First Impressions: Backcountry pilots everywhere have heard of this almost-mythological bush plane with the exotic name. Its performance seems to defy the laws of physics, even fully loaded. We’re not talking about an ultra-lightweight, two-seat fabric plane with gigantic bush tires. The Helio Courier can do things no other fixed wing aircraft can and has been doing so for almost 70 years in some of the most remote places on Earth!
Background: The Helio Courier is the brainchild of MIT (Massachusetts Institute of Technology) Professor Otto Koppen. Dr. Koppen was a graduate of MIT and served there for 61 years as Professor of Aeronautics (1929 to 1965) and Professor Emeritus (1965 to 1990). Prior to designing the Helio Courier, Dr. Koppen worked at the Stout Metal Airplane Division of the Ford Motor Company, where he designed the tiny Ford Flivver in 1926 and had a significant role in developing the Ford Trimotor. Throughout his teaching career, he was widely considered an authority on aircraft stability and control. He wanted to design a Short Takeoff and Landing (STOL) aircraft that could be flown from very short airstrips. The “airplane in every garage” idea was popular in the late 40s and 50s, and the Helio STOL concept would make it possible for people even from semi-suburban neighborhoods to commute to work, as long as they had access to a small strip… or even a tennis court!
Dr. Koppen’s “proof of concept”, Helioplane #1, utilized a modified Piper PA-17 Vagabond fuselage with strut-braced, highly modified wings. The wings had leading-edge slats, a lengthened flap span, shortened ailerons, and lengthened main landing gear, giving it a high, three-point angle of attack. Even though the Helioplane #1 utilized a Continental C-85, Professor Koppen knew that a vital key to a short takeoff is low-end torque powering a large diameter prop. He devised a multi-belt, speed reduction unit that, when coupled to a gigantic 9-foot prop (allowed by the lengthened landing gear), developed heaps of static thrust with only 85-horsepower. Dr. Koppen did not subscribe to the theory that STOL airplanes need to be aerodynamically dirty. His self-described “proof-of-concept” two-seat Helioplane was developed into a 145 horsepower, four-seat prototype, sporting relatively low-drag cantilever wings with the flaps and slats retracted. With the big problems worked out, the Helio Aircraft Company was founded in 1954 and began producing the four-seat (with a fifth optional seat), 260-horsepower H-391B Courier. In 1959, the 290-horsepower GO-480-powered H-395 Super Courier was introduced. The Helio Aircraft Company produced the six-seat H-295 from 1965 to 1974.
Many variants of the Courier were developed, including floatplanes, a tricycle-gear model, turbine-powered Stallions, gunship Stallions, and even ultra secret Twin Couriers. The L-24 and L-28 (later redesignated U-10) were military variants of the H-391 and H-395, respectively. The same STOL characteristics that make for an extraordinary missionary bush plane were also ideally suited for the clandestine work of the CIA’s Air America branch. The Helio could insert and extract agents and partisans into places no other fixed-wing plane would dare venture. It served notably in Laos before and during the Vietnam War. Army, Air Force, and Air America Helios served in Southeast Asia (including Vietnam), Latin America, and even West Germany during The Cold War. Most of the mission sets of the Helios were ulta-secret.
JAARS (Jungle Aviation and Relay Service) has operated Helio Couriers and Super Couriers since 1956. Because they support missions and Bible translators in some of the most inaccessible places on the globe, the Helio was the perfect plane for that mission. They have operated Helios in Peru, Ecuador, Colombia, Panama, Liberia, Indonesia, Cameroon and the Amazon River on floats! JAARS has more Helio Courier pilot and maintainer experience than all other operators put together.
Design Features: The Super Courier is a six-seat, all-metal (except the ailerons) taildragger with cantilever high wings. The cantilever wing obtains its strength from a carry-through steel truss spar. Distinguishing features of the Helio Courier include the forward-positioned main landing gear legs that somewhat resemble a stiff-legged stubborn dog. The H-295 is easily distinguishable from the earlier H-395 and H-391 by the trapezoidal rear windows that replaced the round porthole windows.
The safety record of the Helio speaks for itself and is based on a few design characteristics; some of which were intentional and some of which are second-order effects. The cabin is framed with a chrome-moly steel cage. The front four seats in JAARS Helios are S-frame style and the back two seats use a thick energy-absorbing foam (all designed by JAARS R&D engineers). These seats are attached to the airframe with high strength Brownline tracks and have been tested for up to 30 Gs of protection for the occupants. Safety is paramount at JAARS, and their Helio Couriers are equipped with four-point restraints. If the pilot and passengers are retained in their seats and the seats stays in the steel cage, everyone has a good chance of surviving a crash. The JAARS record speaks volumes; in over 67 years of Helio operations in the most austere settings on Earth, they have never had a fatality in one of their Couriers.
