High-voltage air surface gap High-voltage surface gap High-voltage recessed surface gap Low-voltage shunted surface gap Insulator Terminal screw Upper shell Gasket Lower shell Gasket Coupling nut Sealing wire Cement Center electrode Figure 4-69.  Typical annular gap igniter plug. Figure 4-68.  Ignitor plugs. Inspection of the ignition system normally includes the  following: with turbine ignition systems can cause injury or death to  personnel coming into contact with the activated system. Tighten and secure as required and replace faulty components  and wiring. Secure, tighten, and safety as required. The following instructions are typical procedures suggested  by many gas turbine manufacturers. These instructions are  applicable to the engine ignition components. Always consult  the applicable manufacturer’s instructions before performing  any ignition system maintenance. The igniter can be checked by listening for a snapping noise  as the engine begins to turn, driven by the starter. Though  the following procedure is not common practice and should  only be used when the maintenance manual suggests it as  an alternative method, the igniter can also be checked by  removing it and activating the start cycle, noting the spark  across the igniter.  CAUTION: The high energy level and voltage associated  4-43 Ignition System Leads Check System Operation Repair •  Ignition lead terminal inspection; ceramic terminal  should be free of arcing, carbon tracking and cracks.  •  The grommet seal should be free of flashover and  carbon tracking.  [Figure 4-71]  •  The wire insulation should remain flexible with no  evidence of arcing through the insulation.  •  Inspect the complete system for security of component  mounting, shorts or high-voltage arcing, and loose  connections.  Removal, Maintenance, and Installation  of Ignition System Components