LEA 23

By Thomaas Bircher

NOTE:  The section below was sent to TWITT in late 2001 and has since been updated.  Click here for the latest update.

(ed. - The following text and pictures were provided by Thomas Bircher of Davos-Dorf, Switzerland.  This has been an on-going project with this model being the latest iteration of design changes over the years.  This a collaboration between Thomas and several other designers and builders.)

Flight testing the LEA 23, first results:

1. Roll, Liftoff - On a beautiful evening in May the little airport at the village of "Bad-Ragaz" was made available to us, to have the biggest possible area for a first flight.  Everything looked good so we taxied it out to centerline. Taxiing is very simple and smooth with the steerable nosewheel.

ABOVE:  LEA23 on takeoff roll.  Good view of the wing planform.

     Accelerating with the full power of the 29 cell Nicad 2400 Batteries, LEA took up speed fast, got un-steerable and broke of into the grass.  Pulling on the stick did not change anything.  Result:
     A - The lever of the elevator was to short you could not rotate the aircraft, you just pushed the wheels into the ground.
     B - The inertial mass of a wing-only type is so small that it starts to move quickly around the vertical axis, if it is allowed to do so.
     Changes: Increase the angle of attack of the wing and use flaps down for take-off,

ABOVE:  Another view showing the span and before the wing started achieving lift.

First Flight: May 23, 2000

In Thannhausen, Germany there is a very nice model flying club with their own runway(250 feet asphalt).  Best place now for the first flight.  Results:

     A - It behaved as expected. For take off we had to use a second pilot "at the flaps" because with full power and flaps down a great pitch-up moment was expected and nobody was sure if it would be possible to counteract with elevator only.
     B - The flight was rather uneventful and the landing took place right in the middle of the runway. It flies!!!.

2.  Later Problems:

     A - Structure: The carbon fiber joints between the inner and outer wing were too weak in stiffness, allowing vibrations off the outer wing panels.
     B - The layout of the antenna and the nearness of the carbon parts caused a interruption of signals on approach, giving a crash landing (bank angle blanked out the antenna’s reception).  Finally in February 2001 the prototype was totally destroyed in trying to fly at 4,000 ft above sea level with floats attached.  This caused a combination of too much additional drag, and bad contrasts in low sun conditions furthermore aggravated by the tendency of the model to turn very fast around the Z-Axis if rudder was applied.

3.  Final conclusions:

     A - Theoretically: On Track
     B - Performance: None yet measured.
     C - Decision: Build another prototype with some detail improvements.
     D - Expected to fly: Summer 2002

Thomas Bircher

ABOVE:  Thomas Bircher (at the controls) and a friend getting ready for a flight of the LEA23.
Note the clean lines in the aft fuselage from using an electric motor.  This also gives you an idea of the overall size of the model.

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