When the slats are deployed and the ailerons travel past approximately 10 degrees up, two sets of “interceptor” blades will deploy up on the respective wing, immediately behind the slat opening. This spoils the lift flowing over the wings, thereby causing a rolling moment on that side, even at very low airspeeds. Interceptors function similarly to spoilerons but differ by operating in conjunction with actual ailerons. The interceptors work with mechanical connection to the ailerons. All four slats are not mechanically-driven, but will deploy and retract independently based on the airflow and angle of attack. When deployed, the air flowing through the slot between the slats and the leading edge of the upper surface of the wing is redirected, maintaining boundary layer control and contributing to the allowable high angles of attack.
The Frise-style ailerons are the only fabric-covered surface and have a deep chord in order to maintain a lot of flight control area while not robbing flap “real estate”. The Fowler flaps span 66% of the wing span and extend to 40 degrees with 18 clockwise turns of the overhead flap crank. The stabilator is 14 feet from end to end - longer than an entire Piper Cherokee wing! It is all-moving and trims with an overhead knob that controls a jack screw in the tail. The airplane does need a lot of small trim inputs, but a little movement of the crank goes a long way. One of the Courier’s safety features is how difficult it is to stall. The stabilator is purposely travel-limited. The plane will not result in a stall “break” unless the pilot is very deliberately attempting to stall and using considerable power to do so. The critical angle of attack is an incredible 30 degrees!
Helio Couriers have a long list of available STCs, and the JAARS engineering and maintenance team is responsible for the majority of them. The airframe I flew had 26 STCs and two field approvals incorporated, including a belly pod and cargo door. The max gross weight for the H-295 is 3400 lbs. and the U-10D has a max gross weight of 3600 lbs. All JAARS Helios have a gross weight STC; increasing the max gross weight to 3800 lbs.
Powerplant: The H-295 Super Courier uses a 295-horsepower GO-480 to power a Hartzell 96-inch three-bladed constant-speed propeller. Of course, the geared engine was purposefully selected and the gearbox produces a 77:120 reduction ratio, enabling the eight-foot, three-bladed prop to deliver more torque at lower RPM. Each wing has a 30-gallon bladder tank and the fuel system is gravity-fed. Some H-295s are equipped with auxiliary fuel tanks, adding an additional 30 gallons per wing for a total of 120 gallons.
A pressure carburetor with Automatic Mixture Control (AMC) lightens the workload to fly the Courier, which is a good thing. Interestingly, the prop clearance for the initial H-391B (102-inch prop) from the ground was an initial concern for the Civil Aviation Authority, but after four test pilots tried (repeatedly) to get the prop to hit the ground, the CAA was appeased and issued the type certificate. The combination of the forward-positioned main landing gear, the heavy tail, limited stabilator travel, and the landing gear “tuck” keeps those blade tips out of the dirt.
Preflight: One unique preflight check of a geared engine is to check for “play” in the gearbox. This is done by slightly moving the prop in either direction to ensure there is no more than ½ inch of movement. Fuel is checked by stepping on a main wheel and then two handy fuselage steps. During preflight, the slats will be fully deployed, providing a great opportunity to check all the “tomahawks” (slat support tubes) and rollers. After all, when in flight with the slats fully extended, 64% of the aircraft’s weight is carried by the slats and associated tomahawks! Take time to move each slat and check for smoothness of operation. An interesting detail you may notice during preflight inspection is a small ridgeline bump that runs along the upper trailing edge of the ailerons. During the certification process, the CAA (Civil Aviation Authority) test pilot declared that the roll control was too light. Rather than going back to the drawling board and redesigning an engineering solution, Dr. Koppen had someone glue a piece of cord to the trailing edge of the ailerons. The CAA was satisfied with the resulting “heavier feel”. Since then, a segment of cord is laid onto the wing and doped in during the fabric-covering process.
Takeoff: A STOL takeoff requires 15 clockwise turns of the overhead flap crank to reach 30 degrees. After pre-takeoff checks are completed, lineup on the runway and wiggle your feet. You’re going to need to keep them moving on the takeoff roll! Smoothly add-in full power, which will give you about 3400 RPM at the crankshaft and 2182 RPM at the prop. The heavy-duty main landing gear legs are splayed out with a stance of approximately nine feet with the aircraft’s weight on wheels. With weight off the wheels, the stance is only about five feet. This means that during takeoff, as the Helio wings develop lift, the wheels begin to tuck in. This makes the nose rise, almost like a floatplane getting on “step”. This rise indicates that the stabilator is developing lift and it is time to lift the tail to just off the ground. Once the tail is up and the aircraft is accelerating, the nose will want to pitch down. Back pressure is now required to hold the tailwheel just clear of the ground. The Helio will lift off and fly away in this attitude. Also, full throws of the rudder pedals may be required to track straight. If the takeoff sounds like a lot of work, it’s because it is! At a typical training weight, the Super Courier will be off the ground in 450 feet and clear of a 50-foot obstacle in only 700 feet.
