In heavy rain during takeoff, the igniters in a gas turbine engine will be:

• A. High energy continuous
• B. Low energy high output
• C. Medium energy intermittent
• D. Low energy low output

Answer: (B)

In heavy rain, moisture can dampen the ignition gap, so the spark needs to be strong enough to jump that gap quickly but not delivered as a long, continuous discharge. The best approach is short, high-peak-energy pulses—low energy per pulse but with high instantaneous output. This gives a reliable ignition across a wet gap, while keeping the average energy and heating low to reduce wear and the chance of moisture causing a sustained arc. Continuous high-energy or medium-energy pulses would either waste energy and increase wear or fail to provide the abrupt, reliable ignition needed in rain. Likewise, a low-energy, low-output approach wouldn’t reliably ignite the mixture in wet conditions.