Introduction to Ultralight Airplanes

What Factors Rule The Performance Of Ultralight Airplanes?

You have to ascertain that you have good flying conditions and your aircraft is in good operating condition before setting out on your flight. The performance of your ultralight aircraft is affected by multitude of environmental factors.

Atmospheric Density

One of the major factors that impact on performance is atmospheric density. Atmospheric density reduces with height and this affects the lift generation and the angle of attack. The concept of establishing a safe aircraft flight envelope within the critical range for best performance airspeeds emerges from this fact. This is the range within which the aircraft can be safely operated by an average pilot at varying density altitudes, airframe states, power outputs, wing loading and atmospheric turbulence.

ASI Position Error

The pilot also needs to know the ASI position error on his ultralight. The static vent is an opening connected to the cockpit via a tube and supplies ambient atmospheric pressure to the pressure sensing instruments. At specific altitudes disturbances can result in a position error. The ASI may under read by 10 knots at stalling.

If there is a sideslip the fuselage mounted static vent may experience dynamic pressure and the ASI and VSI readings may be erroneous. Consequently position error corrections for instruments should be noted and corrected in the Pilots Operating Handbook and placed in a placard on the instrument panel for ready reference. Before take off, the pilot should also check validity of claimed stall speeds and the type of wings used for evaluating performance.

Other Factors

Ultralights and microlights apply the same principles of flying as other aircraft. If speed is reduced the aircraft becomes less efficient. The elevator will normally deflect more downwards than upwards and this has to be taken advantage of, to have better elevator control at low speed (especially during descent or stall). However, the downwards deflection can be a hazard if the nose wheel has to hit the ground while one flares a little high and allows the speed to bleed off. Many microlights have stall speeds of 35Kt mark approximately and the elevator loses the ability to raise the nose at 40-45 Kt. This can have an impact on the calculation of approach speed.

Ultralights like microlights have high drag at low speed. Therefore a slightly higher approach speed is recommended to ensure that you won't have problems. These airplanes also have very little inertia. If the throttle is closed at 4 or 5 feet then, the aircraft will slow down rapidly and fall down to the ground. In cross winds the low inertia makes the crab technique difficult and the wing technique will have to be used. Sufficient bank should be used to keep the aircraft centerline and the nose pointing down the runway. However, you will find that there is not enough rudder to do so and the crosswing is too much. It would be better to keep power on till the aircraft hits the ground in a strong wind.

In short, you need to know his aircraft well and must be aware of its specific characteristics if you want the best performance out of it.

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