Curious craft

It is essentially a twin-engine Aeronca Champ—although I’m not so sure that it was wise for me to admit having flown one. There was another equally weird airplane that I had almost forgotten about having flown, the Transavia PL-12U Airtruk. (Forgetting about having flown this strange machine might have been intentional.)

Bizarre airplanes have lured me all over the world; variety helps me maintain my passion for flight. It took only one look at the image of an Airtruk in 1974 to accept an invitation to visit Australia for the purpose of getting checked out in one and flying it in the Outback. The airplane has such an unconventional appearance that whenever I landed, the local press came out to investigate the curious craft. What they saw evoked quizzical expressions, poorly disguised chuckles, and a deluge of questioning.

The airplane has a double-deck fuselage shaped much like a Volkswagen Beetle, giving it an ungainly, homely appearance. The pilot sits in the front seat of the upper deck, and one passenger sits behind him facing aft. That passenger has no access to the cockpit in case of pilot incapacitation. He or she cannot see out the front window and must be content to sit in isolation. The pilot, however, has remarkable visibility; it is almost like flying from a control tower. Sitting above the engine instead of behind it also allows remarkable downward visibility.

The lower deck accommodates three additional passengers who also sit facing aft. (Sitting backwards usually provides improved survivability in the event of an accident.) One problem with sitting in the lower deck is that during the approach and landing, the lowered left-wing flap blocks the cabin door, making it impossible to open. If the pilot does not or cannot raise the flaps after landing, those seated below become imprisoned.

The Airtruk was originally designed to be an agricultural aircraft, a crop duster, and its designer was less concerned about form than function. As an aerial applicator, the pod-shape fuselage accommodates a cavernous 220-gallon hopper that carries up to 2,000 pounds of agricultural material. The unique twin-boom tail configuration allows a wide loading truck to approach from the rear and eliminates the need for the pilot to shut down the engine while loading. The Airtruk was then remodeled and recertificated as a passenger aircraft—what might have been the first time an airplane has undergone such an evolutionary change—but it did not meet with much success.

A problem with twin tail booms is that they keep the rudders outboard of the propwash. They cannot provide effective ground steering during the takeoff roll until the airplane has gathered some airspeed. If the nosewheel isn’t held down with full forward stick, initial ground steering can be marginal.

When leveling off at cruise altitude, retarding the throttle will reveal something strange. Reducing power does not cause the nose to lower as it does in other airplanes. Nor does adding power cause the nose to rise. This is because the elevators, too, are out of the propwash. Power changes have little effect on pitch. If the pilot wants the nose to go up or down, he’d better make it happen with the control stick. And, as airspeed increases while establishing cruise flight, nose-up trim can be needed to maintain level flight, and vice versa, a mild case of longitudinal instability.

The agricultural model of the Airtruk has a dump system that allows the pilot to jettison a 2,000-pound payload in three seconds in case he is otherwise unable to clear an obstacle. Unfortunately, passenger loads cannot be dumped. Threatening a passenger with jettisoning would certainly be a novel way to silence a loquacious back-seat pilot.

BarrySchiff.com