Hello,

On my new to me 69 206 my throttle surges forward when running. When running, especially with airflow, if I don’t lock the vernier down it surges forward at least 1000 RPM. It feels like a spring is pulling the throttle forward but when the engine is off it stays in the same position, guessing this is something to do with airflow on a loose butterfly valve but wanted ask for opinions.

Thanks,

Mike

I have heard of and seen springs installed on throttle arms, so that in the event of a throttle cable failure it fails at full power so that the ship doesn’t become a glider. The symptoms sound like they could be related to such an arrangement.

Good point about the spring, but when the airplane is off there seems to be no pressure on the throttle, it only seems happens when there is airflow.

AZ Flyer wrote:Good point about the spring, but when the airplane is off there seems to be no pressure on the throttle, it only seems happens when there is airflow.

It seems like airflow should produce a Force couple about the shaft in the throttle-body, resulting in a moment that would act on the throttle valve in the same direction as the spring. I would look to see if there is a spring installed.