Magneto madness: Pilot Safety Meeting


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Our March safety meeting on why pilots need to know and understand magnetos. What are they and how do they work? Find out here . . .

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Magneto madness: Pilot Safety Meeting

  1. 1. Magneto Madness Steve Berube, A&P TakeWING Safety Meeting 541-895-5935
  2. 2. The Magic of Magnetos <ul><li>We will discuss (and tell stories about)…. How a magneto works (at a simple level) How magneto knowledge will make you a safer pilot Why the P-Lead can kill you What to look for during run-up What to do if the engine begins running rough in flight </li></ul>
  3. 3. Close encounters? <ul><li>What & when was your first encounter with a magneto? </li></ul>
  4. 4. Everyday machines <ul><li>Lawn mower Chain saw Outboard boat motor Weed eater Leaf blower Mini-bike Go-cart Any small portable gasoline engine uses a magneto. </li></ul>
  5. 5. Magneto Madness <ul><li>Magnet Magneto Magnetism Magnetism fundamentals </li></ul>
  6. 6. Magnetic Madness <ul><li>Magnetic Field Lines of Flux </li></ul>
  7. 7. Magnetic Properties <ul><li>Magnetic Field Concentration </li></ul>
  8. 8. Magnets and Electricity Magnetic Induced Electricity Wire passing through a magnetic field creates electricity.
  9. 9. Electromagnetism Electromagnetism Magnetic Field Electricity flowing through a wire creates a magnetic field.
  10. 10. Magneto Madness <ul><li>Automotive Ignition Systems put the Magnetos into context. </li></ul>
  11. 11. Automotive Ignition System Battery Speaking of Sparks 12 Volts Spark Plugs Ignition Wires Distributor Coil Step-up Transformer (12 Volts to 20,000 Volts) Rotor Points Ignition Switch
  12. 12. Ignition Coil (Electromagnetic Induction & Step-up Transformer) Battery Switch Primary Coil Secondary Coil 200 turns 13,000 turns 12V 20,000V Ignition Systems Coil Step-up Transformer (12 Volts to 20,000 Volts)
  13. 13. Automobile Distributor Rotor Points Ignition systems
  14. 14. Coil Distributor Spark Plug Ignition Systems
  15. 15. Automotive Ignition System Battery Ignition Systems 12 Volts Spark Plugs Ignition Wires Distributor Coil Step-up Transformer (12 Volts to 20,000 Volts) Rotor Points Ignition Switch
  16. 16. Aircraft Ignition System Magnetos No Battery!! Spark Plugs Ignition Harness Ignition Switch Auto to Airplane
  17. 17. Aircraft Ignition System Aircraft Engine
  18. 18. Aircraft Ignition System Magneto Rotor Coil Points Magnet Distributor P-Lead The Magnet replaces the Battery Aircraft Ignition System
  19. 19. Aircraft Magnetos Magneto Madness
  20. 20. Magnetic Circuit Magneto Madness Coil Magnet Iron Pole Shoes
  21. 21. Rotating Magnet Magneto Magneto Madness
  22. 22. Rotating Magnet Magneto Magneto Madness
  23. 23. Magneto Ignition System & MAGNET & MAGNET Ignition Switch On P-Lead Primary Winding Secondary Winding
  24. 24. Aircraft Ignition System Spark Plugs Magnetos Ignition Harness No Battery!!
  25. 25. Magnetos <ul><li>The ignition system is completely independent of the aircraft electrical system. </li></ul><ul><ul><li>If the aircraft electrical system were to fail the engine would continue to run! </li></ul></ul><ul><li>A spinning magnet induces current in the primary coil. This current creates an electromagnetic field around the primary coil. The current is interrupted by a set of breaker points, causing the primary coil magnetic field to collapse. The collapsing field induces current in the secondary coil which generates a high voltage spark. The spark is directed through the distributor via the rotor to the proper spark plug. </li></ul>
  26. 26. Rotating Magnet—Magneto <ul><li>Aids To Starting </li></ul><ul><ul><ul><li>Magnetos provide a good, hot spark at idle, at cruise, and at high speed. </li></ul></ul></ul><ul><ul><ul><li>But not when the engine is turning slowly during start. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Impulse Coupling </li></ul></ul></ul></ul></ul>
  27. 27. Provides momentary high rotation speed and a retarded spark for engine starting Impulse Coupling Impulse Coupling
