Dream Aircraft

by Schiff, Barry

  Although no longer a household word in general aviation, Aeronca currently is a major manufacturer of aircraft, missile and jet-engine components. The Middletown, Ohio corporation, however, is quick to acknowledge its humble beginning in the era of rag-covered taildraggers.

  The first thing a writer learns is to start his story with an attention-getting paragraph, something to arouse the reader’s interest. Well, sports fans, how does this grab you? The Helio Courier Mark II can maintain altitude at an indicated airspeed of 28 mph while in a 43-degree nose-high attitude and be fully controllable. It can take off in 300 feet and land to a stop in 245 feet. It can do all of this and cruise at more than 160 mph.

  According to John Day, an executive at WHDH-TV in Boston, “The Helio Courier seemed to hover above a spot as our reporters broadcast peak-hour traffic information to our listeners. When we needed to change locations, it got there faster and more economically than a helicopter.”

  The psychological warfare squadron of the Air Force had need for an aircraft with both high- and low-speed capability. The U-10 (military designation for the Helio Courier) was flown over Viet Cong concentrations in Vietnam at low speed while playing taped propaganda broadcasts over a powerful loudspeaker. The U-10 often dropped 100,000 propaganda leaflets at a time over small, hard-to-reach targets. Load discharged, the U-10 scooted away at redline speeds.

  U-10s were subject to ground fire that would have been fatal to a helicopter. But the Helio Couriers were quickly repaired with simple patchwork and returned to their jobs.

  In Vietnam, the Helio Courier was affectionately and colloquially known as the “Litter Bug.”

  If you have a spare acre of unused land in your backyard, you can have your very own “Helio-Port,” as did Alan Bemis of Concord, Massachusetts. Bemis used his 425 by 100-foot strip for more than 10 years to cut down on the portal-to-portal time between his home and various destinations, thus eliminating the frustrating, time-consuming, and often dangerous drive to and from the airport.

  For many years, the Helio Courier was the only STOL (short takeoff and landing) aircraft manufactured in the United States. It was designed to be an STOL airplane from the wheels up by Lynn Bollinger, Professor of Aviation Research at Harvard University, and Professor Otto Koppen, who taught aeronautical engineering at the Massachusetts Institute of Technology. These men shared belief in the need for a super-safe aircraft capable of operating into and out of short fields yet having the speed, range, and economy of conventional single-engine aircraft.

  After intensive study and research, the Bollinger-Koppen team produced its first Helio. What was to be only a taxi test at the Canton Airport in Massachusetts in April, 1949, resulted in the Helio Courier’s maiden flight. Modifications and refinements were made to the prototype, which eventually was certificated in 1954 and offered for sale a year later.

  Approximately 500 aircraft rolled off the production line in Pittsburgh, Kansas.

  At first glance, the Helio gives the appearance of a cumbersome airplane, one that might be underpowered, but this is an illusion. The fuselage, long and lean, is well mated to its 250-hp Lycoming engine. The wings are fully-cantilevered (no struts), which contributes to the cleanliness of the design.

  Curiously, the wing was designed for low-drag, high-speed flight, certainly not the crawling approach speeds that helped to establish the Helio Courier’s reputation. The airfoil is an NACA 23012, the same one that was used on the North American P-51 Mustang.

  At slow speeds, however, the wing does not do much except hold the high-lift devices in place while they produce more than 60 per cent of the total lift.

  The wings are equipped with automatically operated, full-span, leading-edge slats. When the aircraft is on the ground, the slats (two per wing) are extended forward and downward on the leading edges of the wings. They have the appearance of smaller wings attached to larger wings. At large angles of attack, low pressure at the leading edge of the wings holds them in this position (open). As the aircraft’s angle of attack decreases after takeoff, however, the wing’s center of pressure moves rearward and ram-air pressure pushes the slats closed. They are then flush with and form the leading edge of the wing.

  With the slats tucked neatly away, the wing becomes extraordinarily clean.

