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Why Hummingbird?

Whither Aerobatics?
From War to Dance
A Flight in Hummingbird

Hummingbird is more than just a new aircraft design. While technically it is an original configuration, psychologically it is a paradigm shift for both pilots and spectators. To understand why this aircraft is being created, we first need to understand where aerobatics came from and where it stands today. Then, when we guide you through a flight in Hummingbird, you will perhaps appreciate the airplane's extraordinary appeal.

Whither Aerobatics?

The Carter Hummingbird aerobatic aircraft is being developed to bring about a new type of aerobatics. One only has to observe the dismal public interest in competition aerobatics to know that it is time for aerobatics to change. Even airshow routines have become largely ho-hum as engineers and pilots hit up against the inherent, conceptual limitations of the standard biplanes and monoplanes.

In order to maintain their marketing edge, airshow pilots are pushing the bipes and monos into extreme territory. A few modern "muscle biplanes" and high-powered Sukhoi variants have more static thrust than weight, and thus can approach a "hover". Countering engine torque remains a problem, however, leaving little margin for control. Consequently, such "hovering" at low altitude remains as much a feat of pilot skill and daring as of technical prowess, and one dares not think of the consequences of a hesitation in power. The Turbine Raven, a PT-6 powered Giles machine with a power-to-weight ratio off the scale and climb rate to match, was perhaps the extreme example of monoplane development before its unfortunate accident. From all accounts, spin characteristics were less than benign, however, likely due to the destabilising influence of the huge propeller mounted far forward.

One well-known pilot took exception to my observation (as an airshow spectator) that aerobatics has become predictable and routine, responding with: “Go to an airshow and see what pilots can do these days!”. What I see at airshows are mainly the same old “ball in a bowl” routines, relying on airspeed for vertical performance, incorporating the occasional incremental development in controlled maneuvers and lots of “out-of-control” tumbling. Since the technical limitations of classical configurations preclude any significant development of new controlled maneuvers, airshow pilots are resorting increasingly to tumbling maneuvers to wow crowds. Even the Four Minute Freestyle competition flight has become, in the words of a Russian pilot, “four minutes of out-of-control flight.” This raises the question: Is tumbling truly aerobatics, or is it just acrobatics? Is it “flight,” or is it simply Newton’s laws applied to a rapidly gyrating mass?

This is what aerobatics has come to: To be interesting or different, pilots are resorting either to precarious flight conditions or out-of-control flight. This harks back to the old “daredevil” or “stunt” flying of yesteryear. Meanwhile, what is to become of aerobatics as an artistic discipline?

From War to Dance

Human consciousness tends to run in grooves of familiarity until something comes along to create a new groove. Such a switch is called “revolution,” and this is what Hummingbird is all about. The ultimate benefactor will be aerobatics itself, and all who practice it.

Aerobatics today has its roots in the powerful symbol of the military “dogfight.” The aerobatic biplanes are configured identically to WW1 fighters; a Pitts is nothing more than a compact, slightly modernized Sopwith Camel, Fokker D7, or Spad. Likewise, the modern monoplanes are conceptually identical to the Spitfires, Mustangs, and Messerschmitts of WWII. Engines and structures may have advanced somewhat, the aerodynamic shapes matured, but the configurations are identical.

The military connection goes further than hardware. How many of us have imagined being a fighter pilot at the controls of an SE-5A or a Spitfire, or perhaps a Fokker Triplane or Messerschmitt 109, gyrating in the sky, lining up the enemy in our sights! We underestimate the power of such images in the mass-psyche, and how powerfully they have determined the course of aerobatics as a sport. And of course, one only has to go to Oshkosh to observe that the connection between aerobatics and the military endures to this day.

Hummingbird does away with all that. We are doing away with the “fly like a fighter” syndrome. Instead, we are creating a new paradigm, simply stated as:

Aerobatics is free and precise maneuvering on three axes, in three dimensions in space, relying upon classical physics and interaction with the atmosphere.

The ability to hover—to literally stop in the air, under full control—is an essential part of our new aerobatic paradigm. Stopping, stationary, is an essential part of maneuvering.

With the exception of the Harrier (for vertical takeoff and landing) and its Russian counterpart, no fighter has been able to hover, and for good reason. Why hover? If one stops still in the air, one will be shot down very quickly! For those of us steeped in the customary idea of aerobatics, hovering makes no sense, simply because it has never been necessary (other than to take off and land), besides never (in almost every case) being possible.

The military connection explains also the common obsession with speed. While a fighter must be fast to catch or elude its opponent, the physics of maneuverability is enhanced at lower speeds. While speed certainly allows an airplane to store energy, allowing it to “go up fast,” high speeds and high wing-loadings generally degrade maneuverability. If speed was fundamental to aerobatics, there would be no competition box and we would see only jet fighters in aerobatic contests!

The aerobatics I am proposing is closely related to gymnastics. Stillness is an essential component of the modern gymnastics paradigm, which combines elements of acrobatics and dance in a thoroughly artistic manner. All forms of dance—ballet being the classical Western archetype—use stillness to establish the environment and perspective for movement. Stillness and motion play off of each other. Aerobatics can, and should, do likewise. For the first time in history, we have the technical ability—the airplane—to make this possible.