  28. 28. Impulse coupling Retarded Spark Intake Compression Power Exhaust BTDC ATDC
  29. 29. Inside the Impulse Coupling Body Coil Spring Flyweight Cam
  30. 30. Impulse Coupling
  31. 31. OK, so what does all this magneto stuff mean to the pilot? Magneto Madness
  32. 32. Understanding Your Checklists <ul><li>P-Lead ground (pre-flight) </li></ul><ul><ul><li>During pre-flight always spin the prop backwards (except Rotax 912)! </li></ul></ul><ul><ul><li>Broken P-lead, poorly grounded P-Lead, or faulty ignition switch will leave the magneto HOT! </li></ul></ul><ul><li>Run-up /Before Takeoff Checks </li></ul><ul><ul><li>Magneto Safety Check (ignition switch test) </li></ul></ul><ul><ul><ul><li>Idle RPM, turn ignition switch from “both” to “off” </li></ul></ul></ul><ul><ul><ul><li>Listen for complete cutting off of the engine </li></ul></ul></ul><ul><ul><ul><li>Engine cut off indicates proper P-lead connection and ignition switch operation </li></ul></ul></ul>Ignition System Operational
  33. 33. Magneto Safety Check (con’t) Run-up <ul><li>“ Both” to “Right” and “Both” to “Left” — what should the Tachometer do? Here’s what five POHs said . </li></ul>Notice the RPM between left and right magnetos, the difference between the magnetos should not exceed 50 RPM A slight RPM drop approximately the same on each magneto. Regardless of the drop, the engine should run smoothly . <ul><li>100 RPM drop max. </li></ul><ul><li>RPM drop should not exceed 125 RPM on either magneto or 50 RPM differential between magnetos. </li></ul><ul><li>Drop off on either magneto should not exceed 175 RPM. </li></ul><ul><li>The difference between the magnetos should not exceed 50RPM. </li></ul><ul><li>200 RPM maximum drop, 50 RPM maximum differential </li></ul>
  34. 34. Magneto Checks (con’t) <ul><li>Run-up checks (con’t) </li></ul><ul><ul><li>Magneto Operation Check </li></ul></ul><ul><ul><ul><li>Rapid RPM drop or rough engine may indicate a fouled spark plug or faulty ignition harness </li></ul></ul></ul><ul><ul><ul><li>Slow RPM drop is usually caused by improper timing or valve adjustment </li></ul></ul></ul><ul><ul><ul><li>Excessive RPM differential between the mags indicates a difference in timing between the left and right magnetos. </li></ul></ul></ul><ul><ul><ul><li>Absence of RPM drop indicates a defective P-lead ground connection </li></ul></ul></ul><ul><ul><ul><li>If the engine is rough regardless of the magneto setting then the problem may not be ignition, but an air intake leak or valve train problem instead. </li></ul></ul></ul>
  35. 35. Common Causes of Engine Roughness—Before Takeoff <ul><ul><li>Spark plug fouling </li></ul></ul><ul><ul><ul><li>A slight engine roughness found before flight may be caused by one or more spark plugs becoming fouled by carbon or lead deposits. </li></ul></ul></ul><ul><ul><ul><li>This may be discovered by turning the ignition switch momentarily from BOTH to either L or R position to determine if one mag is “rougher” (greater than expected RPM drop) than the other. </li></ul></ul></ul><ul><ul><ul><li>Assuming that spark plugs are the more likely cause, increase RPM then lean the mixture to the recommended lean setting. Enrich the mixture again and retest. If the problem does not clear up within one or two attempts to clear the spark return the aircraft to the school for maintenance . </li></ul></ul></ul>
  36. 36. Causes of In-Flight Engine Roughness <ul><ul><li>Magneto malfunction </li></ul></ul><ul><ul><ul><li>A sudden engine roughness or misfiring is usually evidence of magneto problems. Switching from BOTH to either L or R ignition switch position will identify which magneto is malfunctioning. Select different power settings and enrich the mixture to determine if continued operation on BOTH magnetos is practicable. If not, switch to the good magneto and proceed to the nearest airport for repairs. </li></ul></ul></ul>
  37. 37. Magneto Madness Thank you! TakeWING Safety Meeting 541-895-5935 TakeWING Aviation Club and Maintenance Center