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   how to fly a 3 axis microlight
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Microlights, Ultralights and ULMs
we would like to thank Steve Jones of Sabre Air Sports for checking this section for Start Flying

Ultralights and microlights are defined differently in different countries. Essentially, they are very light airplanes, either single-seat or dual seat, and the licensing regulations for both pilots and aircraft are less stringent than for conventional light aircraft. The low stall speeds and weights mean that, while crashes may be more frequent, they are usually less painful! The aircraft are also a lot cheaper, and you fly slowly enough to appreciate the scenery. There are two main types: 3-axis - which have conventional controls, and weightshift, or trikes, which use a similar control system to hang gliders. The new category of ULM requires the same skills of flying as conventional aircraft and frankly, some of the newer models out-perform some conventional aircraft.

The world of Microlighting has advanced so much over the last 15-20 years that it has become the most affordable and safest form of motorised flight in the UK.

The advancement of four stroke dedicated aviation engines now make the aircraft more reliable than before, faster, as well as sleeker looking.

There are two types of Microlight aircraft, one is derived from hang-glider technology and the basic principle to operating the weight-shift, as it is called, is by moving the wing in the airflow to manoeuvre the aircraft in the air, usually you are open to the elements in this type of aircraft.

The other type of Microlight aircraft is the simple stick and rudder control, very similar to normal aircraft, being in an enclosed cockpit, these have surfaces on the wings and tail-plane which can be moved in the airflow, to manoeuvre the aircraft in the air, they are better known as 3-Axis types.


this Xair is typical of 3 axis microlights

The weight-shift aircraft are able to carry two people and fuel up to 4 hours duration in the air. Pilot and passenger sit in tandem like a motorbike; they have been likened to 3D motor biking. The 3-Axis types usually have side by side seating arrangements like the normal cockpit of a small aircraft.

During your trial lesson, you will, depending on the length of the lesson have an opportunity to have a go at flying the aircraft yourself, in the 3-Axis type this is a simple matter of passing control, from the Qualified Instructor to yourself with the instructor overseeing your every move. In the weight-shift, passing control, because of the tandem seating arrangement can be a little difficult, so initially you have a choice. If you want to have a go at flying the aircraft your instructor will generally ask you to sit in the P1 seat at the front, don’t worry all instructors on these types prefer to sit in the rear seat anyway, it’s the norm for them. Its then a simple matter of the instructor showing you what to do, how much, and when, and he can oversee you all the time in the air.

The weather plays a very important part in all forms of flying, but Microlights are a little more susceptible to the elements than other forms, so bear that in mind. Contrary to popular belief, the wintertime is the best time to fly in the UK, ok its cold, but we can wrap up against that. The difference is the stability of the air, cold crisp winter days are the best, saying that though, last thing on a summers evening can be just as enjoyable.


the new generation of 3 axis microlights are virtually indistinguishable from conventional aircraft, such as this CT (see ultralight revolution)

UK
In the UK the definition of a microlight is under review with a view to more standardisation across Europe. You need to obtain a NPPL (microlight) to fly one. You will also have to sit written examinations. Your licence will allow you to fly weightshift microlights (trike) or three-axis microlights. If you want to change from one to the other it is advisable to take a conversion course. One thing to bear in mind when selecting a school is that some do not allow you to fly the school aircraft once you have flown your first solo, which means you have to then purchase your own machine.

USA
In the US an ultralight is a single-place airplane under a certain maximum weight and with a maximum attainable speed, with additional definitions involving stall speed and fuel capacity. They are flown under the FAR Part 103 regulations, which do not require any form of pilot licence or certification provided they are flown within certain operating rules. However, teaching yourself to fly an ultralight is not recommended, and the single-seat requirement is waived for approved training establishments, who will teach you on a two-seat ultralight. A new category has been approved in the USA, the sport class, which allows many light conventional aircraft.

If you think microlights aren't capable of keeping up with the big guys, think again. Read on, and maybe you'll change your mind.

  The longest distance ever to be covered on a microlight is 1,627.78km. This was done by the Austrian Wilhelm Lischak. The flight took him from Volsau, Austria all the way to Brest, in France. The flight was done on 8 June 1988.

  The longest distance to be covered in a closed circuit by a microlight was 2701.16km. This too was done by Wilhelm Lischak on the 18 June 1988.

  The highest altitude ever reached in a microlight was 31,890ft. This record altitude was done by Serge Zin of France on the 18 September 1994.

  Highest speed to be reached in a microlight over a closed circuit is 293.04 km/h. This record speed was done by C.T. Andrews of the USA .

  Eve Jackson flew from Biggin Hill, Kent, UK, to Sydney, Australia from 26 April 1986 to 1 August 1987. The flight took 279 hours and 55 minutes, and covered 21,950 km.

  From 1 December 1987 to 29 January 1988, Brian Milton of Great Britain covered a distance of 21,968 km from London, UK, to Sydney, Australia. His flying time was 241 hours, 20 minutes.

Historically, ultralights and ultralight trainers with wings mounted above a tricycle undercarriage have been called trikes and powered hang gliders. In sport pilot/light-sport aircraft the FAA officially named this two-place lightsport aircraft category a “weight shift aircraft.”

