The P.D.4 was a four-seat helicopter with two rotors placed in tandem. Initially it had to be equipped with 450hp Alpha Romeo engine but then a 215hp Franklin was adopted.

The helicopter flew in the first half of 1952, demonstrating good handling characteristics although being seriously underpowered. In a wrong maneuver during a landing with lateral wind it was seriously damaged and wasn't repaired.

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Technical data for PD.4

Engine: 1 x Franklin, 215hp, rotor diameter: 9.0m, loaded weight: 1400kg