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The Rise and Stall of the Piper PA-47 PiperJet Program

The airframe configuration of the single-engine Piper PA-47 PiperJet presented a unique set of engineering challenges.

The PiperJet utilized a unique airframe configuration which created benefits and drawbacks. [Courtesy: Piper Aircraft]
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Key Takeaways:

  • Piper developed a single-engine Very Light Jet (VLJ) with a unique design that mounted the engine on top of the fuselage, integrated with the vertical stabilizer, to simplify design and ensure clean airflow.
  • This innovative engine placement introduced significant engineering challenges, notably a high thrust line causing pitch coupling, which was ingeniously solved using a fixed nozzle system leveraging the Coanda effect for variable thrust angle.
  • Another challenge, tail-plane stall with full flaps, was addressed by redesigning the horizontal stabilizer with increased span, elevator size, and sweep.
  • Despite these engineering successes and pre-orders, the PiperJet program (later Altaire) was ultimately canceled due to adverse economic and market forecasts, with the sole prototype now displayed at the Florida Air Museum.
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When designing a single-engine jet, there are only so many places one can mount the engine. To avoid asymmetric thrust, it must be mounted on the centerline of the fuselage, and doing so introduces new challenges. Something must be done to provide the engine with clean, undisturbed air for the intake, for example, and the design must somehow prevent the hot exhaust from damaging tail surfaces.

In mid 2007, when many manufacturers were developing new designs for the newly-identified very light jet (VLJ) category, Piper began development of their own VLJ with the goal of finding the simplest solution possible. They decided against housing the engine within the fuselage, as this would present complex challenges with regard to ducting airflow cleanly through inlets. Additionally, an engine housed within the fuselage must be engineered to minimize the risk to the occupants in the event of an uncontained compressor blade or disk failure.

Jason McDowell

Jason McDowell is a private pilot and Cessna 170 owner based in Madison, Wisconsin. He enjoys researching obscure aviation history and serves as a judge for the National Intercollegiate Flying Association. He can be found on Instagram as @cessnateur.

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