Accident Details
The airline transport pilot of a multiengine airplane fueled the main (inboard) fuel tanks to capacity before a cross-country flight. As the flight approached the destination airport, an air traffic controller instructed the pilot to turn right for a visual approach, and the pilot acknowledged. Subsequently, the pilot reported that he might have to land on a highway. The airplane impacted a marsh area about 15 miles from the destination airport.
Engine and Propeller Findings
Review of data from an onboard engine monitor revealed that the right engine momentarily lost and regained power before experiencing a total loss of power. Examination of the wreckage showed that the left propeller was feathered and the right propeller was in the normal operating range. Sufficient fuel to complete the flight was drained from the left wing fuel tanks. The right wing fuel tanks were compromised during the impact, but sufficient fuel was likely present in the right main fuel tanks before impact because both main tanks were fueled to capacity concurrently before the flight; however, it likely was in a low fuel state due to fuel used during the flight.
Maintenance and Fuel System Issues
The right wing main fuel tank was not equipped with a flapper valve, which should have been located on the baffle nearest the wing root where the fuel pickup was located. The flapper valve traps fuel near the pickup and prevents it from flowing outboard. Maintenance records did not indicate that the right main fuel tank bladder had been replaced; however, the manufacture year printed on the bladder was about 20 years before the accident and 16 years after the manufacture of the airplane, indicating that the bladder had been replaced at some point. When the bladder was replaced, the flapper valve would have been removed. Based on the evidence, it is likely that maintenance personnel failed to reinstall the flapper valve after installing the new fuel bladder. This missing valve would not affect operation unless the tank was in a low fuel state, when fuel could flow outboard away from the pickup (such as in a right turn, which the pilot was making when the engine lost power), and result in fuel starvation.
Pilot Toxicology and Actions
Toxicology testing of the pilot revealed that his blood alcohol level during the flight was likely between 0.077 gm/dl and 0.177 gm/dl, which is above the level generally considered impairing. It is likely that, during the right turn, fuel in the right main tank moved outboard, causing fuel starvation to the right engine. When the right engine lost power, the pilot should have secured it by feathering the propeller to reduce drag; however, given the position of the propellers at the accident site, the pilot likely incorrectly feathered the operating (left) engine, rendering the airplane incapable of maintaining altitude. It is very likely that the pilot's impairment due to alcohol ingestion led to his errors.