MP gauge
I got a question about my MP gauge. Its a reverse reading vacuum gauge connected across the carburettor butterfly right? So it reads 30" (atmospheric pressure) till I start the engine when it winds back to the idle reading of 12" or so.
As I feed in throttle & the butterfly opens the vacuum decreases & the gauge climbs again. If I test carby heat the warm air is less dense so the gauge climbs another inch or two. So far so good.
But when I descend from altitude in flight the MP gauge also climbs. But a descent should be into denser air which means the gauge should fall shouldn't it?