The vibration of the engine as a result of piston damage remains unchanged when both magneto 1 and magneto 2 are switched on, so that it is possible to confuse it with the a damaged sparking plug. On the bench, bursts of blue vapour are emitted from the housing ventillator when a piston is damaged. In engines with reinforced pistons the danger of their burning through is not so great as in the older version of the piston, but the take-off and emergency output may still not be used. The following engines are fitted with reinforced pistong headsÉ