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How to install aircraft sparkplugs


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How to install aircraft sparkplugs

  1. 1. HOW TO INSTALL AIRCRAFT SPARK PLUGS STEP 1 <ul><li>When performing any inspection or maintenance on the powerplant, propeller or that requires turning on the master switch, or pulling the propeller through by hand; treat the propeller as if the ignition switch were on. DO NOT stand, nor allow anyone else to stand, within the arc of the propeller as a loose or broken wire or component malfunction could cause the propeller to rotate. </li></ul>
  2. 2. STEP 2 <ul><li>When you have finished viewing this tutorial, use the “CAPS” program found on the home page of Select the proper spark plugs for your aircraft. </li></ul>
  3. 3. STEP 3 <ul><li>Remove the necessary cowling to gain access to the spark plugs. </li></ul>
  4. 4. STEP 4 <ul><li>Hold the small hex nut on the ignition lead while turning the large hex nut on the spark plug. This prevents the lead from twisting and damaging the ignition lead. </li></ul>
  5. 5. STEP 5 <ul><li>CAUTION : Be careful not to touch the spark plug connector or harness spring with your fingers. Residual contamination could cause arcing in the terminal well and a resulting misfire. </li></ul><ul><li>Replace any parts that show signs of damage or wear. </li></ul><ul><li>After the ignition leads have been removed and before removing the spark plugs, inspect the terminal ends of the spark plug leads for damage and wear. </li></ul><ul><li>Clean the terminal ends with a fast drying solvent, such as acetone. </li></ul>
  6. 6. STEP 6 <ul><li>Now remove the spark plugs using a deep-socket wrench or equivalent. </li></ul><ul><li>CAUTION : Take a clean cloth and cover the spark plug holes in the cylinders. This prevents anything from falling into the cylinders. </li></ul>
  7. 7. STEP 7 <ul><li>Inspect the new spark plugs for damage before installing them. </li></ul><ul><li>Check that the spark plug gap is correct using a spark plug gap gauge. The correct gap setting is printed on a tag that comes with the plug. </li></ul>
  8. 8. STEP 8 <ul><li>Follow the instructions on the bottle and apply a small amount of spark plug thread lubricant and anti-seize compound to the new plug threads. </li></ul>
  9. 9. STEP 9 <ul><li>Install the washers on the spark plugs. </li></ul><ul><li>If you can not install the plugs by hand to within one or two threads, the cylinder threads need to be cleaned. Use the T555 thread cleaning tool to remove any deposits from the cylinder head threads until hand tightening is possible. </li></ul>T555 Thread Cleaning Tool
  10. 10. STEP 10 <ul><li>Install the spark plugs. </li></ul><ul><li>Now torque the plugs to the proper torque value. Use the chart shown below. </li></ul>Torque Reference Engine Foot Inch Newton Manufacturer Pounds Pounds Meters Textron Lycoming 30-35 360-420 41-47 TCM 25-30 300-360 34-41 Pratt & Whitney 25-30 300-360 34-41 Wright Aeronautical 35-40 420-480 47-54 Franklin Engine Co. 25-30 300-360 34-41
  11. 11. STEP 11 <ul><li>Install the ignition lead, by hand. Hold the small hex nut on the ignition lead and tighten the large hex nut an additional 1/8” turn. </li></ul>
  12. 12. STEP 12 <ul><li>Remove any tools or supplies from the engine compartment. </li></ul><ul><li>Reinstall the cowling. </li></ul><ul><li>Perform a ground run per manufacturer’s flight manual including magneto check. </li></ul>
  13. 13. AIRCRAFT SPARK PLUG INSTALLATION COMPLETE <ul><li>Make appropriate logbook entry of the work performed. The FAA has a sample logbook entry shown in the free video on our home page at </li></ul><ul><li>This educational video contains information that is consistent with FAR 65.83 “Recent Experience Requirements.” </li></ul><ul><li>Please visit to view a free video that reviews Basic Maintenance for Pilots and Technicians as part of FAR 43 and 91. </li></ul>