Half painted Fw 190 wing undersides - the purpose?

[Kari Lumppio]

Hello!

I'm wondering about the Fw 190 wing undersides where the leading edge was painted with some colour (grey or light blue) when the rest was left unpainted. Period of time latter half of 1944 and on.

The books I have read explain the thing as camouflage against low flying strafers. Can't help myself of the nagging thought that Luftwaffe was at the time abandoning the underside camouflage alltogether. Why there suddenly arose a new need for underside camouflage at that same point of time? Plus one doesn't see the half-painted wing undersides on other LW a/c types (or any other Air Force of any period for that matter).

Related question: what colour is the Warnecke & Böhm filler 119 D? It is somehow related to the unpainted Fw 190 wing undersides.

It is this filler thing which makes me to propose another hypothesis. What if the half-painted area is actually area aerodynamically smoothed with filler? Germans were still in 1944 trying to make the most out of their planes. Why not copy the P-51 Mustang wing surface finish (= wing forward half smoothed with filler)? The smoothing of Fw 190 wing leading edge would make at least some aerodynamic sense as it did not have slats like Bf 109 (disruption at slat trailing edge makes the flow turbulent no matter what). IIRC Hoerner in his aerodynamics book (title escapes my mind now) complained about the uneven finish of German planes (Bf 109) and the resulting drag and drop in performance.

The proof would lie in finding if the Fw 190 wing upperside has the same paint/filler as the leading 50% of the underside of "unpainted" wings.

So there. Antitheses, other hypotheses and especially syntheses welcomed.


Regards to every researcher on this field,
Kari