Focus On Detented Fuel Selector Valve System
The FAA has issued a Special Airworthiness Information
Bulletin (SAIB) for some Cessna twin reciprocating engine powered
airplanes, and they say this issue may be applicable to other
airplanes that use a detented fuel selector valve system.
FAA records show that, during the fourth flight of the day, a
Cessna Model 402C experienced a total loss of engine power on both
engines due to several missed opportunities to detect, investigate,
and correct an apparent lack of detent positions in the fuel tank
selector valve system. This lack of detectable detents led to
failure of the fuel tank selector valve to move to the commanded
position. The condition was not identified by the pilot in command
during preflight and normal procedures or by maintenance personnel
during maintenance inspections.
The Cessna Pilots Operating Handbook and FAA Approved Airplane
Flight Manual consistently states to “Feel for Detent”
throughout the preflight, normal, amplified, and emergency
procedures sections of the POH/AFM. Additionally, the various
service and maintenance manuals require operational checks, which
include a “feel for the detents”, binding and smooth
operation, inspections and checks for condition, security and
servicing.
The maintenance manual also clearly states a Caution which
advises:
“If a definite detent is not present in each position,
the system is improperly adjusted."
Cessna 402 File Photo
The term “Service” is used consistently throughout
the Cessna documentation to convey a multi-faceted approach to
maintaining the airplane systems. Servicing may include the need to
perform tasks such as inspection, cleaning, and lubrication at
certain intervals as defined in the maintenance manual.
Additionally, FAA Advisory Circular 43.13-1B, Chapter 8, Section
2, Paragraph 8-34 offers the following guidance with respect to
fuel tank selector valves:
- “c. Selector Handles. Check the operation of each handle
or control to see that it indicates the actual position of the
selector valve to the placard location. Movement of the selector
handle should be smooth and free of binding. Assure that stops and
detents have positive action and smooth operational feel. Worn or
missing detents and stops can cause unreliable positioning of the
fuel selector valve.”
The FAA recommends that owners, operators, and maintenance
personnel thoroughly review, understand, and adhere to the
information published in the documentation provided by Cessna,
which addresses the need to evaluate the performance and identify
the service requirements to properly maintain the fuel tank
selector valve system.
At this time, this airworthiness concern is not an unsafe
condition that would warrant AD action under Title 14 of the Code
of Federal Regulations (14 CFR) part 39.