COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/61 Alternate Static Source Valve Inspection 3/98 DM Applicability: All Cessna Model 172R Aircraft with the following serial numbers: 17280003 through 17280171 inclusive; 17280173 through 17280175 inclusive; 17280177 through 17280179 inclusive; 17280182 through 17280184 inclusive; 17280186, 17280189, 17280190, 17280192 through 17280212 inclusive; 17280214, 17280216 through 17280221 inclusive; 17280214, 17280216 through 17280221 inclusive; 17280223 through 17280236 inclusive; 17280239 through 17280251 inclusive; 17280253 through 17280263 inclusive; 17280265, 17280268, 17280270 through 17280272 inclusive; and 17280283, 17280297, and 17280301 inclusive. Requirement: 1. Fabricate placards with the following words, using letters at least 3mm (1/8-inch) in height, and install these placards in the cockpit within the pilot's clear view: 1. 'IFR operation is prohibited.' b. 'Use of the alternate static air source is prohibited.' 2. Inspect the alternate static air source valve to assure that the alternate static air source valve is not restricted by the identification placard and to assure that the valve body does not separate from the valve flange in accordance with Cessna Service Bulletin No. SB97-34-02, Revision 1, dated December 22, 1997. 3. If the alternate static air source valve is restricted, rework the alternate static air source assembly in accordance with Cessna Service Bulletin No. SB97-34-02, Revision 1, dated December 22, 1997. 4. If the valve body separates from the valve flange, replace the alternate static air source assembly in accordance with the maintenance manual. Note: FAA Priority Letter AD 98-01-01. Compliance: 1. Prior to further flight, after the effective date of this AD. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES 2. Within the next 100 hours time-in-service (TIS) after the effective date of this AD or the 21st May 1998, whichever occurs first. Accomplishment of the applicable parts of Requirement 2 is terminating action for the placard requirements detailed in Paragraph 1 if no fault is found. 3. Prior to further flight after the inspection detailed by Requirement 2 of this AD. Rework of the alternate static air source assembly is terminating action for the placard requirements detailed in Paragraph 1. 4: Either: 1. Prior to further flight to eliminate the operating limitations required by the placards in paragraph 1; or b. Within the next 25 hours time in service after the inspection provided the operating limitations required by the placards in Paragraph 1 of this AD are adhered to. This airworthiness directive becomes effective on 21 January 1998. Background: The FAA has received reports from Cessna about the improper installation of the identification placard on the alternate static source. The placard was installed on the valve body in a location that covers the external orifice, which is the inlet for static air reference into the valve. If these assemblies are not corrected selection of alternate static air source will cause the altimeter, airspeed and vertical speed indicators to display erroneous indications.