I remember having heard a story of a midair between an army Alouette 2 and a Cessna 150 in Freiburg (germany) in 73 or 74,
The Cessna had come in climbing under the descending Alouette...in airport pattern.
The left seat passenger (who was an enginneer) in Alouette suffered a cut leg by the Cessna propeler.
I think the Cessna crashed, with casuaties, since the Alouette made a forced barrely controled landing on the city's hospital lawn!. Engineer survived.