Expert: Ned Dolan - 11/6/2005

Question
Hi Ned,The other day when I has flying with my father on a southwest plane, I noticed that the engine sound changed. It sounded like the engine was going up and down, from a high pitch to a low pitch, like it was whinnying. Is this normal? What was happening?

Answer
Hi Brian, this sounds like an out of sync pair of engines. If the engine speed (rotation speed) is different for each engine you can hear a sound like the one you heard. Some ships have an auto sync feature that automatically keeps the engines in sync and some have to be done manually.

When doing the job manually the pilot uses his engine instruments and his ears. Often the sound in the cockpit is a little different than that in the cabin and the result is the sound you may have heard.

Out of sync engines cause no other problem than the sounds you may have heard.

Hope this answers your question.   Ned