The Apache was the first twin-engined design to emerge from the Piper factory and helped Piper move away from the 'Cub' image. It was developed from a proposal found in the files at the Stinson factory and was originally known as the 'Twin Stinson'. The PA-23 development started in January 1951.
The experimental aircraft was s/n 23-01 registration N1953A and first flew on the 2nd of March 1952. It was a low wing twin-engined four seater, the engines being 125 hp Lycoming 0-290-D's. It had a retractable tricycle undercarriage and was of steel tube construction with fabric covered fuselage and outer wing panels. Flight tests showed up a number of problems. Firstly it had single-engine handling problems. This was followed by engine cooling problems which were fixed by cowling and exhaust changes. The aircraft was under powered so full-feathering propellers with 135 hp Lycoming engines were fitted. Also it had a bad case of the 'shakes'. Aircraft N1953A was a twin-finned design, so Piper engineering modified it to the more orthodox single fin and rudder layout (from PA-6 s/n 6-1 registration N4000M) in a high configuration to get the tail out of the air-flow. Penn State University wind tunnel tests showed that the airflow was being disrupted over the upper surface of the inboard wing by airflow between the fuselage and engine nacelle. Wing fillets solved this problem, so they put the tail back down in the conventional low position. They added more power by installing 150 hp Lycoming engines.
For the prototype aircraft Piper replaced the fabric covering with metal and re-designed completely from the rear of the cabin backwards. The engines were the 150 hp Lycoming 0-320-A with constant speed propellers. The prototype PA-23 Apache s/n 23-1 registration N23P and first flew on the 29th of July 1953. A pre-production aircraft s/n 23-2 registration N1000P was completed on the 21st of December 1953. These two aircraft were used for certification trials and the Type Certificate 1A10 was issued on 29th of January 1954. Deliveries to customers started with s/n 23-4 registration N1002P on the 30th of April. It was priced at $32,000.