  When the Helio’s speed is reduced (angle of attack increased) during the approach, the center of pressure above the wing moves forward and the slots are “sucked” open automatically. The pilot does not have to operate them. They are there when you need them and out of the way when you do not.

  Photo courtesy Austin John Brown

  The slats can be a cause for alarm to novice Helio pilots. During my initiation flight in N6310V, Hunter Blackwell, Helio’s engineering test pilot, demonstrated a maximum-performance takeoff from Hanscom Field in Bedford, Massachusetts. The takeoff was dramatic. With about 10 knots of wind on the nose, we lifted off before reaching the runway numbers (less than 200 feet). The exceptionally steep climb is equally impressive.

  Although I never saw it, I was certain that there had to have been a control in the cockpit that does to the Helio Courier what the Up button does to the express elevator in the Empire State Building. The angle of climb is staggering. No sooner had I recovered from the initial shock than Blackwell lowered the nose and began to pick up speed. Then came a quick series of loud bangs that I imagined were cracking wing spars. Aware of my anxiety, Blackwell said, “It’s the slats!” I responded with a sheepish, “Oh!”

  The slats do not open and close slowly; they slam shut. I do not think that I was the first to suffer a panic attack during their first experience with slat retraction in a Helio. But one quickly learns that the banging is an asset because you know that they have closed without need of a cockpit instrument. (They can be observed from the cockpit, too.)

  The possibility of a slat sticking closed is remote, but the Helio was required to demonstrate during certification that it could be flown safely with both slats open on one wing and taped shut on the other. There were no controllability problems. Some low-speed potential is lost and the approach must be made at a relatively high speed, about 60 mph. Normal short-field approaches are made at less than 50 mph.

  There is nothing new about the Helio’s Handley-Page slats. They were designed in 1923 and have been used to lower landing speeds on the Messerschmitt ME-l09, the North American F-86 Sabre, the F-100, and a host of other aircraft.

  When the slats pop out at 50 mph, the angle of attack at which the wing stalls almost doubles. The slats are literally auxiliary wings that appear automatically when needed most.

  Blackwell pointed out the ease with which a climb can be made at the optimum angle of climb airspeed. “After takeoff, allow airspeed to increase to the point where the slats begin to close. Hold precisely that airspeed. If the slats are closed, you’re too fast; if they’re fully open, you’re climbing too slowly. At precisely the right point, the slats should be wiggling in and out.”

  The slotted wing flaps extend over 66 percent of the trailing edge, contributing greatly to the Helio’s low-speed capability. The flaps are lowered to their maximum of 40 degrees by turning a large crank on the cockpit ceiling between the pilots’ seats. At first, this cranking seems a nuisance. But there is a good reason for everything in the Helio, and the flap crank is no exception.

  Blackwell explained, “Suppose you’re skimming over a dense jungle at 50 mph indicated, preparing to land in a 300-foot clearing. If the flaps were controlled by an electric switch or a Johnson bar, there would always be the possibility of inadvertent flap retraction. During this type of approach, flap retraction and the resultant loss of lift could be catastrophic.”

  The elevator trim tab is operated by a smaller handle, concentric with the flap crank. Trim changes are made in the same manner as on many of the older single-engine Piper aircraft.

  Because the
flaps occupy so much of the trailing edge, there is little room for long ailerons. Instead, the ailerons are quite wide (large chord) and resemble squares rather than the customary narrow rectangles typical of other aircraft.

  In most aircraft, the use of right or left aileron to begin a roll results in adverse yaw that requires the use of coordinating rudder. But adverse yaw on the Helio Courier is almost non-existent because of its Frise ailerons.

  When such an aileron is deflected upward, the lower leading edge (lip) of the aileron moves downward into the airflow beneath the wing. The drag created by this lip extending into the relative wind counters the additional drag of the opposite, downward-deflected aileron. This effect, called “proverse yaw,” eliminates most of the need for rudder input during turn entry and recovery.

