Avery JA-5 Walrus

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The Avery JA-5 Walrus was a home-built experimental American single-engined aircraft designed and built by John Avery and first flown in 2002. It was damaged by fire in 2010 after eight flights and the project was abandoned.

Design and development

The JA5 aircraft was originally developed to demonstrate low-cost composite construction methods using a novel configuration. The program can be broken down into three phases. In each phase the aircraft utilizes a difference engine configuration. Aerodynamic modifications were also done. The airplane flew up-and-away eight times over many years.[no citations needed here]

Phase I – Initial Aircraft Configuration Through First Flight

The first phase consisted of initial construction and design using minimal expense for the instrumentation and engine. It took three years and six months from start of construction to first flight. Design was done concurrently with construction. The aircraft was originally powered by a Rotax 503 engine with single carburetor, producing 46 horsepower at standard sea level (SSL) conditions and had anemic climb performance. It also had tip stall issues because of the wings vertical placement, aggressive taper and sweep. The test pilot almost lost control when the airplane began to oscillate around all axis as it flew in slowflight down the runay. A vertical outboard fence seemed to fix the bad handing qualities at low speed but later allowed the wing to stall instantly. The aircraft pitched up, struck the wing tips and folded the nose gear. It flew one up-and-away flight in this configuration. However, many hours of runway flights were used to understand its slow-fight characteristics.[no citations needed here]

Phase II – Upgrade Configuration with Normally Aspirated 914UL Engine

The second phase of the program consisted of upgrading the Rotax 503 engine with a 4-cycle Rotax 914UL engine run normally aspirated, producing 80 horsepower (hp) at SSL conditions. Other upgrades include structural reinforcements to the airframe and landing gear to support the additional engine weight, and replacement of engine instrumentation to those compatible with the 914 series engine. The battery was also moved from the rear of the aircraft to the nose, to offset the additional weight of the newly installed engine. Aerodynamic modifications include cutting 11 inches from the tips of the canard to reduce control power by operating the surface at a higher coefficient of lift (CL). Other modifications include installing 45 degree wing fences on the wing-to-winglet transition to reduce the span-wise flow at slow speeds, thereby reducing the boundary layer, and postponing stall on the main wing under steady-state trim conditions. An outboard, leading edge cuff, and two fences were also added along the span to also increase stall margin of the wing. To increase rudder authority for crosswind landing, an additional rudder was added to each of the verticals (winglets). Each rudder was driven by an electric actuator. The 2nd and 3rd flights were flown in this configuration.[no citations needed here]

Phase III – Upgrade Configuration with Turbocharger, Fuel Injection, and Electric Rudders

The third phase of the program was to further increase the climb performance of the aircraft by increasing the usable power though the use of a turbocharger. The normally aspirated engine was retrofitted with a turbocharger, and two independent fuel injection and ignition systems controlled by separate engine management computers powered by independent power buses. Power available was increased from 80 hp to 115 hp. The aircraft was also retrofitted with an electrically powered, three-bladed, constant-speed propeller and electronic controller.[no citations needed here]

Fairings were installed over the main and nose landing gear legs to reduce drag. All configurations were flown without wheel pants. The 4th through 8th flights were flown in this configuration.[no citations needed here]

Side-view
engine installation

End of Program

On July 6, 2010 the JA-5 aircraft was damaged beyond repair by an engine fire. A failure of a secondary fuel injector housing caused high-pressure fuel to spray inside the engine compartment, where it was probably ignited by the exhaust/turbocharger. With the fuel source removed, the epoxy in the cowlings continued to burn. The firewall made of stainless steel backed with fiberfrax worked as designed by insulating the fuel tank from the fire until the fire crews could arrive and extinguish the fire.[no citations needed here]

The prototype on fire in July 2010

Specifications (Rotax 503)

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References

External links

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