Ximango and aerodynamics - May 2003

The Aeromot AT-20 Super Ximango is a conventional retractable gear, single
engine, propeller driven, motorglider. It is a very docile aircraft. On the
ground as any tail dragger, needs appropriate rudder pedal action to control
its turning tendency along its vertical axis.

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Date:         Fri, 23 May 2003 15:52:28 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         "Dr. Douglas Bournigal" <dr.bournigal@CODETEL.NET.DO>
Subject:      Ximango and Aerodynamics
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The Aeromot AT-20 Super Ximango is a conventional retractable gear, single
engine, propeller driven, motorglider. It is a very docile aircraft. On the
ground as any tail dragger, needs appropriate rudder pedal action to control
its turning tendency along its vertical axis.



The left turning forces that act on a fixed wing aircraft such as this
include:

1)     Engine/ Propeller Torque

2)     Gyroscopic  Precession

3)     Asymmetrical Thrust

4)     Spiraling slipstream



To these, we have to add the normal weather vane effect of its large
vertical stabilizer. This last force plays a major role and together with
the above listed four, can amount to a violent bearing to the left on the
take off roll.





These are to be expected and magnified on the following situation:

a)     Quarterly Left wind (Weather Vane effect)

a)   Speed of 25-40 knots (Vertical stabilizer authority greater than 
rudder)

c)     Tail raising ( Loss of tail wheel control and presence of Gyroscopic
Precession)

d)    Take-off power (Engine/ Propeller Torque, Asymmetrical Thrust,
Spiraling slipstream )





 Even on the ground, while taxiing with winds in excess of 10 knots, you
will notice that the nose will bear to place it self directly against the
wind. Sometimes the use of rudder pedals and brakes are not sufficient to
overcome the weather vane effect at low ground speeds and significant
surface winds.

When facing a left crosswind of let's say 15 knots, is preferable to takeoff
on the opposite runway and make that wind a right crosswind component.



I do not agree on using the speed brakes on the takeoff roll, the power
quadrant hand belongs on the throttle. On landing, belongs on the speed
brake lever.



Dr.Bournigal

s/n 122

600 hrs Ximango TT