NTSB Factual Report

On August 20, 2018, at 0620 central daylight time, a Beech B36TC single-engine airplane, N6860W, was destroyed when the engine lost power and the pilot made a forced landing in a wooded area 1/4-mile southeast of La Porte Municipal Airport (T41), La Porte, Texas. The airplane was registered to and operated by RD Airways, Channelview, Texas, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed for local flight. The flight was originating from T41 at the time of the accident.

The pilot reported that after taking off and starting a climb, the airplane began to make a "weird very loud sound and the engine started to lose power." The pilot verified the throttle, mixture, and propeller controls were full forward. The engine noise "started getting louder and power was almost gone." When the pilot activated the auxiliary fuel pump, the engine "just got real loud and sounded very deep. I knew I was descending." The airplane continued to descend, and the pilot made a forced landing near a housing development on unsuitable terrain. Both wings were separated from the airplane. The pilot was not injured.

A Federal Aviation Administration (FAA) inspector examined the airplane, and reported "the exhaust section looks like it had been having some issues for a while. Also disturbing is the v-band clamp condition." He also stated an Airworthiness Directive (A.D. 2018-06-11) had been issued in June 2018. That AD added a life limit to the exhaust tailpipe v-band clamp that attaches the exhaust tailpipe to the turbocharger and requires an annual visual inspection of the exhaust tailpipe v-band coupling (clamp).

The engine was sent to Continental Motors, Mobile, Alabama, where, on March 13, 2019, it was functionally tested under the oversight of an FAA inspector. The engine performed with no anomalies. According to Continental Motors, the v-band may have been loose enough to allow manual rotation of the turbo outlet collar. A hose used to connect the aftermarket intercooler was oil-soaked and did not appear to be freshly torn. If the hose failed in flight, manifold pressure would have immediately dropped and the "weird" sound could have been turbo discharge pressure escaping through the tear. When the engine lost turbo pressure, the fuel pump would have continued to operate with a much richer mixture, not sensing the loss of induction pressure to the engine. When the pilot turned on the auxiliary fuel pump, the engine would have been further flooded with excess fuel pressure.