I had an engine bay fire during my first lesson in an R22. A runaway clutch overstretched the drivebelts snapping one which then broke an oil line. The resulting oil spraying over the engine burst into flames. Bit disconcerting.
My instructor had full control the whole time, we were returning due to the clutch problem. The only indication of fire was the reflection from the concrete as we came to a hover, then the reduced airflow allowed flames to become visible around the exterior of the cockpit.
We landed somewhat rapidly and as my instructor shut down I put the fire out with the onboard extinguisher, prior to the AFS arriving and making the world all white and foamy.
The R22 in question was repaired and I've flown it many times since.