  It seems strange to see fabric-covered ailerons on such a sturdy and otherwise all-metal aircraft, but Blackwell explained, “If the aileron were made of aluminum, it would be off balance. Since most of the wide aileron is behind the hinge point, lead weights would have to be added to fill the ailerons’ leading edges.

  “The addition of such dead weight simply isn’t justified.”

  The final stroke of low-speed genius incorporated in the Helio wing are 4 “interceptors,” two of which are on the top of each wing at the point of maximum camber and behind the outboard slats. The interceptors consist of curved blades that operate in conjunction with the ailerons and are like small spoilers. With the control wheel neutralized, the interceptors are recessed within the wings. If left aileron is applied, for example, the interceptors above the left wing rise into the airstream and kill some of that wing’s lift (just as small spoilers would do). The result is enhanced roll control and high roll rates at minimum flying speeds.

  The interceptors are recessed half an inch below the surface of the wing so that they do not extend above the upper wing surface and have no effect during normal, relatively minor aileron operation in cruise flight.

  Now step away from the Helio and take a cold, hard look at this machine. You will notice that the main landing gear is located exceptionally far forward. It is actually attached to the engine firewall and for good reason. So much of the weight of the aircraft is located behind the main gear that even when flown at the maximum-allowable forward center of gravity, the Helio can be landed with the brakes locked without nosing over, an interesting way to really make a short-field landing. The landing gear is tough and resilient, too. The Helio can be flown in and out of freshly bulldozed fields without a whimper.

  The reason for such unusually long landing gear legs is to allow ample space between the large-diameter propeller and a field full of destructive rocks and pebbles.

  Because so much aircraft weight is behind the main landing gear, the Helio is slightly more prone to ground loops than other taildraggers. Using the cockpit-controlled tailwheel lock is recommended during takeoff and landing until experienced in the airplane.

  Photo courtesy Austin John Brown

  The Helio does not have a conventional horizontal stabilizer. It has instead a stabilator or “flying tail,” the first American airplane to have this feature.

  There are 2 doors for climbing into the Helio, and inside are 6 roomy seats, a cavernous interior that can hold a ton of cargo with a full load of fuel. The instrument panel is one of the largest you will find in a single-engine airplane.

  The Helio was built employing the concept that accidents are bound to happen because of the hazardous duty for which the airplane was designed. This is why it was equipped with shoulder harnesses long before they became required. What cannot be seen is the crashworthiness of the seats and welded-steel tubular cocoon that protects the cabin. Each is stressed for 15 Gs of deceleration.

  A Helio pilot once experienced an engine failure shortly after takeoff from a jungle clearing. He landed straight ahead and into a population of thick trees and vines that took a positive stand against the powerless aircraft. The Helio was totally demolished, but the pilot climbed down and walked away unscathed amid the excited cries of the monkeys and birds that inhabited said trees.

  Attempting to stall a Helio Courier is ludicrous. It simply cannot be done, which is why the airplane does not have a stall-warning indicator.

  Power off, the nose can be raised until the elevator hits the stops. The Helio will porpoise slightly and settle down at an indicated airspeed of 50 mph and a 1,000 fpm sink rate. Thanks to the interceptors, excellent lateral control can be maintained at all times, even with the control wheel held fully aft.

  Do not try a full-power stall in a Helio. The nose goes up and up until the nose is pointed almost straight up. Finally, when there is insufficient power to support the aircraft, the Helio begins to slide downward tail first.

  A partial-power stall with full flaps produces a buffet, but this is not from stalling. It is from downwash above the wing striking the tail.

  If you feel like spinning, go ahead and try. With the control wheel held fully aft, kick full rudder in either direction. The Helio will begin to autorotate. This is technically a spin but is not quite the same because a wing has not stalled. No dive or forward movement of the yoke is required to recover. Simply crank in opposite aileron (or rudder) and the interceptors will do the work. With full right rudder, for example, applying left aileron stops the “spin” and can be used to turn in the opposite direction.

