JUNEAU, AK, USA
N9120M
CESSNA 206
THE PILOT WAS PREPARING FOR LANDING AND HE POSITIONED THE FUEL SELECTOR ON THE FULLEST FUEL TANK. THE ENGINE STOPPED PRODUCING POWER AND HE PLACED THE AUXILIARY FUEL BOOST PUMP SWITCHES IN THE ON, 'HI AND MAX HI,' POSITIONS. BOTH SWITCHES REMAINED IN THE ON POSITION. EXAMINATION OF THE SWITCH SHOWED THAT THE SPRING LOADED SIDE OF THE ROCKER SWITCH WAS NOT SPRING LOADED AND WOULD CONTINUE TO PROVIDE 'MAX HI' PRESSURE. THE OPERATOR'S MANUAL STATES THIS WILL FLOOD THE MANIFOLDS IF LEFT ON, WITH THE MASTER SWITCH ON, AND THE ENGINE NOT OPERATING.
On August 5, 1994, at 1100 Alaska daylight time, a wheel equipped Cessna 206 airplane, N9120M, registered to and operated by Richard H. Levitt, Gustavus Dray Inc., of Gustavus, Alaska, experienced a power loss and subsequent forced landing in a field located 1 mile northwest of the Juneau Airport, Juneau, Alaska. The personal flight, operating under 14 CFR Part 91, departed Gustavus and the destination was Juneau. Visual meteorological conditions prevailed and no flight plan was filed. The Private Certificated Pilot and the three passengers were not injured and the airplane was substantially damaged. According to the pilot he was listening to the ATIS information when he switched fuel tanks from the left tank to the right tank. The engine stopped producing power and continued to windmill. He landed in a field and the airplane nosed over. The airplane was recovered from the field and the engine was set up for a test run. The engine started and ran with the fuel selector positioned for either tank. The engine ran for 25 to 26 minutes without failure. However, full power could not be achieved due to the amount of damage to the airplane. Further examination of the engine fuel system and airplane fuel system revealed that the fuel boost pump switch did not operate properly. The operator's manual describes the Auxiliary fuel pump switch as a "split rocker type; the right half positions are "HI," "LO" and off and the left positions are "MAX HI" and off. The right half of the switch incorporates an intermediate "LO" position used for normal starting, and a "HI" position (when the top of the switch is fully depressed) for vapor purging during hot engine starts. Maximum fuel flow is produced when the left half of the switch is held in the spring-loaded "MAX HI" position. In the "MAX HI" position, an interlock within the switch automatically trips the right half of the switch to its "HI" position. When the spring-loaded left half of the switch is released, the right half will remain in the "HI" position until manually returned to the off position...." "....With the right half of the switch in the "HI" position, the pump operates at one of two flow rates that are dependent upon the setting of the throttle. With the throttle open to a cruise setting, the pump is operating at a high capacity to supply sufficient fuel flow to maintain flight. When the throttle is moved toward the closed position (as during letdown, landing and taxiing), the fuel pump flow rate is automatically reduced, preventing an excessively rich mixture during these periods of reduced engine speed." "If it is desired to completely exhaust a fuel tank quantity in flight, the auxiliary fuel pump will be needed to assist in restarting the engine when fuel exhaustion occurs. Therefore, it is recommended that proper operation of the auxiliary fuel pump be verified prior to running a fuel tank dry by turning the auxiliary fuel pump on momentarily and checking for a slight rise in fuel flow indication. To ensure a prompt engine restart in flight after running a fuel tank dry, immediately switch to a tank containing fuel at the first indication of fuel pressure fluctuation and /or power loss. Then place the right half of the auxiliary fuel pump switch in the "HI" position momentarily (3 to 5 seconds) with the throttle at least 1/2 open. Excessive use of the "HI" position at high altitude and full rich mixture can cause flooding of the engine...." "If the auxiliary fuel pump switch is accidentally on "HI" (with master switch on) with the engine stopped, the intake manifolds will be flooded." Examination of the auxiliary fuel boost switch showed that both switches, when placed in the on, "HI" and "MAX HI" position, would remain in the on position. The left side rocker switch was not spring loaded. The "LO" position did not provide and fuel pressure and the "HI" and "MAX HI" position provided the correct pressure. According to the pilot, he had just selected the most full fuel tank for landing. He stated, he did not run the fuel tank dry before switching to the "right" fuel tank. The engine stopped producing power. He selected the boost pump "both sides on," but was unable to restart the engine. The pilot stated that "both sides on" meant that he positioned both rocker switches in the "HI" and "MAX HI" position.
THE TOTAL LOSS OF POWER FOR UNDETERMINED REASONS. THE PILOT'S FAILURE TO FOLLOW THE PRESCRIBED PROCEDURE FOR THE USE OF THE AUXILIARY FUEL BOOST PUMP SWITCH, OPERATING THE AIRPLANE WITH A IMPROPERLY OPERATING SWITCH, AND THE LACK OF SUITABLE TERRAIN IN THE FORCED LANDING AREA.
Source: NTSB Aviation Accident Database
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