Every aircraft design is a series of compromises, and the Helio Courier is no different. The same STOL characteristics that make it an incredible bush plane are what cause it to be somewhat of a handful, notably on the ground. The landing gear of a Cessna 185 is positioned 21 inches forward of the aft-most CG. On a Helio, the gear is a full 50 inches forward of the aft-most CG! When you factor in landing gear that “tucks” in, you have an airplane that would like to swap ends, particularly if you have a CG approaching aft limits! This is certainly an airplane that requires attention and perhaps this is why JAARS continues to use it both in evaluating and training new potential missionary pilots.
Flight Characteristics: The Helio’s performance airborne is just as impressive as the takeoff and landing. It is, however, a very “hands-on” airplane in all phases of flight. JAARS does not have autopilots in their Helio Couriers, mostly because every ounce of weight saved means available useful load for medical supplies, food, fuel drums, livestock, missionaries, etc. In the pre-mission brief, JAARS Chief Pilot Steve Bevelhymer stated that we would be doing steep turns (45 degrees) with 40 degrees of flaps at only 50 knots, while maintaining altitude! I had a hard time believing that, but he proved it airborne! This canyon-turn performance is certainly a good tool to have when flying over the mountainous jungles of Papua, Indonesia! It does not have much adverse yaw tendency, but there are some over-banking tendencies and lots of torque, so it’s important not to spend too much time heads-down in the cockpit.
Landing: The missionary pilots at JAARS have perfected the Helio STOL technique over the past 67 years, and there is no tolerance for “cowboy” techniques or attitudes. Every landing strip is carefully evaluated and performance is methodically calculated. Margins of safety are built-in and pilots must fly their approaches precisely. Many of their landing strips are one-way in and one-way out with a landing commit point early in the approach. Their precision STOL landing techniques are similar to U.S. Navy carrier operations and likewise have narrow margins for error. JAARS teaches a very precise pattern with a completely stabilized approach using angle of attack (gauged from slat position) and power for glideslope. On downwind, slow to 60 knots and crank in 30 degrees of flaps. After the base turn, slow to 55 knots and crank in 40 degrees of flaps. Approaching the final turn, you’ll need to slow and stabilize at the “on-speed AOA”. Rather than using an AOA indexer light system or instrument, the pilot references the slat position. As you slow, the inboard slats will extend first. I’m not sure how long it takes to get used to the slats slamming down, but it’s more than just one flight! Every time they moved up or down, I’d see the movement with my peripheral vision and flinch, thinking it was traffic or a bird. The pilot gauges on-speed AOA based on the outboard slat position. The outboard slats should be about 1 ½ -inches short of fully extended. Once this AOA is attained, a quick glance at the airspeed indicator will show approach speed for the current weight. Landing speeds can indicate as low as 28 (NOT a typo) knots! The STOL approach is steep (5.5 - 6˚) and will usually be a 450 to 500 fpm rate of descent.
JAARS does not teach a flare as such; it is simply a transition to landing attitude. At about one wingspan’s distance from the runway, the pilot will close the throttle and pull the yoke back, setting a three-point attitude. There is no float whatsoever because the pilot has managed energy to the minimum. The Helio simply plants and sticks to terra firma. Air-oil shocks on all three landing gear do much to absorb the landing. Heavy braking can be used after touchdown, with no chance of nosing over due to the unique forward position of the main landing gear legs and heavy tail. Using this technique, the H-295 can be stopped within 200 feet. And no, JAARS pilots do not expect “smooth landing” comments from deplaning passengers.
Toña History: The H-295 I flew (serial no. 1436) was picked up new from the factory in 1972 by JAARS and has spent its entire life as a missionary airplane. It has served in Ecuador, Indonesia, and the United States. It has over 10,700 airframe hours and 18,000 landings. Before the airplane was delivered to South America, a young native Ecuadorian convert to Christianity, named Toña, was martyred by a neighboring village. Upon delivery to Ecuador, serial no. 1436 was dedicated and named Toña in his honor. Just from its service in Indonesia alone, Toña carried 10,114 passengers and over 2,500,000 pounds of payload more than 550,000 nautical miles. It recently completed a top to bottom restoration by JAARS mechanics and was rededicated in May of 2023 at JAARS 75th anniversary celebration (see EAA Sport Aviation article June 2023, Mission: Possible 75 Years of Flying Goodwill).
Wrap-Up: The Helio Courier is truly a remarkable airplane and deserves the reverence it receives in the bush pilot world. In the words of JAARS president, Steve Russell (EAA#1203140), “The Helio Courier is to JAARS what the Spitfire is to the Royal Air Force, or what the P-51 is to the U.S. Army Air Corps”. For almost 70 years, Helio Couriers have flown in and out of the most hostile environments in the most isolated corners of our planet. Toña’s mission is far from over as it continues the task of evaluating and training some of the world’s best missionary pilots!