NTSB Factual Report

HISTORY OF FLIGHT

On August 12, 2015, about 0930 eastern daylight time, a Beech N35, N390Z, was destroyed when it impacted trees and terrain shortly after takeoff from Love's Landing (97FL), Weirsdale, Florida. The airline transport pilot and the pilot-rated passenger were fatally injured. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. An instrument flight rules flight plan was filed for the personal flight from 97FL to Page Field (FMY), Fort Myers, Florida.

According to a witness, the airplane took off from runway 36. At the departure end of the runway, there was a crossing runway, designated 9/27. The witness, who was a pilot working outside his home located near the departure end of runway 36, reported that airplanes using runway 9/27 would typically stay low during takeoff, while those taking off from runway 36 would typically climb at a relatively high angle to avoid airplanes using the crossing runway.

The witness had seen the accident airplane take off many times on runway 36 and use a high climb angle, but, on the day of the accident, when he expected to see the airplane climb above houses about halfway along the runway, he was surprised when he did not see it. When he finally saw the airplane at a point about 300 to 400 ft before the departure end of the runway, it was about 50 ft in the air, with landing gear retracted, and about level with the eaves of the houses lining the runway. The witness then lost sight of the airplane and subsequently heard two loud "bangs."

The witness further noted that the airplane's engine sounded normal until takeoff, when it then started to "stall" as if a cylinder was "missing." He also noted that, when he saw the airplane, it appeared to be flying in ground effect and that it was in slow flight with a high angle of attack.

PERSONNEL INFORMATION

The pilot, age 78, held an airline transport pilot certificate with airplane single-engine land and airplane multi-engine land ratings. He also held a flight instructor certificate with airplane single-engine, airplane multi-engine, and instrument airplane ratings, a ground instructor certificate, a flight engineer certificate, and a mechanic certificate (airframe and powerplant). He held a Federal Aviation Administration (FAA) third-class medical certificate with a restriction to wear corrective lenses.

A review of the pilot's personal logbook revealed that, as of the last recorded flight on August 9, 2015, he had logged about 10,545 hours, including 9,891 hours as pilot-in-command and 7,069 hours in single-engine airplanes. His most recent flight review was recorded on July 19, 2014.

AIRCRAFT INFORMATION

The four-seat, low-wing, retractable landing gear airplane was manufactured in 1961. It was powered by a 260-horsepower Continental IO-470-N reciprocating engine, which drove a Hartzell two-bladed, constant-speed propeller.

According to the maintenance logbooks, the airplane's most recent annual inspection was completed on July 15, 2015. At that time, the airframe total time was 6,663 hours. Based on pilot logbook entries, at the time of the accident, the airplane had accumulated about 5.5 hours since the last annual inspection.

METEOROLOGICAL INFORMATION

Leesburg International Airport (LEE), Leesburg, Florida, was located about 10 nm east-southeast of the accident site. The LEE 0853 weather observation included wind from 220° at 5 knots, visibility 10 statute miles, sky clear, temperature 28°C, dew point 24°C, and altimeter setting 30.01 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

The wreckage path began with broken tree branches about 40 ft up a tree, located about 355° true, and about 1,000 ft from the airport fence at the north end of the runway. The path continued at a downward angle of about 20° for about 130 ft to a ground impact mark containing the two-bladed propeller and spinner, which had separated from the engine crankshaft. One propeller blade exhibited "S" bending and blade twist signatures, and the other had relatively light twisting. Both blades exhibited leading edge burnishing and chordwise scratching.

About 10 ft beyond the propeller, the airplane was resting vertically against two trees, nose down, with the empennage bent over the fuselage. The right wing and the cabin area were consumed in a postcrash fire; there was no evidence of an inflight fire. The left wing and the right ruddervator exhibited tree impact marks.

All flight control surfaces were accounted for at the accident site, and control continuity was confirmed from the cockpit to the empennage and the wings.

The throttle and propeller controls were found full forward, and the mixture control was found pulled out about ½ inch as measured from the panel bulkhead. The fuel boost pump was found in the "ON" position. The pump switch did not appear to be impact-damaged and could be switched on and off without binding.

Engine crankshaft continuity was confirmed. Eleven of the 12 spark plugs were removed and examined. One plug was broken off in the cylinder and could not be removed. No anomalies were observed in the removed plugs. Five fuel injectors were examined and found to be internally clear of debris; one had molten metal around it and could not be removed.

The engine's throttle body metering unit was broken from its mount and was held onto the engine by fuel lines. The mixture control arm remained attached to the unit; however, when turned, it rotated on the shaft with no shaft movement. The throttle body metering unit was shipped to the manufacturer's facility for further examination.

MEDICAL AND PATHOLOGICAL INFORMATION

The Office of the Medical Examiner, District 5, Leesburg, Florida, performed autopsies of the pilot and pilot-rated passenger. The cause of death of the pilot was blunt force and thermal injuries, and the manner of death was accident. The cause of death of the pilot-rated passenger was multiple blunt force injuries, and the manner of death was accident.

The FAA's Bioaeronautical Research Sciences Laboratory, Oklahoma City, Oklahoma performed toxicology testing on specimens from the pilot and pilot-rated passenger.

Testing of the pilot identified 0.053 (ug/ml, ug/g) diphenhydramine in blood and diphenhydramine in urine. Ibuprofen was also detected in urine. Testing was negative for cyanide, ethanol, and major drugs of abuse, and 17% carbon monoxide was detected in blood.

Testing of the pilot-rated passenger identified cetirizine, quinine, and tolterodine in the liver and blood. Testing was negative for carbon monoxide, ethanol, and major drugs of abuse. Testing for cyanide was not performed.

TESTS AND RESEARCH

The engine's throttle body metering unit was examined on April 5, 2017, at the Continental Motors facility at Mobile, Alabama. The unit displayed fire and impact damage; the fire damage appeared to be greater on the mixture side of the unit than on the throttle side of the unit. The mixture and throttle control lever arms were secured to their respective shafts by attachment nuts. The attachment nuts were removed, and the spline areas of both arms were inspected. The internal splines of both arms were stripped, and brass material from the bronze arms was transferred to the external splines of the steel shafts.

The throttle and mixture control arms were manufactured from bronze. According to the engine manufacturer, both lever arms should have been replaced with stainless steel arms per Continental Motors Category 2 Critical Service Bulletin (CSB) CSB08-3C, dated March 14, 2008. The CSB was issued after reports that bronze mixture and throttle control arms were inadequately torqued and became loose, which could lead to a loss of engine control or engine power. A copy of the CSB is included in the public docket for this investigation.

NTSB Probable Cause

A partial loss of engine power during takeoff. The reason for the partial loss of power could not be determined due to the extensive fire and impact damage to the engine.