在维修活动中应执行三清点制度（）以确保工具管理的有效性

20.Install the valve and the correct gasket.

19.Make sure that the latch isfully engaged.

18.Holdthe cylinder tightly

17.Examine the seal for defects.

16.The control unit is installed aft of the cockpit.

15.Install the manifold

14.Documents must be readily revisable.

13.Deactivation/Reactivationprocedures for circuits,systems,units,etc,shall be included

12.The user of the schematicdiagram is the pilot

11.Corrosion can have many causes.