Plane & Pilot
Tuesday, April 10, 2012

Setting The Selector

In some aircraft, you have to be a contortionist to see where the fuel-tank selector is pointing

The airplane crashed about 6⁄10 of a mile beyond the runway, hitting a grass median between the lanes of a highway, then traveling across the two westbound lanes and coming to rest in a ditch.

Examination of the cockpit revealed the short end of the fuel selector handle that points to the tank selected was in the "off" range. During testing, no air could be blown through the valve when it was in the position in which it was found. The fuel-selector valve, handle, plastic shroud and guard were retained for further examination.

The pilot was 45 years old and held a private pilot certificate with an airplane single-engine land rating. His second class medical certificate was current. He had logged over 468 hours with 5.7 hours in the accident airplane.

Review of the maintenance records of the 1974 airplane revealed it had been signed off for an annual inspection on April 10, 2009, and a 100-hour inspection on August 12, 2009. The airplane total time at the time of the accident was approximately 6,003 hours. No record could be found of any maintenance involving the fuel selector valve. The manufacturer of the valve reported there's no required overhaul interval.

A pilot and mechanic who flew the accident airplane the day before reported that during their preflight the fuel tanks were within one inch of being full. They flew in the traffic pattern for only about a half-hour. They told investigators that flight was performed with the fuel selector positioned to the left tank, and it wasn't moved during or after the flight. A CFI with the operator visually looked into both fuel tanks before the accident flight departed, and noted the level of fuel in both was within two inches from the top of the tank.

An Airworthiness Directive from 1985 applicable to the accident airplane required modification of the fuel selector guard by installation of a "Selector Stop" and a decal with markings. Records indicated that the AD had been complied with during an annual inspection on December 13, 1985.

The fuel-selector valve has four detents, one each for the "left" and "right" positions, and two "off" positions. A one-piece handle attached to the fuel selector valve has a raised "arrow." The end of the handle with the raised arrow points to the desired fuel tank to supply fuel to the engine, or to one of the two "off" positions. The arrow is painted white, and the handle is painted red. A fuel-selector guard made of plastic surrounds the fuel-selector valve. The "selector stop" installed in accordance with the AD consisted of a stainless-steel spring to prevent inadvertent movement of the fuel selector to the "off" detent position. The fuel-selector guard did have three individual placards labeled "L Tank 26 Gal," "R Tank 26 Gal" and "off." The portion of the shroud beneath the lower edge of the fuel selector stop exhibited two green-line radial marks consistent with the positions of the left- and right-tank detents; however, the fuel-selector stop didn't exhibit continuation of either green line radial onto the full width of the stop, nor did the shroud exhibit continuation of the green-line radials above the upper edge of the stop. The shroud also didn't exhibit a red-line arc above the upper edge of the fuel selector stop between the green-line radials, nor did it have red arcs adjacent to the slots in the fuel selector guard.

The NTSB determined that the probable cause of this accident was the pilot's improper placement of the fuel-selector valve during takeoff, and his failure to maintain airspeed following a total loss of engine power resulting in an inadvertent stall. Contributing to the accident was the failure of maintenance personnel to detect the lack of proper markings on the fuel selector stop and fuel selector valve shroud at the last 100-hour inspection.


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