Hummingbird has been designed to make such aerobatics possible. The propulsive, aerodynamic, structural, and ergonomic requirements of aerobatic flight have been investigated from fundamental principles and integrated into a technically elegant configuration ideally suited to the mission of precise aerobatic flight. The Hummingbird configuration is perhaps optimum for aerobatics. At least I cannot conceive of a better one.

Old habits die hard. People have said to me, “But a bird doesn’t have a duct!”. My answer is that a bird doesn’t have a propeller either, but a bird develops power in its midriff and has its eyes and brain in its head. Hummingbird places the pilot where she/he belongs, out in front, where visibility is unrestricted by wing, fuselage, and engine, and where G-forces correspond correctly with attitude changes. Like that of a bird, Hummingbird’s propulsion system is symmetrical and positioned near the CG, where it best enhances maneuverability and stability.

A Flight in Hummingbird

Imagine yourself at the controls of Hummingbird. You are ready for takeoff, engines idling. The view is superb; you can see all around, even straight down between your legs to the runway surface. Straight ahead is an unrestricted view of the runway, along with a unique sighting device at eye level. You can look along the leading edge of each wing, but the wings don’t block your view.

Shove the throttles forward and the response from the little 2-cycles is immediate: You are thrown forward by a thrust equivalent to as much as 150% of your takeoff weight—straight ahead, torque free. You can scarcely hear the engines, since the exhaust note of both engines is whisked away aft of the propellers. There is some vibration to reassure you that power is happening. You surge straight ahead, attaining flying speed in less than 100 feet of runway.

If you are daring, you can pull back on the side-stick and go straight up into the hover. Look out sideways to align the wing-mounted sighting device with the horizon. You hear the tone of the audio variometer in your headphones as you ease back on the throttles to slow your ascent. At perhaps 200 feet you hear zero climb, and your left hand manages the throttles to maintain it. You are stationary in the air.

Your controls work just the same as in forward flight. Apply rudder and you yaw, elevator and you pitch, aileron and you nimbly roll right or left. Or you can remain quite still, hovering stationary in the air. Hummingbird is comfortable in this condition, with control at your fingertips. You have power to spare; it is not an effort. You can roll to the right or left, climb or descend, or translate horizontally in any direction. With some practice you can hold full rudder and the aircraft will rotate through 360 degrees on the yaw axis, losing some altitude in the process. Back to the hover, apply full elevator, and you will do the same on the pitch axis.

Try doing this in any other aerobatic airplane. Or in any helicopter or tilt-rotor. Or in the Harrier. Never before has such maneuverability been possible, in any flying machine, ever.

If you were to lose an engine in this condition, you have choices. One engine remains, and you still have as much as 70% thrust and control on all axes. If you have sufficient altitude, rotate around (in yaw or pitch) to get your nose down, accelerate to flying speed, and fly out of it. Or, you can reach behind your head and pull the handle. Even from 200 feet, the ballistic parachute will fill within 2 seconds and lower you and the airplane safely to the ground. The lower fin will probably be smashed, and maybe the landing gear, but you will walk away and the airplane will fly again.

But the airplane is in good health and you are hovering comfortably. Apply full throttle and you begin ascending. Feed in a little rudder and you begin to translate sideways, gathering horizontal airspeed, yawing increasingly towards your direction of motion. You feel the buffet of turbulent air entering the propellers off the stalled wing or fins. Apply aileron to rotate onto your wing, pitch down, and 1500 lb of thrust propel you back to forward flight before you can think. This is flying!

Your airspeed builds rapidly. Roll to the right, onto the knife-edge, using the forward sighting device for precise roll information. Pitch up with rudder and loop through 360 degrees, pulling 4 G’s or more, on your side! Or you can work on your rolling loop. The airplane can do it; can you?

Having flown maneuvers that no other airplane can fly, you might want to try some of the standard Aresti maneuvers. You quickly realize that Hummingbird will change attitude, direction, and airspeed more rapidly than anything you have flown. Moreover, the forward cockpit, reclining seat, and superb visibility and attitude reference make everything seem easier. You discover that the aircraft behaves identically to the right or the left, and you can perform many maneuvers at any angle of bank. The aircraft rolls and snaps like other aerobatic ships, while spins rotate rapidly with quick and predictable entry and exit. Rudder takes some getting used to: Apply rudder alternately left and right, and you are thrown from side to side. From straight and level, hold hard rudder while keeping your wings level with opposing aileron. Your body is thrust sideways at up to 4 lateral G’s as you fly tight, flat orbits.

We have just begun. This is but a sampling of the new aerobatics, divorced of its military heritage. This is what Hummingbird will usher in.

Hummingbird is the first of a new breed of specialized aerobatic aircraft, divorced of military connections, built solely and simply to maneuver freely and precisely in the sky. It will provide pilots with greater flexibility, control, and safety, and as such, is a statement of the beauty and artistry of flight. It will liberate pilots to explore new vistas of their discipline, and lead to renewed public interest in aerobatics as entertainment and as a sport. And that will be good for everybody.

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© Copyright 1992-2009 Philip Carter