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  • Flying the Swearingen SX-300
    Posted by Fred George 5:00 PM on Jul 30, 2009


    blog post photo
    photo:  Fred George at AirVenture Oshkosh 2009

    A few years ago, it was quite a treat when I got the chance to fly N6L, one of the rare Swearingen SX-300 kit-built hot rods on display at this year’s AirVenture Oshkosh. The airplane, so named for its top speed in mph, took San Diego builders Harold Arnhardt, recently deceased, and Frank Curry six years to complete. And they were master craftsmen in the aviation trade, having owned and operated a local general aviation salvage, repair, maintenance and overhaul business for years before taking on the challenge of constructing an airplane requiring the labor hour build time of an F-16. Finishing a hand-built, high-performance aluminum airplane with retractable gear is no mean feat.

    I watched these two master craftsmen build this complex kit through every step, beginning with constructing the wooden assembly fixtures in the early 1980s to its first flight in 1990. The parts and plans provided by Swearingen were far from perfect, requiring numerous changes, modifications, replacements, adaptations and custom alterations during construction.

    Following the original kit assembly instructions, for example, some builders counter-sunk the holes for installing flush rivets. But, that involved removing structural metal and the construction method later proved to compromise the +6G / -3G design strength of the aircraft.

    Old salts Arnhardt and Curry, in contrast, ignored the original instructions. They took the precaution of dimpling all the mounting holes for the flush rivets to preserve the thickness of the aluminum monococque. They also liberally used structural adhesive to bond parts where higher strength was needed. Such assembly methods later would be recommended for future builders.

    When Curry first flew the aircraft in 1990, I flew chase in my Mooney 201 with his wife in the right seat taking photos.

    Arnhardt, in contrast, thought the SX-300 was too hot for him to fly alone. He was content to be a co-owner and co-builder. Curry, having flown fighters and bombers in WW II, loved to fly the airplane. He configured it to be flown from the right seat so that his left hand could deftly move the throttle, prop and mixture levers in the center console as though playing a musical instrument.

    One day a few weeks later, I asked Curry if I could fly his pride and joy. He just tossed me the keys and said, “Don’t break it.” It didn’t take long before I had carefully pre-flighted the airplane and yelled “Clear prop!”

    When the 300 hp Lycoming fired up, everyone in the vicinity could hear the sweet sound of six cylinders speaking through individual pipes. Part 36 noise compliance? Yeh, right. The SX-300 was about as quiet as a P-51 Mustang.

    As you can see from my photo above, the SX-300 has comparatively restrictive outward visibility, at least with this canopy configuration. Some other SX-300 airplanes have more Plexiglas, but Arnhardt and Curry wanted to minimize the solar heating of the interior. So, I taxied with the canopy hinged up to improve my view.

    Typical of other Swearingen designs, the SX-300 has a tiny wing and tiny landing gear. It doesn’t have good short-field performance and soft-field operations strictly are off limits. Takeoff and landing speeds are similar to those of light jets. You need jetliner-length runways for no-flap operations.

    When cleared for takeoff on San Diego – Montgomery Field’s 4,600 ft long Runway 28R, I pushed up the throttle to the stops and smiled at the raucous sound of the half-dozen cylinders, each screaming to onlookers at the airport, as well as to everyone else in the adjoining neighborhoods. With the aircraft weighing 200 lb less than its 2,400 lb MTOW, and having 300 horsepower, the SX-300 picked up speed quite sportingly.

    I rotated at 90 KIAS and, with only 70.3 square feet of wing, the little aircraft begrudging lifted off at 110 KIAS. Immediately, I retracted the gear to reduce drag and the aircraft quickly began to accelerate through 120 KIAS. Now, it behaved more like a Walter Mitty-like fighter plane. I retracted the flaps at 140 KIAS and settled into a 160 KIAS climb toward the La Jolla coast line. By the time I reached the beach, the SX-300 was passing through 3,500 ft. I turned northwest on V-23 and continued the climb to 4,500 ft. Once level, I let it accelerate to 220 KIAS, said goodbye to San Diego approach [now SOCAL] and headed west toward W-291, calling Beaver Control for flight following.

    This evoked memories of my old days flying F-4J Phantoms out of NAS Miramar, now repossessed by USMC. Granted, the SX-300 didn’t burn kerosene and it wouldn’t fly Mach 2, but I could afford to refill its tanks back at the fuel island. I certainly couldn’t have paid for an hour of flying Old Big Ugly with its 6,000 pph to 90,000 pph fuel thirst. [No, that’s not a typo. Those twin GE J79-10 turbojets together sucked down 1,500 pounds / minute in max burner at sea-level].

    N6L, being so stoutly built, was fully capable of aerobatics. Once I was safely established in the warning area, away from the airway, I reveled at its ability to perform loops and rolls, chandelles and Immelmanns, split esses and Cuban eights, wing overs and barrel rolls, displaying nice control harmony and very light stick forces. Big Ugly never was this mannerly. Thank you Ed Swearingen.

    About then, I imagined Curry was getting anxious to see his precious airplane return, so I turned back toward KMYF and called Approach for flight following. Mindful of the 156 KIAS speed limit for Airport Traffic Areas [Class D airspace now] in force at the time, I throttled way, way back and slowed to meet it.

    The aircraft mushed below 150 KIAS, so I extended the flaps half way and flew it like a Citation I at 140 KIAS. But unlike flying the Cessna twin, I had to use plenty of power to maintain the comparatively slow airspeed because of the induced drag rise.

    Cleared for landing, I dropped the gear, slowed to 130 KIAS and turned base, allowing plenty of room on final to stabilize the approach at 110 KIAS. Gee, just about the same Vref as a first-generation Citation, I thought.

    Over the threshold at 100 KIAS, I flared while consciously adding a little power to check the descent. Ground effect cushioning was next to nil. I touched down at 90 KIAS, let the airplane decelerate for 1,500 ft before gingerly pressing the brake pedals to avoid skidding the skateboard-sized tires. I rolled to the far end of Runway 28R and taxied back to the fuel pumps.

    It cost me no more than 30 gallons of avgas for the hour-long adventure in Arnhardt’s and Curry’s aluminum masterwork. I indeed felt privileged and honored for their trust in me. Frank, thank you again for that rare treat.

    For the next 19 years, no one outside of Curry and me ever soloed N6L prior to his selling the airplane to Jim Cianci, Jr of Port Orange, FL in May 2009.

    Jim, if you’re reading this, I hope you’ll weigh in and blog about your experience flying your newly acquired SX-300. I’ll bet you grin as wide as the wing span every time you strap yourself in.

    Tags: OSH09 BA99 Oshkosh

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