The Piper PA-34 Seneca is a twin-engined light aircraft, produced in the United States by Piper Aircraft. It has been in non-continuous production since 1971. The Seneca is primarily used for personal and business flying. Development The Seneca was developed as a twin-engined version of the Piper Cherokee Six. The prototype was a Cherokee Six that had wing-mounted engines installed, retaining its nose engine. The prototype was flown as a tri-motor aircraft in the initial stages of the test-flying program. PA-34-180 Twin Six With the decision to abandon the three-engined design tested on the PA-32-3M, the PA-34 was developed as a twin-engined aircraft. The prototype PA-34-180 Twin Six, registered as N3401K, first flew on 25 April 1967. The prototype had two Lycoming O-360 engines, a fixed nosewheel landing gear and a Cherokee Six vertical tail. The second prototype flew on 30 August 1968, still with the Lycomings but had retractable landing gear and a taller vertical tail. During development flying the wingspan was increased by two feet. The third prototype was closer to the production standard and flew on 20 October 1969; it was fitted with Lycoming IO-360-A1A engines. PA-34-200 Seneca Certified on 7 May 1971 and introduced in late 1971 as a 1972 model, the PA-34-200 Seneca is powered by a pair of Lycoming IO-360-C1E6 engines. The righthand engine is a Lycoming LIO-360-C1E6 engine variant, the "L" in its designation indicating that the crankshaft turns in the opposite direction, giving the Seneca counter-rotating engines. The counter-rotating engines eliminate the critical engine limitations of other light twins and make the aircraft more controllable in the event of a shut down or failure of either engine. A total of 934 Seneca models were built, including one prototype. The early Seneca models have a maximum gross weight of , while later serial numbers allowed a takeoff weight of . PA-34-200T Seneca II Responding to complaints about the aircraft's handling qualities, Piper introduced the PA-34-200T Seneca II. The aircraft was certified on 18 July 1974 and introduced as a 1975 model. The new model incorporated changes to the aircraft's control surfaces, including enlarged and balanced ailerons, the addition of a rudder anti-servo tab, and a stabilator bobweight. The "T" in the new model designation reflected a change to turbocharged, six-cylinder Continental TSIO-360E or EB engines for improved performance, particularly at higher altitudes. The Seneca II retained the counter-rotating engine arrangement of the earlier