Trikes first appeared in the late 1970s when hang gliders evolved from primitive delta wings to efficient flying wings with higher aspect ratios, defined airfoils, and wing twist providing stability and performance. The wings have evolved over 25 years along with hang glider wings to be highly refined performance machines. Trikes have been certificated to strict government standards in Europe and Australia.

how a trike flies

First, it’s important to understand that a trike is trimmed to fly at a certain speed (we’ll use 45 mph). In calm air you can let go of the controls and the trike will fly straight and seek the trim speed designed into the aircraft. Just as is in cars and airplanes, flying hands off requires slight corrections in direction. Unlike airplanes, which have three axes—ailerons (roll); elevators (pitch);
and rudder (yaw)—controlled by a stick/yoke and rudder pedals, the trike has two axes—roll and pitch—that are controlled by a bar connected to the wing.

The design of the trike’s swept wing, with a certain amount of twist and airfoil shape, provides automatic yaw control. In other words, trikes are comparatively easy to fly because you are only controlling two axes rather than three axes. An easy touch on the controls is the key to learning to fly a trike. When you shift your  weight to one side of the trike, it warps the wing by providing more twist on one side than the other. Similar to the Wright brothers’ wing warping, the increased twist generates more lift on that side, and that produces roll.

In the 1980s, when hang gliders evolved from crude delta wings to flying wings, the “floating crossbar” became the industry standard control system. This simple wing warping is the key to the weight-shift wing efficiency and rapid roll response. To pitch the nose up you simply push on the bar, and you pull it toward you to pitch the you pull it toward you to pitch the nose down. Control is intuitive because you have hold of the wing, and it goes wherever you move it. The motions are similar to riding a bicycle or motorcycle.

control differences

Airplane and trike controls are different, so airplane pilots will have to “unlearn” their stick and rudder skills when learning to fly a trike. Adding to the difference is the sitting in the open and the loss of the airplane’s “window” reference to the horizon. Typically, airplane pilots feel disoriented for the first 20 minutes and must think about the necessary control inputs for the first hour or two. Normally, airplane pilots are comfortable flying trikes after about two hours in the air, and many have developed the proper “habits” and are ready to solo after five hours. Some pilots pick it up immediately, and others take a little longer. It is no big deal to learn to “fly the wing” rather than move and coordinate the controls.

stalling

Stalling the wing of a trike is an easy, gentle, and forgiving manoeuvre. The wing’s “nose” is at a higher angle of attack than the wingtips. At high angles of attack the nose buffets first, loses lift, and naturally falls through while the tips in back keep flying. In addition, with the weight of the cart and occupants below, the pendulum effect naturally brings the nose down. Both factors result in a stall-resistant aircraft.

speed and range

Traditionally, trikes have flown in the slow—30-40 mph cruise and 25 mph stall—and medium—40-60 mph cruise and 30 mph stall—speed ranges. With newer wings and larger engines, trikes are now moving into the fast speed range, cruising at 60 to 90 mph. The wing’s size affects speed. A trike with a large 19-meter wing (200 square feet) will fly slowly. A 16-meter wing (170 square feet) gives you the medium speed range. And a small wing, 11 meters (115 square feet), provides the fast speeds range.

A trike undercarriage (or chariot) can be fitted with different wings, which means you can easily expand your flying options by having more than one size wing. Generally, the wing represents about 25 percent of the trike’s total cost, but smaller wings generally need more engine power. New trikes currently being tested have enclosed cockpits to keep the wind off you at higher speeds. We will see trikes evolve into higher speed machines considering creature comfort and fuel efficiency. Speed is one part of the range equation. Endurance—how much time you have in the fuel tank—is the other. A trike cruising at 50 mph for three hours will travel roughly 150 miles— nless it’s flying into a head wind, which reduces the distance. Trikes are powered by two- or four- ycle engines. With the same fuel capacity, four-cycle engines give better range because they use significantly less fuel than the two-cycle engines.

crosswind landings

Generally, an intermediate or advanced trike pilot can fly in a head wind that’s about two-thirds your stall speed and a crosswind of one-half your stall speed. Trikes and fixed-wing aircraft can taxi, take off, and land in comparable crosswind conditions. The configuration and size of the wing affects crosswind capabilities for both types of aircraft. Higher-speed aircraft typically have greater crosswind capabilities because higher speeds mean less crab angle on approach.

To land a trike in a crosswind, you line up on the runway centreline naturally crabbed into the wind and fly it crabbed to touchdown. As your back wheels touch, the nose wheel swings around straight down the runway. Crosswind takeoffs are similar. When you lift off the runway, the wing naturally weathervanes into the wind setting up a crab angle for you to proceed directly down the centreline of the runway. Naturally, each pilot’s wind limits depend on his or her experience. In turbulence, the wing moves more than the undercarriage resulting in less bumping around. Because the weight is under the wing, the undercarriage naturally wants to seek level flight. In moderate to severe turbulence you must hold onto the bar, which takes some muscle and can be fatiguing on long flights.

efficiency

Trikes have an advantage over airplanes —no tail—meaning they are not burdened by the weight, drag, and down-force associated with the tail structure. This gives trikes better climb rates and the ability to carry greater loads.

For example, with a small but efficient 50-hp engine, a medium trike can climb 1,000 feet per minute, and (with oxygen) it is possible to climb to 17,000 feet. Fully loaded with two people, it will climb at 500 fpm at sea level and can reach 11,000 feet. In this configuration of small engine, low drag, and medium wing, the trike stalls at 30 mph, flies hands-off at 45 mph, and has a maximum cruise of 65 mph. A large engine (100 hp) on a single-seat chariot with a smaller wing (13 meters) climbs at 60 mph and 2,000 fpm. Your speed, climb rate, and service ceiling depend on your configuration.

Trikes are efficient aircraft and glide nicely at about a 6-to-1 glide ratio with the engine shut off. It is common practice to shut down the engine and land on a spot.
 

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