NTSB Safety Alert SA-076 - Mechanics Be Wary of Worn Fuel Selectors

HIGHWAY

MARINE

RAILROAD

PIPELINE

AVIATION

SAFETY

ALERT 076 September 2018

MECHANICS : Be Wary of Worn

Fuel Selectors

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.

Undetected wear of fuel selector components during required maintenance inspections could lead to fuel starvation. 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 emer -

gency 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 instruc -

tor 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 ex -

cessive force would have been required to move the han-dle from one position to another, thus causing the wear.

Figure 1. Photograph of accident airplane. The failure of the fuel selector valve in a position that

2 / NTSB Safety Alert 076 / September 2018restricted 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. (ERA17FA112 )

Figure 2. Fuel selector

valve housing and section of selector handle (above) and fuel selector insert with fractured pieces (right).

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 )

Figure 3. Photograph of fuel selector.

(Source: FAA) 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 wreck -

age at the end of the runway and saw that fuel was flow-ing 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 exces -

sive 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 to-tal 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 )

Figure 4. Photograph of accident airplane.

Figure 5. Plug cock showing discoloration, scoring, wear, debris, and a worn detent.

NTSB Safety Alert 076 / September 2018 / 3

What can mechanics do?

Inspect fuel selectors according to the airplane

maintenance manual, checking the operation, condition, and security of the fuel selector.

Ensur e that stops or detents for the fuel selector valve

position the valve properly.

Ser vice or replace any worn components, as necessary,

according to the airplane maintenance manual and check your work to ensure accuracy.

Be informed and review and comply with any applicable

airworthiness directives and service bulletins regarding the fuel selector and components.

4 / NTSB Safety Alert 076 / September 2018Interested in more information?

Federal Aviation Administration (FAA) Advisory Circular

43-13-1B , “Acceptable Methods, Techniques, and

Practices—Aircraft Inspection and Repair,” provides specific information for mechanics about inspecting tank selector valves, including checking the operation of the handle, ensuring smooth movement, ensuring positive action for stops and detents, and checking for wear that could prevent the valve from positioning accurately.

In addition, the FAA’s Aviation Maintenance Technician

Handbook—Airframe provides basic information on

principles, fundamentals, and technical procedures relating to the airframe and specifically discusses fuel selectors in chapter 14, “Aircraft Fuel System.”

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.Refer to the airplane maintenance manual and airplane manufacturer for instructions about suggested inspec -

tions and maintenance of the fuel selector valve as part of the 100-hour or annual inspection.

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 Dock ets

link for the Docket Management System.

The NTSB’s Aviation Information Resources web page, www.ntsb.gov/air ,

provides convenient access to NTSB aviation safety products. This Safety

Alert and others can be accessed from the Aviation Safety Alerts link at

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The NTSB is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—highway, marine, railroad, and pipeline. The NTSB determines the probable cause of the accidents and issues safety recommendations aimed at preventing future accidents. For more information, visit www.ntsb.gov .