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Piper PA-23-250 Aztec (Nomad)
- J.K. Caldwell
- 5 hours ago
- 6 min read
Introduction: The Piper Aztec, converted to a straight float seaplane, makes a great multi-engine seaplane trainer with an impressive useful load carrying capability. Oh yeah, it’s fast (especially for a seaplane)!
Background: The evolution of the Nomad began in 1953 with the snub-nosed, four-seat PA-23-160 Piper Apache, which some pilots affectionately dubbed the “flying sweet potato”. Interestingly, the prototype was called the Twin Stinson, whose twin tails gave it the appearance of a small Beech 18. With passing years, the PA-23’s nose grew (no lies!), along with its horsepower and carrying capacity. The six-seat Aztec, first produced in 1960, had a longer nose, 250-horsepower IO-540s, and a swept tail.
To create this rare floatplane, Aztec Nomad, Inc. takes an Aztec C or later model, removes the landing gear, and replaces it with Edo 4930 straight floats (commonly found on the DeHavilland Beaver). It also seals up the wheel wells, adds a left-side pilot door, and makes a few other modifications. The load-carrying capability is around 1800 pounds and the Aztec offers speed, twin engine redundancy, and relatively low water damage to the props (thanks to being located over the floats). Most Pipers leave the factory fully primed, requiring minimal corrosion control treatment before their conversions to seaplanes. The Aztec’s large vertical stabilizer means no additional ventral fin is necessary, as is the case with other seaplane conversions. Southern Seaplane (§ 141 flight school and § 135 Charter) in New Orleans, owns one of the first converted Aztecs. Some differences from what Aztec Nomad, Inc currently offers are a right-side gull-wing door and hydraulically operated water rudder extension and retraction. Twin IO-540s produce 500 total horsepower and means the time to get “on step” and airborne is fantastic but, as with any low-winged floatplane, there are a few limitations for docking and beaching that must be observed.
Preflight/Runup: Most seaplane bases have a seaplane ramp. Amphibious seaplanes can simply taxi up and down the ramp under their own power but straight float seaplanes, require a little ingenuity to get in and out of the water. The most common means is a special trailer that can be hydraulically lifted and towed behind a truck or tractor. Pre-flight the Aztec while it’s on land is easy! When inspecting the floats, check for integrity compromises to ensure there is no water in any of the 6 float compartments. Likewise, be sure to inspect the water rudders, associated cables, springs, and rolling cable guides. All three fuel drain sumps are conveniently located in the same door under the engine nacelle of each wing.
Seaplanes are understandably more prone to corrosion than landplanes, so it is important to take note of any potential problem areas. Because the Aztec’s tail is subjected to water spray during takeoff and landing, carefully inspect the elevator hinge points around the tailcone for corrosion. The best time to warm up the engine and prep for the boat ramp launch is while the seaplane is still on land. Use the checklist for either cold or hot starts, and the IO-540s will fire-up with no issues. If the run-up is done on the trailer, run up only one engine up at a time to no more than 1600 rpm. Otherwise the Aztec may try to jump off the trailer! When flying straight float seaplanes, I occasionally find myself holding pressure on the brake pedals (and yes, I feel silly when I catch myself doing it).
Because the Aztec has no reverse thrust capability, it makes sense to back it down the boat ramp nose first. After gently setting it down on the ramp with ¾ of the floats in the water, tie each float to anchor points on the shore to ensure it doesn’t pivot after the first engine is started. Once in the pilot’s seat, start the left engine first. This is important because the left engine houses the hydraulic pump that operates the flaps and water rudders.
Water Taxi: Most multi-engine seaplanes don’t require water rudders because of their ability to use differential thrust to turn while water taxiing. Seaplane pilots in Louisiana operate primarily in narrow canals and waterways, often with currents and crosswinds, making water rudders necessary. Lyle Panepinto, long time seaplane pilot and owner of Southern Seaplane, said that Alaskan seaplane pilots call themselves “bush pilots”, but Louisiana seaplane pilots prefer the term “ditch pilots”. Even with differential thrust, a seaplane operating in a narrow “ditch” with crosswinds and currents must have good directional capability to avoid hitting banks, sandbars, and the occasional gator! Southern Seaplane owns and operates the only Nomad outside of Canada, using it for Multi Engine Sea rating training.
