could not be performed. The magneto case appeared undamaged, and the housing assembly was removed by the group. There was no indication of catastrophic internal failure, and all of the plastic rotor and distributor gear teeth were present. All internal components were intact, clean, and free of arcing signatures. The Hall Effect sensor was still attached to its mount, and the sensor trigger remained affixed to the rotor gear. The internal timing was visually examined in accordance with the maintenance manual timing instructions, and appeared to be set to the correct "E" gap. Right: Slick Model 4755 The right magneto case appeared undamaged, and the rotor shaft could be rotated smoothly by hand. The drive gear and spark plug wire harness were removed to facilitate installation in a Champion magneto test bench. The test stand was configured for the "LASAR/Epic Mode Test" which tested the operation of the magneto in LASAR ignition (automatic) mode. The magneto was run throughout its operating speed range, and sparks were observed in firing order at all output leads (with gaps set to 7 mm). The magneto test stand was then configured for the "Magneto Mode Test", which tested the magneto in standard backup ignition mode. Sparks were observed intermittently at all four output leads throughout the speed range, and the timing gauge indicated that the internal timing ("E" gap) was set to 41 degrees, rather than the nominal 25 degrees. In an effort to determine the timing discrepancy, the housing assembly was removed and all internal components examined. All components were of the correct type, and were intact, clean, and free of arcing signatures. The contact point assembly remained firmly locked in place, and all plastic rotor and distributor gear teeth were present. The group then "pinned" the rotor drive gear at the "X" location, however the notches on the rotor and distributor gear did not line up. The pin was then removed and the gear was rotated until the notches lined up; under this condition the contact points appeared in the fully open position, indicating incorrectly adjusted "E" gap timing. In this state, the magnetos rotor magnets would be out of synchronization with the engine timing, thereby resulting in a reduction of energy induced into the coil windings and available to the spark plugs. The group then adjusted the points visually to the correct "E" gap utilizing an exemplar magneto for reference, and the magneto was again tested on the test stand. It then operated correctly in both LASAR and Magneto modes; sparking at all output leads at all speeds, and the magneto internal timing gauge now correctly indicated about 25 degrees. The LASAR controller unit was then disassembled and examined, and no damage was noted. It was connected to a Unison LASAR test bench, and an acceptance test procedure was performed. The unit passed all applicable tests except the left and right coil current test, which registered a current flow about 12 percent greater than nominal.
Improper overhaul of the right magneto, which eliminated system redundancy, and resulted in a loss of engine power when the left magneto failed during aerobatic flight maneuvers.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
