History of Flight
On May 7, 2016, at about 1655 mountain standard time, a Beechcraft G35 Bonanza airplane, registration N4401D, sustained substantial damage during a forced landing following a loss of engine power near Surprise, Arizona. The flight instructor was fatally injured, and the private pilot receiving instruction was seriously injured. The airplane was registered to a private individual and was operated by the flight instructor under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed. The maintenance test/instructional flight departed Glendale Municipal Airport (GEU), Glendale, Arizona, about 1630.
According to a statement from a Federal Aviation Administration (FAA) inspector who interviewed the pilot, the purpose of the flight was an instructional check flight. The pilot reported that an "engine confidence check" was performed before departure, with no anomalies noted. The flight took off, completed one circuit in the traffic pattern, and radar data indicated they then departed to the northeast. The pilot reported that the flight was normal until they "experienced no response from the throttle control." The pilots followed the checklist, but the engine remained at idle. They attempted to land at an auxiliary field but realized they would not make it and elected to turn "to brush off some speed (by hitting about 25-ft to 40-ft trees), before smashing into a very large pine tree."
Radar data indicated that, about 10 miles north of GEU, at about 3,725 ft, the airplane began a descent and made a 180° right turn followed by a 270° left turn and continued to descend, before making another 180° turn to the right. The last radar return was located about 0.15 mile southeast of the accident site, at about 1,450 ft.
A witness who observed the airplane descending over a parking lot stated that the airplane appeared low, slow, and quiet. The airplane then disappeared behind a building and subsequently impacted trees in a residential area. Multiple residents near the accident site heard the impact and alerted first responders.
Personnel Information
The flight instructor, age 31, held a commercial pilot and a flight instructor certificate, both with airplane single-engine land and airplane multi-engine land ratings. He held a first-class airman medical certificate issued on January 26, 2016, with the limitation "not valid for any class after July 31, 2016." At the time of his last medical examination, he reported 900 hours total flight experience, of which 25 hours were in the last 6 months.
The pilot receiving instruction, age 32, held a private pilot certificate with an airplane single-engine land rating. He held a first-class airman medical certificate issued on October 28, 2014, with no limitations. At the time of the medical examination, he reported 11 hours total flight experience.
Aircraft Information
The four-seat, single-engine, low-wing, retractable landing gear airplane, serial number D4599, was manufactured in 1956. It was powered by a Continental Motors E-225-8 engine, serial number 40062D, rated at 225 horsepower, and equipped with a Hartzell two-bladed adjustable-pitch propeller. Maintenance records showed that the most recent annual inspection was completed February 5, 2016, at a total airplane time of 5,968.69 hours. At that time, the engine had accumulated 1,677.47 hours since its most recent major overhaul.
The most recent maintenance was performed on April 21, 2016, at a tachometer time of 1,520.9 hours; the tachometer time at the accident was 1,521.31. The logbook entry stated: "Removed and Re-installed carburetor after repair, see 8130. All work done referencing Continental E225 maintenance manual." This entry was signed by an airframe and powerplant (A&P) mechanic.
In an interview with the National Transportation Safety Board investigator-in-charge, the A&P mechanic who installed the carburetor stated that the person who removed the carburetor left all hardware "really nicely," making installation easier. He added that he performed the installation by following the engine maintenance manual.
A fuel receipt showed the airplane was fueled with about 30 gallons of 100LL aviation fuel at 1602 on the day of the accident.
Meteorological Information
At 1658, the weather reporting facility at Luke Air Force Base (LUF), located about 5 miles south of the accident site, reported wind 340° at 5 knots, visibility 10 miles, few clouds at 12,000 ft above ground level, temperature 25°C, dew point 5°C, and an altimeter setting of 29.82 inches of mercury.
Wreckage and Impact Information
The initial impact point (IIP) was identified by several broken tree branches partially attached to a eucalyptus tree about 30 ft above ground level. The next impact was a large pine tree about 100 ft on a magnetic heading of about 242° from the eucalyptus tree. The fuselage came to rest inverted about 30 ft from the pine tree, and the wings and empennage separated from the fuselage. All major components were accounted for at the accident site.
During the on-scene examination, the carburetor throttle cable was found detached from the throttle body linkage. The bolt and castellated nut used to secure the throttle cable to the throttle body were found lying separately in the engine cowling; there was no evidence of a cotter pin, which should have been used to secure the nut on the bolt. Initial examination showed no evidence of thread stripping, and neither the bolt nor nut was fractured.
Medical and Pathological Information
The Maricopa County Coroner, Phoenix, Arizona, conducted an autopsy on the flight instructor. The medical examiner determined the cause of death as "multiple blunt force injuries."
The FAA's Bioaeronautical Sciences Research Laboratory performed toxicology tests on the flight instructor. The following drugs were detected: unspecified amounts of citalopram in liver; 1.995 (ug/ml, ug/g) ketamine in liver; 1.446 (ug/ml, ug/g) ketamine in blood; unspecified amounts of midazolam in liver and blood; 1.618 (ug/ml, ug/g) norketamine in liver; and 0.405 (ug/ml, ug/g) norketamine in blood. Review of medical records indicated that midazolam and ketamine were administered as part of resuscitation attempts following the accident. Citalopram is an antidepressant medication available by prescription; while not generally considered impairing, underlying depression can be cognitively impairing.
Tests and Research
On December 14, 2016, the carburetor was examined, partially disassembled, and bench tested by NTSB investigators. The carburetor exhibited impact damage to the mixture control arm and the bottom of the carburetor scoop. The mixture and throttle controls moved freely from stop to stop. The fuel inlet screen and fuel strainer assembly were free of debris.
The bench test indicated that the flow rates on 9 of the 11 test points were about 3 pounds per hour lower than the lower limit specified in the test parameters. According to the manufacturer, the low readings would have had minimal impact on the engine's ability to produce power.