questions about 109

[Hristo]

From W. Green’s “Warplanes of  the Third Reich”, 1973 edition, Doubleday, page 568:


 

…In the interim, futher modifications were introduced on the Bf 109G and, by the late summer, yet another G-series variant, the Bf 109G-14, was rolling of the lines. Earlier, geared tabs had been fitted to the ailerons and elevators in order to lighten the controls, but delays in deliveries of the modified elevators had led to some aircraft reaching service units with only the aileron tabs fitted. This resulted in an unacceptable difference between the effort required from the pilot by the ailerons and the elevators, and instructions were therefore issued to disconnect the aileron tabs and lock them by means of rivetted dural strips…

Well, since English is not my first language, nor I am an aeronautical engineer, would someone please explain me the folowing:

What exactly are geared tabs ?

If unacceptable difference was achieved in aileron and elevator forces, they had to be effective. How did they work ?

W. Green says some aircraft reached units with only aileron tabs fitted. Does it mean other aircraft had complete set of tabs ?

I gather this is related to G-14 version. Did later versions have full set of tabs ?

[juzz]

I *think* they might be refering to "Flettner" trim tabs, which I am guessing from some vague comments I've read are an automatic spring-loaded device designed to give better control forces over a wider speed range. I see "Flettner geared tab" named in alot of cutaway drawings of late-war German planes. Eg: Bf109G-14/U4, Me262A-1a.
 
Here's something about it...and some other interesting control surface bits.

One would have liked to have more effective ailerons, as well as lower control forces, at high speeds. I do not remember all the different methods tried to improve this, but the following two are still clear in my mind. One was designed by Blohm & Voss, adding a Flettner trim tab which resulted in a reduction of control forces: however, performance was not as smooth and effectiveness had not improved at all. A later form was the 'Keulenquerruder'(a shape of aileron tested at Memmingen in 1944) which had seemed promising, but had never been introduced. The rudder had no trim: it was 'ironed out' especially for the dive and produced fairly high aerodynamic forces during the climb. Nevertheless, it seemed the best of compromises: a spring to counteract the strong forces during the climb was considered, but never incorporated.

Dipl. Ing. Heinrich Beauvais, test pilot. From the (english version) book "Test Pilots" by W.Späte, ISBN 1-872836-20-8