Had my most scary moment just recently, Cabin filling rapidly with smoke just after turning downwind!
after giving a radio call advising others in the circuit of my intention to land immediately and aiming for mid runway, everything turned off, except ignition, smoke didnt stop, it only took about a minute to land, but it felt like an eternity, especially when your expecting to see flames in the cab or feel the heat of a fire on my feet at any moment.
cause was leaking oil vent pipe allowing oil to leak onto the exhaust manifold