The U.S. FAA has issued a Special Airworthiness Information Bulletin to alert owners, operators and maintenance personnel of Cessna 172R, 172S, 182S, 182T, 206H and T206H airplanes. These aircraft may have been equipped from the factory with oil pressure switches bearing the part number 83278, or they may have been supplied as spares.
This oil pressure switch is used to supply information to a warning annunciator on pre-Garmin G1000-equipped planes and the annunciator on the primary flight display of G1000-equipped planes. It is also used to drive the Hobbs hour meter on all the above-mentioned planes. Oil pressure gauges are not affected as they are driven by a separate transducer.
These switches have been subject in the past to an airworthiness directive (AD2013-11-11) where a life limit of 3000 hours of time in service (TIS) was specified. The existing AD remains in effect. However, the FAA is considering additional AD action based on their investigation of recent events.
In seven recent events, premature oil pressure switch failures led to oil leaks around the switch housing, which could lead to oil leaking onto the aircraft’s windshield and obscuring vision, or to the loss of engine oil, resulting in engine failure.
The FAA is recommending that operators of the affected aircraft become aware of the issue, be alert to oil residue on or around the forward fuselage upper cowling or the windshield, and inspect the switch housing for the presence of any oil or wrench marks that might indicate over-torqueing of the switch.
The FAA recommends that corrective action be taken before further flight should any of the conditions outlined above be observed. They also recommend that switch be replaced after 1000 hours TIS.
The complete bulletin is available below for viewing.CE-19-01