Smoke On Go

Piper’s three engine oddity

Three engine aircraft were the almost the norm in the 1920s and 1930s. The reasoning behind this was actually quite simple.

Aircraft engines were vastly overweight and underpowered. If a twin engine aircraft lost power to an engine, it was only going one way, down. So in order to build redundancy, just add another engine. One must also remember that early aircraft created a lot of drag, from wires, struts, fixed undercarriage and all sorts of paraphernalia hanging out in the slipstream.

During and after WWII, aircraft improved significantly with bigger engines, better construction methods, and retractable gear and so on, and three-engine aircraft started to slowly disappear. 

The most numerous being the good ol’ Junkers Ju52, three of which were first used here in South Africa by our then Suid-Afrikaanse Lugdiens/South African Airways (SAL/SAA). A total of 14 Ju 52/3’s were flown by our airline.

By the early 50s and 60s general aviation aircraft design was accelerating, with new singles and twins from the stable manufacturers like Piper, Beech and Cessna. No one even thought of making a three engine aircraft anymore. Until 1967, when a three engine aircraft was spotted at the Piper Aircraft Company.

This aircraft had three Lycoming engines, fixed landing gear and a Cherokee Six fuselage. Named the PA-32-3M, the aircraft had no official name. This aircraft was the prototype of what was initially to become the PA-34-180 Twin Six. The beginning of the Piper Seneca.

It never performed very well, as the wings were too short and the fixed gear was also quite draggy. It was also quite heavy on the ailerons and not really liked by the test pilots. So it was abandoned, with Piper building a new twin instead, based on the Cherokee six fuselage.

The first prototype PA-34 still had a fixed nosewheel, but at least the mains retracted, and the aircraft used the same vertical fin of the Cherokee six, flying on 25 April 1967. The second prototype flew on 30 August 1968, with the 180 hp (134 kW) Lycomings, but at least had fully 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 200 hp (149 kW) Lycoming IO-360-A1A engines. Certified on 7 May 1971 and introduced in late 1971 as a 1972 model, as the PA-34-200.

So, the PA-34 Seneca is, basically, what you get when you turn a Cherokee Six into a twin, sharing the trademark Hershey-bar wing, stabilator empennage and fuselage.

The Seneca had counter-rotating Lycoming IO-360C1E6 engines producing 200 HP each. One of the prototypes was written off in June 1970, when crashed it into the sea off Vero Beach, Florida, due to structural failure of the starboard wing during a test flight. The pilot, the sole person on board, escaped from the aircraft safely. Piper strengthened the wing. NTSB states: “Rapid pitch up during power descent. Starboard outboard section of wings failed upwards. Aircraft examined underwater but not recovered”

The Seneca was introduced at the height of the general aviation boom to serve as a less-expensive companion to Pipers successful but ageing Aztec. The Seneca was about a third less costly than the Aztec to operate, also replacing the Twin Comanche in the line-up. The Seneca was about the same price as the Twin Comanche C/R, while sporting larger engines, a higher gross weight and a roomier cabin. Both the Seneca and the Twin Comanche were built in 1972, but the latter was discontinued afterwards, albeit in part due to the flooding of Pipers Lock Haven, Penn., factory that year. The Seneca was built in Vero Beach, Fla.

But the story of the three engine Piper does not end here. The French, under a company called Potez tried building another. They took a Piper Comanche fuselage and built themselves a prototype called the Potez X. Very little is known of this aircraft, but one presumes it was not a success.




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