Takeoff: After turning on the electric fuel pumps, set 10 degrees of flaps and pull the yoke back in your lap. In a laterally confined area like a canal, push the throttles full forward and immediately raise the landing gear handle to retract the water rudders, which takes up to 15 seconds to fully retract. They will continue to give directional control until airspeed is adequate for normal rudder control. Most seaplanes require the pilot to wait until a second “rise” before allowing the nose to lower “on plane”. A Nomad, however, vaults out of the water like an ornery gator and is almost immediately “on step.” Relax the back pressure and find the “sweet spot” of minimum hydrodynamic drag for the Edo floats. When the plane is ready to fly, it will free itself from the water with a “sling shot” of acceleration. Retract the flaps as the Nomad accelerates to the 97 mph “blue line” (best single engine performance).
Performance: The cruise speed (up to 160 mph at higher altitudes) is high for a seaplane, and burns about 34 gph (17 per side) when operating with mixtures rich at low altitudes. Although the PA-23-250 has more than seven times the horsepower of a J-3 Cub, it shares the same airfoil shape (US-35B) and possesses similar pleasant flying qualities. The Met-Co-Aire winglets decrease wingtip vortices, which increases cruise speed by 2 to 3 mph and decreasing stall speed by 4 to 5 mph. Vortex generators also improve low-speed characteristics. With a gentlemanly 80 mph Vmc, the Nomad is easy to control while single-engine. If at max gross weight (5,200 lbs.), the single-engine performance yields a 220 fpm rate-of-descent, which is more than adequate to find a suitable waterway in southern Louisiana.
Landing: For landing, smoothly pull the manifold pressures back to 21 inches, allowing the plane to decelerate to inside the 125 mph “white arc” of the flap range. Hold the flap switch down for 1.5 seconds before recentering to stop the flaps at 10-degrees down. Then pull the throttles to about 16 inches of manifold pressure and set the pitch attitude to hold 97 mph. Trim is accomplished with either an overhead crank handle or an electric trim switch on the yoke. Turning final, ensure that mixtures and props are full forward – all while vigilantly scanning for obstacles (or creatures) on or under the water. For a normal water landing, begin your flare about one wingspan’s height above the surface and ease down toward the water. You will float about 150 feet before the Nomad is in the proper touch down attitude. As with any seaplane, it’s critical not to touch down too fast, as it can lead to dangerous “porpoising”. Once you’ve touched down, ensure the throttles are at idle as you hold the yoke back until fully settled in the water.
As you are decelerating, reach over to raise the flap lever. Wait until you hear the “click” of the flap lever recentering itself before lowering the landing gear handle to deploy the water rudders. Because both the flaps and water rudders use a single hydraulic pump, do not actuate both at the same time or neither one will have enough pressure to work. While the water rudders are deploying and before they become fully effective, the pilot can use differential thrust for directional stability. In the event of a hydraulic pump failure, a manual wobble pump lever can be extended from the center of the pedestal.
Docking can be a challenge due to the low wings and the inability to get to the left float quickly from the cockpit (there is a very small pilot side door). One technique is to shut down the right engine first (mags off!), steering with water rudders while the right-seat instructor climbs out the right-side gull-wing door and forward off the leading edge of the wing and onto the right float. From there, he/she can step onto the dock and tie the float to the cleats. Beaching and anchoring are more common for the Nomad.
Wrap-Up: The Piper Aztec (Nomad) is a fast and powerful, multi-engine seaplane with good load-carrying capability and docile handling characteristics. If you’re up for the challenge of earning a multi-engine seaplane rating, the Nomad makes a good tutor!
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