By MEG GODLEWSKI
When is the last time you checked the alternate static source on your Cessna Aircraft?
You may be doing it soon, to comply with a new Airworthiness Directive from the FAA. According to the FAA, 15 Cessna aircraft in the field were found to have alternate static air source valves obstructed by the static port part number identification placard.
The AD effects Cessna models ranging from C-172s through series 300 airplanes. It requires the removal of the placard if obstruction is found.
“The placard is a sticker that is on the outside of the valve that covers the port,” explained Ann Johnson, an aerospace engineer for the FAA. “When the placards were installed on the valve there were not clear instructions on where the placards should be placed.”
Aircraft owners are required to notify the FAA if they find the alternate static port blocked by the placard, “Just so we know that we have covered the effected aircraft,” said Johnson.
“This is actually the third AD for blocked static port valves. The two prior Airworthiness Directives were 98-01-01 and 2008-10-02. We found aircraft that fell outside those, which is why this new AD was issued.”
The AD covers aircraft manufactured between Jan. 1, 1993 to March 31, 2008.
The alternate static port is connected to the airspeed, altimeter and vertical speed indicators. The alternate static port is usually accessed by pulling a knob inside the cockpit that opens a hole, allowing the instruments to receive atmospheric input from inside the cockpit when the regular static ports, located outside the aircraft, are blocked.
Blocked static ports provide incorrect flight information that can lead to a loss of aircraft control.
The AD becomes effective on Jan. 5, 2009.
Comments on the AD and being accepted through Feb. 23, 2009. To submit comments: regulation.gov and follow the instructions.
For service information: cessna.com
For more information on the aircraft effected: