NTSB Factual Report

On August 27, 2018, at 1036 mountain standard time, an experimental amateur-built Stoddard Hamilton Glasair Super IIS RG airplane, N8162H, lost engine power and landed in a parking lot just short of Yuma Marine Corps Air Station/Yuma International Airport (NYL), Yuma, Arizona. The private pilot was not injured, and the airplane sustained substantial damage to the aft fuselage during the forced landing. The airplane was registered to Rich Airplanes LLC., and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The cross-country flight originated from Montgomery-Gibbs Executive Airport, San Diego, California, at 0942 Pacific daylight time and destined for Marana Regional Airport, Marana, Arizona.

The pilot stated that he completed a preflight inspection prior to departure, and the airplane performed appropriately during the runup. The departure and climb were uneventful, and after reaching 9,500 ft mean sea level, he configured the airplane for cruise. About 35 minutes later the airplane's multifunction display indicated an "electrical problem, check voltage" alert. He noticed that the airplane's main battery was not charging, and that the alternator field toggle switch/circuit breaker had tripped off, but the alternator circuit breaker was still in. He reset the toggle switch, and the battery began to charge again, and all systems appeared normal. About 5 minutes later, the display indicated the same warning, and the toggle switch again tripped. He cycled the switch and the battery started to charge again.

About 2 minutes later he noticed that the engine manifold pressure was beginning to drop along with the airplane's airspeed. He stated that the fuel flow, fuel pressure, and oil pressure appeared normal, and he could not discern an appreciable reduction in cylinder head or exhaust gas temperatures (CHT, EGT). He selected an alternate fuel tank, turned on the auxiliary electrical fuel pump, and adjusted the throttle, with no change, and by now the multifunction displayed indicated the engine was producing 30% of its rated power.

The pilot declared an emergency with Yuma Radar Approach Control and was provided a local control frequency for NYL. He stated that the engine was still producing partial power when the local tower controller cleared him for an emergency landing on runway 17, and then changed the clearance to runway 21L, which was longer. The pilot stated that he was too high to land, so performed a 360° turn at the north end of the runway, but during the turn the engine lost all power, and the airplane landed short.

The airplane's multifunction display system was a Dynon SkyView Touch, which was configured to record an array of airframe and engine parameters, including main bus voltage. Examination of the recorded data revealed a voltage drop from 14.3 to 12.9 volts at 1017 and 1021, consistent with the pilot's recollection. The drops lasted 20 and 30 seconds respectively, after which normal voltage and current draw was restored. All other engine parameters remained unchanged during the excursions.

Forty seconds after the last voltage drop was restored, the manifold pressure decreased from 21 to 10 inches of mercury and the fuel flow from 10 to 4 gallons per hour (gph). A few seconds later the EGT and CHT's began to decrease. The manifold pressure and fuel flow remained steady for the next 9 minutes, following which they dropped to 7 inches of mercury and 0.7 gph respectively. The data ended about 3 minutes later.

The airplane was equipped with a fuel-injected XP series IO-361-J1HD2 engine, manufactured by Superior Air Parts. The engine was installed new on April 1, 2018, and a condition inspection was completed on April 24, 2018 before the first flight with the engine. At the time of the accident, the engine had accumulated about 91 hours of flight time since installation. Maintenance records indicated that during the period between the engine installation and accident, maintenance events were limited to routine oil changes, magneto timing adjustments, replacement of EGT and CHT probes, and the installation of a replacement alternator.

Postaccident examination of the engine revealed that the throttle linkage had detached from the throttle arm of the fuel injection servo. The rod end bearing (Heim joint) for the linkage, and the throttle arm were intact and undamaged, but the connecting bolt and its associated washers, castellated nut and cotter pin were not present (Photo 1). The butterfly valve within the throttle body was in the closed position, and the throttle lever in the cabin was in the full forward, "open" position.