  Flying a Helio Courier is an extraordinary experience. You can shoot an ILS approach at 40 mph or make a precautionary landing due to weather in almost any clearing. If you get tired of touching down on a runway and stopping by the numbers, you can land the Helio across the runway, just for a change of pace.

  The flag of Alaska is a field of blue containing the 7 stars of the Big Dipper, the handle of which points to an eighth star, Polaris. But according to Bill Diehl, President of Arctic Aircraft Company in Anchorage, this bright star in the northern sky is not Polaris. Instead, he says, it represents a star soaring across the Alaskan skies, the Interstate S-1B2, a modern, more powerful version of the Interstate Cadet, which also is known as the Arctic Tern.

  For those unfamiliar with the Cadet, it is a member of that nostalgic family of low-powered taildraggers that taught the lessons of flight to untold thousands of pilots in the late thirties, throughout the forties, and into the early fifties. Other such aircraft include the Aeronca 7AC Champion, the Piper J-3 Cub, and the Taylorcraft BD-12.

  Although the original Cadet was powered by a modest 65-hp engine, the S-lB2 has a 150-hp Lycoming O-320 engine giving the aircraft a quantum increase in performance, yet it retains the high-lift wing and NACA 23012 airfoil that gave the Cadet such remarkable slow-flight, short-field agility.

  Because the emphasis today is on airplanes with nosewheels, satellite navigations systems, and speed, it might seem anachronistic for a manufacturer to enter the market with a 2-place tandem taildragger, but there seems to be a growing demand for these small, fun machines, especially in Alaska where the tailwheel is the rule rather than the exception.

  Bill Diehl used to own a war-surplus L-6 liaison airplane, a 102-hp version of the Interstate Cadet that was developed for the Army Air Force at the outbreak of World War II. Diehl felt that with certain improvements, the L-6 could become a successful, lightweight bush plane capable of carrying respectable loads into and out of Alaska’s small, isolated bush strips that sometimes are little more than rough clearings.

  He also believed that the L-6 could be redesigned as a fully aerobatic trainer and fill a variety of roles.

  When Diehl learned that the manufacturing rights to the Interstate could be purchased from the Call Aircraft Company in Wyoming, he pursued his ambition with typical Alaskan perseverance. The rights to the Interstate became his in 1969. From an acorn of an idea, an oak tree began to grow. A redesigned, newly-manufactured Interstate made its maiden flight only a year later.

 
Changes made to the L-6 design included boosting the maximum-allowable gross weight, adding horsepower, increasing structural integrity, and expanding wing and flap area. Diehl also added Horner-type fiberglass wingtips, reduced drag, replaced the 3-piece windshield with wrap-around Plexiglas, redesigned the cowling, used stronger, more contemporary components, and generally gave the aircraft a major facelift and some streamlining.

  Anchorage might seem an improbable place to manufacture airplanes, but not when you consider that this is where the Arctic Tern has the greatest potential for success. Also, Diehl contends that since Alaska is so aviation oriented—20 percent of the population is licensed to fly—he has a labor pool already familiar with airplanes. He admits, however, that shipping parts and raw material to Alaska increases manufacturing costs.

  “Big Diehl,” as he is called by his friends, introduced me to N49128, the second production Interstate. At first blush, it looks like every other taildragger of the pre-war era. It is almost nondescript except for the distinctive shape of the vertical fin.

  A close inspection, however, reveals unusual features that may qualify the S-1B2 as the easiest and least expensive aircraft in its class to maintain, important not only to the bush pilot who occasionally needs to make emergency repairs in the field but to any pilot who has an aversion to sending monthly support payments to his local repair shop.

  For example, removing either of the two 20-gallon fuel tanks from its wing takes less than 10 minutes. Simply unscrew a panel on the bottom of the wing, loosen a few bolts, and the tank drops out. In other aircraft, this is a major and costly procedure. Want to replace an instrument? Simple. Whip out a dime and twist a few fasteners at the top of the hinged instrument panel. It then plops in your lap exposing everything to which you might want access. With that same dime you can remove the entire cowling in only a minute.