PILOTS: Ensure Your Fuel Selector Works.
Worn components can lead to fuel starvation and sudden loss of engine power
The problem
- Worn fuel selectors have led to fuel starvation and loss of engine power, resulting in serious and fatal injuries.
As fuel selectors wear, the fuel selector handles may be difficult or even impossible to turn. If a pilot applies too much force, the internal components can fracture and obstruct the fuel flow, resulting in a total loss of engine power.
In addition, worn detents could make it difficult for a pilot to properly position the fuel selector to the desired tank. Positioning the fuel selector incorrectly to an empty tank or in between tanks could ultimately starve the engine of fuel.
Related accidents
Since 2008, the National Transportation Safety Board (NTSB) has cited the fuel selector in 104 accidents; 63 of those accidents involved incorrect use/operation of the fuel selector, and 28 cited degraded function of the fuel selector. Typically,
these types of accidents result in fuel starvation and loss of engine power.
During the initial climb after a touch-and-go landing in a
Piper PA-38-112, the flight instructor reported an emergency
and indicated that he would return to the airport.
The airplane then spun to the left and impacted a marsh.
The airplane was destroyed (figure 1); the flight instructor
sustained serious injuries, and the student pilot died.
Although the fuel selector handle was positioned to the
right main fuel tank, an insert in the fuel selector had
fractured into multiple pieces that showed overstress
and wear (figure 2, next page). The fuel selector handle
likely had been difficult to move for some time, and excessive
force would have been required to move the handle
from one position to another, thus causing the wear.
The failure of the fuel selector valve in a position that restricted fuel flow to the engine led to the total loss of engine power due to fuel starvation. The operator failed
to detect and resolve the wear of the fuel selector valve.
The pilot of a Mooney M20 airplane reported that, during
the initial climb from the airport, he noted the engine
power slowing, turned on the boost pump, checked the
magnetos and fuel mixture, and then attempted to switch
the fuel selector to the other fuel tank, which had usable
fuel. The engine experienced a total loss of power, and
the airplane impacted the ground. A passenger sustained
minor injuries, and the pilot and another passenger were
uninjured. The fuel selector handle screw was loose
and prevented the fuel selector from moving to the fuel
tank position for the tank with usable fuel, resulting in
fuel starvation and the subsequent total loss of engine
power (see figure 3). (GAA17CA260)
A witness observed the pilot of a Piper PA-28-140
airplane perform an engine run up, and two witnesses
reported that the takeoff sounded normal. However, after
they did not hear the airplane continue around the airport
traffic pattern, one of the witnesses located the wreckage
at the end of the runway and saw that fuel was flowing
out of the wing area. The airplane was substantially
damaged when it collided with trees and terrain (figure
4), and the private pilot died. Although the fuel selector
valve handle was in the right tank position at the time
of the accident, testing of the valve with air indicated
that the valve was closed. The selector valve was stiff
to rotate, and positive engagement of the detents could
not be consistently obtained. Disassembly of the valve
revealed rotational scoring in the valve and on the plug
cock, which had heavily worn detents (figure 5). Debris
was also found in the valve and was the result of excessive
wear. Both the owner, who was also the operator,
and maintenance personnel stated that they checked the
fuel selector valve during an annual inspection that was
completed about 11 hours before the accident. The total
loss of engine power after takeoff occurred due to
fuel starvation as a result of excessive wear of the fuel
selector valve. Also causal was the owner/operator and
maintenance personnel's inadequate maintenance and
inadequate postmaintenance inspection. (ERA15FA128)
What can pilots do?
- Check the fuel selectors for proper operation during your preflight
assessment, ensuring that the fuel selector moves freely and stays in the
correct detent when selected and that fuel selector placards are accurate
and legible. - Do not force a handle that is difficult to turn; it could lead to fractured
components inside the fuel selector that may prevent proper operation. - Do not fly if your fuel selector exhibits any of the following:
• Sticking and binding,
• Requires greater-than-average pressure to turn or move, or
• Worn detents that do not stop the selector in the desired position.
- If you encounter any problems with the proper operation of the fuel selector,
do not attempt the flight. Report the anomaly to maintenance personnel for
inspection or repair.
Be informed and review and comply with any applicable airworthiness
directives and service bulletins regarding the fuel selector and components.
Interested in more information?
The Federal Aviation Administration’s (FAA) Airplane Flying Handbook, FAA-H-8083-3B, Chapter 2, “Ground Operations,” page 2-3, contains tips for pilots performing preflight assessments, including checking the fuel selectors for proper operation in all positions, including the OFF position. The handbook notes that “[s]tiff fuel selectors or where the tank position is not legible or lacking detents are unacceptable.” In addition, your airplane flight manual/pilot operating handbook will also likely include instructions in the preflight checklist regarding checking the fuel selector valve.
FAA Special Airworthiness Information Bulletin (SAIB) CE-14-22, “Fuel Selector/Shut-Off Valve,” alerts owners and operators of certain Piper model airplanes that the fuel selector valve may bind when switching fuel tanks and can cause a loss of power in flight. To reduce the possibility of binding in flight, the SAIB recommends inspection and maintenance of fuel selector valves.
The Experimental Aircraft Association article “Avoiding Fuel Related Problems” indicates that fuel problems can occur due to malfunction or failure of a fuel system component or poor preventative maintenance and cites situations with fuel selector handles that were difficult to turn.
A companion video to this safety alert can be accessed from the Safety Alerts web page.
The reports for the accidents referenced in this safety alert are accessible by NTSB accident number from the Aviation Accident Database link, and each accident’s public docket is accessible from the Accident Dockets link for the Docket Management System.