Rock Springs, WY, USA
N49DS
PIPER PA-28-235
After an uneventful cross-country flight, the pilot initiated the landing descent by reducing engine power. As the airplane approached the airport's base leg, he performed the landing checklist, which included switching the fuel selector valve to the left tip tank. As the airplane turned from the base to final leg, it descended too low, and he applied full engine power. The engine did not respond, and a few seconds later lost all power. With limited altitude to complete a thorough emergency check, he performed a forced landing into rough terrain. During the landing sequence, the airplane struck a fence and berm, sustaining substantial damage to both wings. Following the accident, the pilot expressed concern that he may have inadvertently starved the engine of fuel during the approach, by turning the fuel selector valve beyond its left tip tank travel limit, and to the OFF position. The airplane's fuel selector lever was fitted with an interlock mechanism, which was designed to prevent the pilot from inadvertently shutting off the fuel in this manner. Examination revealed that the mechanism had shifted, such that the fuel selector lever could be moved to a position in-between the left tip tank, and OFF detent without engaging the interlock, therefore possibly resulting in an interruption of fuel flow to the engine. Data extracted from the engine monitor, as well as the minimal quantities of fuel recovered from the fuel system components within the engine compartment, were consistent with a fuel starvation event. A postaccident examination of the engine and successful engine run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
HISTORY OF FLIGHT On January 18, 2013, about 1300 mountain standard time, a Piper PA-28-235, N49DS, collided with a fence during a forced landing in Rock Springs, Wyoming. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The private pilot was not injured, and the airplane sustained substantial damage during the accident sequence. The cross-country flight departed Gillette-Campbell County Airport, Gillette, Wyoming, about 1110 with a planned destination of Rock Springs-Sweetwater County Airport, Rock Springs. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that after initiating a descent from 12,500 feet, he approached the right base for runway 27 at Rock Springs Airport. During the approach, he switched the fuel selector valve to the left tip tank, and turned on both the carburetor heat and auxiliary fuel pump. During the turn from right base to final, the airplane descended too low, and he applied full engine power. The engine did not respond, and a few seconds later lost all power. He subsequently elected to land the airplane in rough terrain ahead. During the landing sequence, the airplane struck a fence and berm, sustaining substantial damage to both wings. The pilot expressed concern that he may have inadvertently starved the engine of fuel during the approach, by turning the fuel selector valve beyond its left tip tank travel limit, and over to the OFF position. He stated that after the engine lost power, he performed a cursory check of emergency items, but did not reach down to check the fuel selector valve, for fear that he may become disoriented, and stall the airplane. He could not specifically recall the position of the valve after the accident, but confirmed that he switched it to the OFF position while securing the airplane on the ground. A fuel receipt recovered from Fligthline Incorporated of Gillette, indicated that the he purchased 27.3 gallons of fuel for the airplane the day prior to the accident. He stated that this fuel purchase resulted in a total of 64 gallons of fuel onboard. ADDITIONAL INFORMATION The FAA approved airplane flight manual and pilot's operating manual, did not prohibit the use of tip tanks during landing, stating that their total capacity is useable, and that for approach and landing the selector valve should be set to the "Proper Tank." TESTS AND RESEARCH Fuel Selector Valve The airplane was equipped with a combination fuel selector valve/fuel drain, located underneath the cabin floor, just behind the forward right seat. The valve was connected to a selection lever in the center console in the forward cabin. During the examination, the valve was moved through its entire travel range, and appropriate friction was felt within the detents at each tank position. The selection lever was equipped with an override button (interlock) between the left tip, and OFF positions, which was designed to prevent the pilot from inadvertently turning the valve to the OFF position in-flight. During testing of the valve, it was noted that the lever could be moved midway between the OFF and left tip detents before the button prevented further movement. Engine and Airframe Examination The left tip tank was ruptured during the accident sequence, and as such an accurate assessment of its fuel quantity could not be made. The engine sustained minimal damage, exhibiting primarily crushing of the lower cowling and induction airbox. All the fuel lines forward of the firewall were intact, and contained residual droplets of fuel. About 1/2 ounce of blue-colored fuel was present within the combination fuel selector valve/fuel drain, and about 3 tablespoons of fuel was drained from the carburetor at its bowl plug. The fuel line from the left tip tank through to the selector valve was examined, and was free of obstruction. An external engine examination was performed, and no anomalies were noted that would have precluded normal operation. Engine Test Run The airplane was connected to a fuel source via the left tip tank inlet at the selector valve. The engine was subsequently started, and operated at varying speeds for a period of about 5 minutes. During that time, the engine operated smoothly throughout its speed range, with a nominal speed drop observed during a magneto check. Engine Monitor The airplane was equipped with a JP Instruments EDM 730 engine data monitoring system. The EDM 730 was configured to record engine exhaust (EGT) and cylinder head (CHT) temperatures, fuel flow, fuel used, and battery voltage at 6-second intervals. The data from the accident flight was downloaded and examined. For the majority of the flight, EGT and CHT values remained relatively constant, with a fuel flow of between 12 and 15 gph (gallons per hour). About 5 minutes before the recording ended, the data indicated a reduction in fuel flow to 9 gph, with a corresponding decrease in EGT from 1,400 to 1,250, and CHT from 325 to 285 degrees Fahrenheit (F). The reduced temperatures and fuel flow were consistent with the pilot initiating a reduction in engine power for descent. About 45 seconds before the recording ended, the fuel flow increased to 15 gph, and the EGT exhibited a spike in temperature of about 100 degrees. Shortly thereafter, the fuel pressure dropped to zero, and the CHT to fell to 500 degrees.
The pilot's inadvertent movement of the fuel selector valve beyond its tank detent, which resulted in a total loss of engine power due to fuel starvation. Contributing to the accident was the failure of the fuel selector interlock mechanism.
Source: NTSB Aviation Accident Database
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