The Pilatus P-4 represented another attempt by the company to get into the market for civil aircraft, but this five-seat cabin monoplane had little more success than its SB-2 predecessor. Of braced high-wing monoplane configuration, with fixed tailwheel landing gear, a braced tail unit and a 142kW Avco Lycoming O-435 engine, the P-4 had accommodation for a pilot and four passengers. All passenger seats were removable easily so that the P-4 could be used as a cargo carrier, or as an air ambulance accommodating two stretchers and two medical attendants. With a wing span of 11.85m and maximum take-off weight of 1500kg, the P-4 had a maximum speed of 245km/h.