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.
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.
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 1800NaN0 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 1800NaN0 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 2000NaN0 Lycoming IO-360-A1A engines.
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 4000-1NaN-1, while later serial numbers allowed a takeoff weight of 4200-1NaN-1.
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 in 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 Seneca I.
The Seneca II also introduced optional "club seating" whereby the two center-row seats face rearwards and the two back seats face forward allowing more legroom in the passenger cabin. A total of 2,588 Seneca IIs were built.
Gross weights are 4570lb for takeoff and 4342lb for landing, with all weight in excess of 4000lb required to be fuel.
In 1981, the PA-34-220T Seneca III was introduced, having completed certification on 17 December 1980.
The change in model designation reflected an engine upgrade. Continental TSIO-360-KB engines were used which produced 220 horsepower (165 kW), although only rated as such for five minutes and then dropping to 2000NaN0.
The horsepower increase, with the new engines limit of 2800 rpm (up from 2575 rpm), combined for much improved climb and cruise performance. The new aircraft also incorporated a one-piece windshield and a bare metal instrument panel instead of one covered with a removable plastic fascia. Because of the raised zero-fuel weight and the raised maximum take-off weight, the Seneca III has the highest useful load of all the PA-34 variants. Some later models have electrically-actuated flaps. More than 930 Seneca IIIs were built; the last 37 Seneca IIIs built had a 28-volt electrical system rather than the 14-volt system of previous aircraft.
The aircraft's gross weight was increased to 47500NaN0 for takeoff and 45130NaN0 for landing. A typical Seneca III with air conditioning and deicing equipment has a useful load of 13770NaN0.
In 1994, the "New" Piper Aircraft company introduced the Seneca IV, having achieved certification on 17 November 1993. This model was similar to the Seneca III offering minor improvements, such as a streamlined engine cowl for increased cruise performance. It continued to use the counter-rotating Continental TSIO-360-KB engines and gross weights remained unchanged. A total of 71 Seneca IVs were built.
Certified on 11 December 1996, the Seneca V was put into production as a 1997 model year. Again the cowls were redesigned for increased performance, several cockpit switches were relocated from the panel to the headliner, and an improved engine variant, the Continental TSIO-360-RB, fitted with an intercooler, was used.
The Seneca V's gross weights remain the same as the Seneca III and IV at 47500NaN0 for takeoff and 45130NaN0 for landing, therefore, with all of the added features, the useful load is reduced by about 2000NaN0. The standard useful load for the 2014 model is 13310NaN0 but typically is 11340NaN0 when the aircraft is equipped with air conditioning, deicing equipment and co-pilot instruments.
From 1975 the Seneca was built under licence in Brazil by Embraer as the EMB-810. The PA-34-200T was produced as the EMB-810C Seneca (452 built) and the PA-34-220T as the EMB-810D (228 built).
The aircraft is popular with air charter companies and small feeder airlines, and is operated by private individuals and companies. One notable civil operator is the Costa Rican Air Surveillance Service.