A technician is comparing a low-tension magneto ignition system to a conventional high-tension system on a reciprocating engine. What is the main operational advantage of the low-tension system?
- AIt eliminates the need for spark plugs altogether
- BIt reduces the risk of high-voltage leakage or flashover through the ignition harness at high altitude
- CIt produces a higher voltage spark than a high-tension system at all altitudes
- DIt allows the magneto to operate without an impulse coupling
Show answer & explanationAnswer & explanation
Correct answer: B. It reduces the risk of high-voltage leakage or flashover through the ignition harness at high altitude
In a low-tension system, only low voltage is carried through the distributor and harness to individual step-up coils located near each spark plug, where the voltage is stepped up just before the plug. This reduces the length of high-voltage wiring exposed to reduced air density at altitude, minimizing flashover and insulation breakdown. It still uses spark plugs, still may use an impulse coupling, and does not inherently produce higher voltage overall.
Why the other options are wrong
- A. Low-tension systems still require spark plugs to fire the mixture.
- C. Voltage output for ignition is similar; the difference is where step-up occurs, not overall magnitude.
- D. Impulse couplings can still be used with low-tension magnetos for starting.
Low-Tension Ignition System
An ignition system where low voltage is distributed to individual transformer coils near each spark plug, which then step up the voltage just before the plug fires.
- Reduces high-voltage wire length exposed to low air pressure
- Minimizes flashover/leakage at altitude
- Step-up coils located near spark plugs, not at the magneto
- Common on some radial and high-altitude engines
Memory trick: Keep the high voltage short and close to the plug